1
|
Camargo de Lima J, Floriani MA, Debarba JA, Paludo GP, Monteiro KM, Moura H, Barr JR, Zaha A, Ferreira HB. Dynamics of protein synthesis in the initial steps of strobilation in the model cestode parasite Mesocestoides corti (syn. vogae). J Proteomics 2020; 228:103939. [PMID: 32798775 PMCID: PMC10491476 DOI: 10.1016/j.jprot.2020.103939] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2020] [Revised: 08/05/2020] [Accepted: 08/10/2020] [Indexed: 01/24/2023]
Abstract
Mesocestoides corti (syn. vogae) is a useful model for developmental studies of platyhelminth parasites of the Cestoda class, such as Taenia spp. or Echinococcus spp. It has been used in studies to characterize cestode strobilation, i.e. the development of larvae into adult worms. So far, little is known about the initial molecular events involved in cestode strobilation and, therefore, we carried out a study to characterize newly synthesized (NS) proteins upon strobilation induction. An approach based on bioorthogonal noncanonical amino acid tagging and mass spectrometry was used to label, isolate, identify, and quantify NS proteins in the initial steps of M. corti strobilation. Overall, 121 NS proteins were detected exclusively after induction of strobilation, including proteins related to development pathways, such as insulin and notch signaling. Metabolic changes that take place in the transition from the larval stage to adult worm were noted in special NS protein subsets related to developmental processes, such as focal adhesion, cell leading edge, and maintenance of location. The data shed light on mechanisms underlying early steps of cestode strobilation and enabled identification of possible developmental markers. We also consider the use of developmental responsive proteins as potential drug targets for developing novel anthelmintics. BIOLOGICAL SIGNIFICANCE: Larval cestodiases are life-threatening parasitic diseases that affect both man and domestic animals worldwide. Cestode parasites present complex life cycles, in which they undergo major morphological and physiological changes in the transition from one life-stage to the next. One of these transitions occurs during cestode strobilation, when the mostly undifferentiated and non-segmented larval or pre-adult form develops into a fully segmented and sexually differentiated (strobilated) adult worm. Although the proteomes of bona fide larvae and strobialted adults have been previously characterized for a few cestode species, little is still known about the dynamic of protein synthesis during the early steps of cestode strobilation. Now, the assessment of newly synthesized (NS) proteins within the first 48 h of strobilation the model cestode M. corti allowed to shed light on molecular mechanisms that are triggered by strobilation induction. The functional analyses of this repertoire of over a hundred NS proteins pointed out to changes in metabolism and activation of classical developmental signaling pathways in early strobilation. Many of the identified NS proteins may become valuable cestode developmental markers and their involvement in vital processes make them also good candidate targets for novel anthelmintic drugs.
Collapse
Affiliation(s)
- Jeferson Camargo de Lima
- Programa de Pós-Graduação em Biologia Molecular e Celular, Centro de Biotecnologia, Universidade Federal do Rio Grande do Sul (UFRGS), Brazil; Laboratório de Genômica Estrutural e Funcional, Centro de Biotecnologia, UFRGS, Porto Alegre, RS, Brazil
| | - Maiara Anschau Floriani
- Laboratório de Genômica Estrutural e Funcional, Centro de Biotecnologia, UFRGS, Porto Alegre, RS, Brazil
| | - João Antônio Debarba
- Programa de Pós-Graduação em Biologia Molecular e Celular, Centro de Biotecnologia, Universidade Federal do Rio Grande do Sul (UFRGS), Brazil; Laboratório de Biologia Molecular de Cestódeos, Centro de Biotecnologia, UFRGS, Porto Alegre, RS, Brazil
| | - Gabriela Prado Paludo
- Programa de Pós-Graduação em Biologia Molecular e Celular, Centro de Biotecnologia, Universidade Federal do Rio Grande do Sul (UFRGS), Brazil; Laboratório de Genômica Estrutural e Funcional, Centro de Biotecnologia, UFRGS, Porto Alegre, RS, Brazil
| | - Karina Mariante Monteiro
- Programa de Pós-Graduação em Biologia Molecular e Celular, Centro de Biotecnologia, Universidade Federal do Rio Grande do Sul (UFRGS), Brazil; Laboratório de Genômica Estrutural e Funcional, Centro de Biotecnologia, UFRGS, Porto Alegre, RS, Brazil; Laboratório de Biologia Molecular de Cestódeos, Centro de Biotecnologia, UFRGS, Porto Alegre, RS, Brazil
| | - Hercules Moura
- Biological Mass Spectrometry Laboratory, Clinical Chemistry Branch, Division of Laboratory Sciences, National Center for Environmental Health, Centers for Disease Control and Prevention, Atlanta, GA, United States of America
| | - John R Barr
- Biological Mass Spectrometry Laboratory, Clinical Chemistry Branch, Division of Laboratory Sciences, National Center for Environmental Health, Centers for Disease Control and Prevention, Atlanta, GA, United States of America
| | - Arnaldo Zaha
- Programa de Pós-Graduação em Biologia Molecular e Celular, Centro de Biotecnologia, Universidade Federal do Rio Grande do Sul (UFRGS), Brazil; Laboratório de Biologia Molecular de Cestódeos, Centro de Biotecnologia, UFRGS, Porto Alegre, RS, Brazil
| | - Henrique Bunselmeyer Ferreira
- Programa de Pós-Graduação em Biologia Molecular e Celular, Centro de Biotecnologia, Universidade Federal do Rio Grande do Sul (UFRGS), Brazil; Laboratório de Genômica Estrutural e Funcional, Centro de Biotecnologia, UFRGS, Porto Alegre, RS, Brazil; Laboratório de Biologia Molecular de Cestódeos, Centro de Biotecnologia, UFRGS, Porto Alegre, RS, Brazil.
| |
Collapse
|
2
|
Bondos SE, Geraldo Mendes G, Jons A. Context-dependent HOX transcription factor function in health and disease. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2020; 174:225-262. [PMID: 32828467 DOI: 10.1016/bs.pmbts.2020.05.003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
During animal development, HOX transcription factors determine the fate of developing tissues to generate diverse organs and appendages. The power of these proteins is striking: mis-expressing a HOX protein causes homeotic transformation of one body part into another. During development, HOX proteins interpret their cellular context through protein interactions, alternative splicing, and post-translational modifications to regulate cell proliferation, cell death, cell migration, cell differentiation, and angiogenesis. Although mutation and/or mis-expression of HOX proteins during development can be lethal, changes in HOX proteins that do not pattern vital organs can result in survivable malformations. In adults, mutation and/or mis-expression of HOX proteins disrupts their gene regulatory networks, deregulating cell behaviors and leading to arthritis and cancer. On the molecular level, HOX proteins are composed of DNA binding homeodomain, and large regions of unstructured, or intrinsically disordered, protein sequence. The primary roles of HOX proteins in arthritis and cancer suggest that mutations associated with these diseases in both the structured and disordered regions of HOX proteins can have substantial functional effects. These insights lead to new questions critical for understanding and manipulating HOX function in physiological and pathological conditions.
Collapse
Affiliation(s)
- Sarah E Bondos
- Department of Molecular and Cellular Medicine, Texas A&M University, College Station, TX, United States.
| | - Gabriela Geraldo Mendes
- Department of Molecular and Cellular Medicine, Texas A&M University, College Station, TX, United States
| | - Amanda Jons
- Department of Molecular and Cellular Medicine, Texas A&M University, College Station, TX, United States
| |
Collapse
|
3
|
Banerjee A, Percival-Smith A. Post-translational modifications of Drosophila melanogaster HOX protein, Sex combs reduced. PLoS One 2020; 15:e0227642. [PMID: 31931520 PMCID: PMC6957346 DOI: 10.1371/journal.pone.0227642] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2019] [Accepted: 12/23/2019] [Indexed: 11/23/2022] Open
Abstract
Homeotic selector (HOX) transcription factors (TFs) regulate gene expression that determines the identity of Drosophila segments along the anterior-posterior (A-P) axis. The current challenge with HOX proteins is understanding how they achieve their functional specificity while sharing a highly conserved homeodomain (HD) that recognize the same DNA binding sites. One mechanism proposed to regulate HOX activity is differential post-translational modification (PTM). As a first step in investigating this hypothesis, the sites of PTM on a Sex combs reduced protein fused to a triple tag (SCRTT) extracted from developing embryos were identified by Tandem Mass Spectrometry (MS/MS). The PTMs identified include phosphorylation at S185, S201, T315, S316, T317 and T324, acetylation at K218, S223, S227, K309, K434 and K439, formylation at K218, K309, K325, K341, K369, K434 and K439, methylation at S19, S166, K168 and T364, carboxylation at D108, K298, W307, K309, E323, K325 and K369, and hydroxylation at P22, Y87, P107, D108, D111, P269, P306, R310, N321, K325, Y334, R366, P392 and Y398. Of the 44 modifications, 18 map to functionally important regions of SCR. Besides a highly conserved DNA-binding HD, HOX proteins also have functionally important, evolutionarily conserved small motifs, which may be Short Linear Motifs (SLiMs). SLiMs are proposed to be preferential sites of phosphorylation. Although 6 of 7 phosphosites map to regions of predicted SLiMs, we find no support for the hypothesis that the individual S, T and Y residues of predicted SLiMs are phosphorylated more frequently than S, T and Y residues outside of predicted SLiMs.
Collapse
Affiliation(s)
- Anirban Banerjee
- Department of Biology, The University of Western Ontario, London, Ontario, Canada
- * E-mail:
| | | |
Collapse
|
4
|
Primon M, Hunter KD, Pandha HS, Morgan R. Kinase Regulation of HOX Transcription Factors. Cancers (Basel) 2019; 11:cancers11040508. [PMID: 30974835 PMCID: PMC6521248 DOI: 10.3390/cancers11040508] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2019] [Revised: 04/02/2019] [Accepted: 04/07/2019] [Indexed: 01/03/2023] Open
Abstract
The HOX genes are a group of homeodomain-containing transcription factors that play important regulatory roles in early development, including the establishment of cell and tissue identity. HOX expression is generally reduced in adult cells but is frequently re-established as an early event in tumour formation and supports an oncogenic phenotype. HOX transcription factors are also involved in cell cycle regulation and DNA repair, along with normal adult physiological process including stem cell renewal. There have been extensive studies on the mechanism by which HOX proteins regulate transcription, with particular emphasis on their interaction with cofactors such as Pre-B-cell Leukaemia Homeobox (PBX) and Myeloid Ecotropic Viral Integration Site 1 (MEIS). However, significantly less is known of how the activity of HOX proteins is regulated. There is growing evidence that phosphorylation may play an important role in this context, and in this review, we draw together a number of important studies published over the last 20 years, and discuss the relevance of phosphorylation in the regulation and function of HOX proteins in development, evolution, cell cycle regulation, and cancer.
Collapse
Affiliation(s)
- Monika Primon
- Institute of Cancer Therapeutics, Faculty of Life Sciences, University of Bradford, Bradford BD7 1DP, UK.
| | - Keith D Hunter
- Unit of Oral and Maxillofacial Pathology, School of Clinical Dentistry, University of Sheffield, Sheffield S10 2TN, UK.
| | - Hardev S Pandha
- Faculty of Health and Medical Sciences, University of Surrey, Guildford GU2 7XH, UK.
| | - Richard Morgan
- Institute of Cancer Therapeutics, Faculty of Life Sciences, University of Bradford, Bradford BD7 1DP, UK.
| |
Collapse
|
5
|
Yamamoto S, Uchida Y, Ohtani T, Nozaki E, Yin C, Gotoh Y, Yakushiji-Kaminatsui N, Higashiyama T, Suzuki T, Takemoto T, Shiraishi YI, Kuroiwa A. Hoxa13 regulates expression of common Hox target genes involved in cartilage development to coordinate the expansion of the autopodal anlage. Dev Growth Differ 2019; 61:228-251. [PMID: 30895612 PMCID: PMC6850407 DOI: 10.1111/dgd.12601] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2018] [Revised: 01/22/2019] [Accepted: 01/23/2019] [Indexed: 02/04/2023]
Abstract
To elucidate the role of Hox genes in limb cartilage development, we identified the target genes of HOXA11 and HOXA13 by ChIP‐Seq. The ChIP DNA fragment contained evolutionarily conserved sequences and multiple highly conserved HOX binding sites. A substantial portion of the HOXA11 ChIP fragment overlapped with the HOXA13 ChIP fragment indicating that both factors share common targets. Deletion of the target regions neighboring Bmp2 or Tshz2 reduced their expression in the autopod suggesting that they function as the limb bud‐specific enhancers. We identified the Hox downstream genes as exhibiting expression changes in the Hoxa13 knock out (KO) and Hoxd11‐13 deletion double mutant (Hox13 dKO) autopod by Genechip analysis. The Hox downstream genes neighboring the ChIP fragment were defined as the direct targets of Hox. We analyzed the spatial expression pattern of the Hox target genes that encode two different categories of transcription factors during autopod development and Hox13dKO limb bud. (a) Bcl11a, encoding a repressor of cartilage differentiation, was expressed in the E11.5 autopod and was substantially reduced in the Hox13dKO. (b) The transcription factors Aff3, Bnc2, Nfib and Runx1t1 were expressed in the zeugopodal cartilage but not in the autopod due to the repressive or relatively weak transcriptional activity of Hox13 at E11.5. Interestingly, the expression of these genes was later observed in the autopodal cartilage at E12.5. These results indicate that Hox13 transiently suspends the cartilage differentiation in the autopodal anlage via multiple pathways until establishing the paddle‐shaped structure required to generate five digits.
Collapse
Affiliation(s)
- Shiori Yamamoto
- Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya-shi, Aichi-ken, Japan
| | - Yuji Uchida
- Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya-shi, Aichi-ken, Japan
| | - Tomomi Ohtani
- Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya-shi, Aichi-ken, Japan
| | - Erina Nozaki
- Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya-shi, Aichi-ken, Japan
| | - Chunyang Yin
- Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya-shi, Aichi-ken, Japan
| | - Yoshihiro Gotoh
- Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya-shi, Aichi-ken, Japan
| | | | - Tetsuya Higashiyama
- Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya-shi, Aichi-ken, Japan.,Institute of Transformative Bio-Molecules (WPI-ITbM), Nagoya University, Nagoya-shi, Aichi-ken, Japan
| | - Takamasa Suzuki
- Department of Biological Chemistry, College of Bioscience and Biotechnology, Chubu University, Kasugai-shi, Aichi-ken, Japan
| | - Tatsuya Takemoto
- Laboratory for Embryology, Institute for Advanced Medical Sciences, Tokushima University, Tokushima, Japan
| | - Yo-Ichi Shiraishi
- Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya-shi, Aichi-ken, Japan
| | - Atsushi Kuroiwa
- Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya-shi, Aichi-ken, Japan
| |
Collapse
|
6
|
Gil RS, Vagnarelli P. Protein phosphatases in chromatin structure and function. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2018; 1866:90-101. [PMID: 30036566 PMCID: PMC6227384 DOI: 10.1016/j.bbamcr.2018.07.016] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/10/2018] [Revised: 06/29/2018] [Accepted: 07/18/2018] [Indexed: 12/19/2022]
Abstract
Chromatin structure and dynamics are highly controlled and regulated processes that play an essential role in many aspects of cell biology. The chromatin transition stages and the factors that control this process are regulated by post-translation modifications, including phosphorylation. While the role of protein kinases in chromatin dynamics has been quite well studied, the nature and regulation of the counteracting phosphatases represent an emerging field but are still at their infancy. In this review we summarize the current literature on phosphatases involved in the regulation of chromatin structure and dynamics, with emphases on the major knowledge gaps that should require attention and more investigation.
Collapse
Affiliation(s)
- Raquel Sales Gil
- Colleges of Health and Life Science, Research Institute for Environment Health and Society, Brunel University London, London UB8 3PH, UK
| | - Paola Vagnarelli
- Colleges of Health and Life Science, Research Institute for Environment Health and Society, Brunel University London, London UB8 3PH, UK.
| |
Collapse
|
7
|
Rezsohazy R, Saurin AJ, Maurel-Zaffran C, Graba Y. Cellular and molecular insights into Hox protein action. Development 2016; 142:1212-27. [PMID: 25804734 DOI: 10.1242/dev.109785] [Citation(s) in RCA: 89] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Hox genes encode homeodomain transcription factors that control morphogenesis and have established functions in development and evolution. Hox proteins have remained enigmatic with regard to the molecular mechanisms that endow them with specific and diverse functions, and to the cellular functions that they control. Here, we review recent examples of Hox-controlled cellular functions that highlight their versatile and highly context-dependent activity. This provides the setting to discuss how Hox proteins control morphogenesis and organogenesis. We then summarise the molecular modalities underlying Hox protein function, in particular in light of current models of transcription factor function. Finally, we discuss how functional divergence between Hox proteins might be achieved to give rise to the many facets of their action.
Collapse
Affiliation(s)
- René Rezsohazy
- Institut des Sciences de la Vie, Université Catholique de Louvain, Louvain-la-Neuve B-1348, Belgium
| | - Andrew J Saurin
- Aix Marseille Université, CNRS, IBDM, UMR 7288, Marseille 13288, Cedex 09, France
| | | | - Yacine Graba
- Aix Marseille Université, CNRS, IBDM, UMR 7288, Marseille 13288, Cedex 09, France
| |
Collapse
|
8
|
Papadopoulos DK, Krmpot AJ, Nikolić SN, Krautz R, Terenius L, Tomancak P, Rigler R, Gehring WJ, Vukojević V. Probing the kinetic landscape of Hox transcription factor-DNA binding in live cells by massively parallel Fluorescence Correlation Spectroscopy. Mech Dev 2015; 138 Pt 2:218-225. [PMID: 26428533 DOI: 10.1016/j.mod.2015.09.004] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2015] [Revised: 09/23/2015] [Accepted: 09/24/2015] [Indexed: 11/25/2022]
Abstract
Hox genes encode transcription factors that control the formation of body structures, segment-specifically along the anterior-posterior axis of metazoans. Hox transcription factors bind nuclear DNA pervasively and regulate a plethora of target genes, deploying various molecular mechanisms that depend on the developmental and cellular context. To analyze quantitatively the dynamics of their DNA-binding behavior we have used confocal laser scanning microscopy (CLSM), single-point fluorescence correlation spectroscopy (FCS), fluorescence cross-correlation spectroscopy (FCCS) and bimolecular fluorescence complementation (BiFC). We show that the Hox transcription factor Sex combs reduced (Scr) forms dimers that strongly associate with its specific fork head binding site (fkh250) in live salivary gland cell nuclei. In contrast, dimers of a constitutively inactive, phospho-mimicking variant of Scr show weak, non-specific DNA-binding. Our studies reveal that nuclear dynamics of Scr is complex, exhibiting a changing landscape of interactions that is difficult to characterize by probing one point at a time. Therefore, we also provide mechanistic evidence using massively parallel FCS (mpFCS). We found that Scr dimers are predominantly formed on the DNA and are equally abundant at the chromosomes and an introduced multimeric fkh250 binding-site, indicating different mobilities, presumably reflecting transient binding with different affinities on the DNA. Our proof-of-principle results emphasize the advantages of mpFCS for quantitative characterization of fast dynamic processes in live cells.
Collapse
Affiliation(s)
| | - Aleksandar J Krmpot
- Department of Clinical Neuroscience (CNS), Center for Molecular Medicine (CMM), Karolinska Institutet, 17176 Stockholm, Sweden; Institute of Physics, University of Belgrade, 11080 Belgrade, Serbia
| | - Stanko N Nikolić
- Department of Clinical Neuroscience (CNS), Center for Molecular Medicine (CMM), Karolinska Institutet, 17176 Stockholm, Sweden; Institute of Physics, University of Belgrade, 11080 Belgrade, Serbia
| | - Robert Krautz
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, 10691 Stockholm, Sweden
| | - Lars Terenius
- Department of Clinical Neuroscience (CNS), Center for Molecular Medicine (CMM), Karolinska Institutet, 17176 Stockholm, Sweden
| | - Pavel Tomancak
- Max-Planck Institute for Molecular Cell Biology and Genetics, 01307 Dresden, Germany
| | - Rudolf Rigler
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, 17177 Stockholm, Sweden; Laboratory of Biomedical Optics, Swiss Federal Institute of Technology, 1015 Lausanne, Switzerland
| | - Walter J Gehring
- Department of Cell Biology, Biozentrum, University of Basel, 4056 Basel, Switzerland
| | - Vladana Vukojević
- Department of Clinical Neuroscience (CNS), Center for Molecular Medicine (CMM), Karolinska Institutet, 17176 Stockholm, Sweden.
| |
Collapse
|
9
|
Bondos SE, Swint-Kruse L, Matthews KS. Flexibility and Disorder in Gene Regulation: LacI/GalR and Hox Proteins. J Biol Chem 2015; 290:24669-77. [PMID: 26342073 DOI: 10.1074/jbc.r115.685032] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
To modulate transcription, a variety of input signals must be sensed by genetic regulatory proteins. In these proteins, flexibility and disorder are emerging as common themes. Prokaryotic regulators generally have short, flexible segments, whereas eukaryotic regulators have extended regions that lack predicted secondary structure (intrinsic disorder). Two examples illustrate the impact of flexibility and disorder on gene regulation: the prokaryotic LacI/GalR family, with detailed information from studies on LacI, and the eukaryotic family of Hox proteins, with specific insights from investigations of Ultrabithorax (Ubx). The widespread importance of structural disorder in gene regulatory proteins may derive from the need for flexibility in signal response and, particularly in eukaryotes, in protein partner selection.
Collapse
Affiliation(s)
- Sarah E Bondos
- From the Department of Molecular and Cellular Medicine, Texas A&M Health Science Center, College Station, Texas 77843
| | - Liskin Swint-Kruse
- the Department of Biochemistry and Molecular Biology, the University of Kansas Medical Center, Kansas City, Kansas 66160, and
| | | |
Collapse
|
10
|
Sivanantharajah L, Percival-Smith A. Differential pleiotropy and HOX functional organization. Dev Biol 2014; 398:1-10. [PMID: 25448696 DOI: 10.1016/j.ydbio.2014.11.001] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2014] [Revised: 10/31/2014] [Accepted: 11/01/2014] [Indexed: 12/14/2022]
Abstract
Key studies led to the idea that transcription factors are composed of defined modular protein motifs or domains, each with separable, unique function. During evolution, the recombination of these modular domains could give rise to transcription factors with new properties, as has been shown using recombinant molecules. This archetypic, modular view of transcription factor organization is based on the analyses of a few transcription factors such as GAL4, which may represent extreme exemplars rather than an archetype or the norm. Recent work with a set of Homeotic selector (HOX) proteins has revealed differential pleiotropy: the observation that highly-conserved HOX protein motifs and domains make small, additive, tissue specific contributions to HOX activity. Many of these differentially pleiotropic HOX motifs may represent plastic sequence elements called short linear motifs (SLiMs). The coupling of differential pleiotropy with SLiMs, suggests that protein sequence changes in HOX transcription factors may have had a greater impact on morphological diversity during evolution than previously believed. Furthermore, differential pleiotropy may be the genetic consequence of an ensemble nature of HOX transcription factor allostery, where HOX proteins exist as an ensemble of states with the capacity to integrate an extensive array of developmental information. Given a new structural model for HOX functional domain organization, the properties of the archetypic TF may require reassessment.
Collapse
Affiliation(s)
- Lovesha Sivanantharajah
- Department of Biology, The University of Western Ontario, BGS231, London, Ontario, Canada N6A 5B7.
| | - Anthony Percival-Smith
- Department of Biology, The University of Western Ontario, BGS231, London, Ontario, Canada N6A 5B7
| |
Collapse
|
11
|
Acquisition of a leucine zipper motif as a mechanism of antimorphy for an allele of the Drosophila Hox gene Sex combs reduced. G3-GENES GENOMES GENETICS 2014; 4:829-38. [PMID: 24622333 PMCID: PMC4025482 DOI: 10.1534/g3.114.010769] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
In 1932, Müller first used the term "antimorphic" to describe mutant alleles that have an effect that is antagonistic to that of the wild-type allele from which they were derived. In a previous characterization of mutant alleles of the Drosophila melanogaster Hox gene, Sex combs reduced (Scr), we identified the missense, antimorphic allele Scr14, which is a Ser10-to-Leu change in the N-terminally located, bilateran-specific octapeptide motif. Here we propose that the cause of Scr14 antimorphy is the acquisition of a leucine zipper oligomerization motif spanning the octapeptide motif and adjacently located protostome-specific LASCY motif. Analysis of the primary and predicted secondary structures of the SCR N-terminus suggests that while the SCR+ encodes a short, α-helical region containing one putative heptad repeat, the same region in SCR14 encodes a longer, α-helical region containing two putative heptad repeats. In addition, in vitro cross-linking assays demonstrated strong oligomerization of SCR14 but not SCR+. For in vivo sex comb formation, we observed reciprocal inhibition of endogenous SCR+ and SCR14 activity by ectopic expression of truncated SCR14 and SCR+ peptides, respectively. The acquisition of an oligomerization domain in SCR14 presents a novel mechanism of antimorphy relative to the dominant negative mechanism, which maintains oligomerization between the wild-type and mutant protein subunits.
Collapse
|
12
|
Percival-Smith A, Sivanantharajah L, Pelling JJH, Teft WA. Developmental competence and the induction of ectopic proboscises in Drosophila melanogaster. Dev Genes Evol 2013; 223:375-387. [DOI: 10.1007/s00427-013-0454-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2013] [Accepted: 09/02/2013] [Indexed: 10/26/2022]
|
13
|
Casaca A, Santos AC, Mallo M. Controlling Hox gene expression and activity to build the vertebrate axial skeleton. Dev Dyn 2013; 243:24-36. [DOI: 10.1002/dvdy.24007] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2013] [Revised: 06/18/2013] [Accepted: 06/21/2013] [Indexed: 11/10/2022] Open
Affiliation(s)
- Ana Casaca
- Instituto Gulbenkian de Ciência; Oeiras Portugal
| | | | - Moisés Mallo
- Instituto Gulbenkian de Ciência; Oeiras Portugal
| |
Collapse
|
14
|
Seshacharyulu P, Pandey P, Datta K, Batra SK. Phosphatase: PP2A structural importance, regulation and its aberrant expression in cancer. Cancer Lett 2013; 335:9-18. [PMID: 23454242 DOI: 10.1016/j.canlet.2013.02.036] [Citation(s) in RCA: 319] [Impact Index Per Article: 29.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2012] [Revised: 02/10/2013] [Accepted: 02/13/2013] [Indexed: 12/28/2022]
Abstract
Protein Phosphatase 2A (PP2A) is an important and ubiquitously expressed serine threonine phosphatase and regulates the function by dephosphorylating many critical cellular molecules like Akt, p53, c-Myc and β-catenin. It plays a critical role in cellular processes, such as cell proliferation, signal transduction and apoptosis. Structurally, it is multifarious as it is composed of catalytic, scaffold and regulatory subunits. The catalytic and scaffold subunits have two isoforms and the regulatory subunit has four different families containing different isoforms. The regulatory subunit is the most diverse with temporal and spatial specificity. PP2A undergoes post-translational modifications (i.e. phosphorylation and methylation), which in turn, regulates its enzymatic activity. Aberrant expression, mutations and somatic alterations of the PP2A scaffold and regulatory subunits have been observed in various human malignancies, including lung, breast, skin and colon cancer, highlighting its role as a 'tumor suppressor'. This review is focused on the structural complexity of serine/threonine phosphatase PP2A and summarizes its expression pattern in cancer. Additionally, the PP2A interacting and regulatory proteins and substrates are also discussed. Finally, the mouse models developed to understand the biological role of PP2A subunits in an in vivo model system are also reviewed in this article.
Collapse
Affiliation(s)
- Parthasarathy Seshacharyulu
- Department of Biochemistry and Molecular Biology, Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, NE 68198-5870, USA.
| | | | | | | |
Collapse
|
15
|
Guerreiro I, Casaca A, Nunes A, Monteiro S, Nóvoa A, Ferreira RB, Bom J, Mallo M. Regulatory role for a conserved motif adjacent to the homeodomain of Hox10 proteins. Development 2012; 139:2703-10. [DOI: 10.1242/dev.081448] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Development of the vertebrate axial skeleton requires the concerted activity of several Hox genes. Among them, Hox genes belonging to the paralog group 10 are essential for the formation of the lumbar region of the vertebral column, owing to their capacity to block rib formation. In this work, we explored the basis for the rib-repressing activity of Hox10 proteins. Because genetic experiments in mice demonstrated that Hox10 proteins are strongly redundant in this function, we first searched for common motifs among the group members. We identified the presence of two small sequences flanking the homeodomain that are phylogenetically conserved among Hox10 proteins and that seem to be specific for this group. We show here that one of these motifs is required but not sufficient for the rib-repressing activity of Hox10 proteins. This motif includes two potential phosphorylation sites, which are essential for protein activity as their mutation to alanines resulted in a total loss of rib-repressing properties. Our data indicates that this motif has a significant regulatory function, modulating interactions with more N-terminal parts of the Hox protein, eventually triggering the rib-repressing program. In addition, this motif might also regulate protein activity by alteration of the protein's DNA-binding affinity through changes in the phosphorylation state of two conserved tyrosine residues within the homeodomain.
Collapse
Affiliation(s)
| | - Ana Casaca
- Instituto Gulbenkian de Ciência, 2780-156 Oeiras. Portugal
| | - Andreia Nunes
- Instituto Gulbenkian de Ciência, 2780-156 Oeiras. Portugal
| | - Sara Monteiro
- Instituto Superior de Agronomia, Technical University of Lisbon, 1349-017 Lisbon, Portugal
| | - Ana Nóvoa
- Instituto Gulbenkian de Ciência, 2780-156 Oeiras. Portugal
| | - Ricardo B. Ferreira
- Instituto Superior de Agronomia, Technical University of Lisbon, 1349-017 Lisbon, Portugal
- Instituto de Tecnologia Química e Biológica, New University of Lisbon, 2780-157 Oeiras, Portugal
| | - Joana Bom
- Instituto Gulbenkian de Ciência, 2780-156 Oeiras. Portugal
| | - Moisés Mallo
- Instituto Gulbenkian de Ciência, 2780-156 Oeiras. Portugal
- Department of Histology and Embryology, Faculty of Medicine, University of Lisbon, 1649-028 Lisbon, Portugal
| |
Collapse
|
16
|
Papadopoulos DK, Skouloudaki K, Adachi Y, Samakovlis C, Gehring WJ. Dimer formation via the homeodomain is required for function and specificity of Sex combs reduced in Drosophila. Dev Biol 2012; 367:78-89. [DOI: 10.1016/j.ydbio.2012.04.021] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2011] [Revised: 04/12/2012] [Accepted: 04/16/2012] [Indexed: 10/28/2022]
|
17
|
Gehring WJ. How do Hox transcription factors find their target genes in the nucleus of living cells? Biol Aujourdhui 2011; 205:75-85. [PMID: 21831338 DOI: 10.1051/jbio/2011012] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2011] [Indexed: 11/14/2022]
Abstract
Homeotic mutations first found in Drosophila led to the identification of Hox genes in all bilateria. These genes are exceptional in that they are arranged in an ordered cluster, in which they are positioned in the same order along the chromosome as they are expressed along the antero-posterior axis to specify the corresponding body regions. They share a highly conserved DNA sequence of 180 bp, the homeobox which encodes the homeodomain, a 60 amino acid polypeptide involved in specific DNA and RNA binding and in protein-protein interactions. The discovery of the homeobox has uncovered for the first time a universal principle of specification of the body plan along the antero-posterior axis. The structure of the homeodomain has been determined by NMR spectroscopy and by X-ray crystallography. However, the mechanism by which the Hox proteins find their target genes in the nucleus of a living cell has been enigmatic. Transcriptome analysis indicates that there are hundreds of target genes to be regulated, both positively and negatively to ensure normal development. In the following, we show by Fluorescence Correlation Spectroscopy (FCS) and single molecule imaging in live salivary gland cells, that the mechanism of recognition is purely stochastic. The homeodomain associates and dissociates rapidly (in the ms range) with chromatin all along the chromosomes. If, however, it associates with a specific binding site in a puffed chromosome region, it remains bound for seconds or minutes to exert its function, by forming a complex with co-activators or co-repressors respectively. These direct measurements solve an old enigma of how Hox transcription factors find their target genes in the nucleus of live cells.
Collapse
Affiliation(s)
- Walter J Gehring
- Growth and Development, Biozentrum University of Basel, Klingelbergstrasse, Basel, Switzerland.
| |
Collapse
|
18
|
Guergnon J, Godet AN, Galioot A, Falanga PB, Colle JH, Cayla X, Garcia A. PP2A targeting by viral proteins: a widespread biological strategy from DNA/RNA tumor viruses to HIV-1. Biochim Biophys Acta Mol Basis Dis 2011; 1812:1498-507. [PMID: 21856415 DOI: 10.1016/j.bbadis.2011.07.001] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2011] [Revised: 06/22/2011] [Accepted: 07/05/2011] [Indexed: 12/27/2022]
Abstract
Protein phosphatase 2A (PP2A) is a large family of holoenzymes that comprises 1% of total cellular proteins and accounts for the majority of Ser/Thr phosphatase activity in eukaryotic cells. Although initially viewed as constitutive housekeeping enzymes, it is now well established that PP2A proteins represent a family of highly and sophistically regulated phosphatases. The past decade, multiple complementary studies have improved our knowledge about structural and functional regulation of PP2A holoenzymes. In this regard, after summarizing major cellular regulation, this review will mainly focus on discussing a particulate biological strategy, used by various viruses, which is based on the targeting of PP2A enzymes by viral proteins in order to specifically deregulate, for their own benefit, cellular pathways of their hosts. The impact of such PP2A targeting for research in human diseases, and in further therapeutic developments, is also discussed.
Collapse
Affiliation(s)
- Julien Guergnon
- Laboratoire E3 Phosphatases-Unité Signalisation Moléculaire et Activation Cellulaire, Institut Pasteur 25, rue du Dr Roux, 75015 Paris, France
| | | | | | | | | | | | | |
Collapse
|
19
|
Su Y, Ospina JK, Zhang J, Michelson AP, Schoen AM, Zhu AJ. Sequential phosphorylation of smoothened transduces graded hedgehog signaling. Sci Signal 2011; 4:ra43. [PMID: 21730325 PMCID: PMC3526344 DOI: 10.1126/scisignal.2001747] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The correct interpretation of a gradient of the morphogen Hedgehog (Hh) during development requires phosphorylation of the Hh signaling activator Smoothened (Smo); however, the molecular mechanism by which Smo transduces graded Hh signaling is not well understood. We show that regulation of the phosphorylation status of Smo by distinct phosphatases at specific phosphorylated residues creates differential thresholds of Hh signaling. Phosphorylation of Smo was initiated by adenosine 3',5'-monophosphate (cAMP)-dependent protein kinase (PKA) and further enhanced by casein kinase I (CKI). We found that protein phosphatase 1 (PP1) directly dephosphorylated PKA-phosphorylated Smo to reduce signaling mediated by intermediate concentrations of Hh, whereas PP2A specifically dephosphorylated PKA-primed, CKI-phosphorylated Smo to restrict signaling by high concentrations of Hh. We also established a functional link between sequentially phosphorylated Smo species and graded Hh activity. Thus, we propose a sequential phosphorylation model in which precise interpretation of morphogen concentration can be achieved upon versatile phosphatase-mediated regulation of the phosphorylation status of an essential activator in developmental signaling.
Collapse
Affiliation(s)
| | | | | | - Andrew P. Michelson
- Department of Cell Biology, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195, USA
| | - Adam M. Schoen
- Department of Cell Biology, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195, USA
| | - Alan Jian Zhu
- Department of Cell Biology, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195, USA
| |
Collapse
|
20
|
Gharbi-Ayachi A, Labbé JC, Burgess A, Vigneron S, Strub JM, Brioudes E, Van-Dorsselaer A, Castro A, Lorca T. The substrate of Greatwall kinase, Arpp19, controls mitosis by inhibiting protein phosphatase 2A. Science 2010; 330:1673-1677. [PMID: 21164014 DOI: 10.1016/b978-0-12-374145-5.00168-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Initiation and maintenance of mitosis require the activation of protein kinase cyclin B-Cdc2 and the inhibition of protein phosphatase 2A (PP2A), which, respectively, phosphorylate and dephosphorylate mitotic substrates. The protein kinase Greatwall (Gwl) is required to maintain mitosis through PP2A inhibition. We describe how Gwl activation results in PP2A inhibition. We identified cyclic adenosine monophosphate-regulated phosphoprotein 19 (Arpp19) and α-Endosulfine as two substrates of Gwl that, when phosphorylated by this kinase, associate with and inhibit PP2A, thus promoting mitotic entry. Conversely, in the absence of Gwl activity, Arpp19 and α-Endosulfine are dephosphorylated and lose their capacity to bind and inhibit PP2A. Although both proteins can inhibit PP2A, endogenous Arpp19, but not α-Endosulfine, is responsible for PP2A inhibition at mitotic entry in Xenopus egg extracts.
Collapse
Affiliation(s)
- Aicha Gharbi-Ayachi
- Universités Montpellier 2 et 1, Centre de Recherche de Biochimie Macromoléculaire, CNRS UMR 5237, IFR 122, 1919 Route de Mende, 34293 Montpellier cedex 5, France
| | | | | | | | | | | | | | | | | |
Collapse
|
21
|
Yang J, Phiel C. Functions of B56-containing PP2As in major developmental and cancer signaling pathways. Life Sci 2010; 87:659-66. [PMID: 20934435 DOI: 10.1016/j.lfs.2010.10.003] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2010] [Revised: 09/08/2010] [Accepted: 09/23/2010] [Indexed: 12/20/2022]
Abstract
Members of the B'/B56/PR61 family regulatory subunits of PP2A determine the subcellular localization, substrate specificity, and catalytic activity of PP2A in a wide range of biological processes. Here, we summarize the structure and intracellular localization of B56-containing PP2As and review functions of B56-containing PP2As in several major developmental/cancer signaling pathways.
Collapse
Affiliation(s)
- Jing Yang
- The Research Institute at Nationwide Children's Hospital, Department of Pediatrics, the Ohio State University, 700 Children's Dr., Columbus, OH, 43205, United States.
| | | |
Collapse
|
22
|
Surprising flexibility in a conserved Hox transcription factor over 550 million years of evolution. Proc Natl Acad Sci U S A 2010; 107:18040-5. [PMID: 20921393 DOI: 10.1073/pnas.1010746107] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Although metazoan body plans are remarkably diverse, the structure and function of many embryonic regulatory genes are conserved because large changes would be detrimental to development. However, the fushi tarazu (ftz) gene has changed dramatically during arthropod evolution from Hox-like to a pair-rule segmentation gene in Drosophila. Changes in both expression and protein sequence contributed to this new function: ftz expression switched from Hox-like to stripes and changes in Ftz cofactor interaction motifs led to loss of homeotic and gain of segmentation potential. Here, we reconstructed ftz changes in a rigorous phylogenetic context. We found that ftz did not simply switch from Hox-like to segmentation function; rather, ftz is remarkably labile, having undergone multiple changes in sequence and expression. The segmentation LXXLL motif was stably acquired in holometabolous insects after the appearance of striped expression in early insect lineages. The homeotic YPWM motif independently degenerated multiple times. These "degen-YPWMs" showed varying degrees of homeotic potential when expressed in Drosophila, suggesting variable loss of Hox function in different arthropods. Finally, the intensity of ftz Hox-like expression decreased to marginal levels in some crustaceans. We propose that decreased expression levels permitted ftz variants to arise and persist in populations without disadvantaging organismal development. This process, in turn, allowed evolutionary transitions in protein function, as weakly expressed "hopeful gene variants" were coopted into alternative developmental pathways. Our findings show that variation of a pleiotropic transcription factor is more extensive than previously imagined, suggesting that evolutionary plasticity may be widespread among regulatory genes.
Collapse
|
23
|
Chen E, Huang X, Zheng Y, Li YJ, Chesney A, Ben-David Y, Yang E, Hough MR. Phosphorylation of HOX11/TLX1 on Threonine-247 during mitosis modulates expression of cyclin B1. Mol Cancer 2010; 9:246. [PMID: 20846384 PMCID: PMC2949800 DOI: 10.1186/1476-4598-9-246] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2010] [Accepted: 09/16/2010] [Indexed: 12/20/2022] Open
Abstract
BACKGROUND The HOX11/TLX1 (hereafter referred to as HOX11) homeobox gene was originally identified at a t(10;14)(q24;q11) translocation breakpoint, a chromosomal abnormality observed in 5-7% of T cell acute lymphoblastic leukemias (T-ALLs). We previously reported a predisposition to aberrant spindle assembly checkpoint arrest and heightened incidences of chromosome missegregation in HOX11-overexpressing B lymphocytes following exposure to spindle poisons. The purpose of the current study was to evaluate cell cycle specific expression of HOX11. RESULTS Cell cycle specific expression studies revealed a phosphorylated form of HOX11 detectable only in the mitotic fraction of cells after treatment with inhibitors to arrest cells at different stages of the cell cycle. Mutational analyses revealed phosphorylation on threonine-247 (Thr247), a conserved amino acid that defines the HOX11 gene family and is integral for the association with DNA binding elements. The effect of HOX11 phosphorylation on its ability to modulate expression of the downstream target, cyclin B1, was tested. A HOX11 mutant in which Thr247 was substituted with glutamic acid (HOX11 T247E), thereby mimicking a constitutively phosphorylated HOX11 isoform, was unable to bind the cyclin B1 promoter or enhance levels of the cyclin B1 protein. Expression of the wildtype HOX11 was associated with accelerated progression through the G2/M phase of the cell cycle, impaired synchronization in prometaphase and reduced apoptosis whereas expression of the HOX11 T247E mutant restored cell cycle kinetics, the spindle checkpoint and apoptosis. CONCLUSIONS Our results demonstrate that the transcriptional activity of HOX11 is regulated by phosphorylation of Thr247 in a cell cycle-specific manner and that this phosphorylation modulates the expression of the target gene, cyclin B1. Since it is likely that Thr247 phosphorylation regulates DNA binding activity to multiple HOX11 target sequences, it is conceivable that phosphorylation functions to regulate the expression of HOX11 target genes involved in the control of the mitotic spindle checkpoint.
Collapse
Affiliation(s)
- Edwin Chen
- Institute of Medical Science, University of Toronto, Toronto, Ontario M5S1A8, Canada
| | | | | | | | | | | | | | | |
Collapse
|
24
|
Vukojević V, Papadopoulos DK, Terenius L, Gehring WJ, Rigler R. Quantitative study of synthetic Hox transcription factor-DNA interactions in live cells. Proc Natl Acad Sci U S A 2010; 107:4093-8. [PMID: 20147625 PMCID: PMC2840106 DOI: 10.1073/pnas.0914612107] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Transcription factor-DNA interactions are life sustaining and therefore the subject of intensive research. In spite of vast effort, quantitative in vivo studies of the molecular mechanisms underlying these fundamental interactions remain challenging. In the preceding paper, we designed synthetic Sex combs reduced (Scr) peptides and validated genetically their function as transcriptional regulators. Here we present a controllable system for quantitative studies of protein-DNA interactions in live cells that enables us to "titrate" the concentration of the synthetic Scr peptides in a single cell. Using methods with single-molecule sensitivity, advanced fluorescence imaging and fluorescence correlation spectroscopy (FCS), we were able to study the kinetics of Scr-DNA interactions in live salivary gland cells, where Scr is normally expressed during development. We discerned freely moving Scr molecules, characterized the specific and nonspecific Scr peptide-DNA interactions, and estimated their corresponding dissociation constants (K(d)) in vivo. Our results suggest that the synthetic Scr transcription factors find their specific target sites primarily by multiple association/dissociation events, the rapidity of which is largely owed to electrostatic interactions. Based on these new findings, we formulate a model mechanism and emulate the kinetics of Scr homeodomain-DNA interactions in live cells using numerical simulations.
Collapse
Affiliation(s)
- Vladana Vukojević
- Department of Clinical Neuroscience, Karolinska Institutet, 17176 Stockholm, Sweden
| | | | - Lars Terenius
- Department of Clinical Neuroscience, Karolinska Institutet, 17176 Stockholm, Sweden
| | - Walter J. Gehring
- Department of Cell Biology, Biozentrum, University of Basel, 4056 Basel, Switzerland
| | - Rudolf Rigler
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, 17177 Stockholm, Sweden; and
- Laboratory of Biomedical Optics, Swiss Federal Institute of Technology, 1015 Lausanne, Switzerland
| |
Collapse
|
25
|
Function and specificity of synthetic Hox transcription factors in vivo. Proc Natl Acad Sci U S A 2010; 107:4087-92. [PMID: 20147626 DOI: 10.1073/pnas.0914595107] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Homeotic (Hox) genes encode transcription factors that confer segmental identity along the anteroposterior axis of the embryo. However the molecular mechanisms underlying Hox-mediated transcription and the differential requirements for specificity in the regulation of the vast number of Hox-target genes remain ill-defined. Here we show that synthetic Sex combs reduced (Scr) genes that encode the Scr C terminus containing the homedomain (HD) and YPWM motif (Scr-HD) are functional in vivo. Synthetic Scr-HD peptides can induce ectopic salivary glands in the embryo and homeotic transformations in the adult fly, act as transcriptional activators and repressors during development, and participate in protein-protein interactions. Their transformation capacity was found to be enhanced over their full-length counterpart and mutations known to transform the full-length protein into constitutively active or inactive variants behaved accordingly in the synthetic peptides. Our results show that synthetic Scr-HD genes are sufficient for homeotic function in Drosophila and suggest that the N terminus of Scr has a role in transcriptional potency, rather than specificity. We also demonstrate that synthetic peptides behave largely in a predictable way, by exhibiting Scr-specific phenotypes throughout development, which makes them an important tool for synthetic biology.
Collapse
|
26
|
Moazzen H, Rosenfeld R, Percival-Smith A. Non-requirement of a regulatory subunit of Protein Phosphatase 2A, PP2A-B′, for activation of Sex comb reduced activity in Drosophila melanogaster. Mech Dev 2009; 126:605-10. [DOI: 10.1016/j.mod.2009.06.1084] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2009] [Revised: 06/12/2009] [Accepted: 06/19/2009] [Indexed: 01/17/2023]
|
27
|
Analysis of the sequence and phenotype of Drosophila Sex combs reduced alleles reveals potential functions of conserved protein motifs of the Sex combs reduced protein. Genetics 2009; 182:191-203. [PMID: 19293143 DOI: 10.1534/genetics.109.100438] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The Drosophila Hox gene, Sex combs reduced (Scr), is required for patterning the larval and adult, labial and prothoracic segments. Fifteen Scr alleles were sequenced and the phenotypes analyzed in detail. Six null alleles were nonsense mutations (Scr(2), Scr(4), Scr(11), Scr(13), Scr(13A), and Scr(16)) and one was an intragenic deletion (Scr(17)). Five hypomorphic alleles were missense mutations (Scr(1), Scr(3), Scr(5), Scr(6), and Scr(8)) and one was a small protein deletion (Scr(15)). Protein sequence changes were found in four of the five highly conserved domains of SCR: the DYTQL motif (Scr(15)), YPWM motif (Scr(3)), Homeodomain (Scr(1)), and C-terminal domain (CTD) (Scr(6)), indicating importance for SCR function. Analysis of the pleiotropy of viable Scr alleles for the formation of pseudotracheae suggests that the DYTQL motif and the CTD mediate a genetic interaction with proboscipedia. One allele Scr(14), a missense allele in the conserved octapeptide, was an antimorphic allele that exhibited three interesting genetic properties. First, Scr(14)/Df had the same phenotype as Scr(+)/Df. Second, the ability of the Scr(14) allele to interact intragenetically with Scr alleles mapped to the first 82 amino acids of SCR, which contains the octapeptide motif. Third, Scr(6), which has two missense changes in the CTD, did not interact genetically with Scr(14).
Collapse
|
28
|
Mann RS, Lelli KM, Joshi R. Hox specificity unique roles for cofactors and collaborators. Curr Top Dev Biol 2009; 88:63-101. [PMID: 19651302 DOI: 10.1016/s0070-2153(09)88003-4] [Citation(s) in RCA: 257] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Hox proteins are well known for executing highly specific functions in vivo, but our understanding of the molecular mechanisms underlying gene regulation by these fascinating proteins has lagged behind. The premise of this review is that an understanding of gene regulation-by any transcription factor-requires the dissection of the cis-regulatory elements that they act upon. With this goal in mind, we review the concepts and ideas regarding gene regulation by Hox proteins and apply them to a curated list of directly regulated Hox cis-regulatory elements that have been validated in the literature. Our analysis of the Hox-binding sites within these elements suggests several emerging generalizations. We distinguish between Hox cofactors, proteins that bind DNA cooperatively with Hox proteins and thereby help with DNA-binding site selection, and Hox collaborators, proteins that bind in parallel to Hox-targeted cis-regulatory elements and dictate the sign and strength of gene regulation. Finally, we summarize insights that come from examining five X-ray crystal structures of Hox-cofactor-DNA complexes. Together, these analyses reveal an enormous amount of flexibility into how Hox proteins function to regulate gene expression, perhaps providing an explanation for why these factors have been central players in the evolution of morphological diversity in the animal kingdom.
Collapse
Affiliation(s)
- Richard S Mann
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY, USA
| | | | | |
Collapse
|
29
|
Eichhorn PJA, Creyghton MP, Bernards R. Protein phosphatase 2A regulatory subunits and cancer. Biochim Biophys Acta Rev Cancer 2008; 1795:1-15. [PMID: 18588945 DOI: 10.1016/j.bbcan.2008.05.005] [Citation(s) in RCA: 273] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2008] [Revised: 05/20/2008] [Accepted: 05/21/2008] [Indexed: 01/06/2023]
Abstract
The serine/threonine protein phosphatase (PP2A) is a trimeric holoenzyme that plays an integral role in the regulation of a number of major signaling pathways whose deregulation can contribute to cancer. The specificity and activity of PP2A are highly regulated through the interaction of a family of regulatory B subunits with the substrates. Accumulating evidence indicates that PP2A acts as a tumor suppressor. In this review we summarize the known effects of specific PP2A holoenzymes and their roles in cancer relevant pathways. In particular we highlight PP2A function in the regulation of MAPK and Wnt signaling.
Collapse
Affiliation(s)
- Pieter J A Eichhorn
- Division of Molecular Carcinogenesis, Center for Cancer Genomics and Center for Biomedical Genetics, The Netherlands Cancer Institute, Amsterdam, The Netherlands
| | | | | |
Collapse
|
30
|
Taghli-Lamallem O, Hsia C, Ronshaugen M, McGinnis W. Context-dependent regulation of Hox protein functions by CK2 phosphorylation sites. Dev Genes Evol 2008; 218:321-32. [PMID: 18504607 PMCID: PMC2443945 DOI: 10.1007/s00427-008-0224-1] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2008] [Accepted: 04/21/2008] [Indexed: 10/22/2022]
Abstract
Variations in Hox protein sequences and functions have been proposed to contribute to evolutionary changes in appendage shape and number in crustaceans and insects. One model is that insect Hox proteins of the Ultrabithorax (UBX) ortholog class evolved increased abilities to repress Distal-less (Dll) transcription and appendage development in part through the loss of serine and threonine residues in casein kinase 2 (CK2) phosphorylation sites. To explore this possibility, we constructed and tested the appendage repression function of chimeric proteins with insertions of different CK2 consensus sites or phosphomimetics of CK2 sites in C-terminal regions of Drosophila melanogaster UBX. Our results indicate that CK2 sites C-terminal to the homeodomain can inhibit the appendage repression functions of UBX proteins, but only in the context of specific amino acid sequences. Our results, combined with previous findings on evolutionary changes in Hox protein, suggest how intra-protein regulatory changes can diversify Hox protein function, and thus animal morphology.
Collapse
Affiliation(s)
- Ouarda Taghli-Lamallem
- Neuroscience & Aging Research Center, The Burnham Institute for Medical Research, 10901 North Torrey Pines Rd, La Jolla, CA 92037, USA
| | - Cheryl Hsia
- Section in Cell and Developmental Biology, Division of Biology, University of California, San Diego, La Jolla, CA 92093, USA, e-mail:
| | - Matthew Ronshaugen
- The Healing Foundation Centre, Faculty of Life Sciences, University of Manchester, Oxford Road, Manchester M13 9PT, UK
| | - William McGinnis
- Section in Cell and Developmental Biology, Division of Biology, University of California, San Diego, La Jolla, CA 92093, USA, e-mail:
| |
Collapse
|
31
|
Prince F, Katsuyama T, Oshima Y, Plaza S, Resendez-Perez D, Berry M, Kurata S, Gehring WJ. The YPWM motif links Antennapedia to the basal transcriptional machinery. Development 2008; 135:1669-79. [DOI: 10.1242/dev.018028] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
HOX genes specify segment identity along the anteroposterior axis of the embryo. They code for transcription factors harbouring the highly conserved homeodomain and a YPWM motif, situated amino terminally to it. Despite their highly diverse functions in vivo, HOX proteins display similar biochemical properties in vitro, raising the question of how this specificity is achieved. In our study, we investigated the importance of the Antennapedia(Antp) YPWM motif for homeotic transformations in adult Drosophila. By ectopic overexpression, the head structures of the fly can be transformed into structures of the second thoracic segment, such as antenna into second leg, head capsule into thorax (notum) and eye into wing. We found that the YPWM motif is absolutely required for the eye-to-wing transformation. Using the yeast two-hybrid system, we were able to identify a novel ANTP-interacting protein, Bric-à-brac interacting protein 2(BIP2), that specifically interacts with the YPWM motif of ANTP in vitro, as well as in vivo, transforming eye to wing tissue. BIP2 is a TATA-binding protein associated factor (also known as dTAFII3) that links ANTP to the basal transcriptional machinery.
Collapse
Affiliation(s)
- Frédéric Prince
- Biozentrum, University of Basel, Klingelberstrasse 70, CH-4056 Basel,Switzerland
| | | | - Yoshiteru Oshima
- ETH Zurich, Department of Biosystems, CH-4058 Basel, Switzerland
| | - Serge Plaza
- CNS-Centre de Biologie du Developpement, 118 route de NARBONNE, Bat 4R3, 31062 Toulouse, France
| | | | - Meera Berry
- Micromet AG, Am Klopferspitz 19, 82152 Martinsried/Munich, Germany
| | - Shoichiro Kurata
- ETH Zurich, Department of Biosystems, CH-4058 Basel, Switzerland
| | - Walter J. Gehring
- Biozentrum, University of Basel, Klingelberstrasse 70, CH-4056 Basel,Switzerland
| |
Collapse
|
32
|
Liu W, Silverstein AM, Shu H, Martinez B, Mumby MC. A functional genomics analysis of the B56 isoforms of Drosophila protein phosphatase 2A. Mol Cell Proteomics 2006; 6:319-32. [PMID: 17121811 DOI: 10.1074/mcp.m600272-mcp200] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Members of the B56 family of protein phosphatase 2A (PP2A) regulatory subunits play crucial roles in Drosophila cell survival. Distinct functions of two B56 subunits were investigated using a combination of RNA interference, DNA microarrays, and proteomics. RNA interference-mediated knockdown of the B56-1 subunit (PP2A-B') but not the catalytic (mts) or B56-2 subunit (wdb) of PP2A resulted in increased expression of the apoptotic inducers reaper and sickle. Co-knockdown of B56-1 with reaper, but not with sickle, reduced the apoptosis caused by depletion of the B56 subunits. Two-dimensional gel electrophoresis and mass spectrometry identified proteins modified in cells depleted of PP2A subunits. These included generation of caspase-dependent cleavage products, increases in protein abundance, and covalent modifications. Results suggested that up-regulation of the ribosome-associated protein stubarista can serve as a sensitive marker of apoptosis. Up-regulation of transcripts for multiple glutathione transferases and other proteins suggested that loss of PP2A affected pathways involved in the response to oxidative stress. Knockdown of PP2A elevated basal JNK activity and substantially decreased activation of ERK in response to oxidative stress. The results reveal that the B56-containing isoform of PP2A functions within multiple signaling pathways, including those that regulate expression of reaper and the response to oxidative stress, thus promoting cell survival in Drosophila.
Collapse
Affiliation(s)
- Wei Liu
- Department of Pharmacology, The University of Texas Southwestern Medical Center, Dallas, Texas 75390-9041, USA
| | | | | | | | | |
Collapse
|
33
|
Abstract
Micro RNAs (miRNAs) have been shown to control many cellular processes including developmental timing in different organisms. The prediction that miRNAs are involved in regulating hox genes of flies and mouse is quite a recent idea and is supported by the finding that mir-196 represses Hoxb8 gene expression. The non-coding regions that encode these miRNAs are also conserved across species in the same way as other mechanisms that regulate expression of hox genes. On the contrary, until now no homeotic phenotype, a hallmark of any hox gene mutation, had been associated with any hox miRNA. Recent work on bithorax complex miRNA (miR-iab-4-5p) shows, for the first time, that miRNAs can lead to homeotic transformation. This miRNA regulates Ultrabithorax (Ubx) and results in the transformation of haltere to wing. This study unveils a new complexity and finesse to the regulation of hox gene expression pattern that is needed for determining the anteroposterior body axis in all bilaterians.
Collapse
Affiliation(s)
- Vivek S Chopra
- Centre for Cellular and Molecular Biology, Hyderabad, India.
| | | |
Collapse
|
34
|
Chen S, Ji M, Paris M, Hullinger RL, Andrisani OM. The cAMP pathway regulates both transcription and activity of the paired homeobox transcription factor Phox2a required for development of neural crest-derived and central nervous system-derived catecholaminergic neurons. J Biol Chem 2005; 280:41025-36. [PMID: 16204240 DOI: 10.1074/jbc.m503537200] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Pluripotent neural crest (NC) cells differentiate to diverse lineages, including the neuronal, sympathoadrenal lineage. In primary NC cultures, bone morphogenetic protein 2 (BMP2) requires moderate activation of cAMP signaling for induction of the sympathoadrenal lineage. However, the mechanism by which cAMP signaling synergizes with BMP2 to induce the sympathodrenal lineage is unknown. Herein, we demonstrate that moderate activation of cAMP signaling induces both transcription and activity of proneural transcription factor Phox2a. In NC cultures inhibition of cAMP-response element-binding protein (CREB)-mediated transcription by expression of dominant-negative CREB suppresses Phox2a transcription and sympathoadrenal lineage development. Interestingly, the constitutively active CREB(DIEDML), despite inducing Phox2a transcription, is insufficient for sympathoadrenal lineage development, requiring activation of the cAMP pathway. Because CREB(DIEDML)-mediates cAMP-dependent transcription without requiring activation by the cAMP-dependent protein kinase A (PKA), these results identify PKA activation as necessary in sympathoadrenal lineage development. Treatment of NC cultures with the PKA inhibitor H89 or 1-10 nm okadaic acid (OA), a serine/threonine PP2A-like phosphatase inhibitor, suppresses sympathoadrenal lineage development. Likewise, OA treatment of the CNS-derived catecholaminergic CAD cell line inhibits cAMP-mediated neuronal differentiation. Specifically, OA inhibits cAMP-mediated Phox2a dephosphorylation, cAMP-dependent Phox2a DNA binding in vitro, and cAMP- and Phox2a-dependent dopamine-beta-hydroxylase-luciferase reporter expression. Together, these results support cAMP-dependent Phox2a dephosphorylation is required for its activation. We conclude that moderate activation of cAMP signaling has dual inputs in catecholaminergic, sympathoadrenal lineage development; that is, regulation of both Phox2a transcription and activity. These results provide the first mechanistic understanding of how moderate activation of the cAMP pathway in synergy with BMP2 promotes sympathoadrenal lineage development.
Collapse
Affiliation(s)
- Sigeng Chen
- Department of Basic Medical Sciences, Purdue University, West Lafayette, Indiana 47906, USA
| | | | | | | | | |
Collapse
|
35
|
Van Kanegan MJ, Adams DG, Wadzinski BE, Strack S. Distinct protein phosphatase 2A heterotrimers modulate growth factor signaling to extracellular signal-regulated kinases and Akt. J Biol Chem 2005; 280:36029-36. [PMID: 16129692 DOI: 10.1074/jbc.m506986200] [Citation(s) in RCA: 105] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A key regulator of many kinase cascades, heterotrimeric protein serine/threonine phosphatase 2A (PP2A), is composed of catalytic (C), scaffold (A), and variable regulatory subunits (B, B', B'' gene families). In neuronal PC12 cells, PP2A acts predominantly as a gatekeeper of extracellular signal-regulated kinase (ERK) activity, as shown by inducible RNA interference of the Aalpha scaffolding subunit and PP2A inhibition by okadaic acid. Although okadaic acid potentiates Akt/protein kinase B and ERK phosphorylation in response to epidermal, basic fibroblast, or nerve growth factor, silencing of Aalpha paradoxically has the opposite effect. Epidermal growth factor receptor Tyr phosphorylation was unchanged following Aalpha knockdown, suggesting that chronic Akt and ERK hyperphosphorylation leads to compensatory down-regulation of signaling molecules upstream of Ras and blunted growth factor responses. Inducible exchange of wild-type Aalpha with a mutant with selective B' subunit binding deficiency implicated PP2A/B' heterotrimers as Akt modulators. Conversely, silencing of the B-family regulatory subunits Balpha and Bdelta led to hyperactivation of ERK stimulated by constitutively active MEK1. In vitro dephosphorylation assays further support a role for Balpha and Bdelta in targeting the PP2A heterotrimer to dephosphorylate and inactivate ERKs. Thus, receptor tyrosine kinase signaling cascades leading to Akt and ERK activation are modulated by PP2A holoenzymes with distinct regulatory properties.
Collapse
Affiliation(s)
- Michael J Van Kanegan
- Department of Pharmacology, University of Iowa Carver College of Medicine, Iowa City, Iowa 52242, USA
| | | | | | | |
Collapse
|
36
|
Rogers EM, Hsiung F, Rodrigues AB, Moses K. Slingshot cofilin phosphatase localization is regulated by receptor tyrosine kinases and regulates cytoskeletal structure in the developing Drosophila eye. Mech Dev 2005; 122:1194-205. [PMID: 16169194 DOI: 10.1016/j.mod.2005.07.002] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2005] [Revised: 07/08/2005] [Accepted: 07/19/2005] [Indexed: 11/18/2022]
Abstract
Animal development requires that positional information act on the genome to control cell fate and cell shape. The primary determinant of animal cell shape is the cytoskeleton and thus the mechanisms by which extracellular signals influence the cytoskeleton are crucial for morphogenesis. In the developing Drosophila compound eye, localized polymerization of actin functions to constrict the apical surface of epithelial cells, both at the morphogenetic furrow and later to maintain the coherence of the nascent ommatidia. As elsewhere, actin polymerization in the developing eye is regulated by ADF/cofilin ('Twinstar', or 'Tsr' in Drosophila), which is activated by Slingshot (Ssh), a cofilin phosphatase. Here we show that Ssh does act in the developing eye to limit actin polymerization in the assembling ommatidia, but not in the morphogenetic furrow. While Ssh does control cell shape, surprisingly there are no direct or immediate consequences for cell type. Ssh protein becomes apically concentrated in cells that express elevated levels of the Sevenless (Sev) receptor-tyrosine kinase (RTK), even those which receive no ligand. We interpret this as a non-signal driven, RTK-dependent localization of Ssh to allow for locally increased actin filament turnover. We suggest that there are two modes of actin remodeling in the developing eye: a non-RTK, non-Ssh mediated mechanism in the morphogenetic furrow, and an RTK and Ssh-dependent mode during ommatidial assembly.
Collapse
Affiliation(s)
- Edward M Rogers
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA 30322-3030, USA
| | | | | | | |
Collapse
|
37
|
Mahaffey JW. Assisting Hox proteins in controlling body form: are there new lessons from flies (and mammals)? Curr Opin Genet Dev 2005; 15:422-9. [PMID: 15979870 DOI: 10.1016/j.gde.2005.06.009] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2005] [Accepted: 06/07/2005] [Indexed: 11/24/2022]
Abstract
Hox proteins regulate specific sets of target genes to give rise to morphological distinctions along the anterior-posterior body axis of metazoans. Though they have high developmental specificity, Hox proteins have low DNA binding specificity, so how they select the appropriate target genes has remained enigmatic. There is general agreement that cofactors provide additional specificity, but a comprehensive model of Hox control of gene expression has not emerged. There is now evidence that a global network of zinc finger transcription factors contributes to patterning of the Drosophila embryo. These zinc finger proteins appear to establish fields in which certain Hox proteins can function. Though the nature of these fields is uncertain at this time, it is possible that these zinc finger proteins are Hox cofactors, providing additional specificity during Hox target-gene selection. Furthermore, these zinc finger proteins are conserved, as are aspects of their anterior-posterior expression, suggesting that their roles might be conserved, as well. Perhaps this layer in the genetic control of body patterning will help bridge some of the chasms that remain in our understanding of the genetic control of pattern formation.
Collapse
Affiliation(s)
- James W Mahaffey
- Department of Genetics, Campus Box 7614, North Carolina State University, Raleigh, NC 27695-7614, USA.
| |
Collapse
|
38
|
Viallet J, Garcia A, Weydert A. Protein phosphatase 2A as a new target for morphogenetic studies in the chick limb. Biochimie 2004; 85:753-62. [PMID: 14585542 DOI: 10.1016/j.biochi.2003.09.009] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The family of ser/thr protein phosphatases 2A (PP2A) is a major regulator of cell proliferation and cell death and is critically involved in the maintenance of homeostasis. In order to analyse the importance of PP2A proteins in apoptotic and developmental processes, this review focuses on previous studies concerning the role of PP2A in morphogenesis. We first analyse wing formation in Drosophila, a model for invertebrates, then chick limb bud, a model for vertebrates. We also present a pioneer experiment to illustrate the potential relevance of PP2A studies in BMP signalling during chicken development and we finally discuss the BMP downstream signalling pathways.
Collapse
Affiliation(s)
- Jean Viallet
- Faculté de Médecine, LEDAC UMR 5538 Institut Albert Bonniot, Rond Point de la Chantourne, 38706 La Tronche cedex, France
| | | | | |
Collapse
|
39
|
Vijapurkar U, Fischbach N, Shen W, Brandts C, Stokoe D, Lawrence HJ, Largman C. Protein kinase C-mediated phosphorylation of the leukemia-associated HOXA9 protein impairs its DNA binding ability and induces myeloid differentiation. Mol Cell Biol 2004; 24:3827-37. [PMID: 15082777 PMCID: PMC387750 DOI: 10.1128/mcb.24.9.3827-3837.2004] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
HOXA9 expression is a common feature of acute myeloid leukemia, and high-level expression is correlated with poor prognosis. Moreover, HOXA9 overexpression immortalizes murine marrow progenitors that are arrested at a promyelocytic stage of differentiation when cultured and causes leukemia in recipient mice following transplantation of HOXA9 expressing bone marrow. The molecular mechanisms underlying the physiologic functions and transforming properties of HOXA9 are poorly understood. This study demonstrates that HOXA9 is phosphorylated by protein kinase C (PKC) and casein kinase II and that PKC mediates phosphorylation of purified HOXA9 on S204 as well as on T205, within a highly conserved consensus sequence, in the N-terminal region of the homeodomain. S204 in the endogenous HOXA9 protein was phosphorylated in PLB985 myeloid cells, as well as in HOXA9-immortalized murine marrow cells. This phosphorylation was enhanced by phorbol ester, a known inducer of PKC, and was inhibited by a specific PKC inhibitor. PKC-mediated phosphorylation of S204 decreased HOXA9 DNA binding affinity in vitro and the ability of the endogenous HOXA9 to form cooperative DNA binding complexes with PBX. PKC inhibition significantly reduced the phorbol-ester induced differentiation of the PLB985 hematopoietic cell line as well as HOXA9-immortalized murine bone marrow cells. These data suggest that phorbol ester-induced myeloid differentiation is in part due to PKC-mediated phosphorylation of HOXA9, which decreases the DNA binding of the homeoprotein.
Collapse
Affiliation(s)
- Ulka Vijapurkar
- Department of Medicine, University of California VA Medical Center, San Francisco, California 94121, USA
| | | | | | | | | | | | | |
Collapse
|
40
|
Martens E, Stevens I, Janssens V, Vermeesch J, Götz J, Goris J, Van Hoof C. Genomic Organisation, Chromosomal Localisation Tissue Distribution and Developmental Regulation of the PR61/B′ Regulatory Subunits of Protein Phosphatase 2A in Mice. J Mol Biol 2004; 336:971-86. [PMID: 15095873 DOI: 10.1016/j.jmb.2003.12.047] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2003] [Revised: 12/10/2003] [Accepted: 12/12/2003] [Indexed: 12/16/2022]
Abstract
Protein phosphatase 2A (PP2A) is a major serine/threonine-specific phosphatase playing central roles in development, cell growth and transformation. Regulation is largely accomplished by the regulatory B subunits, which determine substrate specificity, subcellular localisation and catalytic activity. The B' family, also known as the PR61 family, is the most diverse, consisting of five genes (alpha,beta,gamma,delta and epsilon) that give rise to a number of splice variants. We deduced the sequences of the different PR61 proteins in mice and found evidence for the expression of PR61alpha, beta1, gamma1, gamma2, gamma3, delta1 and epsilon. We report the genomic organisation and localisation of the murine PR61 genes (Ppp2r5a-Ppp2r5e). This information will be useful for the future realisation of PR61 knockouts. Using Northern blotting, we examined the expression of the five PR61 isoforms in different tissues. A brain-specific function can be expected for the PR611beta protein based on the high expression levels observed in murine brain. In situ hybridisation analysis of the adult brain revealed a distinct and partially overlapping pattern of mRNA expression of the various PR61 isoforms. The PR61 mRNA expression during embryonic development was examined by Northern blotting. The PR61 transcripts were differentially expressed, suggesting a specific function for each of the PR61 proteins during embryonic development and/or adult life.
Collapse
Affiliation(s)
- Ellen Martens
- Division of Biochemistry, Faculty of Medicine, Katholieke Universiteit Leuven, Herestraat 49, B-3000 Leuven, Belgium
| | | | | | | | | | | | | |
Collapse
|
41
|
Silverstein AM, Mumby MC. Analysis of protein phosphatase function in Drosophila cells using RNA interference. Methods Enzymol 2004; 366:361-72. [PMID: 14674261 DOI: 10.1016/s0076-6879(03)66027-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Double stranded RNA-mediated RNA interference is an effective method to downregulate the levels of protein phosphatases in Drosophila S2 cells. In many cases, nearly complete ablation of the targeted protein can be achieved. RNAi-mediated knockdown of protein phosphatases is akin to pharmacological inhibition with drugs and can be used to determine the roles of specific protein phosphatases in intact cells. RNAi can avoid the problems associated with less than adequate specificity of phosphatase inhibitors. Although information about the signaling pathways present in Drosophila S2 cells is not as well developed as many mammalian cell lines, the Drosophila system is particularly attractive for the study of oligomeric phosphatases like PP2A. Drosophila has far fewer isoforms for the phosphatases we have examined. This is especially true of the genes for PP2A regulatory subunits where over 50 isoforms are present in mammals but only four are present in Drosophila. Once hypotheses regarding phosphatase function have been generated from RNAi experiments in S2 cells, they can potentially be tested utilizing recent advances in the use of siRNAs to conduct RNAi experiments in mammalian cell lines. RNAi in Drosophila S2 cells has proven to be a powerful technique for identifying physiological functions of signaling proteins. The RNAi method is straightforward and works routinely with almost all proteins. RNAi in S2 cells can be used to assess the role of signaling proteins in specific pathways and as a screening tool to identify new roles for signaling molecules. For example, results from RNAi analysis of PP2A show that regulation of MAP kinase signaling involves the R2/B regulatory subunit and that the R5/B56 subunits play a previously unidentified role in apoptosis. While RNAi in Drosophila S2 cells is a powerful tool for analyzing protein function, the method does have limitations. Foremost, cells may exhibit an RNAi response to any nonspecific dsRNA, even in the absence of interferon. Therefore, physiological processes that respond to nonspecific dsRNA will be difficult to study. A second limitation is the need to produce antibodies that react with Drosophila isoforms. We have found that many antibodies to mammalian protein phosphatases do not cross-react with the corresponding Drosophila proteins. Finally, the physiology and signaling pathways of S2 cells have not been extensively studied. This lack of information limits the number of available readouts that can be used when assessing the effects of protein knockdowns.
Collapse
Affiliation(s)
- Adam M Silverstein
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9041, USA
| | | |
Collapse
|
42
|
LaRonde-LeBlanc NA, Wolberger C. Structure of HoxA9 and Pbx1 bound to DNA: Hox hexapeptide and DNA recognition anterior to posterior. Genes Dev 2003; 17:2060-72. [PMID: 12923056 PMCID: PMC196259 DOI: 10.1101/gad.1103303] [Citation(s) in RCA: 152] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2003] [Accepted: 06/23/2003] [Indexed: 01/30/2023]
Abstract
The HOX/HOM superfamily of homeodomain proteins controls cell fate and segmental embryonic patterning by a mechanism that is conserved in all metazoans. The linear arrangement of the Hox genes on the chromosome correlates with the spatial distribution of HOX protein expression along the anterior-posterior axis of the embryo. Most HOX proteins bind DNA cooperatively with members of the PBC family of TALE-type homeodomain proteins, which includes human Pbx1. Cooperative DNA binding between HOX and PBC proteins requires a residue N-terminal to the HOX homeodomain termed the hexapeptide, which differs significantly in sequence between anterior- and posterior-regulating HOX proteins. We report here the 1.9-A-resolution structure of a posterior HOX protein, HoxA9, complexed with Pbx1 and DNA, which reveals that the posterior Hox hexapeptide adopts an altered conformation as compared with that seen in previously determined anterior HOX/PBC structures. The additional nonspecific interactions and altered DNA conformation in this structure account for the stronger DNA-binding affinity and altered specificity observed for posterior HOX proteins when compared with anterior HOX proteins. DNA-binding studies of wild-type and mutant HoxA9 and HoxB1 show residues in the N-terminal arm of the homeodomains are critical for proper DNA sequence recognition despite lack of direct contact by these residues to the DNA bases. These results help shed light on the mechanism of transcriptional regulation by HOX proteins and show how DNA-binding proteins may use indirect contacts to determine sequence specificity.
Collapse
Affiliation(s)
- Nicole A LaRonde-LeBlanc
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205-2185, USA
| | | |
Collapse
|
43
|
Schaffer A, Kim EC, Wu X, Zan H, Testoni L, Salamon S, Cerutti A, Casali P. Selective inhibition of class switching to IgG and IgE by recruitment of the HoxC4 and Oct-1 homeodomain proteins and Ku70/Ku86 to newly identified ATTT cis-elements. J Biol Chem 2003; 278:23141-50. [PMID: 12672812 DOI: 10.1074/jbc.m212952200] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Immunoglobulin (Ig) class switching is central to the maturation of the antibody response as IgG, IgA, and IgE are endowed with more diverse biological effector functions than IgM. It is induced upon engagement of CD40 on B lymphocytes by CD40L expressed by activated CD4+ T cells and exposure of B cells to T cell-secreted cytokines including interleukin-4 and transforming growth factor-beta. It begins with germ line IH-CH transcription and unfolds through class switch DNA recombination (CSR). We show here that the HoxC4 and Oct-1 homeodomain proteins together with the Ku70/Ku86 heterodimer bind as a complex to newly identified switch (S) regulatory ATTT elements (SREs) in the Igamma and Iepsilon promoters and downstream regions to dampen basal germ line Igamma-Cgamma and Iepsilon-Cepsilon transcriptions and repress CSR to Cgamma and Cepsilon. This mechanism is inactive in the Calpha1/Calpha2 loci because of the lack of SREs in the Ialpha1/Ialpha2 promoters. Accordingly, in resting human IgM+IgD+ B cells, HoxC4, Oct-1, and Ku70/Ku86 can be readily identified as bound to the Igamma and Iepsilon promoters but not the Ialpha1/Ialpha2 promoters. CD40 signaling dissociates the HoxC4.Oct-1. Ku complex from the Igamma and Iepsilon promoter SREs, thereby relieving the IH-CH transcriptional repression and allowing CSR to unfold. Dissociation of HoxC4.Oct-1. Ku from DNA is hampered by CD153 engagement, a CD40-signaling inhibitor. Thus, these findings outline a HoxC4.Oct-1. Ku-dependent mechanism of selective regulation of class switching to IgG and IgE and further suggest distinct co-evolution and shared CSR activation pathways in the Cgamma and Cepsilon as opposed to the Calpha1/Calpha2 loci.
Collapse
Affiliation(s)
- András Schaffer
- Division of Molecular Immunology, Department of Pathology and Laboratory Medicine, Joan and Sanford I. Weill Medical College, Cornell University, New York, New York 10021, USA
| | | | | | | | | | | | | | | |
Collapse
|
44
|
Adachi M, Lewis EJ. The paired-like homeodomain protein, Arix, mediates protein kinase A-stimulated dopamine beta-hydroxylase gene transcription through its phosphorylation status. J Biol Chem 2002; 277:22915-24. [PMID: 11943777 DOI: 10.1074/jbc.m201695200] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The homeodomain transcription factor Arix/Phox2a plays a critical role in the specification of noradrenergic neurons by inducing the expression of dopamine beta-hydroxylase (DBH), the terminal enzyme for noradrenaline biosynthesis. In reporter assays, Arix together with activation of cAMP-dependent protein kinase (PKA) potentiates DBH gene transcription. We have evaluated whether post-translational modification of Arix regulates PKA-mediated DBH gene transcription. We found that Arix is constitutively phosphorylated in vivo at the basal level and that the phosphorylation level is substantially decreased upon stimulation of the PKA pathway. The change in the Arix phosphorylation state coincides with DNA binding activity of Arix. Treatment of cells with forskolin results in a robust enhancement of the DNA binding of Arix, which is reversed by treatment with serine/threonine and tyrosine phosphatase inhibitors. Consistent with the DNA binding activity of Arix, treatment of cultured cells with phosphatase inhibitors diminishes transcriptional activation with Arix plus forskolin. Amino acid analysis demonstrates the presence of phosphoserine within Arix. The results collectively suggest that dephosphorylation of Arix is a necessary event to fully activate PKA-mediated DBH transcription. Thus, the present study demonstrates that Arix can integrate extrinsic signals through post-translational modification, regulating DBH gene transcription in response to activation of the PKA pathway.
Collapse
Affiliation(s)
- Megumi Adachi
- Department of Biochemistry and Molecular Biology, Oregon Health & Science University, Portland, Oregon 97201, USA
| | | |
Collapse
|
45
|
Himmelbach A, Hoffmann T, Leube M, Höhener B, Grill E. Homeodomain protein ATHB6 is a target of the protein phosphatase ABI1 and regulates hormone responses in Arabidopsis. EMBO J 2002; 21:3029-38. [PMID: 12065416 PMCID: PMC126069 DOI: 10.1093/emboj/cdf316] [Citation(s) in RCA: 282] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
ABI1, a protein phosphatase 2C, is a key component of signal transduction in Arabidopsis. It regulates diverse responses to the phytohormone abscisic acid (ABA) such as stomatal closure, seed dormancy and inhibition of vegetative growth. By analysing proteins capable of interacting with ABI1, we have identified the homeodomain protein ATHB6 as a regulator of the ABA signal pathway. Critical for interaction between ATHB6 and ABI1 is an intact protein phosphatase domain and the N-terminal domain of ATHB6 containing the DNA-binding site. ATHB6 recognizes a cis-element present in its promoter, which encompasses the core motif (CAATTATTA) that mediated ATHB6- and ABA-dependent gene expression in protoplasts. In addition, transgenic plants containing a luciferase gene controlled by the ATHB6 promoter documented a strong ABA-inducible expression of the reporter which was abrogated in the ABA-insensitive abi1 mutant. Arabidopsis plants with constitutive expression of the transcriptional regulator revealed ABA insensitivity in a subset of ABI1-dependent responses. Thus, the homeodomain protein ATHB6 seems to represent a negative regulator of the ABA signal pathway and to act downstream of ABI1.
Collapse
Affiliation(s)
| | | | | | | | - Erwin Grill
- Lehrstuhl für Botanik, Technische Universität München, Am Hochanger 4, D-85350 Freising, Germany
Corresponding author e-mail:
| |
Collapse
|
46
|
Terol J, Bargues M, Carrasco P, Pérez-Alonso M, Paricio N. Molecular characterization and evolution of the protein phosphatase 2A B' regulatory subunit family in plants. PLANT PHYSIOLOGY 2002; 129:808-22. [PMID: 12068121 PMCID: PMC161703 DOI: 10.1104/pp.020004] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Type 2A serine/threonine protein phosphatases (PP2A) are important components in the reversible protein phosphorylation events in plants and other organisms. PP2A proteins are oligomeric complexes constituted by a catalytic subunit and several regulatory subunits that modulate the activity of these phosphatases. The analysis of the complete genome of Arabidopsis allowed us to characterize four novel genes, AtB'epsilon, AtB'zeta, AtB'eta, and AtB'theta;, belonging to the PP2A B' regulatory subunit family. Because four genes of this type had been described previously, this family is composed of eight members. Reverse transcriptase-polymerase chain reaction experiments showed that AtB'epsilon mRNAs are present in all Arabidopsis tissues analyzed, and their levels do not respond significantly to heat stress. Expressed sequence tags corresponding to AtB'zeta, AtB'eta, and AtB'theta; have been identified, indicating that the new genes are actively transcribed. The genomic organization of this family of PP2A regulatory subunits is reported, as well as its chromosomal location. An extensive survey of the family has been carried out in plants, characterizing B' subunits in a number of different species, and performing a phylogenetic study that included several B' regulatory proteins from animals. Our results indicate that the animal and plant proteins have evolved independently, that there is a relationship between the number of B' isoforms and the complexity of the organism, and that there are at least three main subfamilies of regulatory subunits in plants, which we have named alpha, eta, and kappa.
Collapse
Affiliation(s)
- Javier Terol
- Departament de Genetica, Universitat de València, Doctor Moliner 50, 46100 Burjassot, Spain
| | | | | | | | | |
Collapse
|
47
|
Li X, Scuderi A, Letsou A, Virshup DM. B56-associated protein phosphatase 2A is required for survival and protects from apoptosis in Drosophila melanogaster. Mol Cell Biol 2002; 22:3674-84. [PMID: 11997504 PMCID: PMC133809 DOI: 10.1128/mcb.22.11.3674-3684.2002] [Citation(s) in RCA: 116] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2002] [Revised: 02/18/2002] [Accepted: 02/20/2002] [Indexed: 01/11/2023] Open
Abstract
Protein phosphorylation and specific protein kinases can initiate signal transduction pathways leading to programmed cell death. The specific protein phosphatases regulating apoptosis have been more elusive. Using double-stranded RNA-mediated interference (RNAi), the role of protein phosphatase 2A (PP2A) in cellular signaling was investigated. Knockdown of A or C subunits individually or of combined B subunits led to concurrent loss of nontargeted PP2A subunits, suggesting that PP2A is an obligate heterotrimer in vivo. Global knockdown of PP2A activity or specific loss of redundant B56 regulatory subunits caused cell death with the morphological and biochemical changes characteristic of apoptosis in cultured S2 cells. B56:PP2A-regulated apoptosis required caspases and the upstream regulators dark, reaper, head involution defective, and dp53. In Drosophila embryos, knockdown of B56-regulated PP2A activity resulted in apoptosis and failure of gastrulation, an effect that was blocked by concurrent RNAi of the caspase DRICE: B56-regulated PP2A activity appears to be required upstream of dp53 to maintain a critical proapoptotic substrate in a dephosphorylated, inactive state, thereby preventing apoptosis in Drosophila S2 cells.
Collapse
Affiliation(s)
- Xinghai Li
- Department of Oncological Sciences, Huntsman Cancer Institute, University of Utah, Salt Lake City, Utah 84112-5550, USA
| | | | | | | |
Collapse
|
48
|
Kömüves LG, Michael E, Arbeit JM, Ma XK, Kwong A, Stelnicki E, Rozenfeld S, Morimune M, Yu QC, Largman C. HOXB4 homeodomain protein is expressed in developing epidermis and skin disorders and modulates keratinocyte proliferation. Dev Dyn 2002; 224:58-68. [PMID: 11984874 DOI: 10.1002/dvdy.10085] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
The HOX homeodomain proteins are fundamental regulators of organ and tissue development, where they are thought to function as transcription factors, and HOX gene expression has been associated with numerous types of cancers. Previous studies have demonstrated that enforced expression of the HOXB4 protein transforms cultured fibroblasts and leads to a selective expansion of the hematopoietic stem cell pool, suggesting that this protein might play a role in cellular proliferation. In support of this concept, we now show that enforced expression of HOXB4 in human neonatal keratinocytes results in increased cellular proliferation and colony formation as well as decreased expression of the alpha-2-integrin and CD44 cell surface adhesion molecules. We previously have reported HOXB4 gene expression in the basal and suprabasal layers of developing human skin and now show extensive HOXB4 mRNA in psoriatic skin and basal cell carcinoma. In fetal human skin HOXB4 protein expression was both nuclear and cytoplasmic within epidermal basal cells and in hair follicle inner and outer root sheath cells, whereas strong nuclear signals were observed in the bulge region. In adult skin, HOXB4 protein expression was both nuclear and cytoplasmic, but was predominantly localized to the intermediate and differentiated cell layers. In contrast to the striking gradient patterns of HOX gene and protein expression previously described in developing spinal cord and limb, HOXB4 protein was uniformly detected in all regions of the fetal and adult skin. Although little HOXB4 signal localized to proliferative cell layers, as marked by proliferating cell nuclear antigen (PCNA) staining, in normal adult epidermis, nuclear HOXB4 protein expression substantially overlapped with PCNA-positive cell in a series of samples of hyperproliferative skin. Taken together, these data suggest that nuclear HOXB4 protein may play a role in the regulation of cellular proliferation/adhesion in developing fetal human epidermis and in hyperproliferation conditions, including cancers, in adult epidermis. Published 2002 Wiley-Liss, Inc.
Collapse
Affiliation(s)
- László G Kömüves
- Department of Dermatology, VA Medical Center and University of California-San Francisco, 4150 Clement Street, San Francisco, CA 94121, USA
| | | | | | | | | | | | | | | | | | | |
Collapse
|
49
|
Silverstein AM, Barrow CA, Davis AJ, Mumby MC. Actions of PP2A on the MAP kinase pathway and apoptosis are mediated by distinct regulatory subunits. Proc Natl Acad Sci U S A 2002; 99:4221-6. [PMID: 11904383 PMCID: PMC123629 DOI: 10.1073/pnas.072071699] [Citation(s) in RCA: 217] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2001] [Accepted: 02/06/2002] [Indexed: 11/18/2022] Open
Abstract
Individual subunits of protein phosphatase 2A (PP2A), protein phosphatase 4, and protein phosphatase 5 were knocked out in Drosophila Schneider 2 cells by using RNA interference. Ablation of either the scaffold (A) or catalytic (C) subunits of PP2A caused the disappearance of all PP2A subunits. Treating cells with double-stranded RNA targeting all four of the Drosophila PP2A regulatory subunits caused the disappearance of both the A and C subunits. The loss of PP2A subunits was associated with decreased protein stability indicating that only the heterotrimeric forms of PP2A are stable in intact cells. Ablation of total PP2A by using double-stranded RNA against either the A or C subunit, or specific ablation of the R2/B regulatory subunit, enhanced insulin-induced ERK activation. These results indicated that the R2/B subunit targets PP2A to the mitogen-activated protein (MAP) kinase cascade in Schneider 2 cells, where it acts as a negative regulator. A severe loss of viability occurred in cells in which total PP2A or both isoforms of the Drosophila R5/B56 subunit had been ablated. The reduced viability of these cells correlated with the induction of markers of apoptosis including membrane blebbing and stimulation of caspase-3-like activity. These observations indicated that PP2A has a powerful antiapoptotic activity that is specifically mediated by the R5/B56 regulatory subunits. In contrast to PP2A, ablation of protein phosphatase 4 caused only a slight reduction in cell growth but had no effect on MAP kinase signaling or apoptosis. Depletion of protein phosphatase 5 had no effects on MAP kinase, cell growth, or apoptosis.
Collapse
Affiliation(s)
- Adam M Silverstein
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9041, USA
| | | | | | | |
Collapse
|
50
|
Halder G, Carroll SB. Binding of the Vestigial co-factor switches the DNA-target selectivity of the Scalloped selector protein. Development 2001; 128:3295-305. [PMID: 11546746 DOI: 10.1242/dev.128.17.3295] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The formation and identity of organs and appendages are regulated by specific selector genes that encode transcription factors that regulate potentially large sets of target genes. The DNA-binding domains of selector proteins often exhibit relatively low DNA-binding specificity in vitro. It is not understood how the target selectivity of most selector proteins is determined in vivo. The Scalloped selector protein controls wing development in Drosophila by regulating the expression of numerous target genes and forming a complex with the Vestigial protein. We show that binding of Vestigial to Scalloped switches the DNA-binding selectivity of Scalloped. Two conserved domains of the Vestigial protein that are not required for Scalloped binding in solution are required for the formation of the heterotetrameric Vestigial-Scalloped complex on DNA. We suggest that Vestigial affects the conformation of Scalloped to create a wing cell-specific DNA-binding selectivity. The modification of selector protein DNA-binding specificity by co-factors appears to be a general mechanism for regulating their target selectivity in vivo.
Collapse
Affiliation(s)
- G Halder
- Howard Hughes Medical Institute and Laboratory of Molecular Biology, University of Wisconsin, 1525 Linden Drive, Madison,WI 53706, USA.
| | | |
Collapse
|