1
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Merens HE, Choquet K, Baxter-Koenigs AR, Churchman LS. Timing is everything: advances in quantifying splicing kinetics. Trends Cell Biol 2024:S0962-8924(24)00070-9. [PMID: 38777664 DOI: 10.1016/j.tcb.2024.03.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2023] [Revised: 03/26/2024] [Accepted: 03/27/2024] [Indexed: 05/25/2024]
Abstract
Splicing is a highly regulated process critical for proper pre-mRNA maturation and the maintenance of a healthy cellular environment. Splicing events are impacted by ongoing transcription, neighboring splicing events, and cis and trans regulatory factors on the respective pre-mRNA transcript. Within this complex regulatory environment, splicing kinetics have the potential to influence splicing outcomes but have historically been challenging to study in vivo. In this review, we highlight recent technological advancements that have enabled measurements of global splicing kinetics and of the variability of splicing kinetics at single introns. We demonstrate how identifying features that are correlated with splicing kinetics has increased our ability to form potential models for how splicing kinetics may be regulated in vivo.
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Affiliation(s)
- Hope E Merens
- Harvard University, Department of Genetics, Boston, MA, USA
| | - Karine Choquet
- University of Sherbrooke, Department of Biochemistry and Functional Genomics, Sherbrooke, Québec, Canada
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2
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Forouzanfar F, Plassard D, Furst A, Moreno D, Oliveira KA, Reina-San-Martin B, Tora L, Molina N, Mendoza M. Gene-specific RNA homeostasis revealed by perturbation of coactivator complexes. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.01.30.577960. [PMID: 38352321 PMCID: PMC10862879 DOI: 10.1101/2024.01.30.577960] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 02/23/2024]
Abstract
Transcript buffering entails the reciprocal modulation of mRNA synthesis and degradation rates to maintain stable RNA levels under varying cellular conditions. Current research supports a global, non-sequence-specific connection between mRNA synthesis and degradation, but the underlying mechanisms are still unclear. In this study, we investigated changes in RNA metabolism following acute depletion of TIP60/KAT5, the acetyltransferase subunit of the NuA4 transcriptional coactivator complex, in mouse embryonic stem cells. By combining RNA sequencing of nuclear, cytoplasmic, and newly synthesised transcript fractions with biophysical modelling, we demonstrate that TIP60 predominantly enhances transcription of numerous genes, while a smaller set of genes undergoes TIP60-dependent transcriptional repression. Surprisingly, transcription changes caused by TIP60 depletion were offset by corresponding changes in RNA nuclear export and cytoplasmic stability, indicating gene-specific buffering mechanisms. Similarly, disruption of the unrelated ATAC coactivator complex also resulted in gene-specific transcript buffering. These findings reveal that transcript buffering functions at a gene-specific level and suggest that cells dynamically adjust RNA splicing, export, and degradation in response to individual RNA synthesis alterations, thereby sustaining cellular homeostasis.
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3
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Müller JM, Moos K, Baar T, Maier KC, Zumer K, Tresch A. Nuclear export is a limiting factor in eukaryotic mRNA metabolism. PLoS Comput Biol 2024; 20:e1012059. [PMID: 38753883 DOI: 10.1371/journal.pcbi.1012059] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2023] [Revised: 05/29/2024] [Accepted: 04/09/2024] [Indexed: 05/18/2024] Open
Abstract
The eukaryotic mRNA life cycle includes transcription, nuclear mRNA export and degradation. To quantify all these processes simultaneously, we perform thiol-linked alkylation after metabolic labeling of RNA with 4-thiouridine (4sU), followed by sequencing of RNA (SLAM-seq) in the nuclear and cytosolic compartments of human cancer cells. We develop a model that reliably quantifies mRNA-specific synthesis, nuclear export, and nuclear and cytosolic degradation rates on a genome-wide scale. We find that nuclear degradation of polyadenylated mRNA is negligible and nuclear mRNA export is slow, while cytosolic mRNA degradation is comparatively fast. Consequently, an mRNA molecule generally spends most of its life in the nucleus. We also observe large differences in the nuclear export rates of different 3'UTR transcript isoforms. Furthermore, we identify genes whose expression is abruptly induced upon metabolic labeling. These transcripts are exported substantially faster than average mRNAs, suggesting the existence of alternative export pathways. Our results highlight nuclear mRNA export as a limiting factor in mRNA metabolism and gene regulation.
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Affiliation(s)
- Jason M Müller
- Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany
- Institute of Medical Statistics and Computational Biology, Faculty of Medicine, University of Cologne, Cologne, Germany
| | - Katharina Moos
- Institute of Medical Statistics and Computational Biology, Faculty of Medicine, University of Cologne, Cologne, Germany
- Institute of Medical Bioinformatics and Systems Medicine, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Till Baar
- Institute of Medical Statistics and Computational Biology, Faculty of Medicine, University of Cologne, Cologne, Germany
| | - Kerstin C Maier
- Department of Molecular Biology, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Kristina Zumer
- Department of Molecular Biology, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Achim Tresch
- Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany
- Institute of Medical Statistics and Computational Biology, Faculty of Medicine, University of Cologne, Cologne, Germany
- Center for Data and Simulation Science, University of Cologne, Cologne, Germany
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4
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McShane E, Couvillion M, Ietswaart R, Prakash G, Smalec BM, Soto I, Baxter-Koenigs AR, Choquet K, Churchman LS. A kinetic dichotomy between mitochondrial and nuclear gene expression processes. Mol Cell 2024; 84:1541-1555.e11. [PMID: 38503286 DOI: 10.1016/j.molcel.2024.02.028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2023] [Revised: 12/12/2023] [Accepted: 02/27/2024] [Indexed: 03/21/2024]
Abstract
Oxidative phosphorylation (OXPHOS) complexes, encoded by both mitochondrial and nuclear DNA, are essential producers of cellular ATP, but how nuclear and mitochondrial gene expression steps are coordinated to achieve balanced OXPHOS subunit biogenesis remains unresolved. Here, we present a parallel quantitative analysis of the human nuclear and mitochondrial messenger RNA (mt-mRNA) life cycles, including transcript production, processing, ribosome association, and degradation. The kinetic rates of nearly every stage of gene expression differed starkly across compartments. Compared with nuclear mRNAs, mt-mRNAs were produced 1,100-fold more, degraded 7-fold faster, and accumulated to 160-fold higher levels. Quantitative modeling and depletion of mitochondrial factors LRPPRC and FASTKD5 identified critical points of mitochondrial regulatory control, revealing that the mitonuclear expression disparities intrinsically arise from the highly polycistronic nature of human mitochondrial pre-mRNA. We propose that resolving these differences requires a 100-fold slower mitochondrial translation rate, illuminating the mitoribosome as a nexus of mitonuclear co-regulation.
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Affiliation(s)
- Erik McShane
- Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, MA 02115, USA
| | - Mary Couvillion
- Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, MA 02115, USA
| | - Robert Ietswaart
- Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, MA 02115, USA
| | - Gyan Prakash
- Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, MA 02115, USA
| | - Brendan M Smalec
- Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, MA 02115, USA
| | - Iliana Soto
- Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, MA 02115, USA
| | - Autum R Baxter-Koenigs
- Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, MA 02115, USA
| | - Karine Choquet
- Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, MA 02115, USA
| | - L Stirling Churchman
- Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, MA 02115, USA.
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5
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Coté A, O'Farrell A, Dardani I, Dunagin M, Coté C, Wan Y, Bayatpour S, Drexler HL, Alexander KA, Chen F, Wassie AT, Patel R, Pham K, Boyden ES, Berger S, Phillips-Cremins J, Churchman LS, Raj A. Post-transcriptional splicing can occur in a slow-moving zone around the gene. eLife 2024; 12:RP91357. [PMID: 38577979 PMCID: PMC10997330 DOI: 10.7554/elife.91357] [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] [Indexed: 04/06/2024] Open
Abstract
Splicing is the stepwise molecular process by which introns are removed from pre-mRNA and exons are joined together to form mature mRNA sequences. The ordering and spatial distribution of these steps remain controversial, with opposing models suggesting splicing occurs either during or after transcription. We used single-molecule RNA FISH, expansion microscopy, and live-cell imaging to reveal the spatiotemporal distribution of nascent transcripts in mammalian cells. At super-resolution levels, we found that pre-mRNA formed clouds around the transcription site. These clouds indicate the existence of a transcription-site-proximal zone through which RNA move more slowly than in the nucleoplasm. Full-length pre-mRNA undergo continuous splicing as they move through this zone following transcription, suggesting a model in which splicing can occur post-transcriptionally but still within the proximity of the transcription site, thus seeming co-transcriptional by most assays. These results may unify conflicting reports of co-transcriptional versus post-transcriptional splicing.
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Affiliation(s)
- Allison Coté
- Department of Bioengineering, University of PennsylvaniaPhiladelphiaUnited States
| | - Aoife O'Farrell
- Department of Bioengineering, University of PennsylvaniaPhiladelphiaUnited States
| | - Ian Dardani
- Department of Bioengineering, University of PennsylvaniaPhiladelphiaUnited States
| | - Margaret Dunagin
- Department of Bioengineering, University of PennsylvaniaPhiladelphiaUnited States
| | - Chris Coté
- Department of Bioengineering, University of PennsylvaniaPhiladelphiaUnited States
| | - Yihan Wan
- School of Life Sciences, Westlake UniversityHangzhouChina
| | - Sareh Bayatpour
- Department of Bioengineering, University of PennsylvaniaPhiladelphiaUnited States
| | - Heather L Drexler
- Department of Genetics, Blavatnik Institute, Harvard Medical SchoolBostonUnited States
| | - Katherine A Alexander
- Department of Cell and Developmental Biology, Penn Institute of Epigenetics, Perelman School of Medicine, University of PennsylvaniaPhiladelphiaUnited States
| | - Fei Chen
- Broad Institute of MIT and HarvardCambridgeUnited States
| | - Asmamaw T Wassie
- Department of Cell and Molecular Biology, University of PennsylvaniaPhiladelphiaUnited States
| | - Rohan Patel
- Department of Bioengineering, University of PennsylvaniaPhiladelphiaUnited States
| | - Kenneth Pham
- Department of Cell and Molecular Biology, University of PennsylvaniaPhiladelphiaUnited States
| | - Edward S Boyden
- Departments of Biological Engineering and Brain and Cognitive Sciences, Media Lab and McGovern Institute, Massachusetts Institute of TechnologyCambridgeUnited States
| | - Shelly Berger
- Department of Cell and Developmental Biology, Penn Institute of Epigenetics, Perelman School of Medicine, University of PennsylvaniaPhiladelphiaUnited States
| | | | - L Stirling Churchman
- Department of Genetics, Blavatnik Institute, Harvard Medical SchoolBostonUnited States
| | - Arjun Raj
- Department of Bioengineering, University of PennsylvaniaPhiladelphiaUnited States
- Department of Genetics, Perelman School of Medicine, University of PennsylvaniaPhiladelphiaUnited States
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6
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Calvo-Roitberg E, Carroll CL, Venev SV, Kim G, Mick ST, Dekker J, Fiszbein A, Pai AA. mRNA initiation and termination are spatially coordinated. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.01.05.574404. [PMID: 38260419 PMCID: PMC10802295 DOI: 10.1101/2024.01.05.574404] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2024]
Abstract
The expression of a precise mRNA transcriptome is crucial for establishing cell identity and function, with dozens of alternative isoforms produced for a single gene sequence. The regulation of mRNA isoform usage occurs by the coordination of co-transcriptional mRNA processing mechanisms across a gene. Decisions involved in mRNA initiation and termination underlie the largest extent of mRNA isoform diversity, but little is known about any relationships between decisions at both ends of mRNA molecules. Here, we systematically profile the joint usage of mRNA transcription start sites (TSSs) and polyadenylation sites (PASs) across tissues and species. Using both short and long read RNA-seq data, we observe that mRNAs preferentially using upstream TSSs also tend to use upstream PASs, and congruently, the usage of downstream sites is similarly paired. This observation suggests that mRNA 5' end choice may directly influence mRNA 3' ends. Our results suggest a novel "Positional Initiation-Termination Axis" (PITA), in which the usage of alternative terminal sites are coupled based on the order in which they appear in the genome. PITA isoforms are more likely to encode alternative protein domains and use conserved sites. PITA is strongly associated with the length of genomic features, such that PITA is enriched in longer genes with more area devoted to regions that regulate alternative 5' or 3' ends. Strikingly, we found that PITA genes are more likely than non-PITA genes to have multiple, overlapping chromatin structural domains related to pairing of ordinally coupled start and end sites. In turn, PITA coupling is also associated with fast RNA Polymerase II (RNAPII) trafficking across these long gene regions. Our findings indicate that a combination of spatial and kinetic mechanisms couple transcription initiation and mRNA 3' end decisions based on ordinal position to define the expression mRNA isoforms.
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Affiliation(s)
| | | | - Sergey V. Venev
- Department of Systems Biology, University Massachusetts Chan Medical School, Worcester, MA
| | - GyeungYun Kim
- Department of Biology, Boston University, Boston, MA
| | | | - Job Dekker
- Department of Systems Biology, University Massachusetts Chan Medical School, Worcester, MA
- Howard Hughes Medical Institute, Chevy Chase, MD
| | - Ana Fiszbein
- Department of Biology, Boston University, Boston, MA
- Center for Computing & Data Sciences, Boston University, Boston, MA
| | - Athma A. Pai
- RNA Therapeutics Institute, University of Massachusetts Chan Medical School, Worcester, MA
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7
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Haque N, Will A, Cook AG, Hogg JR. A network of DZF proteins controls alternative splicing regulation and fidelity. Nucleic Acids Res 2023; 51:6411-6429. [PMID: 37144502 PMCID: PMC10325889 DOI: 10.1093/nar/gkad351] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2022] [Revised: 04/12/2023] [Accepted: 05/03/2023] [Indexed: 05/06/2023] Open
Abstract
Proteins containing DZF (domain associated with zinc fingers) modules play important roles throughout gene expression, from transcription to translation. Derived from nucleotidyltransferases but lacking catalytic residues, DZF domains serve as heterodimerization surfaces between DZF protein pairs. Three DZF proteins are widely expressed in mammalian tissues, ILF2, ILF3 and ZFR, which form mutually exclusive ILF2-ILF3 and ILF2-ZFR heterodimers. Using eCLIP-Seq, we find that ZFR binds across broad intronic regions to regulate the alternative splicing of cassette and mutually exclusive exons. ZFR preferentially binds dsRNA in vitro and is enriched on introns containing conserved dsRNA elements in cells. Many splicing events are similarly altered upon depletion of any of the three DZF proteins; however, we also identify independent and opposing roles for ZFR and ILF3 in alternative splicing regulation. Along with widespread involvement in cassette exon splicing, the DZF proteins control the fidelity and regulation of over a dozen highly validated mutually exclusive splicing events. Our findings indicate that the DZF proteins form a complex regulatory network that leverages dsRNA binding by ILF3 and ZFR to modulate splicing regulation and fidelity.
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Affiliation(s)
- Nazmul Haque
- Biochemistry and Biophysics Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD20892, USA
| | - Alexander Will
- Wellcome Centre for Cell Biology, School of Biological Sciences, University of Edinburgh, Max Born Crescent, Edinburgh EH9 3BF, UK
| | - Atlanta G Cook
- Wellcome Centre for Cell Biology, School of Biological Sciences, University of Edinburgh, Max Born Crescent, Edinburgh EH9 3BF, UK
| | - J Robert Hogg
- Biochemistry and Biophysics Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD20892, USA
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8
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Gohr A, Iñiguez LP, Torres-Méndez A, Bonnal S, Irimia M. Insplico: effective computational tool for studying splicing order of adjacent introns genome-wide with short and long RNA-seq reads. Nucleic Acids Res 2023; 51:e56. [PMID: 37026474 PMCID: PMC10250204 DOI: 10.1093/nar/gkad244] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2022] [Revised: 03/13/2023] [Accepted: 03/23/2023] [Indexed: 04/08/2023] Open
Abstract
Although splicing occurs largely co-transcriptionally, the order by which introns are removed does not necessarily follow the order in which they are transcribed. Whereas several genomic features are known to influence whether or not an intron is spliced before its downstream neighbor, multiple questions related to adjacent introns' splicing order (AISO) remain unanswered. Here, we present Insplico, the first standalone software for quantifying AISO that works with both short and long read sequencing technologies. We first demonstrate its applicability and effectiveness using simulated reads and by recapitulating previously reported AISO patterns, which unveiled overlooked biases associated with long read sequencing. We next show that AISO around individual exons is remarkably constant across cell and tissue types and even upon major spliceosomal disruption, and it is evolutionarily conserved between human and mouse brains. We also establish a set of universal features associated with AISO patterns across various animal and plant species. Finally, we used Insplico to investigate AISO in the context of tissue-specific exons, particularly focusing on SRRM4-dependent microexons. We found that the majority of such microexons have non-canonical AISO, in which the downstream intron is spliced first, and we suggest two potential modes of SRRM4 regulation of microexons related to their AISO and various splicing-related features. Insplico is available on gitlab.com/aghr/insplico.
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Affiliation(s)
- André Gohr
- Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, Barcelona, Spain
| | - Luis P Iñiguez
- Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, Barcelona, Spain
| | - Antonio Torres-Méndez
- Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, Barcelona, Spain
| | - Sophie Bonnal
- Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, Barcelona, Spain
| | - Manuel Irimia
- Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, Barcelona, Spain
- Universitat Pompeu Fabra (UPF), Barcelona, Spain
- ICREA, Barcelona, Spain
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9
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How Estrogen, Testosterone, and Sex Differences Influence Serum Immunoglobulin Isotype Patterns in Mice and Humans. Viruses 2023; 15:v15020482. [PMID: 36851695 PMCID: PMC9961480 DOI: 10.3390/v15020482] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2022] [Revised: 01/31/2023] [Accepted: 02/03/2023] [Indexed: 02/11/2023] Open
Abstract
Females often exhibit superior immune responses compared to males toward vaccines and pathogens such as influenza viruses and SARS-CoV-2. To help explain these differences, we first studied serum immunoglobulin isotype patterns in C57BL/6 male and female mice. We focused on IgG2b, an isotype that lends to virus control and that has been previously shown to be elevated in murine females compared to males. Improvements in IgG2b serum levels, and/or IgG2b ratios with other non-IgM isotypes, were observed when: (i) wildtype (WT) female mice were compared to estrogen receptor knockout mice (IgG2b, IgG2b/IgG3, IgG2b/IgG1, and IgG2b/IgA were all higher in WT mice), (ii) unmanipulated female mice were compared to ovariectomized mice (IgG2b/IgA was higher in unmanipulated animals), (iii) female mice were supplemented with estrogen in the context of an inflammatory insult (IgG2b and IgG2b/IgG3 were improved by estrogen supplementation), and (iv) male mice were supplemented with testosterone, a hormone that can convert to estrogen in vivo (IgG2b, IgG2b/IgG3, IgG2b/IgG1, and IgG2b/IgA were all improved by supplementation). We next examined data from three sets of previously described male and female human blood samples. In each case, there were higher IgG2 levels, and/or ratios of IgG2 with non-IgM isotypes, in human females compared to males. The effects of sex and sex hormones in the mouse and human studies were subtle, but frequent, suggesting that sex hormones represent only a fraction of the factors that influence isotype patterns. Examination of the gene loci suggested that upregulation of murine IgG2b or human IgG2 could be mediated by estrogen receptor binding to estrogen response elements and cytosine-adenine (CA) repeats upstream of respective Cγ genes. Given that murine IgG2b and human IgG2 lend to virus control, the isotype biases in females may be sufficient to improve outcomes following vaccination or infection. Future attention to sex hormone levels, and consequent immunoglobulin isotype patterns, in clinical trials are encouraged to support the optimization of vaccine and drug products for male and female hosts.
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10
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Djihinto O, Saizonou HD, Djogbenou LS. Single nucleotide polymorphism (SNP) in the doublesex ( dsx) gene splice sites and relevance for its alternative splicing in the malaria vector Anopheles gambiae. Wellcome Open Res 2023; 7:31. [PMID: 37546169 PMCID: PMC10397894 DOI: 10.12688/wellcomeopenres.17572.3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/02/2023] [Indexed: 08/08/2023] Open
Abstract
Background: Malaria burden continues to be significant in tropical regions, and conventional vector control methods are faced with challenges such as insecticide resistance. To overcome these challenges, additional vector control interventions are vital and include modern genetic approaches as well as classical methods like the sterile insect technique (SIT). In the major human malaria vector Anopheles gambiae, a candidate gene favourable for sterility induction is the doublesex ( dsx) gene, involved in mosquitos' somatic sexually dimorphic traits determination. However, the pathways that trigger the signal of dsx gene exon skipping alternative splicing mechanism in anopheline mosquitoes are not well characterized. This study aims to screen the An. gambiae dsx gene splice site sequences for single-nucleotide polymorphisms (SNPs) that could be critical to its alternative splicing. Methods: Variant annotation data from Ag1000G project phase 2 was analysed, in order to identify splice-relevant SNPs within acceptor and donor splice sites of the An. gambiae dsx gene ( Agdsx). Results: SNPs were found in both donor and acceptor sites of the Agdsx. No splice-relevant SNPs were identified in the female-specific intron 4 acceptor site and the corresponding region in males. Two SNPs (rs48712947, rs48712962) were found in the female-specific donor site of exon 5. They were not specific to either males or females as the rs48712947 was found in female mosquitoes from Cameroon, and in both males and females from Burkina Faso. In the other splice sites, the intron 3 acceptor site carried the greatest abundance of SNPs. Conclusions: There were no gender association between the identified SNPs and the random distribution of these SNPs in mosquito populations. The SNPs in Agdsx splice sites are not critical for the alternative splicing. Other molecular mechanisms should be considered and investigated.
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Affiliation(s)
- Oswald Djihinto
- Tropical Infectious Diseases Research Centre (TIDRC), University of Abomey-Calavi, Abomey-Calavi, 01BP526 Cotonou, Benin
| | - Helga D.M. Saizonou
- Tropical Infectious Diseases Research Centre (TIDRC), University of Abomey-Calavi, Abomey-Calavi, 01BP526 Cotonou, Benin
| | - Luc S. Djogbenou
- Tropical Infectious Diseases Research Centre (TIDRC), University of Abomey-Calavi, Abomey-Calavi, 01BP526 Cotonou, Benin
- Institut Régional de Santé Publique, University of Abomey-Calavi, Ouidah, BP 384 Ouidah, Benin
- Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, UK
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11
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Basu K, Dey A, Kiran M. Inefficient splicing of long non-coding RNAs is associated with higher transcript complexity in human and mouse. RNA Biol 2023; 20:563-572. [PMID: 37543950 PMCID: PMC10405767 DOI: 10.1080/15476286.2023.2242649] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Revised: 07/23/2023] [Accepted: 07/26/2023] [Indexed: 08/08/2023] Open
Abstract
Recent reports show that long non-coding RNAs (lncRNAs) have inefficient splicing and fewer alternative splice variants than mRNAs. Here, we have explored the efficiency of lncRNAs and mRNAs in producing various splice variants, given the number of exons in humans and mice. Intriguingly, lncRNAs produce more splice variants per exon, referred to as Transcript Complexity, than mRNAs. Most lncRNA splice variants are the product of the alternative last exon and exon skipping. LncRNAs and mRNAs with higher transcript complexity have shorter intron lengths. Longer exon length and GC/AG at 5'/3' splice sites are associated with higher transcript complexity in lncRNAs. Lastly, our results indicate that inefficient splicing of lncRNAs may facilitate multiple introns splicing and, thus, more spliced products per exon.
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Affiliation(s)
- Koushiki Basu
- Department of Systems and Computational Biology, School of Life Sciences, University of Hyderabad, Hyderabad, India
| | - Anubha Dey
- Department of Systems and Computational Biology, School of Life Sciences, University of Hyderabad, Hyderabad, India
| | - Manjari Kiran
- Department of Systems and Computational Biology, School of Life Sciences, University of Hyderabad, Hyderabad, India
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12
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Djihinto O, Saizonou HD, Djogbenou LS. Single nucleotide polymorphism (SNP) in the doublesex (dsx) gene splice sites and relevance for its alternative splicing in the malaria vector Anopheles gambiae. Wellcome Open Res 2022. [DOI: 10.12688/wellcomeopenres.17572.2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Background: Malaria burden continues to be significant in tropical regions, and conventional vector control methods are faced with challenges such as insecticide resistance. To overcome these challenges, additional vector control interventions are vital and include modern genetic approaches as well as classical methods like the sterile insect technique (SIT). In the major human malaria vector Anopheles gambiae, a candidate gene favourable for sterility induction is the doublesex (dsx) gene, involved in mosquitos’ somatic sexually dimorphic traits determination. However, the pathways that trigger the signal of dsx gene exon skipping alternative splicing mechanism in anopheline mosquitoes are not well characterized. This study aims to screen the An. gambiae dsx gene splice site sequences for single-nucleotide polymorphisms (SNPs) that could be critical to its alternative splicing. Methods: Variant annotation data from Ag1000G project phase 2 was analysed, in order to identify splice-relevant SNPs within acceptor and donor splice sites of the An. gambiae dsx gene (Agdsx). Results: SNPs were found in both donor and acceptor sites of the Agdsx. No splice-relevant SNPs were identified in the female-specific intron 4 acceptor site and the corresponding region in males. Two SNPs (rs48712947, rs48712962) were found in the female-specific donor site of exon 5. They were not specific to either males or females as the rs48712947 was found in female mosquitoes from Cameroon, and in both males and females from Burkina Faso. In the other splice sites, the intron 3 acceptor site carried the greatest abundance of SNPs. Conclusions: There were no gender association between the identified SNPs and the random distribution of these SNPs in mosquito populations. The SNPs in Agdsx splice sites are not critical for the alternative splicing. Other molecular mechanisms should be considered and investigated.
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13
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Zeng Y, Fair BJ, Zeng H, Krishnamohan A, Hou Y, Hall JM, Ruthenburg AJ, Li YI, Staley JP. Profiling lariat intermediates reveals genetic determinants of early and late co-transcriptional splicing. Mol Cell 2022; 82:4681-4699.e8. [PMID: 36435176 PMCID: PMC10448999 DOI: 10.1016/j.molcel.2022.11.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2021] [Revised: 09/10/2022] [Accepted: 11/02/2022] [Indexed: 11/27/2022]
Abstract
Long introns with short exons in vertebrate genes are thought to require spliceosome assembly across exons (exon definition), rather than introns, thereby requiring transcription of an exon to splice an upstream intron. Here, we developed CoLa-seq (co-transcriptional lariat sequencing) to investigate the timing and determinants of co-transcriptional splicing genome wide. Unexpectedly, 90% of all introns, including long introns, can splice before transcription of a downstream exon, indicating that exon definition is not obligatory for most human introns. Still, splicing timing varies dramatically across introns, and various genetic elements determine this variation. Strong U2AF2 binding to the polypyrimidine tract predicts early splicing, explaining exon definition-independent splicing. Together, our findings question the essentiality of exon definition and reveal features beyond intron and exon length that are determinative for splicing timing.
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Affiliation(s)
- Yi Zeng
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637, USA
| | - Benjamin J Fair
- Department of Medicine, University of Chicago, Chicago, IL 60637, USA
| | - Huilin Zeng
- 855 Jefferson Ave. Redwood City, CA 94063, USA
| | - Aiswarya Krishnamohan
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637, USA
| | - Yichen Hou
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637, USA
| | - Johnathon M Hall
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637, USA
| | - Alexander J Ruthenburg
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637, USA; Department of Biochemistry & Molecular Biology, University of Chicago, Chicago, IL 60637, USA
| | - Yang I Li
- Department of Medicine, University of Chicago, Chicago, IL 60637, USA; Department of Human Genetics, University of Chicago, Chicago, IL 60637, USA.
| | - Jonathan P Staley
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637, USA.
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14
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Agarwal V, Kelley DR. The genetic and biochemical determinants of mRNA degradation rates in mammals. Genome Biol 2022; 23:245. [PMID: 36419176 PMCID: PMC9684954 DOI: 10.1186/s13059-022-02811-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2022] [Accepted: 11/02/2022] [Indexed: 11/26/2022] Open
Abstract
BACKGROUND Degradation rate is a fundamental aspect of mRNA metabolism, and the factors governing it remain poorly characterized. Understanding the genetic and biochemical determinants of mRNA half-life would enable more precise identification of variants that perturb gene expression through post-transcriptional gene regulatory mechanisms. RESULTS We establish a compendium of 39 human and 27 mouse transcriptome-wide mRNA decay rate datasets. A meta-analysis of these data identified a prevalence of technical noise and measurement bias, induced partially by the underlying experimental strategy. Correcting for these biases allowed us to derive more precise, consensus measurements of half-life which exhibit enhanced consistency between species. We trained substantially improved statistical models based upon genetic and biochemical features to better predict half-life and characterize the factors molding it. Our state-of-the-art model, Saluki, is a hybrid convolutional and recurrent deep neural network which relies only upon an mRNA sequence annotated with coding frame and splice sites to predict half-life (r=0.77). The key novel principle learned by Saluki is that the spatial positioning of splice sites, codons, and RNA-binding motifs within an mRNA is strongly associated with mRNA half-life. Saluki predicts the impact of RNA sequences and genetic mutations therein on mRNA stability, in agreement with functional measurements derived from massively parallel reporter assays. CONCLUSIONS Our work produces a more robust ground truth for transcriptome-wide mRNA half-lives in mammalian cells. Using these revised measurements, we trained Saluki, a model that is over 50% more accurate in predicting half-life from sequence than existing models. Saluki succinctly captures many of the known determinants of mRNA half-life and can be rapidly deployed to predict the functional consequences of arbitrary mutations in the transcriptome.
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Affiliation(s)
- Vikram Agarwal
- grid.497059.6Calico Life Sciences LLC, South San Francisco, CA 94080 USA ,grid.417555.70000 0000 8814 392XPresent Address: mRNA Center of Excellence, Sanofi Pasteur Inc., Waltham, MA 02451 USA
| | - David R. Kelley
- grid.497059.6Calico Life Sciences LLC, South San Francisco, CA 94080 USA
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15
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Gildea MA, Dwyer ZW, Pleiss JA. Transcript-specific determinants of pre-mRNA splicing revealed through in vivo kinetic analyses of the 1 st and 2 nd chemical steps. Mol Cell 2022; 82:2967-2981.e6. [PMID: 35830855 PMCID: PMC9391291 DOI: 10.1016/j.molcel.2022.06.020] [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: 10/13/2020] [Revised: 01/31/2022] [Accepted: 06/12/2022] [Indexed: 10/17/2022]
Abstract
We generate high-precision measurements of the in vivo rates of both chemical steps of pre-mRNA splicing across the genome-wide complement of substrates in yeast by coupling metabolic labeling, multiplexed primer-extension sequencing, and kinetic modeling. We demonstrate that the rates of intron removal vary widely, splice-site sequences are primary determinants of 1st step but have little apparent impact on 2nd step rates, and the 2nd step is generally faster than the 1st step. Ribosomal protein genes (RPGs) are spliced faster than non-RPGs at each step, and RPGs share evolutionarily conserved properties that may contribute to their faster splicing. A genetic variant defective in the 1st step of the pathway reveals a genome-wide defect in the 1st step but an unexpected, transcript-specific change in the 2nd step. Our work demonstrates that extended co-transcriptional association is an important determinant of splicing rate, a conclusion at odds with recent claims of ultra-fast splicing.
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Affiliation(s)
- Michael A Gildea
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14850, USA
| | - Zachary W Dwyer
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14850, USA
| | - Jeffrey A Pleiss
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14850, USA.
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16
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Xiong L, Tolen EA, Choi J, Velychko S, Caizzi L, Velychko T, Adachi K, MacCarthy CM, Lidschreiber M, Cramer P, Schöler HR. Oct4 differentially regulates chromatin opening and enhancer transcription in pluripotent stem cells. eLife 2022; 11:71533. [PMID: 35621159 PMCID: PMC9142147 DOI: 10.7554/elife.71533] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2021] [Accepted: 05/17/2022] [Indexed: 12/21/2022] Open
Abstract
The transcription factor Oct4 is essential for the maintenance and induction of stem cell pluripotency, but its functional roles are not fully understood. Here, we investigate the functions of Oct4 by depleting and subsequently recovering it in mouse embryonic stem cells (ESCs) and conducting a time-resolved multiomics analysis. Oct4 depletion leads to an immediate loss of its binding to enhancers, accompanied by a decrease in mRNA synthesis from its target genes that are part of the transcriptional network that maintains pluripotency. Gradual decrease of Oct4 binding to enhancers does not immediately change the chromatin accessibility but reduces transcription of enhancers. Conversely, partial recovery of Oct4 expression results in a rapid increase in chromatin accessibility, whereas enhancer transcription does not fully recover. These results indicate different concentration-dependent activities of Oct4. Whereas normal ESC levels of Oct4 are required for transcription of pluripotency enhancers, low levels of Oct4 are sufficient to retain chromatin accessibility, likely together with other factors such as Sox2.
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Affiliation(s)
- Le Xiong
- Max Planck Institute for Multidisciplinary Sciences, Department of Molecular Biology, Göttingen, Germany
| | - Erik A Tolen
- Max Planck Institute for Molecular Biomedicine, Department of Cell and Developmental Biology, Münster, Germany
| | - Jinmi Choi
- Max Planck Institute for Multidisciplinary Sciences, Department of Molecular Biology, Göttingen, Germany
| | - Sergiy Velychko
- Max Planck Institute for Molecular Biomedicine, Department of Cell and Developmental Biology, Münster, Germany
| | - Livia Caizzi
- Max Planck Institute for Multidisciplinary Sciences, Department of Molecular Biology, Göttingen, Germany
| | - Taras Velychko
- Max Planck Institute for Multidisciplinary Sciences, Department of Molecular Biology, Göttingen, Germany
| | - Kenjiro Adachi
- Max Planck Institute for Molecular Biomedicine, Department of Cell and Developmental Biology, Münster, Germany
| | - Caitlin M MacCarthy
- Max Planck Institute for Molecular Biomedicine, Department of Cell and Developmental Biology, Münster, Germany
| | - Michael Lidschreiber
- Max Planck Institute for Multidisciplinary Sciences, Department of Molecular Biology, Göttingen, Germany
| | - Patrick Cramer
- Max Planck Institute for Multidisciplinary Sciences, Department of Molecular Biology, Göttingen, Germany
| | - Hans R Schöler
- Max Planck Institute for Molecular Biomedicine, Department of Cell and Developmental Biology, Münster, Germany
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17
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Hou R, Huang Y. Genomic sequences and RNA binding proteins predict RNA splicing efficiency in various single-cell contexts. Bioinformatics 2022; 38:3231-3237. [PMID: 35552604 DOI: 10.1093/bioinformatics/btac321] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2021] [Revised: 05/03/2022] [Accepted: 05/09/2022] [Indexed: 11/14/2022] Open
Abstract
MOTIVATION The RNA splicing efficiency is of high interest for both understanding the regulatory machinery of gene expression and estimating the RNA velocity in single cells. However, its genomic regulation and stochasticity across contexts remain poorly understood. RESULTS Here, by leveraging the recent RNA velocity tool, we estimated the relative splicing efficiency across a variety of single-cell RNA-Seq data sets. We further extracted large sets of genomic features and 120 RNA binding protein features and found they are highly predictive to relative RNA splicing efficiency across multiple tissues and organs on human and mouse. This predictive power brings promise to reveal the complexity of RNA processing and to enhance the analysis of single-cell transcription activities. AVAILABILITY AND IMPLEMENTATION In order to ensure reproducibility, all preprocessed data sets and scripts used for the prediction and figure generation are publicly available at https://doi.org/10.5281/zenodo.6513669. SUPPLEMENTARY INFORMATION Supplementary data are available at Bioinformatics online.
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Affiliation(s)
- Ruiyan Hou
- School of Biomedical Sciences, University of Hong Kong, Hong Kong SAR, China
| | - Yuanghua Huang
- School of Biomedical Sciences, University of Hong Kong, Hong Kong SAR, China.,Department of Statistics and Actuarial Science, University of Hong Kong, Hong Kong SAR, China
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18
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Co-transcriptional splicing efficiency is a gene-specific feature that can be regulated by TGFβ. Commun Biol 2022; 5:277. [PMID: 35347226 PMCID: PMC8960766 DOI: 10.1038/s42003-022-03224-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2021] [Accepted: 03/03/2022] [Indexed: 11/26/2022] Open
Abstract
Differential splicing efficiency of specific introns is a mechanism that dramatically increases protein diversity, based on selection of alternative exons for the final mature mRNA. However, it is unclear whether splicing efficiency of introns within the same gene is coordinated and eventually regulated as a mechanism to control mature mRNA levels. Based on nascent chromatin-associated RNA-sequencing data, we now find that co-transcriptional splicing (CTS) efficiency tends to be similar between the different introns of a gene. We establish that two well-differentiated strategies for CTS efficiency exist, at the extremes of a gradient: short genes that produce high levels of pre-mRNA undergo inefficient splicing, while long genes with relatively low levels of pre-mRNA have an efficient splicing. Notably, we observe that genes with efficient CTS display a higher level of mature mRNA relative to their pre-mRNA levels. Further, we show that the TGFβ signal transduction pathway regulates the general CTS efficiency, causing changes in mature mRNA levels. Taken together, our data indicate that CTS efficiency is a gene-specific characteristic that can be regulated to control gene expression. Co-transcriptional splicing efficiency is a gene-specific characteristic that can be regulated by TGFβ to modulate gene expression.
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19
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Djihinto O, Saizonou HD, Djogbenou LS. Single nucleotide polymorphism (SNP) in the doublesex (dsx) gene splice sites and relevance for its alternative splicing in the malaria vector Anopheles gambiae. Wellcome Open Res 2022. [DOI: 10.12688/wellcomeopenres.17572.1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Background: The malaria burden continues to be significant in tropical regions, and conventional vector control methods are faced with challenges such as insecticide resistance. To overcome these challenges, additional vector control interventions are vital and include modern genetic approaches as well as classical methods like the sterile insect technique (SIT). In the major human malaria vector Anopheles gambiae, a candidate gene favourable for sterility induction is the doublesex (dsx) gene, encoding somatic sexually dimorphic traits in mosquitoes. However, the mechanism that regulates the expression of this gene in anopheline mosquitoes is poorly understood. This study aimed to screen the An. gambiae dsx gene splice site sequences for single nucleotide polymorphisms (SNPs) that could be critical to its alternative splicing. Methods: Variant annotation data from Ag1000G project phase 2 was analysed, in order to identify splice-relevant SNPs within acceptor and donor splice sites of the An. gambiae dsx gene (Agdsx). Results: SNPs were found in both donor and acceptor sites of the Agdsx. No splice-relevant SNPs were identified in the female-specific intron 4 acceptor site and the corresponding region in males. Two SNPs (rs48712947, rs48712962) were found in the female-specific donor site of exon 5. They were not specific to either males or females as the rs48712947 was found in female mosquitoes from Cameroon, and in both males and females from Burkina Faso. In the other splice sites, the intron 3 acceptor site carried the greatest abundance of SNPs. Conclusions: There were no gender association between the identified SNPs and the random distribution of these SNPs in mosquito populations. The SNPs in Agdsx splice sites are not critical for the alternative splicing. Other molecular mechanisms should be considered and investigated.
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20
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Abstract
Alternative splicing enables higher eukaryotes to expand mRNA diversity from a finite number of genes through highly combinatorial splice site selection mechanisms that are influenced by the sequence of competing splice sites, cis-regulatory elements binding trans-acting factors, the length of exons and introns harbouring alternative splice sites and RNA secondary structures at putative splice junctions. To test the hypothesis that the intron definition or exon definition modes of splice site recognition direct the selection of alternative splice patterns, we created a database of alternative splice site usage (ALTssDB). When alternative splice sites are embedded within short introns (intron definition), the 5' and 3' splice sites closest to each other across the intron preferentially pair, consistent with previous observations. However, when alternative splice sites are embedded within large flanking introns (exon definition), the 5' and 3' splice sites closest to each other across the exon are preferentially selected. Thus, alternative splicing decisions are influenced by the intron and exon definition modes of splice site recognition. The results demonstrate that the spliceosome pairs splice sites that are closest in proximity within the unit of initial splice site selection.
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Affiliation(s)
- Francisco Carranza
- Department of Microbiology and Molecular Genetics, University of California Irvine, Irvine, California, USA
| | - Hossein Shenasa
- Department of Microbiology and Molecular Genetics, University of California Irvine, Irvine, California, USA
| | - Klemens J Hertel
- Department of Microbiology and Molecular Genetics, University of California Irvine, Irvine, California, USA
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21
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Borao S, Ayté J, Hümmer S. Evolution of the Early Spliceosomal Complex-From Constitutive to Regulated Splicing. Int J Mol Sci 2021; 22:ijms222212444. [PMID: 34830325 PMCID: PMC8624252 DOI: 10.3390/ijms222212444] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2021] [Revised: 11/15/2021] [Accepted: 11/16/2021] [Indexed: 12/14/2022] Open
Abstract
Pre-mRNA splicing is a major process in the regulated expression of genes in eukaryotes, and alternative splicing is used to generate different proteins from the same coding gene. Splicing is a catalytic process that removes introns and ligates exons to create the RNA sequence that codifies the final protein. While this is achieved in an autocatalytic process in ancestral group II introns in prokaryotes, the spliceosome has evolved during eukaryogenesis to assist in this process and to finally provide the opportunity for intron-specific splicing. In the early stage of splicing, the RNA 5' and 3' splice sites must be brought within proximity to correctly assemble the active spliceosome and perform the excision and ligation reactions. The assembly of this first complex, termed E-complex, is currently the least understood process. We focused in this review on the formation of the E-complex and compared its composition and function in three different organisms. We highlight the common ancestral mechanisms in S. cerevisiae, S. pombe, and mammals and conclude with a unifying model for intron definition in constitutive and regulated co-transcriptional splicing.
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Affiliation(s)
- Sonia Borao
- Oxidative Stress and Cell Cycle Group, Universitat Pompeu Fabra, 08003 Barcelona, Spain;
| | - José Ayté
- Oxidative Stress and Cell Cycle Group, Universitat Pompeu Fabra, 08003 Barcelona, Spain;
- Correspondence: (J.A.); (S.H.)
| | - Stefan Hümmer
- Oxidative Stress and Cell Cycle Group, Universitat Pompeu Fabra, 08003 Barcelona, Spain;
- Translational Molecular Pathology, Vall d’Hebron Research Institute (VHIR), CIBERONC, 08035 Barcelona, Spain
- Correspondence: (J.A.); (S.H.)
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22
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Riolo G, Cantara S, Ricci C. What's Wrong in a Jump? Prediction and Validation of Splice Site Variants. Methods Protoc 2021; 4:62. [PMID: 34564308 PMCID: PMC8482176 DOI: 10.3390/mps4030062] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2021] [Revised: 08/27/2021] [Accepted: 09/03/2021] [Indexed: 02/07/2023] Open
Abstract
Alternative splicing (AS) is a crucial process to enhance gene expression driving organism development. Interestingly, more than 95% of human genes undergo AS, producing multiple protein isoforms from the same transcript. Any alteration (e.g., nucleotide substitutions, insertions, and deletions) involving consensus splicing regulatory sequences in a specific gene may result in the production of aberrant and not properly working proteins. In this review, we introduce the key steps of splicing mechanism and describe all different types of genomic variants affecting this process (splicing variants in acceptor/donor sites or branch point or polypyrimidine tract, exonic, and deep intronic changes). Then, we provide an updated approach to improve splice variants detection. First, we review the main computational tools, including the recent Machine Learning-based algorithms, for the prediction of splice site variants, in order to characterize how a genomic variant interferes with splicing process. Next, we report the experimental methods to validate the predictive analyses are defined, distinguishing between methods testing RNA (transcriptomics analysis) or proteins (proteomics experiments). For both prediction and validation steps, benefits and weaknesses of each tool/procedure are accurately reported, as well as suggestions on which approaches are more suitable in diagnostic rather than in clinical research.
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Affiliation(s)
| | | | - Claudia Ricci
- Department of Medical, Surgical and Neurological Sciences, University of Siena, 53100 Siena, Italy; (G.R.); (S.C.)
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23
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Aging, inflammation and DNA damage in the somatic testicular niche with idiopathic germ cell aplasia. Nat Commun 2021; 12:5205. [PMID: 34471128 PMCID: PMC8410861 DOI: 10.1038/s41467-021-25544-0] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2020] [Accepted: 08/18/2021] [Indexed: 12/18/2022] Open
Abstract
Molecular mechanisms associated with human germ cell aplasia in infertile men remain undefined. Here we perform single-cell transcriptome profiling to highlight differentially expressed genes and pathways in each somatic cell type in testes of men with idiopathic germ cell aplasia. We identify immaturity of Leydig cells, chronic tissue inflammation, fibrosis, and senescence phenotype of the somatic cells, as well markers of chronic inflammation in the blood. We find that deregulated expression of parentally imprinted genes in myoid and immature Leydig cells, with relevant changes in the ratio of Lamin A/C transcripts and an active DNA damage response in Leydig and peritubular myoid cells are also indicative of senescence of the testicular niche. This study offers molecular insights into the pathogenesis of idiopathic germ cell aplasia. Molecular mechanisms associated with human germ cell aplasia in infertile men remain undefined. Here the authors perform single-cell transcriptome profiling to highlight differentially expressed genes and pathways in each somatic cell type in testes of men with idiopathic germ cell aplasia.
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24
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The upstream 5' splice site remains associated to the transcription machinery during intron synthesis. Nat Commun 2021; 12:4545. [PMID: 34315864 PMCID: PMC8316553 DOI: 10.1038/s41467-021-24774-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2021] [Accepted: 07/02/2021] [Indexed: 12/28/2022] Open
Abstract
In the earliest step of spliceosome assembly, the two splice sites flanking an intron are brought into proximity by U1 snRNP and U2AF along with other proteins. The mechanism that facilitates this intron looping is poorly understood. Using a CRISPR interference-based approach to halt RNA polymerase II transcription in the middle of introns in human cells, we discovered that the nascent 5′ splice site base pairs with a U1 snRNA that is tethered to RNA polymerase II during intron synthesis. This association functionally corresponds with splicing outcome, involves bona fide 5′ splice sites and cryptic intronic sites, and occurs transcriptome-wide. Overall, our findings reveal that the upstream 5′ splice sites remain attached to the transcriptional machinery during intron synthesis and are thus brought into proximity of the 3′ splice sites; potentially mediating the rapid splicing of long introns. We know that most splicing reactions take place co-transcriptionally, but how the transcription machinery facilitate splicing of introns is unknown. Here the authors show that the 5′ splice site remains associated with the transcription machinery during intron synthesis through U1 snRNP, providing a basis for the rapid splicing reaction of introns.
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25
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Furlan M, de Pretis S, Pelizzola M. Dynamics of transcriptional and post-transcriptional regulation. Brief Bioinform 2021; 22:bbaa389. [PMID: 33348360 PMCID: PMC8294512 DOI: 10.1093/bib/bbaa389] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2020] [Revised: 11/12/2020] [Accepted: 11/27/2020] [Indexed: 02/07/2023] Open
Abstract
Despite gene expression programs being notoriously complex, RNA abundance is usually assumed as a proxy for transcriptional activity. Recently developed approaches, able to disentangle transcriptional and post-transcriptional regulatory processes, have revealed a more complex scenario. It is now possible to work out how synthesis, processing and degradation kinetic rates collectively determine the abundance of each gene's RNA. It has become clear that the same transcriptional output can correspond to different combinations of the kinetic rates. This underscores the fact that markedly different modes of gene expression regulation exist, each with profound effects on a gene's ability to modulate its own expression. This review describes the development of the experimental and computational approaches, including RNA metabolic labeling and mathematical modeling, that have been disclosing the mechanisms underlying complex transcriptional programs. Current limitations and future perspectives in the field are also discussed.
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Affiliation(s)
- Mattia Furlan
- Center for Genomic Science of IIT@SEMM, Fondazione Istituto Italiano di Tecnologia (IIT), 20139 Milan, Italy
| | - Stefano de Pretis
- Center for Genomic Science of IIT@SEMM, Fondazione Istituto Italiano di Tecnologia (IIT), 20139 Milan, Italy
| | - Mattia Pelizzola
- Center for Genomic Science of IIT@SEMM, Fondazione Istituto Italiano di Tecnologia (IIT), 20139 Milan, Italy
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26
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Chanou A, Hamperl S. Single-Molecule Techniques to Study Chromatin. Front Cell Dev Biol 2021; 9:699771. [PMID: 34291054 PMCID: PMC8287188 DOI: 10.3389/fcell.2021.699771] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2021] [Accepted: 05/26/2021] [Indexed: 12/14/2022] Open
Abstract
Besides the basic organization in nucleosome core particles (NCPs), eukaryotic chromatin is further packed through interactions with numerous protein complexes including transcription factors, chromatin remodeling and modifying enzymes. This nucleoprotein complex provides the template for many important biological processes, such as DNA replication, transcription, and DNA repair. Thus, to understand the molecular basis of these DNA transactions, it is critical to define individual changes of the chromatin structure at precise genomic regions where these machineries assemble and drive biological reactions. Single-molecule approaches provide the only possible solution to overcome the heterogenous nature of chromatin and monitor the behavior of individual chromatin transactions in real-time. In this review, we will give an overview of currently available single-molecule methods to obtain mechanistic insights into nucleosome positioning, histone modifications and DNA replication and transcription analysis-previously unattainable with population-based assays.
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Affiliation(s)
| | - Stephan Hamperl
- Chromosome Dynamics and Genome Stability, Institute of Epigenetics and Stem Cells, Helmholtz Zentrum München, Munich, Germany
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27
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Santoliquido BM, Frenquelli M, Contadini C, Bestetti S, Gaviraghi M, Barbieri E, De Antoni A, Albarello L, Amabile A, Gardini A, Lombardo A, Doglioni C, Provero P, Soddu S, Cittaro D, Tonon G. Deletion of a pseudogene within a fragile site triggers the oncogenic expression of the mitotic CCSER1 gene. Life Sci Alliance 2021; 4:4/8/e202101019. [PMID: 34187875 PMCID: PMC8321653 DOI: 10.26508/lsa.202101019] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2021] [Revised: 06/12/2021] [Accepted: 06/14/2021] [Indexed: 11/24/2022] Open
Abstract
The oncogenic role of common fragile sites (CFS), focal and pervasive gaps in the cancer genome arising from replicative stress, remains controversial. Exploiting the TCGA dataset, we found that in most CFS the genes residing within the associated focal deletions are down-regulated, including proteins involved in tumour immune recognition. In a subset of CFS, however, the residing genes are surprisingly overexpressed. Within the most frequent CFS in this group, FRA4F, which is deleted in up to 18% of cancer cases and harbours the CCSER1 gene, we identified a region which includes an intronic, antisense pseudogene, TMSB4XP8. TMSB4XP8 focal ablation or transcriptional silencing elicits the overexpression of CCSER1, through a cis-acting mechanism. CCSER1 overexpression increases proliferation and triggers centrosome amplifications, multinuclearity, and aberrant mitoses. Accordingly, FRA4F is associated in patient samples to mitotic genes deregulation and genomic instability. As a result, cells overexpressing CCSER1 become sensitive to the treatment with aurora kinase inhibitors. Our findings point to a novel tumourigenic mechanism where focal deletions increase the expression of a new class of "dormant" oncogenes.
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Affiliation(s)
- Benedetta M Santoliquido
- Functional Genomics of Cancer Unit, Division of Experimental Oncology, Istituti di Ricovero e Cura a Carattere Scientifico (IRCCS) San Raffaele Scientific Institute, Milan, Italy.,Vita-Salute San Raffaele University, Milan, Italy
| | - Michela Frenquelli
- Functional Genomics of Cancer Unit, Division of Experimental Oncology, Istituti di Ricovero e Cura a Carattere Scientifico (IRCCS) San Raffaele Scientific Institute, Milan, Italy
| | - Claudia Contadini
- Unit of Cellular Networks and Molecular Therapeutic Targets, IRCCS-Regina Elena National Cancer Institute, Rome, Italy
| | - Stefano Bestetti
- Protein Transport and Secretion Unit, Division of Genetics and Cell Biology, IRCCS San Raffaele Scientific Institute, Milan, Italy
| | - Marco Gaviraghi
- Functional Genomics of Cancer Unit, Division of Experimental Oncology, Istituti di Ricovero e Cura a Carattere Scientifico (IRCCS) San Raffaele Scientific Institute, Milan, Italy
| | - Elisa Barbieri
- The Wistar Institute, Gene Expression and Regulation Program, Philadelphia, PA, USA
| | - Anna De Antoni
- DNA Metabolism Laboratory, IFOM-The Firc Institute of Molecular Oncology, Milan, Italy
| | - Luca Albarello
- Pathology Unit, IRCCS San Raffaele Scientific Institute, Milan, Italy
| | - Angelo Amabile
- Vita-Salute San Raffaele University, Milan, Italy.,San Raffaele Telethon Institute for Gene Therapy (SR-Tiget), IRCCS San Raffaele Scientific Institute, Milan, Italy
| | - Alessandro Gardini
- The Wistar Institute, Gene Expression and Regulation Program, Philadelphia, PA, USA
| | - Angelo Lombardo
- Vita-Salute San Raffaele University, Milan, Italy.,San Raffaele Telethon Institute for Gene Therapy (SR-Tiget), IRCCS San Raffaele Scientific Institute, Milan, Italy
| | - Claudio Doglioni
- Vita-Salute San Raffaele University, Milan, Italy.,Pathology Unit, IRCCS San Raffaele Scientific Institute, Milan, Italy
| | - Paolo Provero
- Center for Omics Sciences, IRCCS San Raffaele Scientific Institute, Milan, Italy.,Department of Neurosciences "Rita Levi Montalcini," University of Torino, Turin, Italy
| | - Silvia Soddu
- Unit of Cellular Networks and Molecular Therapeutic Targets, IRCCS-Regina Elena National Cancer Institute, Rome, Italy
| | - Davide Cittaro
- Center for Omics Sciences, IRCCS San Raffaele Scientific Institute, Milan, Italy
| | - Giovanni Tonon
- Functional Genomics of Cancer Unit, Division of Experimental Oncology, Istituti di Ricovero e Cura a Carattere Scientifico (IRCCS) San Raffaele Scientific Institute, Milan, Italy .,Center for Omics Sciences, IRCCS San Raffaele Scientific Institute, Milan, Italy
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28
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Caizzi L, Monteiro-Martins S, Schwalb B, Lysakovskaia K, Schmitzova J, Sawicka A, Chen Y, Lidschreiber M, Cramer P. Efficient RNA polymerase II pause release requires U2 snRNP function. Mol Cell 2021; 81:1920-1934.e9. [PMID: 33689748 DOI: 10.1016/j.molcel.2021.02.016] [Citation(s) in RCA: 33] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2020] [Revised: 01/07/2021] [Accepted: 02/10/2021] [Indexed: 12/21/2022]
Abstract
Transcription by RNA polymerase II (Pol II) is coupled to pre-mRNA splicing, but the underlying mechanisms remain poorly understood. Co-transcriptional splicing requires assembly of a functional spliceosome on nascent pre-mRNA, but whether and how this influences Pol II transcription remains unclear. Here we show that inhibition of pre-mRNA branch site recognition by the spliceosome component U2 snRNP leads to a widespread and strong decrease in new RNA synthesis from human genes. Multiomics analysis reveals that inhibition of U2 snRNP function increases the duration of Pol II pausing in the promoter-proximal region, impairs recruitment of the pause release factor P-TEFb, and reduces Pol II elongation velocity at the beginning of genes. Our results indicate that efficient release of paused Pol II into active transcription elongation requires the formation of functional spliceosomes and that eukaryotic mRNA biogenesis relies on positive feedback from the splicing machinery to the transcription machinery.
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Affiliation(s)
- Livia Caizzi
- Department of Molecular Biology, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
| | - Sara Monteiro-Martins
- Department of Molecular Biology, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
| | - Björn Schwalb
- Department of Molecular Biology, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
| | - Kseniia Lysakovskaia
- Department of Molecular Biology, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
| | - Jana Schmitzova
- Department of Molecular Biology, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
| | - Anna Sawicka
- Department of Molecular Biology, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
| | - Ying Chen
- Department of Molecular Biology, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
| | - Michael Lidschreiber
- Department of Molecular Biology, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
| | - Patrick Cramer
- Department of Molecular Biology, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany.
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29
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Drexler HL, Choquet K, Merens HE, Tang PS, Simpson JT, Churchman LS. Revealing nascent RNA processing dynamics with nano-COP. Nat Protoc 2021; 16:1343-1375. [PMID: 33514943 PMCID: PMC8713461 DOI: 10.1038/s41596-020-00469-y] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2020] [Accepted: 11/20/2020] [Indexed: 01/30/2023]
Abstract
During maturation, eukaryotic precursor RNAs undergo processing events including intron splicing, 3'-end cleavage, and polyadenylation. Here we describe nanopore analysis of co-transcriptional processing (nano-COP), a method for probing the timing and patterns of RNA processing. An extension of native elongating transcript sequencing, which quantifies transcription genome-wide through short-read sequencing of nascent RNA 3' ends, nano-COP uses long-read nascent RNA sequencing to observe global patterns of RNA processing. First, nascent RNA is stringently purified through a combination of 4-thiouridine metabolic labeling and cellular fractionation. In contrast to cDNA or short-read-based approaches relying on reverse transcription or amplification, the sample is sequenced directly through nanopores to reveal the native context of nascent RNA. nano-COP identifies both active transcription sites and splice isoforms of single RNA molecules during synthesis, providing insight into patterns of intron removal and the physical coupling between transcription and splicing. The nano-COP protocol yields data within 3 d.
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Affiliation(s)
- Heather L. Drexler
- Department of Genetics, Harvard Medical School, Boston, Massachusetts, USA
| | - Karine Choquet
- Department of Genetics, Harvard Medical School, Boston, Massachusetts, USA
| | - Hope E. Merens
- Department of Genetics, Harvard Medical School, Boston, Massachusetts, USA
| | - Paul S. Tang
- Ontario Institute for Cancer Research, Toronto, Ontario, Canada
| | - Jared T. Simpson
- Ontario Institute for Cancer Research and Department of Computer Science, University of Toronto, Toronto, Ontario, Canada
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30
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Blumberg A, Zhao Y, Huang YF, Dukler N, Rice EJ, Chivu AG, Krumholz K, Danko CG, Siepel A. Characterizing RNA stability genome-wide through combined analysis of PRO-seq and RNA-seq data. BMC Biol 2021; 19:30. [PMID: 33588838 PMCID: PMC7885420 DOI: 10.1186/s12915-021-00949-x] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2020] [Accepted: 01/05/2021] [Indexed: 01/03/2023] Open
Abstract
BACKGROUND The concentrations of distinct types of RNA in cells result from a dynamic equilibrium between RNA synthesis and decay. Despite the critical importance of RNA decay rates, current approaches for measuring them are generally labor-intensive, limited in sensitivity, and/or disruptive to normal cellular processes. Here, we introduce a simple method for estimating relative RNA half-lives that is based on two standard and widely available high-throughput assays: Precision Run-On sequencing (PRO-seq) and RNA sequencing (RNA-seq). RESULTS Our method treats PRO-seq as a measure of transcription rate and RNA-seq as a measure of RNA concentration, and estimates the rate of RNA decay required for a steady-state equilibrium. We show that this approach can be used to assay relative RNA half-lives genome-wide, with good accuracy and sensitivity for both coding and noncoding transcription units. Using a structural equation model (SEM), we test several features of transcription units, nearby DNA sequences, and nearby epigenomic marks for associations with RNA stability after controlling for their effects on transcription. We find that RNA splicing-related features are positively correlated with RNA stability, whereas features related to miRNA binding and DNA methylation are negatively correlated with RNA stability. Furthermore, we find that a measure based on U1 binding and polyadenylation sites distinguishes between unstable noncoding and stable coding transcripts but is not predictive of relative stability within the mRNA or lincRNA classes. We also identify several histone modifications that are associated with RNA stability. CONCLUSION We introduce an approach for estimating the relative half-lives of individual RNAs. Together, our estimation method and systematic analysis shed light on the pervasive impacts of RNA stability on cellular RNA concentrations.
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Affiliation(s)
- Amit Blumberg
- Simons Center for Quantitative Biology, Cold Spring Harbor Laboratory, Cold Spring Harbor, NY, USA
| | - Yixin Zhao
- Simons Center for Quantitative Biology, Cold Spring Harbor Laboratory, Cold Spring Harbor, NY, USA
| | - Yi-Fei Huang
- Simons Center for Quantitative Biology, Cold Spring Harbor Laboratory, Cold Spring Harbor, NY, USA
- Present Address: Department of Biology and Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, PA, USA
| | - Noah Dukler
- Simons Center for Quantitative Biology, Cold Spring Harbor Laboratory, Cold Spring Harbor, NY, USA
| | - Edward J Rice
- Baker Institute for Animal Health, College of Veterinary Medicine, Cornell University, Ithaca, NY, USA
| | - Alexandra G Chivu
- Baker Institute for Animal Health, College of Veterinary Medicine, Cornell University, Ithaca, NY, USA
| | - Katie Krumholz
- Simons Center for Quantitative Biology, Cold Spring Harbor Laboratory, Cold Spring Harbor, NY, USA
| | - Charles G Danko
- Baker Institute for Animal Health, College of Veterinary Medicine, Cornell University, Ithaca, NY, USA
| | - Adam Siepel
- Simons Center for Quantitative Biology, Cold Spring Harbor Laboratory, Cold Spring Harbor, NY, USA.
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31
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Sawicka A, Villamil G, Lidschreiber M, Darzacq X, Dugast-Darzacq C, Schwalb B, Cramer P. Transcription activation depends on the length of the RNA polymerase II C-terminal domain. EMBO J 2021; 40:e107015. [PMID: 33555055 PMCID: PMC8090853 DOI: 10.15252/embj.2020107015] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2020] [Revised: 01/04/2021] [Accepted: 01/13/2021] [Indexed: 01/02/2023] Open
Abstract
Eukaryotic RNA polymerase II (Pol II) contains a tail‐like, intrinsically disordered carboxy‐terminal domain (CTD) comprised of heptad‐repeats, that functions in coordination of the transcription cycle and in coupling transcription to co‐transcriptional processes. The CTD repeat number varies between species and generally increases with genome size, but the reasons for this are unclear. Here, we show that shortening the CTD in human cells to half of its length does not generally change pre‐mRNA synthesis or processing in cells. However, CTD shortening decreases the duration of promoter‐proximal Pol II pausing, alters transcription of putative enhancer elements, and delays transcription activation after stimulation of the MAP kinase pathway. We suggest that a long CTD is required for efficient enhancer‐dependent recruitment of Pol II to target genes for their rapid activation.
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Affiliation(s)
- Anna Sawicka
- Department of Molecular Biology, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Gabriel Villamil
- Department of Molecular Biology, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Michael Lidschreiber
- Department of Molecular Biology, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Xavier Darzacq
- Department of Molecular and Cell Biology, University of California, Berkeley, CA, USA.,CIRM Center of Excellence, University of California, Berkeley, CA, USA
| | - Claire Dugast-Darzacq
- Department of Molecular and Cell Biology, University of California, Berkeley, CA, USA.,CIRM Center of Excellence, University of California, Berkeley, CA, USA
| | - Björn Schwalb
- Department of Molecular Biology, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Patrick Cramer
- Department of Molecular Biology, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
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32
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Tellier M, Maudlin I, Murphy S. Transcription and splicing: A two-way street. WILEY INTERDISCIPLINARY REVIEWS. RNA 2020; 11:e1593. [PMID: 32128990 DOI: 10.1002/wrna.1593] [Citation(s) in RCA: 46] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/22/2019] [Revised: 12/18/2019] [Accepted: 02/12/2020] [Indexed: 12/11/2022]
Abstract
RNA synthesis by RNA polymerase II and RNA processing are closely coupled during the transcription cycle of protein-coding genes. This coupling affords opportunities for quality control and regulation of gene expression and the effects can go in both directions. For example, polymerase speed can affect splice site selection and splicing can increase transcription and affect the chromatin landscape. Here we review the many ways that transcription and splicing influence one another, including how splicing "talks back" to transcription. We will also place the connections between transcription and splicing in the context of other RNA processing events that define the exons that will make up the final mRNA. This article is categorized under: RNA Processing > Splicing Mechanisms RNA Processing > Splicing Regulation/Alternative Splicing.
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Affiliation(s)
- Michael Tellier
- Sir William Dunn School of Pathology, University of Oxford, Oxford, UK
| | - Isabella Maudlin
- Sir William Dunn School of Pathology, University of Oxford, Oxford, UK
| | - Shona Murphy
- Sir William Dunn School of Pathology, University of Oxford, Oxford, UK
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33
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Taylor K, Sobczak K. Intrinsic Regulatory Role of RNA Structural Arrangement in Alternative Splicing Control. Int J Mol Sci 2020; 21:ijms21145161. [PMID: 32708277 PMCID: PMC7404189 DOI: 10.3390/ijms21145161] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2020] [Accepted: 07/17/2020] [Indexed: 12/14/2022] Open
Abstract
Alternative splicing is a highly sophisticated process, playing a significant role in posttranscriptional gene expression and underlying the diversity and complexity of organisms. Its regulation is multilayered, including an intrinsic role of RNA structural arrangement which undergoes time- and tissue-specific alterations. In this review, we describe the principles of RNA structural arrangement and briefly decipher its cis- and trans-acting cellular modulators which serve as crucial determinants of biological functionality of the RNA structure. Subsequently, we engage in a discussion about the RNA structure-mediated mechanisms of alternative splicing regulation. On one hand, the impairment of formation of optimal RNA structures may have critical consequences for the splicing outcome and further contribute to understanding the pathomechanism of severe disorders. On the other hand, the structural aspects of RNA became significant features taken into consideration in the endeavor of finding potential therapeutic treatments. Both aspects have been addressed by us emphasizing the importance of ongoing studies in both fields.
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34
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Turowski TW, Petfalski E, Goddard BD, French SL, Helwak A, Tollervey D. Nascent Transcript Folding Plays a Major Role in Determining RNA Polymerase Elongation Rates. Mol Cell 2020; 79:488-503.e11. [PMID: 32585128 PMCID: PMC7427326 DOI: 10.1016/j.molcel.2020.06.002] [Citation(s) in RCA: 40] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2020] [Revised: 05/01/2020] [Accepted: 05/28/2020] [Indexed: 12/15/2022]
Abstract
Transcription elongation rates influence RNA processing, but sequence-specific regulation is poorly understood. We addressed this in vivo, analyzing RNAPI in S. cerevisiae. Mapping RNAPI by Miller chromatin spreads or UV crosslinking revealed 5' enrichment and strikingly uneven local polymerase occupancy along the rDNA, indicating substantial variation in transcription speed. Two features of the nascent transcript correlated with RNAPI distribution: folding energy and GC content in the transcription bubble. In vitro experiments confirmed that strong RNA structures close to the polymerase promote forward translocation and limit backtracking, whereas high GC in the transcription bubble slows elongation. A mathematical model for RNAPI elongation confirmed the importance of nascent RNA folding in transcription. RNAPI from S. pombe was similarly sensitive to transcript folding, as were S. cerevisiae RNAPII and RNAPIII. For RNAPII, unstructured RNA, which favors slowed elongation, was associated with faster cotranscriptional splicing and proximal splice site use, indicating regulatory significance for transcript folding.
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Affiliation(s)
- Tomasz W Turowski
- Wellcome Centre for Cell Biology, The University of Edinburgh, Edinburgh, UK.
| | - Elisabeth Petfalski
- Wellcome Centre for Cell Biology, The University of Edinburgh, Edinburgh, UK
| | - Benjamin D Goddard
- School of Mathematics and Maxwell Institute for Mathematical Sciences, The University of Edinburgh, Edinburgh, UK
| | - Sarah L French
- Department of Microbiology, Immunology, and Cancer Biology, University of Virginia, Charlottesville, VA, USA
| | - Aleksandra Helwak
- Wellcome Centre for Cell Biology, The University of Edinburgh, Edinburgh, UK
| | - David Tollervey
- Wellcome Centre for Cell Biology, The University of Edinburgh, Edinburgh, UK.
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35
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Furlan M, Tanaka I, Leonardi T, de Pretis S, Pelizzola M. Direct RNA Sequencing for the Study of Synthesis, Processing, and Degradation of Modified Transcripts. Front Genet 2020; 11:394. [PMID: 32425981 PMCID: PMC7212349 DOI: 10.3389/fgene.2020.00394] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2019] [Accepted: 03/30/2020] [Indexed: 01/24/2023] Open
Abstract
It has been known for a few decades that transcripts can be marked by dozens of different modifications. Yet, we are just at the beginning of charting these marks and understanding their functional impact. High-quality methods were developed for the profiling of some of these marks, and approaches to finely study their impact on specific phases of the RNA life-cycle are available, including RNA metabolic labeling. Thanks to these improvements, the most abundant marks, including N6-methyladenosine, are emerging as important determinants of the fate of marked RNAs. However, we still lack approaches to directly study how the set of marks for a given RNA molecule shape its fate. In this perspective, we first review current leading approaches in the field. Then, we propose an experimental and computational setup, based on direct RNA sequencing and mathematical modeling, to decipher the functional consequences of RNA modifications on the fate of individual RNA molecules and isoforms.
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Affiliation(s)
- Mattia Furlan
- Center for Genomic Science, Istituto Italiano di Tecnologia, Milan, Italy
- Department of Physics, National Institute of Nuclear Physics, University of Turin, Turin, Italy
| | - Iris Tanaka
- Center for Genomic Science, Istituto Italiano di Tecnologia, Milan, Italy
| | - Tommaso Leonardi
- Center for Genomic Science, Istituto Italiano di Tecnologia, Milan, Italy
| | - Stefano de Pretis
- Center for Genomic Science, Istituto Italiano di Tecnologia, Milan, Italy
| | - Mattia Pelizzola
- Center for Genomic Science, Istituto Italiano di Tecnologia, Milan, Italy
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36
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Drexler HL, Choquet K, Churchman LS. Splicing Kinetics and Coordination Revealed by Direct Nascent RNA Sequencing through Nanopores. Mol Cell 2020; 77:985-998.e8. [PMID: 31839405 PMCID: PMC7060811 DOI: 10.1016/j.molcel.2019.11.017] [Citation(s) in RCA: 106] [Impact Index Per Article: 26.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2019] [Revised: 09/17/2019] [Accepted: 11/18/2019] [Indexed: 02/06/2023]
Abstract
Understanding how splicing events are coordinated across numerous introns in metazoan RNA transcripts requires quantitative analyses of transient RNA processing events in living cells. We developed nanopore analysis of co-transcriptional processing (nano-COP), in which nascent RNAs are directly sequenced through nanopores, exposing the dynamics and patterns of RNA splicing without biases introduced by amplification. Long nano-COP reads reveal that, in human and Drosophila cells, splicing occurs after RNA polymerase II transcribes several kilobases of pre-mRNA, suggesting that metazoan splicing transpires distally from the transcription machinery. Inhibition of the branch-site recognition complex SF3B rapidly diminished global co-transcriptional splicing. We found that splicing order does not strictly follow the order of transcription and is associated with cis-acting elements, alternative splicing, and RNA-binding factors. Further, neighboring introns in human cells tend to be spliced concurrently, implying that splicing of these introns occurs cooperatively. Thus, nano-COP unveils the organizational complexity of RNA processing.
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Affiliation(s)
- Heather L Drexler
- Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, MA 02115, USA
| | - Karine Choquet
- Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, MA 02115, USA
| | - L Stirling Churchman
- Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, MA 02115, USA.
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37
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Gregersen LH, Mitter R, Svejstrup JQ. Using TT chem-seq for profiling nascent transcription and measuring transcript elongation. Nat Protoc 2020; 15:604-627. [PMID: 31915390 DOI: 10.1038/s41596-019-0262-3] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2019] [Accepted: 10/29/2019] [Indexed: 01/08/2023]
Abstract
The dynamics of transcription can be studied genome wide by high-throughput sequencing of nascent and newly synthesized RNA. 4-thiouridine (4SU) labeling in vivo enables the specific capture of such new transcripts, with 4SU residues being tagged by biotin linkers and captured using streptavidin beads before library production and high-throughput sequencing. To achieve high-resolution profiles of transcribed regions, an RNA fragmentation step before biotin tagging was introduced, in an approach known as transient transcriptome sequencing (TT-seq). We recently introduced a chemical approach for RNA fragmentation that we refer to as TTchem-seq. We describe how TTchem-seq can be used in combination with transient inhibition of early elongation using the reversible CDK9 inhibitor, 5,6-dichlorobenzimidazole 1-β-D-ribofuranoside (DRB), to measure RNA polymerase II (RNAPII) elongation rates in vivo, a technique we call DRB/TTchem-seq. Here, we provide detailed protocols for carrying out TTchem-seq and DRB/TTchem-seq, including computational analysis. Experiments and data analysis can be performed over a period of 10-13 d and require molecular biology and bioinformatics skills.
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Affiliation(s)
- Lea H Gregersen
- Mechanisms of Transcription Laboratory, The Francis Crick Institute, London, UK
| | - Richard Mitter
- Bioinformatics and Biostatistics, The Francis Crick Institute, London, UK
| | - Jesper Q Svejstrup
- Mechanisms of Transcription Laboratory, The Francis Crick Institute, London, UK.
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38
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Wachutka L, Caizzi L, Gagneur J, Cramer P. Global donor and acceptor splicing site kinetics in human cells. eLife 2019; 8:45056. [PMID: 31025937 PMCID: PMC6548502 DOI: 10.7554/elife.45056] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2019] [Accepted: 04/25/2019] [Indexed: 11/13/2022] Open
Abstract
RNA splicing is an essential part of eukaryotic gene expression. Although the mechanism of splicing has been extensively studied in vitro, in vivo kinetics for the two-step splicing reaction remain poorly understood. Here, we combine transient transcriptome sequencing (TT-seq) and mathematical modeling to quantify RNA metabolic rates at donor and acceptor splice sites across the human genome. Splicing occurs in the range of minutes and is limited by the speed of RNA polymerase elongation. Splicing kinetics strongly depends on the position and nature of nucleotides flanking splice sites, and on structural interactions between unspliced RNA and small nuclear RNAs in spliceosomal intermediates. Finally, we introduce the 'yield' of splicing as the efficiency of converting unspliced to spliced RNA and show that it is highest for mRNAs and independent of splicing kinetics. These results lead to quantitative models describing how splicing rates and yield are encoded in the human genome.
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Affiliation(s)
- Leonhard Wachutka
- Department of Informatics, Technical University of Munich, Garching, Germany
| | - Livia Caizzi
- Department of Molecular Biology, Max-Planck-Institute for Biophysical Chemistry, Göttingen, Germany
| | - Julien Gagneur
- Department of Informatics, Technical University of Munich, Garching, Germany
| | - Patrick Cramer
- Department of Molecular Biology, Max-Planck-Institute for Biophysical Chemistry, Göttingen, Germany
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