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Zhou H, Yuan W, Lei W, Zhou T, Qin P, Zhang B, Hu M. Domain definition and preliminary functional exploration of the endonuclease NOBP-1 in Strongyloides stercoralis. Parasit Vectors 2023; 16:399. [PMID: 37924155 PMCID: PMC10623843 DOI: 10.1186/s13071-023-05940-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2023] [Accepted: 08/22/2023] [Indexed: 11/06/2023] Open
Abstract
BACKGROUND Ribosome biogenesis is the process of assembling ribosome complexes that regulate cell proliferation and differentiation with potential regulatory effects on development. Many factors regulate ribosome biological processes. Nin one binding protein (Nob1) has received widespread attention as key genes regulating ribosome biogenesis-the 3' end of the 20S rRNA is cleaved by Nob1 at cleavage site D to form 18S rRNA, generating translationally capable 40S subunit. As a ribosome biogenesis factor, Nob1 may regulate the development of organisms, but almost nothing is known about the function of Nob1 for any parasitic nematode. We explored the functional role of NOBP-1 (the homologous gene of Nob1) encoding gene from a parasitic nematode-Strongyloides stercoralis. METHODS The full-length cDNA, gDNA and promoter region of Ss-nobp-1 was identified using protein BLAST in WormBase ParaSite according to the Caenorhabditis elegans NOBP-1 sequence to analyze the gene structure. RNA sequencing (RNA-seq) data in wormbase were retrieved and analyzed to assess the transcript abundance of Ss-nobp-1 in seven developmental stages of S. stercoralis. The standard method for gonadal microinjection of constructs was carried out to determine the anatomic expression patterns of Ss-nobp-1. The interaction between Ss-NOBP-1 and partner of NOBP-1 (Ss-PNO-1) was assessed by yeast two-hybridization and bimolecular fluorescence complementarity (BiFC) experiments. RESULTS The NOBP-1 encoding gene Ss-nopb-1 from the zoonotic parasite S. stercoralis has been isolated and characterized. The genomic DNA representing Ss-nobp-1 includes a 1599-bp coding region and encodes a protein comprising 403 amino acids (aa), which contains conserved PIN domain and zinc ribbon domain. RNA-seq analysis revealed that Ss-nobp-1 transcripts are present throughout the seven developmental stages in S. stercoralis and have higher transcription levels in iL3, L3 and P Female. Ss-nobp-1 is expressed mainly in the intestine of transgenic S. stercoralis larvae, and there is a direct interaction between Ss-NOBP-1 and Ss-PNO-1. CONCLUSIONS Collectively, Ss-NOBP-1 has a potential role in embryo formation and the infective process, and findings from this study provide a sound foundation for investigating its function during the development of parasitic nematode.
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Affiliation(s)
- Huan Zhou
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China.
- National Key Laboratory of Cotton Bio-Breeding and Integrated Utilization, School of Life Sciences, Henan University, Kaifeng, China.
| | - Wang Yuan
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China
| | - Weiqiang Lei
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China
- College of Animal Science and Technology, Jinling Institute of Technology, Nanjing, 210038, China
| | - Taoxun Zhou
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China
| | - Peixi Qin
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China
| | - Biying Zhang
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China
| | - Min Hu
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China.
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Wolters SM, Benninghaus VA, Roelfs KU, van Deenen N, Twyman RM, Prüfer D, Schulze Gronover C. Overexpression of a pseudo-etiolated-in-light-like protein in Taraxacum koksaghyz leads to a pale green phenotype and enables transcriptome-based network analysis of photomorphogenesis and isoprenoid biosynthesis. FRONTIERS IN PLANT SCIENCE 2023; 14:1228961. [PMID: 37841614 PMCID: PMC10569127 DOI: 10.3389/fpls.2023.1228961] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/30/2023] [Accepted: 08/21/2023] [Indexed: 10/17/2023]
Abstract
Introduction Plant growth and greening in response to light require the synthesis of photosynthetic pigments such as chlorophylls and carotenoids, which are derived from isoprenoid precursors. In Arabidopsis, the pseudo-etiolated-in-light phenotype is caused by the overexpression of repressor of photosynthetic genes 2 (RPGE2), which regulates chlorophyll synthesis and photosynthetic genes. Methods We investigated a homologous protein in the Russian dandelion (Taraxacum koksaghyz) to determine its influence on the rich isoprenoid network in this species, using a combination of in silico analysis, gene overexpression, transcriptomics and metabolic profiling. Results Homology-based screening revealed a gene designated pseudo-etiolated-in-light-like (TkPEL-like), and in silico analysis identified a light-responsive G-box element in its promoter. TkPEL-like overexpression in dandelion plants and other systems reduced the levels of chlorophylls and carotenoids, but this was ameliorated by the mutation of one or both conserved cysteine residues. Comparative transcriptomics in dandelions overexpressing TkPEL-like showed that genes responsible for the synthesis of isoprenoid precursors and chlorophyll were downregulated, probably explaining the observed pale green leaf phenotype. In contrast, genes responsible for carotenoid synthesis were upregulated, possibly in response to feedback signaling. The evaluation of additional differentially expressed genes revealed interactions between pathways. Discussion We propose that TkPEL-like negatively regulates chlorophyll- and photosynthesis-related genes in a light-dependent manner, which appears to be conserved across species. Our data will inform future studies addressing the regulation of leaf isoprenoid biosynthesis and photomorphogenesis and could be used in future breeding strategies to optimize selected plant isoprenoid profiles and generate suitable plant-based production platforms.
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Affiliation(s)
- Silva Melissa Wolters
- Fraunhofer Institute for Molecular Biology and Applied Ecology IME, Münster, Germany
| | | | - Kai-Uwe Roelfs
- Fraunhofer Institute for Molecular Biology and Applied Ecology IME, Münster, Germany
| | - Nicole van Deenen
- Institute for Biology and Biotechnology of Plants, University of Münster, Münster, Germany
| | | | - Dirk Prüfer
- Fraunhofer Institute for Molecular Biology and Applied Ecology IME, Münster, Germany
- Institute for Biology and Biotechnology of Plants, University of Münster, Münster, Germany
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Zhou X, Li S, Yang X. The DcPS1 cooperates with OSDLa during pollen development and 2n gamete production in carnation meiosis. BMC PLANT BIOLOGY 2022; 22:259. [PMID: 35610560 PMCID: PMC9128087 DOI: 10.1186/s12870-022-03648-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/08/2022] [Accepted: 05/09/2022] [Indexed: 05/31/2023]
Abstract
BACKGROUND Deciphering the mechanisms of meiosis has important implications for potential applications in plant breeding programmes and species evolution. However, the process of meiosis is poorly understood in carnation, which is famous for its cut flowers. RESULTS We report that Dianthus caryophyllus parallel spindle 1 (DcPS1) regulates omission of second division like a (OSDLa) during pollen development and 2n gamete production in carnation meiosis. In DcPS1 and OSDLa RNAi lines, an absence of the second meiotic division and the abnormal orientation of spindles at meiosis II might be the main reason for dyad/triad formation, resulting in unreduced gametes. We also found that carnation OSDLa interacted with DcPS1 and DcRAD51D. In the DcPS1 RNAi lines, a decrease in OSDLa and DcRAD51D expression was observed. In the OSDLa RNAi lines, a decrease in DcPS1 and DcRAD51D expression was also observed. We propose that DcPS1 regulates OSDLa expression, allowing entry into meiosis II and the proper orientation of the metaphase II spindle in meiosis II. We also propose that OSDLa regulates DcRAD51D expression, allowing for homologous recombination. CONCLUSIONS These results suggest a critical role for DcPS1 and OSDLa in diplogamete production during meiosis and open a new pathway for meiosis-related studies.
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Affiliation(s)
- Xuhong Zhou
- Office of Science and Technology, Yunnan University of Chinese Medicine, 1076 Yuhua Road, Chenggong, Kunming, Yunnan, 650500, PR China.
- Flower Research Institute, Yunnan Academy of Agricultural Sciences, National Engineering Research Center for Ornamental Horticulture, 2238 Beijing Road, Kunming, Yunnan, 650205, PR China.
| | - Shuying Li
- Flower Research Institute, Yunnan Academy of Agricultural Sciences, National Engineering Research Center for Ornamental Horticulture, 2238 Beijing Road, Kunming, Yunnan, 650205, PR China
| | - Xiaomi Yang
- Office of Science and Technology, Yunnan University of Chinese Medicine, 1076 Yuhua Road, Chenggong, Kunming, Yunnan, 650500, PR China
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Miekus K, Kotlinowski J, Lichawska-Cieslar A, Rys J, Jura J. Activity of MCPIP1 RNase in tumor associated processes. JOURNAL OF EXPERIMENTAL & CLINICAL CANCER RESEARCH : CR 2019; 38:421. [PMID: 31639017 PMCID: PMC6805641 DOI: 10.1186/s13046-019-1430-6] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/27/2019] [Accepted: 09/23/2019] [Indexed: 12/31/2022]
Abstract
The monocyte chemoattractant protein-induced protein (MCPIP) family consists of 4 members (MCPIP1–4) encoded by the ZC3h12A-D genes, which are located at different loci. The common features of MCPIP proteins are the zinc finger domain, consisting of three cysteines and one histidine (CCCH), and the N-terminal domain of the PilT protein (PilT-N-terminal domain (PIN domain)). All family members act as endonucleases controlling the half-life of mRNA and microRNA (miRNA). The best-studied member of this family is MCPIP1 (also known as Regnase-1). In this review, we discuss the current knowledge on the role of MCPIP1 in cancer-related processes. Because the characteristics of MCPIP1 as a fundamental negative regulator of immune processes have been comprehensively described in numerous studies, we focus on the function of MCPIP1 in modulating apoptosis, angiogenesis and metastasis.
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Affiliation(s)
- Katarzyna Miekus
- Department of General Biochemistry, Faculty of Biochemistry, Biophysics, and Biotechnology, Jagiellonian University, Gronostajowa 7 Street, 30-387, Krakow, Poland
| | - Jerzy Kotlinowski
- Department of General Biochemistry, Faculty of Biochemistry, Biophysics, and Biotechnology, Jagiellonian University, Gronostajowa 7 Street, 30-387, Krakow, Poland
| | - Agata Lichawska-Cieslar
- Department of General Biochemistry, Faculty of Biochemistry, Biophysics, and Biotechnology, Jagiellonian University, Gronostajowa 7 Street, 30-387, Krakow, Poland
| | - Janusz Rys
- Department of Tumour Pathology, Maria Skłodowska-Curie Memorial Center and Institute of Oncology, Krakow, Poland
| | - Jolanta Jura
- Department of General Biochemistry, Faculty of Biochemistry, Biophysics, and Biotechnology, Jagiellonian University, Gronostajowa 7 Street, 30-387, Krakow, Poland.
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Dehecq M, Decourty L, Namane A, Proux C, Kanaan J, Le Hir H, Jacquier A, Saveanu C. Nonsense-mediated mRNA decay involves two distinct Upf1-bound complexes. EMBO J 2018; 37:embj.201899278. [PMID: 30275269 DOI: 10.15252/embj.201899278] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2018] [Revised: 08/10/2018] [Accepted: 08/22/2018] [Indexed: 11/09/2022] Open
Abstract
Nonsense-mediated mRNA decay (NMD) is a translation-dependent RNA degradation pathway involved in many cellular pathways and crucial for telomere maintenance and embryo development. Core NMD factors Upf1, Upf2 and Upf3 are conserved from yeast to mammals, but a universal NMD model is lacking. We used affinity purification coupled with mass spectrometry and an improved data analysis protocol to characterize the composition and dynamics of yeast NMD complexes in yeast (112 experiments). Unexpectedly, we identified two distinct complexes associated with Upf1: Upf1-23 (Upf1, Upf2, Upf3) and Upf1-decapping Upf1-decapping contained the mRNA decapping enzyme, together with Nmd4 and Ebs1, two proteins that globally affected NMD and were critical for RNA degradation mediated by the Upf1 C-terminal helicase region. The fact that Nmd4 association with RNA was partially dependent on Upf1-23 components and the similarity between Nmd4/Ebs1 and mammalian Smg5-7 proteins suggest that NMD operates through conserved, successive Upf1-23 and Upf1-decapping complexes. This model can be extended to accommodate steps that are missing in yeast, to serve for further mechanistic studies of NMD in eukaryotes.
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Affiliation(s)
- Marine Dehecq
- Génétique des Interactions Macromoléculaires, Genomes and Genetics Department, Institut Pasteur, Paris, France.,Université Pierre et Marie Curie, Paris, France
| | - Laurence Decourty
- Génétique des Interactions Macromoléculaires, Genomes and Genetics Department, Institut Pasteur, Paris, France
| | - Abdelkader Namane
- Génétique des Interactions Macromoléculaires, Genomes and Genetics Department, Institut Pasteur, Paris, France
| | - Caroline Proux
- Transcriptome and Epigenome, CITECH, Institut Pasteur, Paris, France
| | - Joanne Kanaan
- Expression des ARN Messagers Eucaryotes, Biology Department, CNRS UMR8197, Inserm U1024, Institut de Biologie de l'Ecole Normale Supérieure, Paris, France
| | - Hervé Le Hir
- Expression des ARN Messagers Eucaryotes, Biology Department, CNRS UMR8197, Inserm U1024, Institut de Biologie de l'Ecole Normale Supérieure, Paris, France
| | - Alain Jacquier
- Génétique des Interactions Macromoléculaires, Genomes and Genetics Department, Institut Pasteur, Paris, France
| | - Cosmin Saveanu
- Génétique des Interactions Macromoléculaires, Genomes and Genetics Department, Institut Pasteur, Paris, France
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Abstract
Nonsense-mediated mRNA decay is a eukaryotic pathway that degrades transcripts with premature termination codons (PTCs). In most eukaryotes, thousands of transcripts are degraded by NMD, including many important regulators of developmental and stress response pathways. Transcripts can be targeted to NMD by the presence of an upstream ORF or by introduction of a PTC through alternative splicing. Many factors involved in the recognition of PTCs and the destruction of NMD targets have been characterized. While some are highly conserved, others have been repeatedly lost in eukaryotic lineages. Here, I detail the factors involved in NMD, our current understanding of their interactions and how they have evolved. I outline a classification system to describe NMD pathways based on the presence/absence of key NMD factors. These types of NMD pathways exist in multiple different lineages, indicating the plasticity of the NMD pathway through recurrent losses of NMD factors during eukaryotic evolution. By classifying the NMD pathways in this way, gaps in our understanding are revealed, even within well studied organisms. Finally, I discuss the likely driving force behind the origins of the NMD pathway before the appearance of the last eukaryotic common ancestor: transposable element expansion and the consequential origin of introns.
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Affiliation(s)
- James P B Lloyd
- ARC Centre of Excellence in Plant Energy Biology, University of Western Australia, Perth, Australia
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8
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Abstract
Nonsense-mediated mRNA decay is a eukaryotic pathway that degrades transcripts with premature termination codons (PTCs). In most eukaryotes, thousands of transcripts are degraded by NMD, including many important regulators of developmental and stress response pathways. Transcripts can be targeted to NMD by the presence of an upstream ORF or by introduction of a PTC through alternative splicing. Many factors involved in the recognition of PTCs and the destruction of NMD targets have been characterized. While some are highly conserved, others have been repeatedly lost in eukaryotic lineages. Here, I detail the factors involved in NMD, our current understanding of their interactions and how they have evolved. I outline a classification system to describe NMD pathways based on the presence/absence of key NMD factors. These types of NMD pathways exist in multiple different lineages, indicating the plasticity of the NMD pathway through recurrent losses of NMD factors during eukaryotic evolution. By classifying the NMD pathways in this way, gaps in our understanding are revealed, even within well studied organisms. Finally, I discuss the likely driving force behind the origins of the NMD pathway before the appearance of the last eukaryotic common ancestor: transposable element expansion and the consequential origin of introns.
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Affiliation(s)
- James P B Lloyd
- ARC Centre of Excellence in Plant Energy Biology, University of Western Australia, Perth, Australia
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Zaychikova MV, Mikheecheva NE, Belay YO, Alekseeva MG, Melerzanov AV, Danilenko VN. Single nucleotide polymorphisms of Beijing lineage Mycobacterium tuberculosis toxin-antitoxin system genes: Their role in the changes of protein activity and evolution. Tuberculosis (Edinb) 2018; 112:11-19. [PMID: 30205962 DOI: 10.1016/j.tube.2018.06.011] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2018] [Revised: 06/07/2018] [Accepted: 06/09/2018] [Indexed: 11/26/2022]
Abstract
The article investigates SNP in genes of toxin-antitoxin systems type II in Mycobacterium tuberculosis Beijing lineage strains and their possible role in the development and formation of new sublineages. We established the catalog of SNPs in 142 TA systems genes in 1349 sequenced genomes of the M. tuberculosis Beijing lineage. Based on the catalog, 15 new sublineages were identified as part of Beijing lineages by non-synonymous SNP in 21 genes of TA systems. We discovered three toxin genes with mutations specific for epidemiologically dangerous sublineages Beijing-modern (vapC37 A46G, vapC38 T143C) and Beijing-B0/W148 (vapC12 A95G). We proved the functional significance of these polymorphisms by cloning these genes wild-type and with marker mutations for the Beijing lineage vapC12 (A95G), vapC37 (A46G), vapC38 (T143C). In vitro study of their activities revealed effect of mutations on the RNase activity of toxin proteins. Mutations in vapC37 and vapC38 decreased toxin activity, and mutation in the vapC12 increased it. We cloned the toxin vapC37 gene of Mycobacterium smegmatis mc2 155 in both allelic variants: without mutation and with A46G mutation, specific for the Beijing-modern lineage. It was shown that this mutation leads to a loss of toxicity.
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Affiliation(s)
- M V Zaychikova
- Vavilov Institute of General Genetics, Gubkina Str. 3, Moscow, 119333, Russian Federation.
| | - N E Mikheecheva
- Vavilov Institute of General Genetics, Gubkina Str. 3, Moscow, 119333, Russian Federation; Moscow Institute of Physics and Technology, 9 Institutskiy per, Dolgoprudny, Moscow Region, 141701, Russian Federation.
| | - Y O Belay
- Vavilov Institute of General Genetics, Gubkina Str. 3, Moscow, 119333, Russian Federation.
| | - M G Alekseeva
- Vavilov Institute of General Genetics, Gubkina Str. 3, Moscow, 119333, Russian Federation.
| | - A V Melerzanov
- Moscow Institute of Physics and Technology, 9 Institutskiy per, Dolgoprudny, Moscow Region, 141701, Russian Federation.
| | - V N Danilenko
- Vavilov Institute of General Genetics, Gubkina Str. 3, Moscow, 119333, Russian Federation.
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Guan RB, Li HC, Fan YJ, Hu SR, Christiaens O, Smagghe G, Miao XX. A nuclease specific to lepidopteran insects suppresses RNAi. J Biol Chem 2018; 293:6011-6021. [PMID: 29500196 PMCID: PMC5912458 DOI: 10.1074/jbc.ra117.001553] [Citation(s) in RCA: 98] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2017] [Revised: 02/26/2018] [Indexed: 12/12/2022] Open
Abstract
More than 70% of all agricultural pests are insects in the order Lepidoptera, which, unlike other related insect orders, are not very sensitive to RNAi, limiting genetic studies of this insect group. However, the reason for this distinct lepidopteran characteristic is unknown. Previously, using transcriptome analysis of the Asian corn borer Ostrinia furnacalis, we identified a gene, termed up56, that is up-regulated in response to dsRNA. Here we report that this Lepidoptera-specific gene encodes a nuclease that contributes to RNAi insensitivity in this insect order. Its identity was experimentally validated, and sequence analysis indicated that up56 encodes a previously uncharacterized protein with homologous sequences in seven other lepidopteran species. Its computationally predicted three-dimensional structure revealed a high structural similarity to human exonuclease I. Exposure to dsRNA in O. furnacalis strongly up-regulated this gene's expression, and the protein could digest single-stranded RNA (ssRNA), dsRNA, and dsDNA both in vitro and in vivo Of note, we found that this up-regulation of up56 expression is faster than that of the gene encoding the key RNAi-associated nuclease Dicer. up56 knockdown in O. furnacalis significantly enhanced RNAi efficiency. Moreover, up56 overexpression in Drosophila melanogaster suppressed RNAi efficiency. Finally, up56 knockdown significantly increased the amount and diversity of small RNAs. Therefore, we renamed this protein RNAi efficiency-related nuclease (REase). In conclusion, we propose that REase may explain why lepidopterans are refractory to RNAi and that it represents a target for further research of RNAi efficiency in this insect order.
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Affiliation(s)
- Ruo-Bing Guan
- From the Key Laboratory of Insect Developmental and Evolutionary Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China
| | - Hai-Chao Li
- From the Key Laboratory of Insect Developmental and Evolutionary Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China
| | - Yu-Jie Fan
- From the Key Laboratory of Insect Developmental and Evolutionary Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China
| | - Shao-Ru Hu
- From the Key Laboratory of Insect Developmental and Evolutionary Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China
- the University of the Chinese Academy of Sciences, Beijing 100049, China, and
| | - Olivier Christiaens
- the Department of Crop Protection, Faculty of Bioscience Engineering, Ghent University, 9000 Ghent, Belgium
| | - Guy Smagghe
- the Department of Crop Protection, Faculty of Bioscience Engineering, Ghent University, 9000 Ghent, Belgium
| | - Xue-Xia Miao
- From the Key Laboratory of Insect Developmental and Evolutionary Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China,
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11
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Matelska D, Steczkiewicz K, Ginalski K. Comprehensive classification of the PIN domain-like superfamily. Nucleic Acids Res 2017; 45:6995-7020. [PMID: 28575517 PMCID: PMC5499597 DOI: 10.1093/nar/gkx494] [Citation(s) in RCA: 58] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2017] [Accepted: 05/24/2017] [Indexed: 12/21/2022] Open
Abstract
PIN-like domains constitute a widespread superfamily of nucleases, diverse in terms of the reaction mechanism, substrate specificity, biological function and taxonomic distribution. Proteins with PIN-like domains are involved in central cellular processes, such as DNA replication and repair, mRNA degradation, transcription regulation and ncRNA maturation. In this work, we identify and classify the most complete set of PIN-like domains to provide the first comprehensive analysis of sequence–structure–function relationships within the whole PIN domain-like superfamily. Transitive sequence searches using highly sensitive methods for remote homology detection led to the identification of several new families, including representatives of Pfam (DUF1308, DUF4935) and CDD (COG2454), and 23 other families not classified in the public domain databases. Further sequence clustering revealed relationships between individual sequence clusters and showed heterogeneity within some families, suggesting a possible functional divergence. With five structural groups, 70 defined clusters, over 100,000 proteins, and broad biological functions, the PIN domain-like superfamily constitutes one of the largest and most diverse nuclease superfamilies. Detailed analyses of sequences and structures, domain architectures, and genomic contexts allowed us to predict biological function of several new families, including new toxin-antitoxin components, proteins involved in tRNA/rRNA maturation and transcription/translation regulation.
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Affiliation(s)
- Dorota Matelska
- University of Warsaw, CeNT, Laboratory of Bioinformatics and Systems Biology, Zwirki i Wigury 93, 02-089 Warsaw, Poland
| | - Kamil Steczkiewicz
- University of Warsaw, CeNT, Laboratory of Bioinformatics and Systems Biology, Zwirki i Wigury 93, 02-089 Warsaw, Poland
| | - Krzysztof Ginalski
- University of Warsaw, CeNT, Laboratory of Bioinformatics and Systems Biology, Zwirki i Wigury 93, 02-089 Warsaw, Poland
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Bendtsen KL, Xu K, Luckmann M, Winther KS, Shah SA, Pedersen CNS, Brodersen DE. Toxin inhibition in C. crescentus VapBC1 is mediated by a flexible pseudo-palindromic protein motif and modulated by DNA binding. Nucleic Acids Res 2017; 45:2875-2886. [PMID: 27998932 PMCID: PMC5389673 DOI: 10.1093/nar/gkw1266] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2016] [Accepted: 12/05/2016] [Indexed: 12/13/2022] Open
Abstract
Expression of bacterial type II toxin-antitoxin (TA) systems is regulated at the transcriptional level through direct binding of the antitoxin to pseudo-palindromic sequences on operator DNA. In this context, the toxin functions as a co-repressor by stimulating DNA binding through direct interaction with the antitoxin. Here, we determine crystal structures of the complete 90 kDa heterooctameric VapBC1 complex from Caulobacter crescentus CB15 both in isolation and bound to its cognate DNA operator sequence at 1.6 and 2.7 Å resolution, respectively. DNA binding is associated with a dramatic architectural rearrangement of conserved TA interactions in which C-terminal extended structures of the antitoxin VapB1 swap positions to interlock the complex in the DNA-bound state. We further show that a pseudo-palindromic protein sequence in the antitoxin is responsible for this interaction and required for binding and inactivation of the VapC1 toxin dimer. Sequence analysis of 4127 orthologous VapB sequences reveals that such palindromic protein sequences are widespread and unique to bacterial and archaeal VapB antitoxins suggesting a general principle governing regulation of VapBC TA systems. Finally, a structure of C-terminally truncated VapB1 bound to VapC1 reveals discrete states of the TA interaction that suggest a structural basis for toxin activation in vivo.
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Affiliation(s)
- Kirstine L Bendtsen
- Centre for Bacterial Stress Response and Persistence.,Department of Molecular Biology and Genetics, Aarhus University, Gustav Wieds Vej 10c, DK-8000 Aarhus C, Denmark
| | - Kehan Xu
- Centre for Bacterial Stress Response and Persistence.,Department of Molecular Biology and Genetics, Aarhus University, Gustav Wieds Vej 10c, DK-8000 Aarhus C, Denmark
| | - Majbritt Luckmann
- Centre for Bacterial Stress Response and Persistence.,Department of Molecular Biology and Genetics, Aarhus University, Gustav Wieds Vej 10c, DK-8000 Aarhus C, Denmark
| | - Kristoffer S Winther
- Centre for Bacterial Stress Response and Persistence.,Department of Biology, University of Copenhagen, Ole Maaløes Vej 5, DK-2200 København N, Denmark
| | - Shiraz A Shah
- Department of Biology, University of Copenhagen, Ole Maaløes Vej 5, DK-2200 København N, Denmark
| | - Christian N S Pedersen
- Bioinformatics Research Centre (BiRC), Aarhus University, C.F. Møllers Allé 8, DK-8000 Aarhus C, Denmark
| | - Ditlev E Brodersen
- Centre for Bacterial Stress Response and Persistence.,Department of Molecular Biology and Genetics, Aarhus University, Gustav Wieds Vej 10c, DK-8000 Aarhus C, Denmark
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Tomecki R, Sikorski PJ, Zakrzewska-Placzek M. Comparison of preribosomal RNA processing pathways in yeast, plant and human cells - focus on coordinated action of endo- and exoribonucleases. FEBS Lett 2017; 591:1801-1850. [PMID: 28524231 DOI: 10.1002/1873-3468.12682] [Citation(s) in RCA: 69] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Revised: 05/14/2017] [Accepted: 05/15/2017] [Indexed: 12/17/2022]
Abstract
Proper regulation of ribosome biosynthesis is mandatory for cellular adaptation, growth and proliferation. Ribosome biogenesis is the most energetically demanding cellular process, which requires tight control. Abnormalities in ribosome production have severe consequences, including developmental defects in plants and genetic diseases (ribosomopathies) in humans. One of the processes occurring during eukaryotic ribosome biogenesis is processing of the ribosomal RNA precursor molecule (pre-rRNA), synthesized by RNA polymerase I, into mature rRNAs. It must not only be accurate but must also be precisely coordinated with other phenomena leading to the synthesis of functional ribosomes: RNA modification, RNA folding, assembly with ribosomal proteins and nucleocytoplasmic RNP export. A multitude of ribosome biogenesis factors ensure that these events take place in a correct temporal order. Among them are endo- and exoribonucleases involved in pre-rRNA processing. Here, we thoroughly present a wide spectrum of ribonucleases participating in rRNA maturation, focusing on their biochemical properties, regulatory mechanisms and substrate specificity. We also discuss cooperation between various ribonucleolytic activities in particular stages of pre-rRNA processing, delineating major similarities and differences between three representative groups of eukaryotes: yeast, plants and humans.
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Affiliation(s)
- Rafal Tomecki
- Laboratory of RNA Biology and Functional Genomics, Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, Poland.,Department of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Poland
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14
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Two Synechococcus genes, Two Different Effects on Cyanophage Infection. Viruses 2017; 9:v9060136. [PMID: 28574452 PMCID: PMC5490813 DOI: 10.3390/v9060136] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2017] [Revised: 05/22/2017] [Accepted: 05/23/2017] [Indexed: 12/12/2022] Open
Abstract
Synechococcus is an abundant marine cyanobacterium that significantly contributes to primary production. Lytic phages are thought to have a major impact on cyanobacterial population dynamics and evolution. Previously, an investigation of the transcriptional response of three Synechococcus strains to infection by the T4-like cyanomyovirus, Syn9, revealed that while the transcript levels of the vast majority of host genes declined soon after infection, those for some genes increased or remained stable. In order to assess the role of two such host-response genes during infection, we inactivated them in Synechococcus sp. strain WH8102. One gene, SYNW1659, encodes a domain of unknown function (DUF3387) that is associated with restriction enzymes. The second gene, SYNW1946, encodes a PIN-PhoH protein, of which the PIN domain is common in bacterial toxin-antitoxin systems. Neither of the inactivation mutations impacted host growth or the length of the Syn9 lytic cycle. However, the DUF3387 mutant supported significantly lower phage DNA replication and yield of phage progeny than the wild-type, suggesting that the product of this host gene aids phage production. The PIN-PhoH mutant, on the other hand, allowed for significantly higher Syn9 genomic DNA replication and progeny production, suggesting that this host gene plays a role in restraining the infection process. Our findings indicate that host-response genes play a functional role during infection and suggest that some function in an attempt at defense against the phage, while others are exploited by the phage for improved infection.
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15
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Senissar M, Manav MC, Brodersen DE. Structural conservation of the PIN domain active site across all domains of life. Protein Sci 2017; 26:1474-1492. [PMID: 28508407 DOI: 10.1002/pro.3193] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2017] [Revised: 05/08/2017] [Accepted: 05/08/2017] [Indexed: 01/26/2023]
Abstract
The PIN (PilT N-terminus) domain is a compact RNA-binding protein domain present in all domains of life. This 120-residue domain consists of a central and parallel β sheet surrounded by α helices, which together organize 4-5 acidic residues in an active site that binds one or more divalent metal ions and in many cases has endoribonuclease activity. In bacteria and archaea, the PIN domain is primarily associated with toxin-antitoxin loci, consisting of a toxin (the PIN domain nuclease) and an antitoxin that inhibits the function of the toxin under normal growth conditions. During nutritional or antibiotic stress, the antitoxin is proteolytically degraded causing activation of the PIN domain toxin leading to a dramatic reprogramming of cellular metabolism to cope with the new situation. In eukaryotes, PIN domains are commonly found as parts of larger proteins and are involved in a range of processes involving RNA cleavage, including ribosomal RNA biogenesis and nonsense-mediated mRNA decay. In this review, we provide a comprehensive overview of the structural characteristics of the PIN domain and compare PIN domains from all domains of life in terms of structure, active site architecture, and activity.
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Affiliation(s)
- M Senissar
- Centre for Bacterial Stress Response and Persistence, Department of Molecular Biology and Genetics, Aarhus University, Gustav Wieds Vej 10c, Aarhus, 8000, Denmark
| | - M C Manav
- Centre for Bacterial Stress Response and Persistence, Department of Molecular Biology and Genetics, Aarhus University, Gustav Wieds Vej 10c, Aarhus, 8000, Denmark
| | - D E Brodersen
- Centre for Bacterial Stress Response and Persistence, Department of Molecular Biology and Genetics, Aarhus University, Gustav Wieds Vej 10c, Aarhus, 8000, Denmark
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16
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Zhai B, DuPrez K, Doukov TI, Li H, Huang M, Shang G, Ni J, Gu L, Shen Y, Fan L. Structure and Function of a Novel ATPase that Interacts with Holliday Junction Resolvase Hjc and Promotes Branch Migration. J Mol Biol 2017; 429:1009-1029. [PMID: 28238763 PMCID: PMC5565510 DOI: 10.1016/j.jmb.2017.02.016] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2016] [Revised: 01/25/2017] [Accepted: 02/19/2017] [Indexed: 11/15/2022]
Abstract
Holliday junction (HJ) is a hallmark intermediate in DNA recombination and must be processed by dissolution (for double HJ) or resolution to ensure genome stability. Although HJ resolvases have been identified in all domains of life, there is a long-standing effort to search in prokaryotes and eukarya for proteins promoting HJ migration. Here, we report the structural and functional characterization of a novel ATPase, Sulfolobus islandicusPilT N-terminal-domain-containing ATPase (SisPINA), encoded by the gene adjacent to the resolvase Hjc coding gene. PINA is conserved in archaea and vital for S. islandicus viability. Purified SisPINA forms hexameric rings in the crystalline state and in solution, similar to the HJ migration helicase RuvB in Gram-negative bacteria. Structural analysis suggests that ATP binding and hydrolysis cause conformational changes in SisPINA to drive branch migration. Further studies reveal that SisPINA interacts with SisHjc and coordinates HJ migration and cleavage.
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Affiliation(s)
- Binyuan Zhai
- State Key Laboratory of Microbial Technology, Shandong University, 27 Shanda Nan Road, Jinan 250100, PR China
| | - Kevin DuPrez
- Department of Biochemistry, University of California, Riverside, CA 92521, USA
| | - Tzanko I Doukov
- Macromolecular Crystallography Group, Stanford Synchrotron Radiation Light Source, SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94309, USA
| | - Huan Li
- State Key Laboratory of Microbial Technology, Shandong University, 27 Shanda Nan Road, Jinan 250100, PR China
| | - Mengting Huang
- State Key Laboratory of Microbial Technology, Shandong University, 27 Shanda Nan Road, Jinan 250100, PR China
| | - Guijun Shang
- State Key Laboratory of Microbial Technology, Shandong University, 27 Shanda Nan Road, Jinan 250100, PR China
| | - Jinfeng Ni
- State Key Laboratory of Microbial Technology, Shandong University, 27 Shanda Nan Road, Jinan 250100, PR China
| | - Lichuan Gu
- State Key Laboratory of Microbial Technology, Shandong University, 27 Shanda Nan Road, Jinan 250100, PR China
| | - Yulong Shen
- State Key Laboratory of Microbial Technology, Shandong University, 27 Shanda Nan Road, Jinan 250100, PR China.
| | - Li Fan
- Department of Biochemistry, University of California, Riverside, CA 92521, USA.
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17
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Bustamante P, Iredell JR. Carriage of type II toxin-antitoxin systems by the growing group of IncX plasmids. Plasmid 2017; 91:19-27. [PMID: 28267580 DOI: 10.1016/j.plasmid.2017.02.006] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2017] [Revised: 02/19/2017] [Accepted: 02/27/2017] [Indexed: 10/20/2022]
Abstract
The stable maintenance of certain plasmids in bacterial populations has contributed significantly to the current worldwide antibiotic resistance (AbR) emergency. IncX plasmids, long underestimated in this regard, have achieved recent notoriety for their roles in transmission of resistance to carbapenem and colistin, the last-line antibiotics for Gram-negative infections. Toxin-antitoxin (TA) systems contribute to stable maintenance of many AbR plasmids, and a few TA systems have been previously described in the IncX plasmids. Here we present an updated overview of the IncX plasmid family and an in silico analysis of the type II TA systems carried in 153 completely sequenced IncX plasmids that are readily available in public databases at time of writing. The greatest number is in the IncX1 subgroup, followed by IncX3 and IncX4, with only a few representatives of IncX2, IncX5 and IncX6. Toxins from the RelE/ParE superfamily are abundant within IncX1 and IncX4 subgroups, and are associated with a variety of antitoxins. By contrast, the HicBA system is almost exclusively encoded by IncX4 plasmids. Toxins from the superfamily CcdB/MazF were also identified, as were less common systems such as PIN-like and GNAT toxins, and plasmids encoding more than one TA system are probably not unusual. Our results highlight the importance of the IncX plasmid group and update previous much smaller studies, and we present for the first time a detailed analysis of type II TA systems in these plasmids.
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Affiliation(s)
- Paula Bustamante
- Centre for Infectious Diseases and Microbiology, The Westmead Institute for Medical Research, The University of Sydney, Westmead Hospital, Westmead, NSW, Australia
| | - Jonathan R Iredell
- Centre for Infectious Diseases and Microbiology, The Westmead Institute for Medical Research, The University of Sydney, Westmead Hospital, Westmead, NSW, Australia.
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18
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Abstract
Eukaryotic gene expression is extensively controlled at the level of mRNA stability and the mechanisms underlying this regulation are markedly different from their archaeal and bacterial counterparts. We propose that two such mechanisms, nonsense‐mediated decay (NMD) and motif‐specific transcript destabilization by CCCH‐type zinc finger RNA‐binding proteins, originated as a part of cellular defense against RNA pathogens. These branches of the mRNA turnover pathway might have been used by primeval eukaryotes alongside RNA interference to distinguish their own messages from those of RNA viruses and retrotransposable elements. We further hypothesize that the subsequent advent of “professional” innate and adaptive immunity systems allowed NMD and the motif‐triggered mechanisms to be efficiently repurposed for regulation of endogenous cellular transcripts. This scenario explains the rapid emergence of archetypical mRNA destabilization pathways in eukaryotes and argues that other aspects of post‐transcriptional gene regulation in this lineage might have been derived through a similar exaptation route.
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Affiliation(s)
- Fursham M Hamid
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
| | - Eugene V Makeyev
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore.,Centre for Developmental Neurobiology, King's College London, London, UK
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19
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Flood BE, Fliss P, Jones DS, Dick GJ, Jain S, Kaster AK, Winkel M, Mußmann M, Bailey J. Single-Cell (Meta-)Genomics of a Dimorphic Candidatus Thiomargarita nelsonii Reveals Genomic Plasticity. Front Microbiol 2016; 7:603. [PMID: 27199933 PMCID: PMC4853749 DOI: 10.3389/fmicb.2016.00603] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2016] [Accepted: 04/11/2016] [Indexed: 11/23/2022] Open
Abstract
The genus Thiomargarita includes the world's largest bacteria. But as uncultured organisms, their physiology, metabolism, and basis for their gigantism are not well understood. Thus, a genomics approach, applied to a single Candidatus Thiomargarita nelsonii cell was employed to explore the genetic potential of one of these enigmatic giant bacteria. The Thiomargarita cell was obtained from an assemblage of budding Ca. T. nelsonii attached to a provannid gastropod shell from Hydrate Ridge, a methane seep offshore of Oregon, USA. Here we present a manually curated genome of Bud S10 resulting from a hybrid assembly of long Pacific Biosciences and short Illumina sequencing reads. With respect to inorganic carbon fixation and sulfur oxidation pathways, the Ca. T. nelsonii Hydrate Ridge Bud S10 genome was similar to marine sister taxa within the family Beggiatoaceae. However, the Bud S10 genome contains genes suggestive of the genetic potential for lithotrophic growth on arsenite and perhaps hydrogen. The genome also revealed that Bud S10 likely respires nitrate via two pathways: a complete denitrification pathway and a dissimilatory nitrate reduction to ammonia pathway. Both pathways have been predicted, but not previously fully elucidated, in the genomes of other large, vacuolated, sulfur-oxidizing bacteria. Surprisingly, the genome also had a high number of unusual features for a bacterium to include the largest number of metacaspases and introns ever reported in a bacterium. Also present, are a large number of other mobile genetic elements, such as insertion sequence (IS) transposable elements and miniature inverted-repeat transposable elements (MITEs). In some cases, mobile genetic elements disrupted key genes in metabolic pathways. For example, a MITE interrupts hupL, which encodes the large subunit of the hydrogenase in hydrogen oxidation. Moreover, we detected a group I intron in one of the most critical genes in the sulfur oxidation pathway, dsrA. The dsrA group I intron also carried a MITE sequence that, like the hupL MITE family, occurs broadly across the genome. The presence of a high degree of mobile elements in genes central to Thiomargarita's core metabolism has not been previously reported in free-living bacteria and suggests a highly mutable genome.
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Affiliation(s)
- Beverly E Flood
- Department of Earth Sciences, University of Minnesota Minneapolis, MN, USA
| | - Palmer Fliss
- Department of Earth Sciences, University of Minnesota Minneapolis, MN, USA
| | - Daniel S Jones
- Department of Earth Sciences, University of MinnesotaMinneapolis, MN, USA; Biotechnology Institute, University of MinnesotaSt. Paul, MN, USA
| | - Gregory J Dick
- Department of Earth and Environmental Sciences, University of Michigan Ann Arbor, MI, USA
| | - Sunit Jain
- Department of Earth and Environmental Sciences, University of Michigan Ann Arbor, MI, USA
| | - Anne-Kristin Kaster
- German Collection of Microorganisms and Cell Cultures, Leibniz Institute DSMZ Braunschweig, Germany
| | - Matthias Winkel
- Helmholtz Centre Potsdam, GFZ German Research Centre for Geosciences Potsdam, Germany
| | - Marc Mußmann
- Max Planck Institute for Marine Microbiology Bremen, Germany
| | - Jake Bailey
- Department of Earth Sciences, University of Minnesota Minneapolis, MN, USA
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20
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Xu K, Dedic E, Brodersen DE. Structural analysis of the active site architecture of the VapC toxin from Shigella flexneri. Proteins 2016; 84:892-9. [PMID: 26833558 DOI: 10.1002/prot.25002] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2015] [Revised: 01/07/2016] [Accepted: 01/18/2016] [Indexed: 12/12/2022]
Abstract
The VapC toxin from the Shigella flexneri 2a virulence plasmid pMYSH6000 belongs to the PIN domain protein family, which is characterized by a conserved fold with low amino acid sequence conservation. The toxin is a bona fide Mg(2+) -dependent ribonuclease and has been shown to target initiator tRNA(fMet) in vivo. Here, we present crystal structures of active site catalytic triad mutants D7A, D7N, and D98N of the VapC toxin in absence of antitoxin. In all structures, as well as in solution, VapC forms a dimer. In the D98N structure, a Hepes molecule occupies both active sites of the dimer and comparison with the structure of RNase H bound to a DNA/RNA hybrid suggests that the Hepes molecule mimics the position of an RNA nucleotide in the VapC active site. Proteins 2016; 84:892-899. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Kehan Xu
- Department of Molecular Biology and Genetics, Aarhus University, Gustav Wieds Vej 10c, Aarhus C, DK-8000, Denmark
| | - Emil Dedic
- Department of Molecular Biology and Genetics, Aarhus University, Gustav Wieds Vej 10c, Aarhus C, DK-8000, Denmark
| | - Ditlev E Brodersen
- Department of Molecular Biology and Genetics, Aarhus University, Gustav Wieds Vej 10c, Aarhus C, DK-8000, Denmark
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21
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Zhou X, Mo X, Gui M, Wu X, Jiang Y, Ma L, Shi Z, Luo Y, Tang W. Cytological, molecular mechanisms and temperature stress regulating production of diploid male gametes in Dianthus caryophyllus L. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2015; 97:255-63. [PMID: 26492133 DOI: 10.1016/j.plaphy.2015.10.003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/14/2015] [Revised: 10/04/2015] [Accepted: 10/04/2015] [Indexed: 05/02/2023]
Abstract
In plant evolution, because of its key role in sexual polyploidization or whole genome duplication events, diploid gamete formation is considered as an important component in diversification and speciation. Environmental stress often triggers unreduced gamete production. However, the molecular, cellular mechanisms and adverse temperature regulating diplogamete production in carnation remain poorly understood. Here, we investigate the cytological basis for 2n male gamete formation and describe the isolation and characterization of the first gene, DcPS1 (Dianthus Caryophyllus Parallel Spindle 1). In addition, we analyze influence of temperature stress on diploid gamete formation and transcript levels of DcPS1. Cytological evidence indicated that 2n male gamete formation is attributable to abnormal spindle orientation at male meiosis II. DcPS1 protein is conserved throughout the plant kingdom and carries domains suggestive of a regulatory function. DcPS1 expression analysis show DcPS1 gene probably have a role in 2n pollen formation. Unreduced pollen formation in various cultivation was sensitive to high or low temperature which was probably regulated by the level of DcPS1 transcripts. In a broader perspective, these findings can have potential applications in fundamental polyploidization research and plant breeding programs.
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MESH Headings
- Chromosomes, Plant/genetics
- Cloning, Molecular
- Dianthus/cytology
- Dianthus/genetics
- Diploidy
- Flowers/genetics
- Gene Expression Regulation, Developmental
- Gene Expression Regulation, Plant
- Genes, Plant
- Germ Cells, Plant/cytology
- Germ Cells, Plant/metabolism
- Organ Specificity/genetics
- Phylogeny
- Pollen/cytology
- Pollen/genetics
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Stress, Physiological/genetics
- Temperature
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Affiliation(s)
- Xuhong Zhou
- Faculty of Life Science and Technology, Kunming University of Science and Technology, Chenggong, Kunming 650500, China; Faculty of Environmental Science and Engineering, Kunming University of Science and Technology, Chenggong, Kunming 650500, China; Flower Research Institute, Yunnan Academy of Agricultural Science, Kunming 650205, China; National Engineering Research Center for Ornamental Horticulture, Kunming 650205, China
| | - Xijun Mo
- Flower Research Institute, Yunnan Academy of Agricultural Science, Kunming 650205, China; National Engineering Research Center for Ornamental Horticulture, Kunming 650205, China
| | - Min Gui
- Flower Research Institute, Yunnan Academy of Agricultural Science, Kunming 650205, China; National Engineering Research Center for Ornamental Horticulture, Kunming 650205, China
| | - Xuewei Wu
- Flower Research Institute, Yunnan Academy of Agricultural Science, Kunming 650205, China; National Engineering Research Center for Ornamental Horticulture, Kunming 650205, China
| | - Yalian Jiang
- Flower Research Institute, Yunnan Academy of Agricultural Science, Kunming 650205, China; National Engineering Research Center for Ornamental Horticulture, Kunming 650205, China
| | - Lulin Ma
- Flower Research Institute, Yunnan Academy of Agricultural Science, Kunming 650205, China; National Engineering Research Center for Ornamental Horticulture, Kunming 650205, China
| | - Ziming Shi
- Flower Research Institute, Yunnan Academy of Agricultural Science, Kunming 650205, China; National Engineering Research Center for Ornamental Horticulture, Kunming 650205, China
| | - Ying Luo
- Faculty of Life Science and Technology, Kunming University of Science and Technology, Chenggong, Kunming 650500, China; Faculty of Environmental Science and Engineering, Kunming University of Science and Technology, Chenggong, Kunming 650500, China.
| | - Wenru Tang
- Faculty of Life Science and Technology, Kunming University of Science and Technology, Chenggong, Kunming 650500, China; Faculty of Environmental Science and Engineering, Kunming University of Science and Technology, Chenggong, Kunming 650500, China.
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22
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Fatscher T, Boehm V, Gehring NH. Mechanism, factors, and physiological role of nonsense-mediated mRNA decay. Cell Mol Life Sci 2015; 72:4523-44. [PMID: 26283621 PMCID: PMC11113733 DOI: 10.1007/s00018-015-2017-9] [Citation(s) in RCA: 67] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2015] [Revised: 07/10/2015] [Accepted: 08/06/2015] [Indexed: 02/04/2023]
Abstract
Nonsense-mediated mRNA decay (NMD) is a translation-dependent, multistep process that degrades irregular or faulty messenger RNAs (mRNAs). NMD mainly targets mRNAs with a truncated open reading frame (ORF) due to premature termination codons (PTCs). In addition, NMD also regulates the expression of different types of endogenous mRNA substrates. A multitude of factors are involved in the tight regulation of the NMD mechanism. In this review, we focus on the molecular mechanism of mammalian NMD. Based on the published data, we discuss the involvement of translation termination in NMD initiation. Furthermore, we provide a detailed overview of the core NMD machinery, as well as several peripheral NMD factors, and discuss their function. Finally, we present an overview of diseases associated with NMD factor mutations and summarize the current state of treatment for genetic disorders caused by nonsense mutations.
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Affiliation(s)
- Tobias Fatscher
- Institute for Genetics, University of Cologne, Cologne, Germany
| | - Volker Boehm
- Institute for Genetics, University of Cologne, Cologne, Germany
| | - Niels H Gehring
- Institute for Genetics, University of Cologne, Cologne, Germany.
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23
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HUANG WEIYI, ZHONG WEIQING, XU JUN, SU BENHUA, HUANG GUANGHUI, DU JIAJUN, LIU QI. Lentivirus-mediated gene silencing of NOB1 suppresses non-small cell lung cancer cell proliferation. Oncol Rep 2015; 34:1510-6. [DOI: 10.3892/or.2015.4132] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2015] [Accepted: 06/28/2015] [Indexed: 11/05/2022] Open
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24
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Lee IG, Lee SJ, Chae S, Lee KY, Kim JH, Lee BJ. Structural and functional studies of the Mycobacterium tuberculosis VapBC30 toxin-antitoxin system: implications for the design of novel antimicrobial peptides. Nucleic Acids Res 2015; 43:7624-37. [PMID: 26150422 PMCID: PMC4551927 DOI: 10.1093/nar/gkv689] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2015] [Accepted: 06/24/2015] [Indexed: 12/21/2022] Open
Abstract
Toxin-antitoxin (TA) systems play important roles in bacterial physiology, such as multidrug tolerance, biofilm formation, and arrest of cellular growth under stress conditions. To develop novel antimicrobial agents against tuberculosis, we focused on VapBC systems, which encompass more than half of TA systems in Mycobacterium tuberculosis. Here, we report that theMycobacterium tuberculosis VapC30 toxin regulates cellular growth through both magnesium and manganese ion-dependent ribonuclease activity and is inhibited by the cognate VapB30 antitoxin. We also determined the 2.7-Å resolution crystal structure of the M. tuberculosis VapBC30 complex, which revealed a novel process of inactivation of the VapC30 toxin via swapped blocking by the VapB30 antitoxin. Our study on M. tuberculosis VapBC30 leads us to design two kinds of VapB30 and VapC30-based novel peptides which successfully disrupt the toxin-antitoxin complex and thus activate the ribonuclease activity of the VapC30 toxin. Our discovery herein possibly paves the way to treat tuberculosis for next generation.
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Affiliation(s)
- In-Gyun Lee
- Research Institute of Pharmaceutical Sciences, College of Pharmacy, Seoul National University, Seoul 151-742, Korea
| | - Sang Jae Lee
- Research Institute of Pharmaceutical Sciences, College of Pharmacy, Seoul National University, Seoul 151-742, Korea
| | - Susanna Chae
- Research Institute of Pharmaceutical Sciences, College of Pharmacy, Seoul National University, Seoul 151-742, Korea
| | - Ki-Young Lee
- Research Institute of Pharmaceutical Sciences, College of Pharmacy, Seoul National University, Seoul 151-742, Korea
| | - Ji-Hun Kim
- Research Institute of Pharmaceutical Sciences, College of Pharmacy, Seoul National University, Seoul 151-742, Korea
| | - Bong-Jin Lee
- Research Institute of Pharmaceutical Sciences, College of Pharmacy, Seoul National University, Seoul 151-742, Korea
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25
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Cut to the chase--Regulating translation through RNA cleavage. Biochimie 2015; 114:10-7. [PMID: 25633441 DOI: 10.1016/j.biochi.2015.01.009] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2014] [Accepted: 01/19/2015] [Indexed: 11/23/2022]
Abstract
Activation of toxin-antitoxin (TA) systems provides an important mechanism for bacteria to adapt to challenging and ever changing environmental conditions. Known TA systems are classified into five families based on the mechanisms of antitoxin inhibition and toxin activity. For type II TA systems, the toxin is inactivated in exponentially growing cells by tightly binding its antitoxin partner protein, which also serves to regulate cellular levels of the complex through transcriptional auto-repression. During cellular stress, however, the antitoxin is degraded thus freeing the toxin, which is then able to regulate central cellular processes, primarily protein translation to adjust cell growth to the new conditions. In this review, we focus on the type II TA pairs that regulate protein translation through cleavage of ribosomal, transfer, or messenger RNA.
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26
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Structure-function analysis of VapB4 antitoxin identifies critical features of a minimal VapC4 toxin-binding module. J Bacteriol 2015; 197:1197-207. [PMID: 25622615 DOI: 10.1128/jb.02508-14] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
UNLABELLED Bacterial toxin-antitoxin systems play a critical role in the regulation of gene expression, leading to developmental changes, reversible dormancy, and cell death. Type II toxin-antitoxin pairs, composed of protein toxins and antitoxins, exist in nearly all bacteria and are classified into six groups on the basis of the structure of the toxins. The VapBC group comprises the most common type II system and, like other toxin-antitoxin systems, functions to elicit dormancy by inhibiting protein synthesis. Activation of toxin function requires protease degradation of the VapB antitoxin, which frees the VapC toxin from the VapBC complex, allowing it to hydrolyze the RNAs required for translation. Generally, type II antitoxins bind with high specificity to their cognate toxins via a toxin-binding domain and endow the complex with DNA-binding specificity via a DNA-binding domain. Despite the ubiquity of VapBC systems and their critical role in the regulation of gene expression, few functional studies have addressed the details of VapB-VapC interactions. Here we report on the results of experiments designed to identify molecular determinants of the specificity of the Mycobacterium tuberculosis VapB4 antitoxin for its cognate VapC4 toxin. The results identify the minimal domain of VapB4 required for this interaction as well as the amino acid side chains required for binding to VapC4. These findings have important implications for the evolution of VapBC toxin-antitoxin systems and their potential as targets of small-molecule protein-protein interaction inhibitors. IMPORTANCE VapBC toxin-antitoxin pairs are the most widespread type II toxin-antitoxin systems in bacteria, where they are thought to play key roles in stress-induced dormancy and the formation of persisters. The VapB antitoxins are critical to these processes because they inhibit the activity of the toxins and provide the DNA-binding specificity that controls the synthesis of both proteins. Despite the importance of VapB antitoxins and the existence of several VapBC crystal structures, little is known about their functional features in vivo. Here we report the findings of the first comprehensive structure-function analysis of a VapB toxin. The results identify the minimal toxin-binding domain, its modular antitoxin function, and the specific amino acid side chains required for its activity.
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Hamilton B, Manzella A, Schmidt K, DiMarco V, Butler JS. Analysis of non-typeable Haemophilous influenzae VapC1 mutations reveals structural features required for toxicity and flexibility in the active site. PLoS One 2014; 9:e112921. [PMID: 25391136 PMCID: PMC4229260 DOI: 10.1371/journal.pone.0112921] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2014] [Accepted: 10/21/2014] [Indexed: 02/06/2023] Open
Abstract
Bacteria have evolved mechanisms that allow them to survive in the face of a variety of stresses including nutrient deprivation, antibiotic challenge and engulfment by predator cells. A switch to dormancy represents one strategy that reduces energy utilization and can render cells resistant to compounds that kill growing bacteria. These persister cells pose a problem during treatment of infections with antibiotics, and dormancy mechanisms may contribute to latent infections. Many bacteria encode toxin-antitoxin (TA) gene pairs that play an important role in dormancy and the formation of persisters. VapBC gene pairs comprise the largest of the Type II TA systems in bacteria and they produce a VapC ribonuclease toxin whose activity is inhibited by the VapB antitoxin. Despite the importance of VapBC TA pairs in dormancy and persister formation, little information exists on the structural features of VapC proteins required for their toxic function in vivo. Studies reported here identified 17 single mutations that disrupt the function of VapC1 from non-typeable H. influenzae in vivo. 3-D modeling suggests that side chains affected by many of these mutations sit near the active site of the toxin protein. Phylogenetic comparisons and secondary mutagenesis indicate that VapC1 toxicity requires an alternative active site motif found in many proteobacteria. Expression of the antitoxin VapB1 counteracts the activity of VapC1 mutants partially defective for toxicity, indicating that the antitoxin binds these mutant proteins in vivo. These findings identify critical chemical features required for the biological function of VapC toxins and PIN-domain proteins.
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Affiliation(s)
- Brooke Hamilton
- Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, New York, United States of America
| | - Alexander Manzella
- Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, New York, United States of America
| | - Karyn Schmidt
- Department of Biochemistry and Biophysics, University of Rochester Medical Center, Rochester, New York, United States of America
| | - Victoria DiMarco
- Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, New York, United States of America
| | - J. Scott Butler
- Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, New York, United States of America
- Department of Biochemistry and Biophysics, University of Rochester Medical Center, Rochester, New York, United States of America
- Center for RNA Biology, University of Rochester Medical Center, Rochester, New York, United States of America
- * E-mail:
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Petersen LM, Tisa LS. Molecular characterization of protease activity in Serratia sp. strain SCBI and its importance in cytotoxicity and virulence. J Bacteriol 2014; 196:3923-36. [PMID: 25182493 PMCID: PMC4248818 DOI: 10.1128/jb.01908-14] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2014] [Accepted: 08/26/2014] [Indexed: 01/19/2023] Open
Abstract
A newly recognized Serratia species, termed South African Caenorhabditis briggsae isolate (SCBI), is both a mutualist of the nematode Caenorhabditis briggsae KT0001 and a pathogen of lepidopteran insects. Serratia sp. strain SCBI displays high proteolytic activity, and because secreted proteases are known virulence factors for many pathogens, the purpose of this study was to identify genes essential for extracellular protease activity in Serratia sp. strain SCBI and to determine what role proteases play in insect pathogenesis and cytotoxicity. A bank of 2,100 transposon mutants was generated, and six SCBI mutants with defective proteolytic activity were identified. These mutants were also defective in cytotoxicity. The mutants were found defective in genes encoding the following proteins: alkaline metalloprotease secretion protein AprE, a BglB family transcriptional antiterminator, an inosine/xanthosine triphosphatase, GidA, a methyl-accepting chemotaxis protein, and a PIN domain protein. Gene expression analysis on these six mutants showed significant downregulation in mRNA levels of several different types of predicted protease genes. In addition, transcriptome sequencing (RNA-seq) analysis provided insight into how inactivation of AprE, GidA, and a PIN domain protein influences motility and virulence, as well as protease activity. Using quantitative reverse transcription-PCR (qRT-PCR) to further characterize expression of predicted protease genes in wild-type Serratia sp. SCBI, the highest mRNA levels for the alkaline metalloprotease genes (termed prtA1 to prtA4) occurred following the death of an insect host, while two serine protease and two metalloprotease genes had their highest mRNA levels during active infection. Overall, these results indicate that proteolytic activity is essential for cytotoxicity in Serratia sp. SCBI and that its regulation appears to be highly complex.
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Affiliation(s)
- Lauren M Petersen
- Department of Molecular, Cellular, and Biomedical Sciences, University of New Hampshire, Durham, New Hampshire, USA
| | - Louis S Tisa
- Department of Molecular, Cellular, and Biomedical Sciences, University of New Hampshire, Durham, New Hampshire, USA
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High-resolution crystal structure reveals a HEPN domain at the C-terminal region of S. cerevisiae RNA endonuclease Swt1. Biochem Biophys Res Commun 2014; 453:826-32. [PMID: 25450355 DOI: 10.1016/j.bbrc.2014.10.040] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2014] [Accepted: 10/09/2014] [Indexed: 11/21/2022]
Abstract
Swt1 is an RNA endonuclease that plays an important role in quality control of nuclear messenger ribonucleoprotein particles (mRNPs) in eukaryotes; however, its structural details remain to be elucidated. Here, we report the crystal structure of the C-terminal (CT) domain of Swt1 from Saccharomyces cerevisiae, which shares common characteristics of higher eukaryotes and prokaryotes nucleotide binding (HEPN) domain superfamily. To study in detail the full-length protein structure, we analyzed the low-resolution architecture of Swt1 in solution using small angle X-ray scattering (SAXS) method. Both the CT domain and middle domain exhibited a good fit upon superimposing onto the molecular envelope of Swt1. Our study provides the necessary structural information for detailed analysis of the functional role of Swt1, and its importance in the process of nuclear mRNP surveillance.
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Assembly and nuclear export of pre-ribosomal particles in budding yeast. Chromosoma 2014; 123:327-44. [PMID: 24817020 DOI: 10.1007/s00412-014-0463-z] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2013] [Revised: 03/18/2014] [Accepted: 04/07/2014] [Indexed: 11/27/2022]
Abstract
The ribosome is responsible for the final step of decoding genetic information into proteins. Therefore, correct assembly of ribosomes is a fundamental task for all living cells. In eukaryotes, the construction of the ribosome which begins in the nucleolus requires coordinated efforts of >350 specialized factors that associate with pre-ribosomal particles at distinct stages to perform specific assembly steps. On their way through the nucleus, diverse energy-consuming enzymes are thought to release assembly factors from maturing pre-ribosomal particles after accomplishing their task(s). Subsequently, recruitment of export factors prepares pre-ribosomal particles for transport through nuclear pore complexes. Pre-ribosomes are exported into the cytoplasm in a functionally inactive state, where they undergo final maturation before initiating translation. Accumulating evidence indicates a tight coupling between nuclear export, cytoplasmic maturation, and final proofreading of the ribosome. In this review, we summarize our current understanding of nuclear export of pre-ribosomal subunits and cytoplasmic maturation steps that render pre-ribosomal subunits translation-competent.
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SKALNIAK ANNA, BORATYN ELŻBIETA, TYRKALSKA SYLWIAD, HORWACIK IRENA, DURBAS MAŁGORZATA, ŁASTOWSKA MARIA, JURA JOLANTA, ROKITA HANNA. Expression of the monocyte chemotactic protein-1-induced protein 1 decreases human neuroblastoma cell survival. Oncol Rep 2014; 31:2385-92. [DOI: 10.3892/or.2014.3076] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2013] [Accepted: 02/13/2014] [Indexed: 11/05/2022] Open
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Zamariola L, Tiang CL, De Storme N, Pawlowski W, Geelen D. Chromosome segregation in plant meiosis. FRONTIERS IN PLANT SCIENCE 2014; 5:279. [PMID: 24987397 PMCID: PMC4060054 DOI: 10.3389/fpls.2014.00279] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/25/2014] [Accepted: 05/28/2014] [Indexed: 05/18/2023]
Abstract
Faithful chromosome segregation in meiosis is essential for ploidy stability over sexual life cycles. In plants, defective chromosome segregation caused by gene mutations or other factors leads to the formation of unbalanced or unreduced gametes creating aneuploid or polyploid progeny, respectively. Accurate segregation requires the coordinated execution of conserved processes occurring throughout the two meiotic cell divisions. Synapsis and recombination ensure the establishment of chiasmata that hold homologous chromosomes together allowing their correct segregation in the first meiotic division, which is also tightly regulated by cell-cycle dependent release of cohesin and monopolar attachment of sister kinetochores to microtubules. In meiosis II, bi-orientation of sister kinetochores and proper spindle orientation correctly segregate chromosomes in four haploid cells. Checkpoint mechanisms acting at kinetochores control the accuracy of kinetochore-microtubule attachment, thus ensuring the completion of segregation. Here we review the current knowledge on the processes taking place during chromosome segregation in plant meiosis, focusing on the characterization of the molecular factors involved.
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Affiliation(s)
- Linda Zamariola
- Department of Plant Production, Faculty of Bioscience Engineering, University of GhentGhent, Belgium
| | - Choon Lin Tiang
- Department of Plant Breeding and Genetics, Cornell University, Ithaca, NY, USA
| | - Nico De Storme
- Department of Plant Production, Faculty of Bioscience Engineering, University of GhentGhent, Belgium
| | - Wojtek Pawlowski
- Department of Plant Breeding and Genetics, Cornell University, Ithaca, NY, USA
| | - Danny Geelen
- Department of Plant Production, Faculty of Bioscience Engineering, University of GhentGhent, Belgium
- *Correspondence: Danny Geelen, Department of Plant Production, Faculty of Bioscience Engineering, University of Ghent, Coupure Links 653, 9000 Ghent, Belgium e-mail:
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Lu J, Sun M, Ye K. Structural and functional analysis of Utp23, a yeast ribosome synthesis factor with degenerate PIN domain. RNA (NEW YORK, N.Y.) 2013; 19:1815-1824. [PMID: 24152547 PMCID: PMC3860261 DOI: 10.1261/rna.040808.113] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/23/2013] [Accepted: 09/24/2013] [Indexed: 06/02/2023]
Abstract
During synthesis of yeast ribosome, a large complex, called the 90S pre-ribosome or the small subunit processome, is assembled on the nascent precursor rRNA and mediates early processing of 18S rRNA. The Utp23 protein and snR30 H/ACA snoRNA are two conserved components of 90S pre-ribosomes. Utp23 contains a degenerate PIN nuclease domain followed by a long C-terminal tail and associates specifically with snR30. Here, we report the crystal structure of the Utp23 PIN domain at 2.5-Å resolution. The structure reveals a conserved core fold of PIN domain with degenerate active site residues, a unique CCHC Zn-finger motif, and two terminal extension elements. Functional sites of Utp23 have been examined with conservation analysis, mutagenesis, and in vivo and in vitro assays. Mutations in each of three cysteine ligands of zinc, although not the histidine ligand, were lethal or strongly inhibitory to yeast growth, indicating that the Zn-finger motif is required for Utp23 structure or function. The N-terminal helix extension harbors many highly conserved basic residues that mostly are critical for growth and in vitro RNA-binding activity of Utp23. Deletion of the C-terminal tail, which contains a short functionally important sequence motif, disrupted the interaction of Utp23 with snR30 and perturbed the pre-ribosomal association of Utp23. Our data establish a structural framework for dissecting Utp23 function in the assembly and dynamics of 90S pre-ribosomes.
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Affiliation(s)
- Jing Lu
- National Institute of Biological Sciences, Beijing, Beijing 102206, China
- Graduate School of Peking Union Medical College and Chinese Academy of Medical Sciences, Beijing 100730, China
| | - Mengyi Sun
- National Institute of Biological Sciences, Beijing, Beijing 102206, China
- College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Keqiong Ye
- National Institute of Biological Sciences, Beijing, Beijing 102206, China
- Graduate School of Peking Union Medical College and Chinese Academy of Medical Sciences, Beijing 100730, China
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Das U, Kumar N, Gourinath S, Srinivasan A. Preliminary crystallographic analysis of recombinant VapBC-15 toxin-antitoxin complex from Mycobacterium tuberculosis. Acta Crystallogr Sect F Struct Biol Cryst Commun 2013; 69:1242-5. [PMID: 24192359 PMCID: PMC3818043 DOI: 10.1107/s1744309113024822] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2013] [Accepted: 09/05/2013] [Indexed: 12/18/2022]
Abstract
The Mycobacterium tuberculosis vapBC15 locus encodes a toxin-antitoxin complex. VapC-15 is a toxin and possesses ribonuclease activity and VapB-15 is an antitoxin which both binds and inhibits the VapC-15 toxin. In this study, vapBC15 genes were cloned and co-expressed in Escherichia coli. The complex was purified to homogeneity by affinity and size-exclusion chromatography. The VapBC-15 complex was crystallized using the sitting-drop vapour-diffusion technique. The crystals diffracted to 2.6 Å resolution and belonged to space group P2(1)2(1)2(1), with unit-cell parameters a = 85.63, b = 139.09, c = 148.86 Å. The self-rotation function combined with Matthews coefficient and solvent-content calculations suggests the presence of either six or eight molecules of the complex in the asymmetric unit.
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Affiliation(s)
- Uddipan Das
- Department of Biophysics, All India Institute of Medical Sciences, New Delhi, India
| | - Nitesh Kumar
- School of Life Sciences, Jawaharlal Nehru University, New Delhi, India
| | | | - Alagiri Srinivasan
- Department of Biophysics, All India Institute of Medical Sciences, New Delhi, India
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35
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Demidenok OI, Goncharenko AV. Bacterial toxin-antitoxin systems and perspectives for their application in medicine. APPL BIOCHEM MICRO+ 2013. [DOI: 10.1134/s0003683813060070] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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36
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Initiation of mRNA decay in bacteria. Cell Mol Life Sci 2013; 71:1799-828. [PMID: 24064983 PMCID: PMC3997798 DOI: 10.1007/s00018-013-1472-4] [Citation(s) in RCA: 94] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2013] [Revised: 09/01/2013] [Accepted: 09/03/2013] [Indexed: 12/24/2022]
Abstract
The instability of messenger RNA is fundamental to the control of gene expression. In bacteria, mRNA degradation generally follows an "all-or-none" pattern. This implies that if control is to be efficient, it must occur at the initiating (and presumably rate-limiting) step of the degradation process. Studies of E. coli and B. subtilis, species separated by 3 billion years of evolution, have revealed the principal and very disparate enzymes involved in this process in the two organisms. The early view that mRNA decay in these two model organisms is radically different has given way to new models that can be resumed by "different enzymes-similar strategies". The recent characterization of key ribonucleases sheds light on an impressive case of convergent evolution that illustrates that the surprisingly similar functions of these totally unrelated enzymes are of general importance to RNA metabolism in bacteria. We now know that the major mRNA decay pathways initiate with an endonucleolytic cleavage in E. coli and B. subtilis and probably in many of the currently known bacteria for which these organisms are considered representative. We will discuss here the different pathways of eubacterial mRNA decay, describe the major players and summarize the events that can precede and/or favor nucleolytic inactivation of a mRNA, notably the role of the 5' end and translation initiation. Finally, we will discuss the role of subcellular compartmentalization of transcription, translation, and the RNA degradation machinery.
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Ribonucleases in bacterial toxin-antitoxin systems. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2013; 1829:523-31. [PMID: 23454553 DOI: 10.1016/j.bbagrm.2013.02.007] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/17/2012] [Revised: 02/05/2013] [Accepted: 02/14/2013] [Indexed: 11/21/2022]
Abstract
Toxin-antitoxin (TA) systems are widespread in bacteria and archaea and play important roles in a diverse range of cellular activities. TA systems have been broadly classified into 5 types and the targets of the toxins are diverse, but the most frequently used cellular target is mRNA. Toxins that target mRNA to inhibit translation can be classified as ribosome-dependent or ribosome-independent RNA interferases. These RNA interferases are sequence-specific endoribonucleases that cleave RNA at specific sequences. Despite limited sequence similarity, ribosome-independent RNA interferases belong to a limited number of structural classes. The MazF structural family includes MazF, Kid, ParE and CcdB toxins. MazF members cleave mRNA at 3-, 5- or 7-base recognition sequences in different bacteria and have been implicated in controlling cell death (programmed) and cell growth, and cellular responses to nutrient starvation, antibiotics, heat and oxidative stress. VapC endoribonucleases belong to the PIN-domain family and inhibit translation by either cleaving tRNA(fMet) in the anticodon stem loop, cleaving mRNA at -AUA(U/A)-hairpin-G- sequences or by sequence-specific RNA binding. VapC has been implicated in controlling bacterial growth in the intracellular environment and in microbial adaptation to nutrient limitation (nitrogen, carbon) and heat shock. ToxN shows structural homology to MazF and is also a sequence-specific endoribonuclease. ToxN confers phage resistance by causing cell death upon phage infection by cleaving cellular and phage RNAs, thereby interfering with bacterial and phage growth. Notwithstanding our recent progress in understanding ribonuclease action and function in TA systems, the environmental triggers that cause release of the toxin from its cognate antitoxin and the precise cellular function of these systems in many bacteria remain to be discovered. This article is part of a Special Issue entitled: RNA Decay mechanisms.
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Chlebowski A, Lubas M, Jensen TH, Dziembowski A. RNA decay machines: the exosome. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2013; 1829:552-60. [PMID: 23352926 DOI: 10.1016/j.bbagrm.2013.01.006] [Citation(s) in RCA: 171] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/25/2012] [Accepted: 01/03/2013] [Indexed: 10/27/2022]
Abstract
The multisubunit RNA exosome complex is a major ribonuclease of eukaryotic cells that participates in the processing, quality control and degradation of virtually all classes of RNA in Eukaryota. All this is achieved by about a dozen proteins with only three ribonuclease activities between them. At first glance, the versatility of the pathways involving the exosome and the sheer multitude of its substrates are astounding. However, after fifteen years of research we have some understanding of how exosome activity is controlled and applied inside the cell. The catalytic properties of the eukaryotic exosome are fairly well described and attention is now drawn to how the interplay between these activities impacts cell physiology. Also, it has become evident that exosome function relies on many auxiliary factors, which are intensely studied themselves. In this way, the focus of exosome research is slowly leaving the test tube and moving back into the cell. The exosome also has an interesting evolutionary history, which is evident within the eukaryotic lineage but only fully appreciated when considering similar protein complexes found in Bacteria and Archaea. Thus, while we keep this review focused on the most comprehensively described yeast and human exosomes, we shall point out similarities or dissimilarities to prokaryotic complexes and proteins where appropriate. The article is divided into three parts. In Part One we describe how the exosome is built and how it manifests in cells of different organisms. In Part Two we detail the enzymatic properties of the exosome, especially recent data obtained for holocomplexes. Finally, Part Three presents an overview of the RNA metabolism pathways that involve the exosome. This article is part of a Special Issue entitled: RNA Decay mechanisms.
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Abstract
5'-3' Exoribonucleases (XRNs) have important functions in RNA processing, RNA turnover and decay, RNA interference, RNA polymerase transcription, and other cellular processes. Their sequences share two highly conserved regions, CR1 and CR2. The cytoplasmic Xrn1 and the nuclear Xrn2/Rat1 are found in yeast and animals, and XRNs are found in most other eukaryotes. Crystal structures of Xrn1 and Rat1 have been reported recently, offering the first detailed information on these enzymes. The two conserved regions of XRNs form a single, large domain. CR1 has structural homology with the FEN superfamily of nucleases, while CR2 restricts access to the active site, ensuring that XRNs are exclusive exoribonucleases. The structure of Rai1, the protein partner of Rat1, revealed the presence of an active site, and further studies demonstrated that this activity is a novel mechanism for mRNA 5'-end capping quality surveillance.
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Affiliation(s)
- Jeong Ho Chang
- Department of Biological Sciences, Columbia University, New York, NY, USA
| | - Song Xiang
- Department of Biological Sciences, Columbia University, New York, NY, USA; Key Laboratory of Nutrition and Metabolism, Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, PR China
| | - Liang Tong
- Department of Biological Sciences, Columbia University, New York, NY, USA.
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Yoshida R, Sasakura Y. Establishment of enhancer detection lines expressing GFP in the gut of the ascidian Ciona intestinalis. Zoolog Sci 2012; 29:11-20. [PMID: 22233491 DOI: 10.2108/zsj.29.11] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The gut is a tubular, endodermal organ for digesting food and absorbing nutrients. In this study, we characterized eight enhancer detection lines that express green fluorescent protein (GFP) in the whole or part of the digestive tube of the ascidian Ciona intestinalis. Three enhancer detection lines for the pyloric gland, a structure associated with the digestive tube, were also analyzed. These lines are valuable markers for analyzing the mechanisms of development of the gut. Based on the GFP expression of the enhancer detection lines together with morphological characteristics, the digestive tube of Ciona can be subdivided into at least 10 compartments in which different genetic cascades operate. Causal insertion sites of the enhancer detection lines were identified, and the expression pattern of the genes near the insertion sites were characterized by means of whole-mount in situ hybridization. We have characterized four and two genes that were specifically or strongly expressed in the digestive tube and pyloric gland, respectively. The present data provide the basic information and useful resources for studying gut formation in Ciona.
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Affiliation(s)
- Reiko Yoshida
- Shimoda Marine Research Center, University of Tsukuba, Shimoda, Shizuoka 415-0025, Japan
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Veith T, Wurm JP, Duchardt-Ferner E, Weis B, Martin R, Safferthal C, Bohnsack MT, Schleiff E, Wöhnert J. Backbone and side chain NMR resonance assignments for an archaeal homolog of the endonuclease Nob1 involved in ribosome biogenesis. BIOMOLECULAR NMR ASSIGNMENTS 2012; 6:47-50. [PMID: 21732055 DOI: 10.1007/s12104-011-9323-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2011] [Accepted: 06/27/2011] [Indexed: 05/31/2023]
Abstract
Eukaryotic ribosome biogenesis requires the concerted action of ~200 auxiliary protein factors on the nascent ribosome. For many of these factors structural and functional information is still lacking. The endonuclease Nob1 has been recently identified in yeast as the enzyme responsible for the final cytoplasmatic trimming step of the pre-18S rRNA during the biogenesis of the small ribosomal subunit. Here we report the NMR resonance assignments for a Nob1 homolog from the thermophilic archeon Pyrococcus horikoshii as a prerequisite for further structural studies of this class of proteins.
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Affiliation(s)
- Thomas Veith
- Institut für Molekulare Biowissenschaften, Johann-Wolfgang-Goethe-Universität Frankfurt/M, Max-von-Laue-Str. 9, 60438 Frankfurt, Germany
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Sharp JD, Cruz JW, Raman S, Inouye M, Husson RN, Woychik NA. Growth and translation inhibition through sequence-specific RNA binding by Mycobacterium tuberculosis VapC toxin. J Biol Chem 2012; 287:12835-47. [PMID: 22354968 DOI: 10.1074/jbc.m112.340109] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
The Mycobacterium tuberculosis genome harbors an unusually large number of toxin-antitoxin (TA) modules. Curiously, over half of these are VapBC (virulence-associated protein) family members. Nonetheless, the cellular target, precise mode of action, and physiological role of the VapC toxins in this important pathogen remain unclear. To better understand the function of this toxin family, we studied the features and biochemical properties of a prototype M. tuberculosis VapBC TA system, vapBC-mt4 (Rv0596c-Rv0595c). VapC-mt4 expression resulted in growth arrest, a hallmark of all TA toxins, in Escherichia coli, Mycobacterium smegmatis, and M. tuberculosis. Its expression led to translation inhibition accompanied by a gradual decrease in the steady-state levels of several mRNAs. VapC-mt4 exhibited sequence-specific endoribonuclease activity on mRNA templates at ACGC and AC(A/U)GC sequences. However, the cleavage activity of VapC-mt4 was comparatively weak relative to the TA toxin MazF-mt1 (Rv2801c). Unlike other TA toxins, translation inhibition and growth arrest preceded mRNA cleavage, suggesting that the RNA binding property of VapC-mt4, not RNA cleavage, initiates toxicity. In support of this hypothesis, expression of VapC-mt4 led to an increase in the recovery of total RNA with time in contrast to TA toxins that inhibit translation via direct mRNA cleavage. Additionally, VapC-mt4 exhibited stable, sequence-specific RNA binding in an electrophoretic mobility shift assay. Finally, VapC-mt4 inhibited protein synthesis in a cell-free system without cleaving the corresponding mRNA. Therefore, the activity of VapC-mt4 is mechanistically distinct from other TA toxins because it appears to primarily inhibit translation through selective, stable binding to RNA.
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Affiliation(s)
- Jared D Sharp
- Department of Molecular Genetics, Microbiology and Immunology, University of Medicine and Dentistry, New Jersey (UMDNJ)-Robert Wood Johnson Medical School, Piscataway, New Jersey 08854, USA
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Hoareau-Aveilla C, Fayet-Lebaron E, Jády BE, Henras AK, Kiss T. Utp23p is required for dissociation of snR30 small nucleolar RNP from preribosomal particles. Nucleic Acids Res 2011; 40:3641-52. [PMID: 22180534 PMCID: PMC3333846 DOI: 10.1093/nar/gkr1213] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Yeast snR30 is an essential box H/ACA small nucleolar RNA (snoRNA) that promotes 18S rRNA processing through forming transient base-pairing interactions with the newly synthesized 35S pre-rRNA. By using a novel tandem RNA affinity selection approach, followed by coimmunoprecipitation and in vivo cross-linking experiments, we demonstrate that in addition to the four H/ACA core proteins, Cbf5p, Nhp2p, Nop10p and Gar1p, a fraction of snR30 specifically associates with the Utp23p and Kri1p nucleolar proteins. Depletion of Utp23p and Kri1p has no effect on the accumulation and recruitment of snR30 to the nascent pre-ribosomes. However, in the absence of Utp23p, the majority of snR30 accumulates in large pre-ribosomal particles. The retained snR30 is not base-paired with the 35S pre-rRNA, indicating that its aberrant tethering to nascent preribosomes is likely mediated by pre-ribosomal protein(s). Thus, Utp23p may promote conformational changes of the pre-ribosome, essential for snR30 release. Neither Utp23p nor Kri1p is required for recruitment of snR30 to the nascent pre-ribosome. On the contrary, depletion of snR30 prevents proper incorporation of both Utp23p and Kri1p into the 90S pre-ribosome containing the 35S pre-rRNA, indicating that snR30 plays a central role in the assembly of functionally active small subunit processome.
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Affiliation(s)
- Coralie Hoareau-Aveilla
- Laboratoire de Biologie Moléculaire Eucaryote, Université de Toulouse-UPS and Centre National de La Recherche Scientifique, F-31000 Toulouse, France
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The Chp1-Tas3 core is a multifunctional platform critical for gene silencing by RITS. Nat Struct Mol Biol 2011; 18:1351-7. [PMID: 22081013 PMCID: PMC3230742 DOI: 10.1038/nsmb.2151] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2011] [Accepted: 08/30/2011] [Indexed: 01/20/2023]
Abstract
RNA interference (RNAi) is critical for the assembly of heterochromatin at fission yeast centromeres. Central to this process is the RNA-induced Initiation of Transcriptional gene Silencing (RITS) complex, which physically anchors small non-coding RNAs to chromatin. RITS includes Ago1, the chromodomain protein Chp1, and Tas3, which bridges between Chp1 and Ago1. Chp1 is a large protein with, apart from its chromodomain, no recognizable domains. Here we describe how the structured C-terminal half of Chp1 binds the Tas3 N-terminal domain, revealing Chp1's tight embrace of Tas3. The structure also reveals a PIN domain at the C-terminal tip of Chp1 that controls subtelomeric transcripts through a post-transcriptional mechanism. We suggest that the Chp1-Tas3 complex provides a solid and versatile platform to recruit both RNAi-dependent and RNAi-independent gene-silencing pathways for locus-specific regulation of heterochromatin.
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Sealey DCF, Kostic AD, LeBel C, Pryde F, Harrington L. The TPR-containing domain within Est1 homologs exhibits species-specific roles in telomerase interaction and telomere length homeostasis. BMC Mol Biol 2011; 12:45. [PMID: 22011238 PMCID: PMC3215184 DOI: 10.1186/1471-2199-12-45] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2011] [Accepted: 10/18/2011] [Indexed: 12/03/2022] Open
Abstract
Background The first telomerase-associated protein (Est1) was isolated in yeast due to its essential role in telomere maintenance. The human counterparts EST1A, EST1B, and EST1C perform diverse functions in nonsense-mediated mRNA decay (NMD), telomere length homeostasis, and telomere transcription. Although Est1 and EST1A/B interact with the catalytic subunit of yeast and human telomerase (Est2 and TERT, respectively), the molecular determinants of these interactions have not been elaborated fully. Results To investigate the functional conservation of the EST1 protein family, we performed protein-protein interaction mapping and structure-function analysis. The domain in hEST1A most conserved between species, containing a TPR (tricotetrapeptide repeat), was sufficient for interaction of hEST1A with multiple fragments of hTERT including the N-terminus. Two mutations within the hTERT N-terminus that perturb in vivo function (NAAIRS92, NAAIRS122) did not affect this protein interaction. ScEst1 hybrids containing the TPR of hEST1A, hEST1B, or hEST1C were expressed in yeast strains lacking EST1, yet they failed to complement senescence. Point mutations within and outside the cognate ScEst1 TPR, chosen to disrupt a putative protein interaction surface, resulted in telomere lengthening or shortening without affecting recruitment to telomeres. Conclusions These results identify a domain encompassing the TPR of hEST1A as an hTERT interaction module. The TPR of S. cerevisiae Est1 is required for telomerase-mediated telomere length maintenance in a manner that appears separable from telomere recruitment. Discrete residues in or adjacent to the TPR of Est1 also regulate telomere length homeostasis.
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Affiliation(s)
- David C F Sealey
- Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada
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Xuan J, Song X, Wang J, Feng Y. Resonance assignments of a putative PilT N-terminus domain protein SSO1118 from hyperthermophilic archaeon Sulfolobus solfataricus P2. BIOMOLECULAR NMR ASSIGNMENTS 2011; 5:161-164. [PMID: 21229398 DOI: 10.1007/s12104-010-9291-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2010] [Accepted: 12/27/2010] [Indexed: 05/30/2023]
Abstract
PilT N-terminus (PIN) domains exist broadly in all three kingdoms of life, but the functions are not clear for most of them. Archaea species often encode multiple PIN domain-containing proteins, and the signaling and stress response roles have been proposed for these proteins. Some PIN domain proteins possess nuclease activities, which were proposed to be important in toxin-antitoxin stress response, nonsense-mediated mRNA decay, or RNA interference. SSO1118 from hyperthermophilic archaeon Sulfolobus solfataricus P2 is a putative PIN domain protein with low homology to other known PIN domain proteins. Here we report the NMR resonance assignments of SSO1118 for further structural determination and functional studies. The secondary structures predicted from the assigned chemical shifts consist with those of archaeal PIN domain proteins.
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Affiliation(s)
- Jinsong Xuan
- Department of Biological Science and Engineering, School of Chemical and Biological Engineering, University of Science and Technology Beijing, 30 Xueyuan Road, Beijing, 100083, China.
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Enteric virulence associated protein VapC inhibits translation by cleavage of initiator tRNA. Proc Natl Acad Sci U S A 2011; 108:7403-7. [PMID: 21502523 DOI: 10.1073/pnas.1019587108] [Citation(s) in RCA: 204] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Eukaryotic PIN (PilT N-terminal) domain proteins are ribonucleases involved in quality control, metabolism and maturation of mRNA and rRNA. The majority of prokaryotic PIN-domain proteins are encoded by the abundant vapBC toxin--antitoxin loci and inhibit translation by an unknown mechanism. Here we show that enteric VapCs are site-specific endonucleases that cleave tRNA(fMet) in the anticodon stem-loop between nucleotides +38 and +39 in vivo and in vitro. Consistently, VapC inhibited translation in vivo and in vitro. Translation-reactions could be reactivated by the addition of VapB and extra charged tRNA(fMet). Similarly, ectopic production of tRNA(fMet) counteracted VapC in vivo. Thus, tRNA(fMet) is the only cellular target of VapC. Depletion of tRNA(fMet) by vapC induction was bacteriostatic and stimulated ectopic translation initiation at elongator codons. Moreover, addition of chloramphenicol to cells carrying vapBC induced VapC activity. Thus, by cleavage of tRNA(fMet), VapC simultaneously may regulate global cellular translation and reprogram translation initiation.
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Abstract
In eukaryotes, mRNAs harbouring PTCs (premature translation-termination codons) are recognized and eliminated by NMD (nonsense-mediated mRNA decay). In addition to its quality-control function, NMD constitutes a translation-dependent post-transcriptional pathway to regulate the expression levels of physiological mRNAs. In contrast with PTC recognition, little is known about the mechanisms that trigger the rapid degradation of mammalian nonsense mRNA. Studies have shown that mammalian NMD targets can be degraded via both an SMG6 (where SMG is suppressor of morphological defects on genitalia)-dependent endonucleolytic pathway and a deadenylation and decapping-dependent exonucleolytic pathway, with the possible involvement of SMG5 and SMG7. In contrast, Drosophila melanogaster NMD is confined to the former and Saccharomyces cerevisiae NMD to the latter decay pathway. Consistent with this conclusion, mammals possess both SMG6 and SMG7, whereas D. melanogaster lacks an SMG7 homologue and yeast have no SMG6 equivalent. In the present paper, we review what is known about the degradation of PTC-containing mRNAs so far, paying particular attention to the properties of the NMD-specific factors SMG5-SMG7 and to what is known about the mechanism of degrading mRNAs after they have been committed to the NMD pathway.
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De Storme N, Geelen D. The Arabidopsis mutant jason produces unreduced first division restitution male gametes through a parallel/fused spindle mechanism in meiosis II. PLANT PHYSIOLOGY 2011; 155:1403-15. [PMID: 21257792 PMCID: PMC3046594 DOI: 10.1104/pp.110.170415] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2010] [Accepted: 01/20/2011] [Indexed: 05/18/2023]
Abstract
In plants, whole-genome doubling (polyploidization) is a widely occurring process largely contributing to plant evolution and diversification. The generation and fusion of diploid gametes is now considered the major route of plant polyploidization. The parallel arrangement or fusion of meiosis II MII spindles (ps) is one of the most frequently reported mechanisms generating triploid offspring. Through a forward genetics screen of an Arabidopsis (Arabidopsis thaliana) ethyl methanesulfonate population, we identified Arabidopsis thaliana Parallel Spindles1 (AtPS1), which was recently reported as a major gene implicated in the control of the ps meiotic defect. In addition, we describe the isolation and characterization of a novel allele of JASON, involved in male gametophytic ploidy regulation in plants. Similar to atps1 mutants, jason produces more than 25% 2n pollen grains and spontaneously forms triploid offspring. By combining both cytological and genetic approaches, we demonstrate that loss of JASON causes the formation of parallel arranged and fused spindles in male MII, resulting in the production of unreduced first division restitution 2n spores. Although JASON encodes a protein of unknown function, we additionally show that the meiotic ps defect in jason is caused by a reduction in AtPS1 transcript levels, indicating that JASON positively regulates AtPS1 expression, allowing the proper organization and orientation of metaphase II spindle plates in MII.
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Affiliation(s)
| | - Danny Geelen
- Department of Plant Production, Faculty of Bioscience Engineering, University of Ghent, 9000 Ghent, Belgium
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Brownfield L, Köhler C. Unreduced gamete formation in plants: mechanisms and prospects. JOURNAL OF EXPERIMENTAL BOTANY 2011; 62:1659-68. [PMID: 21109579 DOI: 10.1093/jxb/erq371] [Citation(s) in RCA: 98] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Polyploids, organisms with more than two sets of chromosomes, are widespread in flowering plants, including many important crop species. Increases in ploidy level are believed to arise commonly through the production of gametes that have not had their ploidy level reduced during meiosis. Although there have been cytological descriptions of unreduced gamete formation in a number of plants, until recently none of the underlying genes or molecular mechanisms involved in unreduced gamete production have been described. The recent discovery of several genes in which mutations give rise to a high frequency of unreduced gametes in the model plant Arabidopsis thaliana opens the door to the elucidation of this important event and its manipulation in crop species. Here this recent progress is reviewed and the identified genes and the mechanism by which the loss of protein function leads to the formation of unreduced gametes are discussed. The potential to use the knowledge gained from Arabidopsis mutants to design tools and develop techniques to engineer unreduced gamete production in important crop species for use in plant breeding is also discussed.
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Affiliation(s)
- Lynette Brownfield
- Department of Biology and Zurich-Basel Plant Science Center, Swiss Federal Institute of Technology, ETH Centre, Zurich, Switzerland
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