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Zhu S, Wu X, Fu H, Ye C, Chen M, Jiang Z, Ji G. Modeling of Genome-Wide Polyadenylation Signals in Xenopus tropicalis. Front Genet 2019; 10:647. [PMID: 31333724 PMCID: PMC6616101 DOI: 10.3389/fgene.2019.00647] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2019] [Accepted: 06/18/2019] [Indexed: 12/22/2022] Open
Abstract
Alternative polyadenylation (APA) is an important post-transcriptional modification event to process messenger RNA (mRNA) for transcriptional termination, transport, and translation. In the present study, we characterized poly(A) signals in Xenopus tropicalis using 70,918 highly confident poly(A) sites derived from 16,511 protein-coding genes to understand their roles in the regulation of embryo development and gender difference. We examined potential factors, including the gene length, the number of introns in a gene, and the intron length, that may affect the prevalence of APA. We observed 12 prominent poly(A) signal patterns, which accounted for approximately 92% of total APA sites in Xenopus tropicalis. Among them, three patterns are specific to X. tropicalis, so they are absent in other animals such as humans or mice. We catalogued APA sites based on their genomic regions and developed a bioinformatics pipeline to identify over-represented signal patterns for each class. Then the schema of cis elements for APA sites in each genomic region was proposed. More importantly, APA usage is dramatically dynamic in embryos along five developmental stages and well-coordinated with the maternal-to-zygotic transition event. We used an entropy-based method to identify developmental stage-specific APA sites and identified significant signal patterns around specific sites and constitutive sites. We found that the APA frequency in different genomic regions varies with developmental stages and that those sites located in intron or coding sequence regions contribute most to the dynamics of gene expression during developmental stages. This study deciphers the characteristics and poly(A) signal patterns for both canonical APA sites and non-canonical APA sites across different developmental stages and gender dimorphisms in X. tropicalis, providing new insights into the dynamic regulation of distal and proximal APA.
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Affiliation(s)
- Sheng Zhu
- Department of Automation, Xiamen University, Xiamen, China.,National Institute for Data Science in Health and Medicine, Xiamen University, Xiamen, China
| | - Xiaohui Wu
- Department of Automation, Xiamen University, Xiamen, China.,National Institute for Data Science in Health and Medicine, Xiamen University, Xiamen, China.,Innovation Center for Cell Signaling Network, Xiamen University, Xiamen, China
| | - Hongjuan Fu
- Department of Automation, Xiamen University, Xiamen, China
| | - Congting Ye
- National Institute for Data Science in Health and Medicine, Xiamen University, Xiamen, China.,Key Laboratory of the Ministry of Education for Coastal and Wetland Ecosystems, College of the Environment and Ecology, Xiamen University, Xiamen, China
| | - Moliang Chen
- Department of Automation, Xiamen University, Xiamen, China
| | - Zhihua Jiang
- Department of Animal Sciences and Center for Reproductive Biology, Washington State University, Pullman, WA, United States
| | - Guoli Ji
- Department of Automation, Xiamen University, Xiamen, China.,National Institute for Data Science in Health and Medicine, Xiamen University, Xiamen, China.,Innovation Center for Cell Signaling Network, Xiamen University, Xiamen, China
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2
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Rouhana L, Tasaki J, Saberi A, Newmark PA. Genetic dissection of the planarian reproductive system through characterization of Schmidtea mediterranea CPEB homologs. Dev Biol 2017; 426:43-55. [PMID: 28434803 PMCID: PMC5544531 DOI: 10.1016/j.ydbio.2017.04.008] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2017] [Revised: 03/30/2017] [Accepted: 04/18/2017] [Indexed: 01/30/2023]
Abstract
Cytoplasmic polyadenylation is a mechanism of mRNA regulation prevalent in metazoan germ cells; it is largely dependent on Cytoplasmic Polyadenylation Element Binding proteins (CPEBs). Two CPEB homologs were identified in the planarian Schmidtea mediterranea. Smed-CPEB1 is expressed in ovaries and yolk glands of sexually mature planarians, and required for oocyte and yolk gland development. In contrast, Smed-CPEB2 is expressed in the testes and the central nervous system; its function is required for spermatogenesis as well as non-autonomously for development of ovaries and accessory reproductive organs. Transcriptome analysis of CPEB knockdown animals uncovered a comprehensive collection of molecular markers for reproductive structures in S. mediterranea, including ovaries, testes, yolk glands, and the copulatory apparatus. Analysis by RNA interference revealed contributions for a dozen of these genes during oogenesis, spermatogenesis, or capsule formation. We also present evidence suggesting that Smed-CPEB2 promotes translation of Neuropeptide Y-8, a prohormone required for planarian sexual maturation. These findings provide mechanistic insight into potentially conserved processes of germ cell development, as well as events involved in capsule deposition by flatworms.
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Affiliation(s)
- Labib Rouhana
- Department of Biological Sciences, Wright State University, 3640 Colonel Glenn Highway, Dayton, OH 45435, USA; Howard Hughes Medical Institute and Department of Cell and Developmental Biology, University of Illinois at Urbana-Champaign, 601 S. Goodwin Ave., Urbana, IL 61801, USA.
| | - Junichi Tasaki
- Department of Biological Sciences, Wright State University, 3640 Colonel Glenn Highway, Dayton, OH 45435, USA
| | - Amir Saberi
- Howard Hughes Medical Institute and Department of Cell and Developmental Biology, University of Illinois at Urbana-Champaign, 601 S. Goodwin Ave., Urbana, IL 61801, USA
| | - Phillip A Newmark
- Howard Hughes Medical Institute and Department of Cell and Developmental Biology, University of Illinois at Urbana-Champaign, 601 S. Goodwin Ave., Urbana, IL 61801, USA
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3
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Ochi H, Chiba K. Hormonal stimulation of starfish oocytes induces partial degradation of the 3' termini of cyclin B mRNAs with oligo(U) tails, followed by poly(A) elongation. RNA (NEW YORK, N.Y.) 2016; 22:822-829. [PMID: 27048146 PMCID: PMC4878609 DOI: 10.1261/rna.054882.115] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/14/2015] [Accepted: 03/07/2016] [Indexed: 05/30/2023]
Abstract
In yeast, plant, and mammalian somatic cells, short poly(A) tails on mRNAs are subject to uridylation, which mediates mRNA decay. Although mRNA uridylation has never been reported in animal oocytes, maternal mRNAs with short poly(A) tails are believed to be translationally repressed. In this study, we found that 96% of cyclin B mRNAs with short poly(A) tails were uridylated in starfish oocytes. Hormonal stimulation induced poly(A) elongation of cyclin B mRNA, and 62% of long adenine repeats did not contain uridine residues. To determine whether uridylated short poly(A) tails destabilize cyclin B mRNA, we developed a method for producing RNAs with the strict 3' terminal sequences of cyclin B, with or without oligo(U) tails. When we injected these synthetic RNAs into starfish oocytes prior to hormonal stimulation, we found that uridylated RNAs were as stable as nonuridylated RNAs. Following hormonal stimulation, the 3' termini of short poly(A) tails of synthesized RNAs containing oligo(U) tails were trimmed, and their poly(A) tails were subsequently elongated. These results indicate that uridylation of short poly(A) tails in cyclin B mRNA of starfish oocytes does not mediate mRNA decay; instead, hormonal stimulation induces partial degradation of uridylated short poly(A) tails in the 3'-5' direction, followed by poly(A) elongation. Oligo(U) tails may be involved in translational inactivation of mRNAs.
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Affiliation(s)
- Hiroe Ochi
- Department of Biological Sciences, Ochanomizu University, Bunkyo-ku, Tokyo 112-8610, Japan
| | - Kazuyoshi Chiba
- Department of Biological Sciences, Ochanomizu University, Bunkyo-ku, Tokyo 112-8610, Japan
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4
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CPEB and miR-15/16 Co-Regulate Translation of Cyclin E1 mRNA during Xenopus Oocyte Maturation. PLoS One 2016; 11:e0146792. [PMID: 26829217 PMCID: PMC4734764 DOI: 10.1371/journal.pone.0146792] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2015] [Accepted: 12/22/2015] [Indexed: 01/07/2023] Open
Abstract
Cell cycle transitions spanning meiotic maturation of the Xenopus oocyte and early embryogenesis are tightly regulated at the level of stored inactive maternal mRNA. We investigated here the translational control of cyclin E1, required for metaphase II arrest of the unfertilised egg and the initiation of S phase in the early embryo. We show that the cyclin E1 mRNA is regulated by both cytoplasmic polyadenylation elements (CPEs) and two miR-15/16 target sites within its 3’UTR. Moreover, we provide evidence that maternal miR-15/16 microRNAs co-immunoprecipitate with CPE-binding protein (CPEB), and that CPEB interacts with the RISC component Ago2. Experiments using competitor RNA and mutated cyclin E1 3’UTRs suggest cooperation of the regulatory elements to sustain repression of the cyclin E1 mRNA during early stages of maturation when CPEB becomes limiting and cytoplasmic polyadenylation of repressed mRNAs begins. Importantly, injection of anti-miR-15/16 LNA results in the early polyadenylation of endogenous cyclin E1 mRNA during meiotic maturation, and an acceleration of GVBD, altogether strongly suggesting that the proximal CPEB and miRNP complexes act to mutually stabilise each other. We conclude that miR-15/16 and CPEB co-regulate cyclin E1 mRNA. This is the first demonstration of the co-operation of these two pathways.
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Ochi H, Aoto S, Tachibana K, Hara M, Chiba K. Block of CDK1-dependent polyadenosine elongation of Cyclin B mRNA in metaphase-i-arrested starfish oocytes is released by intracellular pH elevation upon spawning. Mol Reprod Dev 2015; 83:79-87. [PMID: 26632330 DOI: 10.1002/mrd.22599] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2015] [Accepted: 11/24/2015] [Indexed: 12/12/2022]
Abstract
Meiotic progression requires the translation of maternal mRNAs in a strict temporal order. In isolated animal oocytes, translation of maternal mRNAs containing a cytoplasmic polyadenylation element (CPE), such as cyclin B, is activated by in vitro stimulation of meiotic resumption which induces phosphorylation of CPEB (CPE-binding protein) and elongation of their polyadenosine (poly(A)) tails; whether or not this model can be applied in vivo to oocytes arrested at metaphase of meiosis I in ovaries is unknown. In this study, we found that active CDK1 (cyclin-dependent kinase 1) phosphorylated CPEB in ovarian oocytes arrested at metphase I in the starfish body cavity, but phosphorylation of CPEB was not sufficient for elongation of cyclin B poly(A) tails. Immediately after spawning, however, mRNA was polyadenylated, suggesting that an increase in intracellular pH (pHi ) upon spawning triggers the elongation of poly(A) tails. Using a cell-free system made from maturing oocytes at metaphase I, we demonstrated that polyadenylation was indeed suppressed at pH below 7.0. These results suggest that a pH-sensitive process, functioning after CPEB phosphorylation, is blocked under physiologically low pHi (<7.0) in metaphase-I-arrested oocytes. The increase in pHi (>7.0) that occurs after spawning triggers polyadenylation of cyclin B mRNA and progression into meiosis II.
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Affiliation(s)
- Hiroe Ochi
- Department of Biological Sciences, Ochanomizu University, Tokyo, Japan
| | - Saki Aoto
- Department of Biological Sciences, Ochanomizu University, Tokyo, Japan
| | - Kazunori Tachibana
- Laboratory of Cell and Developmental Biology, Graduate School of Bioscience, Tokyo Institute of Technology, Yokohama, Japan
| | - Masatoshi Hara
- Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka, Japan
| | - Kazuyoshi Chiba
- Department of Biological Sciences, Ochanomizu University, Tokyo, Japan
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6
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O'Connell ML, Cavallo WC, Firnberg M. The expression of CPEB proteins is sequentially regulated during zebrafish oogenesis and embryogenesis. Mol Reprod Dev 2014; 81:376-87. [DOI: 10.1002/mrd.22306] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2013] [Accepted: 01/25/2014] [Indexed: 12/25/2022]
Affiliation(s)
- Marcia L. O'Connell
- The Department of Biology; The College of New Jersey; Ewing New Jersey 08628
| | - William C. Cavallo
- The Department of Biology; The College of New Jersey; Ewing New Jersey 08628
| | - Maytal Firnberg
- The Department of Biology; The College of New Jersey; Ewing New Jersey 08628
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7
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Fernández-Miranda G, Méndez R. The CPEB-family of proteins, translational control in senescence and cancer. Ageing Res Rev 2012; 11:460-72. [PMID: 22542725 DOI: 10.1016/j.arr.2012.03.004] [Citation(s) in RCA: 115] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2012] [Revised: 03/14/2012] [Accepted: 03/27/2012] [Indexed: 12/31/2022]
Abstract
Cytoplasmic elongation of the poly(A) tail was originally identified as a mechanism to activate maternal mRNAs, stored as silent transcripts with short poly(A) tails, during meiotic progression. A family of RNA-binding proteins named CPEBs, which recruit the translational repression or cytoplasmic polyadenylation machineries to their target mRNAs, directly mediates cytoplasmic polyadenylation. Recent years have witnessed an explosion of studies showing that CPEBs are not only expressed in a variety of somatic tissues, but have essential functions controlling gene expression in time and space in the adult organism. These "new" functions of the CPEBs include regulating the balance between senescence and proliferation and its pathological manifestation, tumor development. In this review, we summarize current knowledge on the functions of the CPEB-family of proteins in the regulation of cell proliferation, their target mRNAs and the mechanism controlling their activities.
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Hafer N, Xu S, Bhat KM, Schedl P. The Drosophila CPEB protein Orb2 has a novel expression pattern and is important for asymmetric cell division and nervous system function. Genetics 2011; 189:907-21. [PMID: 21900268 PMCID: PMC3213381 DOI: 10.1534/genetics.110.123646] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2011] [Accepted: 08/23/2011] [Indexed: 11/18/2022] Open
Abstract
Cytoplasmic polyadenylation element binding (CPEB) proteins bind mRNAs to regulate their localization and translation. While the first CPEBs discovered were germline specific, subsequent studies indicate that CPEBs also function in many somatic tissues including the nervous system. Drosophila has two CPEB family members. One of these, orb, plays a key role in the establishment of polarity axes in the developing egg and early embryo, but has no known somatic functions or expression outside of the germline. Here we characterize the other Drosophila CPEB, orb2. Unlike orb, orb2 mRNA and protein are found throughout development in many different somatic tissues. While orb2 mRNA and protein of maternal origin are distributed uniformly in early embryos, this pattern changes as development proceeds and by midembryogenesis the highest levels are found in the CNS and PNS. In the embryonic CNS, Orb2 appears to be concentrated in cell bodies and mostly absent from the longitudinal and commissural axon tracts. In contrast, in the adult brain, the protein is seen in axonal and dendritic terminals. Lethal effects are observed for both RNAi knockdowns and orb2 mutant alleles while surviving adults display locomotion and behavioral defects. We also show that orb2 funtions in asymmetric division of stem cells and precursor cells during the development of the embryonic nervous system and mesoderm.
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Affiliation(s)
- Nathaniel Hafer
- Department of Molecular Biology, Princeton University, Princeton, New Jersey 08544
| | - Shuwa Xu
- Department of Molecular Biology, Princeton University, Princeton, New Jersey 08544
| | - Krishna Moorthi Bhat
- Department of Neuroscience and Cell Biology, University of Texas Medical Branch School of Medicine, Galveston, Texas 77555
| | - Paul Schedl
- Department of Molecular Biology, Princeton University, Princeton, New Jersey 08544
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Si K, Choi YB, White-Grindley E, Majumdar A, Kandel ER. Aplysia CPEB Can Form Prion-like Multimers in Sensory Neurons that Contribute to Long-Term Facilitation. Cell 2010; 140:421-35. [DOI: 10.1016/j.cell.2010.01.008] [Citation(s) in RCA: 296] [Impact Index Per Article: 21.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2008] [Revised: 07/20/2009] [Accepted: 01/05/2010] [Indexed: 11/24/2022]
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10
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Evsikov AV, Marín de Evsikova C. Gene expression during the oocyte-to-embryo transition in mammals. Mol Reprod Dev 2009; 76:805-18. [PMID: 19363788 DOI: 10.1002/mrd.21038] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The seminal question in modern developmental biology is the origins of new life arising from the unification of sperm and egg. The roots of this question begin from 19th to 20th century embryologists studying fertilization and embryogenesis. Although the revolution of molecular biology has yielded significant insight into the complexity of this process, the overall orchestration of genes, molecules, and cells is still not fully formed. Early mammalian development, specifically the oocyte-to-embryo transition, is essentially under "maternal command" from factors deposited in the cytoplasm during oocyte growth, independent of de novo transcription from the nascent embryo. Many of the advances in understanding this developmental period occurred in tandem with application of new methods and techniques from molecular biology, from protein electrophoresis to sequencing and assemblies of whole genomes. From this bed of knowledge, it appears that precise control of mRNA translation is a key regulator coordinating the molecular and cellular events occurring during oocyte-to-embryo transition. Notably, oocyte transcriptomes share, yet retain some uniqueness, common genetic motifs among all chordates. The common genetic motifs typically define fundamental processes critical for cellular maintenance, whereas the unique genetic features may be a source of variation and a substrate for sexual selection, genetic drift, or gene flow. One purpose for this complex interplay among genes, proteins, and cells may allow for evolution to transform and act upon the underlying processes, at molecular, structural and organismal levels, to increase diversity, which is the ultimate goal of sexual reproduction.
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Translational control in early development: CPEB, P-bodies and germinal granules. Biochem Soc Trans 2008; 36:671-6. [PMID: 18631138 DOI: 10.1042/bst0360671] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Selective protein synthesis in oocytes, eggs and early embryos of many organisms drives several critical aspects of early development, including meiotic maturation and entry into mitosis, establishment of embryonic axes and cell fate determination. mRNA-binding proteins which (usually) recognize 3'-UTR (untranslated region) elements in target mRNAs influence the recruitment of the small ribosomal subunit to the 5' cap. Probably the best studied such protein is CPEB (cytoplasmic polyadenylation element-binding protein), which represses translation in the oocyte in a cap-dependent manner, and activates translation in the meiotically maturing egg, via cytoplasmic polyadenylation. Co-immunoprecipitation and gel-filtration assays revealed that CPEB in Xenopus oocytes is in a very large RNP (ribonucleoprotein) complex and interacts with other RNA-binding proteins including Xp54 RNA helicase, Pat1, RAP55 (RNA-associated protein 55) and FRGY2 (frog germ cell-specific Y-box protein 2), as well as the eIF4E (eukaryotic initiation factor 4E)-binding protein 4E-T (eIF4E-transporter) and an ovary-specific eIF4E1b, which binds the cap weakly. Functional tests which implicate 4E-T and eIF4E1b in translational repression in oocytes led us to propose a model for the specific inhibition of translation of a target mRNA by a weak cap-binding protein. The components of the CPEB RNP complex are common to P-bodies (processing bodies), neuronal granules and germinal granules, suggesting that a highly conserved 'masking' complex operates in early development, neurons and somatic cells.
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Prasad CK, Mahadevan M, MacNicol MC, MacNicol AM. Mos 3' UTR regulatory differences underlie species-specific temporal patterns of Mos mRNA cytoplasmic polyadenylation and translational recruitment during oocyte maturation. Mol Reprod Dev 2008; 75:1258-68. [PMID: 18246541 DOI: 10.1002/mrd.20877] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The Mos proto-oncogene is a critical regulator of vertebrate oocyte maturation. The maturation-dependent translation of Mos protein correlates with the cytoplasmic polyadenylation of the maternal Mos mRNA. However, the precise temporal requirements for Mos protein function differ between oocytes of model mammalian species and oocytes of the frog Xenopus laevis. Despite the advances in model organisms, it is not known if the translation of the human Mos mRNA is also regulated by cytoplasmic polyadenylation or what regulatory elements may be involved. We report that the human Mos 3' untranslated region (3' UTR) contains a functional cytoplasmic polyadenylation element (CPE) and demonstrate that the endogenous Mos mRNA undergoes maturation-dependent cytoplasmic polyadenylation in human oocytes. The human Mos 3' UTR interacts with the human CPE-binding protein and exerts translational control on a reporter mRNA in the heterologous Xenopus oocyte system. Unlike the Xenopus Mos mRNA, which is translationally activated by an early acting Musashi/polyadenylation response element (PRE)-directed control mechanism, the translational activation of the human Mos 3' UTR is dependent on a late acting CPE-dependent process. Taken together, our findings suggest a fundamental difference in the 3' UTR regulatory mechanisms controlling the temporal induction of maternal Mos mRNA polyadenylation and translational activation during Xenopus and mammalian oocyte maturation.
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Affiliation(s)
- C Krishna Prasad
- Department of Obstetrics and Gynecology, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205, USA
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13
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Kelly S, Yamamoto H, Robles LJ. Analysis of the 3' untranslated regions of alpha-tubulin and S-crystallin mRNA and the identification of CPEB in dark- and light-adapted octopus retinas. Mol Vis 2008; 14:1446-55. [PMID: 18682811 PMCID: PMC2493028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2008] [Accepted: 07/15/2008] [Indexed: 11/29/2022] Open
Abstract
PURPOSE We previously reported the differential expression and translation of mRNA and protein in dark- and light-adapted octopus retinas, which may result from cytoplasmic polyadenylation element (CPE)-dependent mRNA masking and unmasking. Here we investigate the presence of CPEs in alpha-tubulin and S-crystallin mRNA and report the identification of cytoplasmic polyadenylation element binding protein (CPEB) in light- and dark-adapted octopus retinas. METHODS 3'-RACE and sequencing were used to isolate and analyze the 3'-UTRs of alpha-tubulin and S-crystallin mRNA. Total retinal protein isolated from light- and dark-adapted octopus retinas was subjected to western blot analysis followed by CPEB antibody detection, PEP-171 inhibition of CPEB, and dephosphorylation of CPEB. RESULTS The following CPE-like sequence was detected in the 3'-UTR of isolated long S-crystallin mRNA variants: UUUAACA. No CPE or CPE-like sequences were detected in the 3'-UTRs of alpha-tubulin mRNA or of the short S-crystallin mRNA variants. Western blot analysis detected CPEB as two putative bands migrating between 60-80 kDa, while a third band migrated below 30 kDa in dark- and light-adapted retinas. CONCLUSIONS The detection of CPEB and the identification of the putative CPE-like sequences in the S-crystallin 3'-UTR suggest that CPEB may be involved in the activation of masked S-crystallin mRNA, but not in the regulation of alpha-tubulin mRNA, resulting in increased S-crystallin protein synthesis in dark-adapted octopus retinas.
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14
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Sequential waves of polyadenylation and deadenylation define a translation circuit that drives meiotic progression. Biochem Soc Trans 2008; 36:665-70. [DOI: 10.1042/bst0360665] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
The maternal mRNAs that drive meiotic progression in oocytes contain short poly(A) tails and it is only when these tails are elongated that translation takes place. Cytoplasmic polyadenylation requires two elements in the 3′-UTR (3′-untranslated region), the hexanucleotide AAUAAA and the CPE (cytoplasmic polyadenylation element), which also participates in the transport and localization, in a quiescent state, of its targets. However, not all CPE-containing mRNAs are activated at the same time during the cell cycle, and polyadenylation is temporally and spatially regulated during meiosis. We have recently deciphered a combinatorial code that can be used to qualitatively and quantitatively predict the translational behaviour of CPE-containing mRNAs. This code defines positive and negative feedback loops that generate waves of polyadenylation and deadenylation, creating a circuit of mRNA-specific translational regulation that drives meiotic progression.
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15
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Papin C, Rouget C, Mandart E. Xenopus Rbm9 is a novel interactor of XGld2 in the cytoplasmic polyadenylation complex. FEBS J 2008; 275:490-503. [PMID: 18177378 DOI: 10.1111/j.1742-4658.2007.06216.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
During early development, control of the poly(A) tail length by cytoplasmic polyadenylation is critical for the regulation of specific mRNA expression. Gld2, an atypical poly(A) polymerase, is involved in cytoplasmic polyadenylation in Xenopus oocytes. In this study, a new XGld2-interacting protein was identified: Xenopus RNA-binding motif protein 9 (XRbm9). This RNA-binding protein is exclusively expressed in the cytoplasm of Xenopus oocytes and interacts directly with XGld2. It is shown that XRbm9 belongs to the cytoplasmic polyadenylation complex, together with cytoplasmic polyadenylation element-binding protein (CPEB), cleavage and polyadenylation specificity factor (CPSF) and XGld2. In addition, tethered XRbm9 stimulates the translation of a reporter mRNA. The function of XGld2 in stage VI oocytes was also analysed. The injection of XGld2 antibody into oocytes inhibited polyadenylation, showing that endogenous XGld2 is required for cytoplasmic polyadenylation. Unexpectedly, XGld2 and CPEB antibody injections also led to an acceleration of meiotic maturation, suggesting that XGld2 is part of a masking complex with CPEB and is associated with repressed mRNAs in oocytes.
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Affiliation(s)
- Catherine Papin
- Centre de Recherche en Biochimie Macromoléculaire, Université Montpellier II, France.
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16
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Minshall N, Reiter MH, Weil D, Standart N. CPEB Interacts with an Ovary-specific eIF4E and 4E-T in Early Xenopus Oocytes. J Biol Chem 2007; 282:37389-401. [PMID: 17942399 DOI: 10.1074/jbc.m704629200] [Citation(s) in RCA: 142] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Affiliation(s)
- Nicola Minshall
- Department of Biochemistry, University of Cambridge, Cambridge, UK
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17
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Abstract
Vertebrate development is directed by maternally inherited messenger RNAs that are synthesized during the very long period of oogenesis. These dormant mRNAs usually contain short poly(A) tails and are stored as mRNA ribonucleoproteins that preclude ribosomal recruitment. In Xenopus laevis oocytes treated with the meiosis-inducing hormone progesterone, their poly(A) tails are elongated, and the mRNAs are mobilized into polysomes. This cytoplasmic polyadenylation is directed by cis-acting elements located in the 3' untranslated region of the mRNAs. However, the cytoplasmic polyadenylation of all the maternal mRNAs does not take place at once, but rather the translational activation of specific mRNAs is regulated in a sequential manner during meiosis and early development. This chapter describes the use of microinjected reporter mRNAs and radiolabeled RNAs into Xenopus oocytes to study the mRNA translational control by cytoplasmic polyadenylation. Cyclin B1 mRNA is used to illustrate the methods described.
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Affiliation(s)
- Maria Piqué
- Centre de Regulació Genòmica, Program of Gene Expression, Barcelona, Spain
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18
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Colegrove-Otero LJ, Devaux A, Standart N. The Xenopus ELAV protein ElrB represses Vg1 mRNA translation during oogenesis. Mol Cell Biol 2005; 25:9028-39. [PMID: 16199879 PMCID: PMC1265794 DOI: 10.1128/mcb.25.20.9028-9039.2005] [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: 11/20/2022] Open
Abstract
Xenopus laevis Vg1 mRNA undergoes both localization and translational control during oogenesis. We previously characterized a 250-nucleotide AU-rich element, the Vg1 translation element (VTE), in the 3'-untranslated region (UTR) of this mRNA that is responsible for the translational repression. UV-cross-linking and immunoprecipitation experiments, described here, revealed that the known AU-rich element binding proteins, ElrA and ElrB, and TIA-1 and TIAR interact with the VTE. The levels of these proteins during oogenesis are most consistent with a possible role for ElrB in the translational control of Vg1 mRNA, and ElrB, in contrast to TIA-1 and TIAR, is present in large RNP complexes. Immunodepletion of TIA-1 and TIAR from Xenopus translation extract confirmed that these proteins are not involved in the translational repression. Mutagenesis of a potential ElrB binding site destroyed the ability of the VTE to bind ElrB and also abolished translational repression. Moreover, multiple copies of the consensus motif both bind ElrB and support translational control. Therefore, there is a direct correlation between ElrB binding and translational repression by the Vg1 3'-UTR. In agreement with the reporter data, injection of a monoclonal antibody against ElrB into Xenopus oocytes resulted in the production of Vg1 protein, arguing for a role for the ELAV proteins in the translational repression of Vg1 mRNA during early oogenesis.
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19
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Abstract
RNA-binding proteins play a major part in the control of gene expression during early development. At this stage, the majority of regulation occurs at the levels of translation and RNA localization. These processes are, in general, mediated by RNA-binding proteins interacting with specific sequence motifs in the 3'-untranslated regions of their target RNAs. Although initial work concentrated on the analysis of these sequences and their trans-acting factors, we are now beginning to gain an understanding of the mechanisms by which some of these proteins function. In this review, we will describe a number of different families of RNA-binding proteins, grouping them together on the basis of common regulatory strategies, and emphasizing the recurrent themes that occur, both across different species and as a response to different biological problems.
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20
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Endo T, Naito K, Aoki F, Kume S, Tojo H. Changes in histone modifications during in vitro maturation of porcine oocytes. Mol Reprod Dev 2005; 71:123-8. [PMID: 15736133 DOI: 10.1002/mrd.20288] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Nuclear core histone modifications influence chromosome structures and functions. Recently, the involvement of histone acetylations in the cell memory of gene expression has been suggested in mouse oocyte maturation. At present, there is little available data on histone modifications in mammalian oocyte maturation. In the present study, we examined changes in the acetylation of histone H3 lysines 9 (H3K9) and 14 (H3K14), and histone H4 lysines 5 (H4K5), 8 (H4K8) and 12 (H4K12), and trimethylation of H3K9 during in vitro maturation of porcine oocytes. Immunocytochemical analyses revealed that the all of the lysines examined were highly acetylated in the germinal vesicle stage, and this level of acetylation was maintained until the first prometaphase. In the first metaphase, the lysines near the N-terminal end, H3K9 and H4K5, were completely deacetylated. The acetylation of the lysines far from the N-terminal end, H3K14, H4K8, and H4K12, was markedly decreased but still present. The acetylations were increased transiently at the first anaphase and telophase, and then decreased again at the second metaphase to the same level as the first metaphase. Since effective concentrations of trichostatin A (TSA) to inhibit the deacetylation were different in various lysine residues, multiple histone deacetylases (HDACs) were suggested to function during meiotic maturation. The trimethylation of H3K9 was maintained in a high level throughout maturation. These results suggest that the histone acetylation during porcine oocyte maturation is precisely controlled by the cell cycle.
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Affiliation(s)
- Tsutomu Endo
- Laboratory of Applied Genetics, Graduate School of Agricultural and Life Sciences, University of Tokyo, Bunkyo-ku, Tokyo, Japan
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21
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Abstract
The temporal and spatial translation control of stored mRNA in oocytes is regulated by elements in their 3'-untranslated region (3'-UTR). The MOS 3'-UTR in pig oocytes is both heterogeneous (180, 480, or 530 nucleotides), and it contains multiple U-rich elements and extensive A-rich sequences (CA13CA5CA5CA6). We have examined the role of these potential regulatory elements by fusing wild-type or mutant MOS 3'-UTRs to luciferase mRNA and then injecting these chimeric transcripts into oocytes. We draw six main conclusions. First, the length of the MOS 3'-UTR tightly controls the level of translation of luciferase during oocyte maturation. Second, two U-rich (U5A) elements and the hexanucleotide signal (AAUAAA) are required for translation. Third, mutations, duplications, or relocations of the A-rich sequence reduce or block translation. Fourth, the relative importance of the A-rich and U-rich elements in controlling the level of translation differs. Fifth, none of our MOS 3'-UTR manipulations relieved translational repression before germinal vesicle breakdown. Sixth, all the MOS mRNA variants underwent polyadenylation during maturation. Whereas mutations to the hexanucleotide signal block both polyadenylation and translation, mutations to either the A-rich sequence or the U-rich elements block translation without fully blocking polyadenylation. We conclude that MOS mRNA translation in pig oocytes is subject to a more extensive series of controls than that in lower vertebrates.
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Affiliation(s)
- Yanfeng Dai
- Laboratory of Molecular Signaling, The Babraham Institute, Cambridge CB2 4AT, United Kingdom.
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22
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Piccioni F, Zappavigna V, Verrotti AC. Translational regulation during oogenesis and early development: the cap-poly(A) tail relationship. C R Biol 2005; 328:863-81. [PMID: 16286077 DOI: 10.1016/j.crvi.2005.05.006] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2005] [Revised: 05/10/2005] [Accepted: 05/10/2005] [Indexed: 11/30/2022]
Abstract
Metazoans rely on the regulated translation of select maternal mRNAs to control oocyte maturation and the initial stages of embryogenesis. These transcripts usually remain silent until their translation is temporally and spatially required during early development. Different translational regulatory mechanisms, varying from cytoplasmic polyadenylation to localization of maternal mRNAs, have evolved to assure coordinated initiation of development. A common feature of these mechanisms is that they share a few key trans-acting factors. Increasing evidence suggest that ubiquitous conserved mRNA-binding factors, including the eukaryotic translation initiation factor 4E (eIF4E) and the cytoplasmic polyadenylation element binding protein (CPEB), interact with cell-specific molecules to accomplish the correct level of translational activity necessary for normal development. Here we review how capping and polyadenylation of mRNAs modulate interaction with multiple regulatory factors, thus controlling translation during oogenesis and early development.
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Affiliation(s)
- Federica Piccioni
- CEINGE-Biotecnologie Avanzate, Via Comunale Margherita 482, 80145 Naples, Italy
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23
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Minshall N, Standart N. The active form of Xp54 RNA helicase in translational repression is an RNA-mediated oligomer. Nucleic Acids Res 2004; 32:1325-34. [PMID: 14982957 PMCID: PMC390291 DOI: 10.1093/nar/gkh303] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Previously, we reported that in clam oocytes, cytoplasmic polyadenylation element-binding protein (CPEB) co-immunoprecipitates with p47, a member of the highly conserved RCK family of RNA helicases which includes Drosophila Me31B and Saccharomyces cerevisiae Dhh1. Xp54, the Xenopus homologue, with helicase activity, is a component of stored mRNP. In tethered function assays in Xenopus oocytes, we showed that MS2-Xp54 represses the translation of non-adenylated firefly luciferase mRNAs and that mutations in two core helicase motifs, DEAD and HRIGR, surprisingly, activated translation. Here we show that wild-type MS2-Xp54 tethered to the reporter mRNA 3'-untranslated region (UTR) represses translation in both oocytes and eggs in an RNA-dependent complex with endogenous Xp54. Injection of mutant helicases or adenylated reporter mRNA abrogates this association. Thus Xp54 oligomerization is a hallmark of translational repression. Xp54 complexes, which also contain CPEB and eIF4E in oocytes, change during meiotic maturation. In eggs, CPEB is degraded and, while eIF4E still interacts with Xp54, this interaction becomes RNA dependent. Supporting evidence for RNA-mediated oligomerization of endogenous Xp54, and RNA-independent association with CPEB and eIF4E in oocytes was obtained by gel filtration. Altogether, our data are consistent with a model in which the active form of the Xp54 RNA helicase is an oligomer in vivo which, when tethered, via either MS2 or CPEB to the 3'UTR, represses mRNA translation, possibly by sequestering eIF4E from the translational machinery.
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Affiliation(s)
- Nicola Minshall
- Department of Biochemistry, University of Cambridge, 80 Tennis Court Road, Cambridge CB2 1GA, UK
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24
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Charlesworth A, Cox LL, MacNicol AM. Cytoplasmic polyadenylation element (CPE)- and CPE-binding protein (CPEB)-independent mechanisms regulate early class maternal mRNA translational activation in Xenopus oocytes. J Biol Chem 2004; 279:17650-9. [PMID: 14752101 PMCID: PMC1817753 DOI: 10.1074/jbc.m313837200] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Meiotic cell cycle progression during vertebrate oocyte maturation requires the correct temporal translation of maternal mRNAs encoding key regulatory proteins. The mechanism by which specific mRNAs are temporally activated is unknown, although both cytoplasmic polyadenylation elements (CPE) within the 3'-untranslated region (3'-UTR) of mRNAs and the CPE-binding protein (CPEB) have been implicated. We report that in progesterone-stimulated Xenopus oocytes, the early cytoplasmic polyadenylation and translational activation of multiple maternal mRNAs occur in a CPE- and CPEB-independent manner. We demonstrate that polyadenylation response elements, originally identified in the 3'-UTR of the mRNA encoding the Mos proto-oncogene, direct CPE- and CPEB-independent polyadenylation of an early class of Xenopus maternal mRNAs. Our findings refute the hypothesis that CPE sequences alone account for the range of temporal inductions of maternal mRNAs observed during Xenopus oocyte maturation. Rather, our data indicate that the sequential action of distinct 3'-UTR-directed translational control mechanisms coordinates the complex temporal patterns and extent of protein synthesis during vertebrate meiotic cell cycle progression.
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Affiliation(s)
- Amanda Charlesworth
- From the Department of Neurobiology and Developmental Sciences , University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205
| | - Linda L. Cox
- From the Department of Neurobiology and Developmental Sciences , University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205
| | - Angus M. MacNicol
- Arkansas Cancer Research Center, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205
- § To whom correspondence should be addressed: ACRC, Slot 814, University of Arkansas for Medical Sciences, 4301 West Markham, Little Rock, AR 72205. Tel.: 501-296-1549; Fax: 501-686-6517; E-mail:
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25
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Theis M, Si K, Kandel ER. Two previously undescribed members of the mouse CPEB family of genes and their inducible expression in the principal cell layers of the hippocampus. Proc Natl Acad Sci U S A 2003; 100:9602-7. [PMID: 12871996 PMCID: PMC170964 DOI: 10.1073/pnas.1133424100] [Citation(s) in RCA: 147] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Cytoplasmic polyadenylation element-binding (CPEB) proteins control polyadenylation-induced translation in early development. Studies in oocytes led to the delineation of Xenopus CPEB, the first member of the family to be identified, and its mouse homologue mCPEB-1. Recently, a second mouse family member, mCPEB-2, has been described in germ cells. Increasing evidence also implicates CPEB proteins as being important in the hippocampus, where these proteins are thought to regulate local protein synthesis and synaptic plasticity. We therefore carried out a systematic screen for CPEB genes in the mouse brain and report two previously undescribed gene family members: mCPEB-3 and -4. We next examined the expression of all four genes in the hippocampus and found that mCPEB-1, -2, and -4 transcripts are expressed in the principal cell layer in the CA3 and CA1 region and in the dentate gyrus of the hippocampus. mCPEB-3 was barely expressed in naïve animals but together with mCPEB-4 was strongly up-regulated after injection of kainate to initiate seizure activity. Whereas mCPEB-1 is regulated by the Aurora kinase, mCPEB-2, -3, and -4 do not contain Aurora kinase phosphorylation sites. However, alternative splice isoforms of mCPEB-2, -3, and -4 encode the so-called B region with phosphorylation sites for cAMP-dependent protein kinase, calcium/calmodulin-dependent protein kinase II, and S6 kinase. Only isoforms that encode the B region were expressed in the principal cell layer. Coexpression of mCPEB-1 and the B region-containing splice isoforms suggests that a variety of different signaling pathways can recruit CPEB activity in hippocampal neurons.
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Affiliation(s)
- Martin Theis
- Howard Hughes Medical Institute and Center for Neurobiology and Behavior, College of Physicians and Surgeons of Columbia University and New York State Psychiatric Institute, New York, NY 10032, USA.
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26
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Abstract
The translational regulation of specific mRNAs is important for controlling gene expression. The past few years have seen a rapid expansion in the identification and characterization of mRNA regulatory elements and their binding proteins. For the majority of these examples, the mechanism by which translational regulation is achieved is not well understood. Nevertheless, detailed analyses of a few examples show that almost every event in the initiation pathway, from binding of the cap complex to the joining of the 60S ribosomal subunit, is subject to regulation.
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Affiliation(s)
- Gavin S Wilkie
- MRC Human Genetics Unit, Western General Hospital, Edinburgh, UK
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27
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Thom G, Minshall N, Git A, Argasinska J, Standart N. Role of cdc2 kinase phosphorylation and conserved N-terminal proteolysis motifs in cytoplasmic polyadenylation-element-binding protein (CPEB) complex dissociation and degradation. Biochem J 2003; 370:91-100. [PMID: 12401129 PMCID: PMC1223136 DOI: 10.1042/bj20021462] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2002] [Revised: 10/17/2002] [Accepted: 10/25/2002] [Indexed: 11/17/2022]
Abstract
Cytoplasmic polyadenylation-element-binding protein (CPEB) is a well-characterized and important regulator of translation of maternal mRNA in early development in organisms ranging from worms, flies and clams to frogs and mice. Previous studies provided evidence that clam and Xenopus CPEB are hyperphosphorylated at germinal vesicle breakdown (GVBD) by cdc2 kinase, and degraded shortly after. To examine the conserved features of CPEB that mediate its modification during meiotic maturation, we microinjected mRNA encoding wild-type and mutated clam CPEB into Xenopus oocytes that were subsequently allowed to mature with progesterone. We observed that (i) ectopically expressed clam CPEB is phosphorylated at GVBD and subsequently degraded, mirroring the fate of the endogenous Xenopus CPEB protein, (ii) mutation of nine Ser/Thr Pro-directed kinase sites prevents phosphorylation and degradation and (iii) deletion of the PEST box, and to a lesser extent of the putative cyclin destruction box, generates a stable and phosphorylated version of CPEB. We conclude that phosphorylation of both consensus and non-consensus sites by cdc2 kinase targets clam CPEB for PEST-mediated destruction. We also show that phosphorylation of CPEB mediates its dissociation from ribonucleoprotein complexes, prior to degradation. Our findings reinforce results obtained in Xenopus, and have implications for CPEB from other invertebrates including Drosophila, Caenorhabditis elegans and Aplysia, which lack PEST boxes.
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Affiliation(s)
- George Thom
- Department of Biochemistry, University of Cambridge, 80 Tennis Court Road, Cambridge CB2 1GA, UK
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28
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Liu J, Schwartz JH. The cytoplasmic polyadenylation element binding protein and polyadenylation of messenger RNA in Aplysia neurons. Brain Res 2003; 959:68-76. [PMID: 12480159 DOI: 10.1016/s0006-8993(02)03729-0] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Translation of some mRNAs in nerve terminals has been shown to be regulated by polyadenylation in an experience-dependent manner. The transcripts whose translation is controlled by regulated polyadenylation contain the cytoplasmic polyadenylation element (CPE), which binds to the highly conserved CPE-binding protein (CPEB). In Aplysia, neuron-specific actin mRNA, which has a CPE in its 3' UTR, is located both in cell bodies and at nerve endings (synaptosomes). We found that actin mRNA from pleural ganglion sensory neurons becomes polyadenylated during long-term facilitation produced by treatment with serotonin or 8-bromo cAMP. We cloned two isoforms of CPEB (ApCPEB77 and ApCEPB49) from Aplysia nervous tissue. The larger form, which is predominant in nervous tissue, is similar to p82, the clam binding protein, as well as to vertebrate CPEBs. Moreover, synaptosomal actin mRNAs are polyadenylated following the treatment with 5-HT. Since both CPEB and polyadenylated actin mRNA are present in synaptosomes and synaptosomal actin protein increases during long-term facilitation, we suggest that the translation of actin message in nerve endings is up-regulated by polyadenylation to grow new synapses.
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Affiliation(s)
- Jinming Liu
- Center for Neurobiology and Behavior, College of Physicians and Surgeons, Columbia University, 1051 Riverside Drive, New York, NY 10032, USA
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29
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Charlesworth A, Ridge JA, King LA, MacNicol MC, MacNicol AM. A novel regulatory element determines the timing of Mos mRNA translation during Xenopus oocyte maturation. EMBO J 2002; 21:2798-806. [PMID: 12032092 PMCID: PMC125381 DOI: 10.1093/emboj/21.11.2798] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Progression through vertebrate oocyte maturation requires that pre-existing, maternally derived mRNAs be translated in a strict temporal order. The mechanism that controls the timing of oocyte mRNA translation is unknown. In this study we show that the early translational induction of the mRNA encoding the Mos proto-oncogene is mediated through a novel regulatory element within the 3' untranslated region of the Mos mRNA. This novel element is responsive to the MAP kinase signaling pathway and is distinct from the late acting, cdc2-responsive, cytoplasmic polyadenylation element. Our findings suggest that the timing of maternal mRNA translation is controlled through signal transduction pathways targeting distinct 3' UTR mRNA elements.
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Affiliation(s)
- Amanda Charlesworth
- Department of Anatomy and Neurobiology, and Arkansas Cancer Research Center, University of Arkansas for Medical Sciences, 4301 West Markham Street Slot 814, Little Rock, AR 72205, and Committee on Developmental Biology, The University of Chicago, 5841 South Maryland Avenue, Chicago, IL 60637, USA Corresponding author e-mail: A.Charlesworth and J.A.Ridge contributed equally to this work
| | - John A. Ridge
- Department of Anatomy and Neurobiology, and Arkansas Cancer Research Center, University of Arkansas for Medical Sciences, 4301 West Markham Street Slot 814, Little Rock, AR 72205, and Committee on Developmental Biology, The University of Chicago, 5841 South Maryland Avenue, Chicago, IL 60637, USA Corresponding author e-mail: A.Charlesworth and J.A.Ridge contributed equally to this work
| | - Leslie A. King
- Department of Anatomy and Neurobiology, and Arkansas Cancer Research Center, University of Arkansas for Medical Sciences, 4301 West Markham Street Slot 814, Little Rock, AR 72205, and Committee on Developmental Biology, The University of Chicago, 5841 South Maryland Avenue, Chicago, IL 60637, USA Corresponding author e-mail: A.Charlesworth and J.A.Ridge contributed equally to this work
| | - Melanie C. MacNicol
- Department of Anatomy and Neurobiology, and Arkansas Cancer Research Center, University of Arkansas for Medical Sciences, 4301 West Markham Street Slot 814, Little Rock, AR 72205, and Committee on Developmental Biology, The University of Chicago, 5841 South Maryland Avenue, Chicago, IL 60637, USA Corresponding author e-mail: A.Charlesworth and J.A.Ridge contributed equally to this work
| | - Angus M. MacNicol
- Department of Anatomy and Neurobiology, and Arkansas Cancer Research Center, University of Arkansas for Medical Sciences, 4301 West Markham Street Slot 814, Little Rock, AR 72205, and Committee on Developmental Biology, The University of Chicago, 5841 South Maryland Avenue, Chicago, IL 60637, USA Corresponding author e-mail: A.Charlesworth and J.A.Ridge contributed equally to this work
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30
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Mendez R, Barnard D, Richter JD. Differential mRNA translation and meiotic progression require Cdc2-mediated CPEB destruction. EMBO J 2002; 21:1833-44. [PMID: 11927567 PMCID: PMC125948 DOI: 10.1093/emboj/21.7.1833] [Citation(s) in RCA: 141] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Translational activation of several dormant mRNAs in vertebrate oocytes is mediated by cytoplasmic polyadenylation, a process controlled by the cytoplasmic polyadenylation element (CPE) and its binding protein CPEB. The translation of CPE-containing mRNAs does not occur en masse at any one time, but instead is temporally regulated. We show here that in Xenopus, partial destruction of CPEB controls the temporal translation of CPE-containing mRNAs. While some mRNAs, such as the one encoding Mos, are polyadenylated at prophase I, the polyadenylation of cyclin B1 mRNA requires the partial destruction of CPEB that occurs at metaphase I. CPEB destruction is mediated by a PEST box and Cdc2-catalyzed phosphorylation, and is essential for meiotic progression to metaphase II. CPEB destruction is also necessary for mitosis in the early embryo. These data indicate that a change in the CPEB:CPE ratio is necessary to activate mRNAs at metaphase I and drive the cells' entry into metaphase II.
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Affiliation(s)
- Raul Mendez
- Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, MA 01605, USA
Present address: Center for Genomic Regulation, C/Dr Aiguader, 80 Barcelona 08003, Spain Corresponding author e-mail:
| | | | - Joel D. Richter
- Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, MA 01605, USA
Present address: Center for Genomic Regulation, C/Dr Aiguader, 80 Barcelona 08003, Spain Corresponding author e-mail:
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31
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Minshall N, Thom G, Standart N. A conserved role of a DEAD box helicase in mRNA masking. RNA (NEW YORK, N.Y.) 2001; 7:1728-42. [PMID: 11780630 PMCID: PMC1370213 DOI: 10.1017/s135583820101158x] [Citation(s) in RCA: 116] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
Clam p82 is a member of the cytoplasmic polyadenylation element-binding protein (CPEB) family of RNA-binding proteins and serves dual functions in regulating gene expression in early development. In the oocyte, p82/CPEB is a translational repressor, whereas in the activated egg, it acts as a polyadenylation factor. Coimmunoprecipitations were performed with p82 antibodies in clam oocyte and egg lysates to identify stage-regulated accessory factors. p47 coprecipitates with p82 from oocyte lysates in an RNA-dependent manner and is absent from egg lysate p92-bound material. Clam p47 is a member of the RCK/p54 family of DEAD box RNA helicases. Xp54, the Xenopus homolog, with bona fide helicase activity, is an abundant and integral component of stored mRNP in oocytes (Ladomery et al., 1997). In oocytes, clam p47 and p82/CPEB are found in large cytoplasmic mRNP complexes. Whereas the helicase level is constant during embryogenesis, in contrast to CPEB, clam p47 translocates to nuclei at the two-cell stage. To address the role of this class of helicase in masking, Xp54 was tethered via 3' UTR MS2-binding sites to firefly luciferase, following microinjection of fusion protein and nonadenylated reporter mRNAs into Xenopus oocytes. Tethered helicase repressed luciferase translation three- to fivefold and, strikingly, mutations in two helicase motifs (DEAD--> DQAD and HRIGR-->HRIGQ), activated translation three- to fourfold, relative to MS2. These data suggest that this helicase family represses translation of maternal mRNA in early development, and that its activity may be attenuated during meiotic maturation, prior to cytoplasmic polyadenylation.
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Affiliation(s)
- N Minshall
- Department of Biochemistry, University of Cambridge, United Kingdom
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32
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Jin SW, Arno N, Cohen A, Shah A, Xu Q, Chen N, Ellis RE. In Caenorhabditis elegans, the RNA-binding domains of the cytoplasmic polyadenylation element binding protein FOG-1 are needed to regulate germ cell fates. Genetics 2001; 159:1617-30. [PMID: 11779801 PMCID: PMC1461887 DOI: 10.1093/genetics/159.4.1617] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
FOG-1 controls germ cell fates in the nematode Caenorhabditis elegans. Sequence analyses revealed that FOG-1 is a cytoplasmic polyadenylation element binding (CPEB) protein; similar proteins from other species have been shown to bind messenger RNAs and regulate their translation. Our analyses of fog-1 mutations indicate that each of the three RNA-binding domains of FOG-1 is essential for activity. In addition, biochemical tests show that FOG-1 is capable of binding RNA sequences in the 3'-untranslated region of its own message. Finally, genetic assays reveal that fog-1 functions zygotically, that the small fog-1 transcript has no detectable function, and that missense mutations in fog-1 cause a dominant negative phenotype. This last observation suggests that FOG-1 acts in a complex, or as a multimer, to regulate translation. On the basis of these data, we propose that FOG-1 binds RNA to regulate germ cell fates and that it does so by controlling the translation of its targets. One of these targets might be the fog-1 transcript itself.
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MESH Headings
- 3' Untranslated Regions
- Alleles
- Amino Acid Sequence
- Animals
- Base Sequence
- Blotting, Northern
- Blotting, Western
- Caenorhabditis elegans/genetics
- Caenorhabditis elegans/physiology
- Caenorhabditis elegans Proteins
- Carrier Proteins/chemistry
- Chromosome Mapping
- Cloning, Molecular
- Crosses, Genetic
- Cytoplasm/metabolism
- DNA, Complementary/metabolism
- Gene Deletion
- Models, Genetic
- Molecular Sequence Data
- Mutation
- Mutation, Missense
- Nuclear Proteins/chemistry
- Plasmids/metabolism
- Polyadenylation
- Precipitin Tests
- Protein Binding
- Protein Biosynthesis
- Protein Structure, Tertiary
- Protein Transport
- RNA/metabolism
- RNA, Messenger/metabolism
- Reverse Transcriptase Polymerase Chain Reaction
- Sequence Homology, Amino Acid
- Sex Determination Processes
- Transfection
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Affiliation(s)
- S W Jin
- Department of Biology, University of Michigan, Ann Arbor, Michigan 48109, USA
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33
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Dickson KS, Thompson SR, Gray NK, Wickens M. Poly(A) polymerase and the regulation of cytoplasmic polyadenylation. J Biol Chem 2001; 276:41810-6. [PMID: 11551905 DOI: 10.1074/jbc.m103030200] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Translational activation in oocytes and embryos is often regulated via increases in poly(A) length. Cleavage and polyadenylation specificity factor (CPSF), cytoplasmic polyadenylation element binding protein (CPEB), and poly(A) polymerase (PAP) have each been implicated in cytoplasmic polyadenylation in Xenopus laevis oocytes. Cytoplasmic polyadenylation activity first appears in vertebrate oocytes during meiotic maturation. Data presented here shows that complexes containing both CPSF and CPEB are present in extracts of X. laevis oocytes prepared before or after meiotic maturation. Assessment of a variety of RNA sequences as polyadenylation substrates indicates that the sequence specificity of polyadenylation in egg extracts is comparable to that observed with highly purified mammalian CPSF and recombinant PAP. The two in vitro systems exhibit a sequence specificity that is similar, but not identical, to that observed in vivo, as assessed by injection of the same RNAs into the oocyte. These findings imply that CPSFs intrinsic RNA sequence preferences are sufficient to account for the specificity of cytoplasmic polyadenylation of some mRNAs. We discuss the hypothesis that CPSF is required for all polyadenylation reactions, but that the polyadenylation of some mRNAs may require additional factors such as CPEB. To test the consequences of PAP binding to mRNAs in vivo, PAP was tethered to a reporter mRNA in resting oocytes using MS2 coat protein. Tethered PAP catalyzed polyadenylation and stimulated translation approximately 40-fold; stimulation was exclusively cis-acting, but was independent of a CPE and AAUAAA. Both polyadenylation and translational stimulation required PAPs catalytic core, but did not require the putative CPSF interaction domain of PAP. These results demonstrate that premature recruitment of PAP can cause precocious polyadenylation and translational stimulation in the resting oocyte, and can be interpreted to suggest that the role of other factors is to deliver PAP to the mRNA.
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Affiliation(s)
- K S Dickson
- Department of Biochemistry, College of Agriculture and Life Sciences, University of Wisconsin, Madison, Wisconsin 53706, USA
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34
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Gebauer F, Hentze MW. Fertility facts: male and female germ cell development requires translational control by CPEB. Mol Cell 2001; 8:247-9. [PMID: 11545727 DOI: 10.1016/s1097-2765(01)00326-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In the August issue of Developmental Cell, Tay and Richter examine the consequences of eliminating CPEB function in mice. Their studies reveal an important role for this translational regulator at the pachytene stage of germ cell differentiation.
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Affiliation(s)
- F Gebauer
- Gene Expression Programme, European Molecular Biology Laboratory, Meyerhofstrasse 1, D-69117, Heidelberg, Germany
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35
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Abstract
The regulated translation of messenger RNA is essential for cell-cycle progression, establishment of the body plan during early development, and modulation of key activities in the central nervous system. Cytoplasmic polyadenylation, which is one mechanism of controlling translation, is driven by CPEB--a highly conserved, sequence-specific RNA-binding protein that binds to the cytoplasmic polyadenylation element, and modulates translational repression and mRNA localization. What are the features and functions of this multifaceted protein?
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Affiliation(s)
- R Mendez
- Department of Molecular Genetics and Microbiology, University of Massachusetts Medical School, Worcester, Massachusetts 01655, USA
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36
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Tan L, Chang JS, Costa A, Schedl P. An autoregulatory feedback loop directs the localized expression of the Drosophila CPEB protein Orb in the developing oocyte. Development 2001; 128:1159-69. [PMID: 11245581 DOI: 10.1242/dev.128.7.1159] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The RRM-type RNA binding protein Orb plays a central role in the establishment of polarity in the Drosophila egg and embryo. In addition to its role in the formation and initial differentiation of the egg chamber, orb is required later in oogenesis for the determination of the dorsoventral (DV) and anteroposterior (AP) axes. In DV axis formation, Orb protein is required to localize and translate gurken mRNA at the dorsoanterior part of the oocyte. In AP axis formation, Orb is required for the translation of oskar mRNA. In each case, Orb protein is already localized at the appropriate sites within the oocyte before the arrival of the mRNAs encoding axis determinants. We present evidence that an autoregulatory mechanism is responsible for directing the on site accumulation of Orb protein in the Drosophila oocyte. This orb autoregulatory activity ensures the accumulation of high levels of Orb protein at sites in the oocyte that contain localized orb message.
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Affiliation(s)
- L Tan
- Department of Molecular Biology, Princeton University, Washington Road, Princeton, NJ 08544, USA
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37
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de Moor CH, Richter JD. Translational control in vertebrate development. INTERNATIONAL REVIEW OF CYTOLOGY 2001; 203:567-608. [PMID: 11131527 DOI: 10.1016/s0074-7696(01)03017-0] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Translational control plays a large role in vertebrate oocyte maturation and contributes to the induction of the germ layers. Translational regulation is also observed in the regulation of cell proliferation and differentiation. The features of an mRNA that mediate translational control are found both in the 5' and in the 3' untranslated regions (UTRs). In the 5' UTR, secondary structure, the binding of proteins, and the presence of upstream open reading frames can interfere with the association of initiation factors with the cap, or with scanning of the initiation complex. The 3' UTR can mediate translational activation by directing cytoplasmic polyadenylation and can confer translational repression by interference with the assembly of initiation complexes. Besides mRNA-specific translational control elements, the nonspecific RNA-binding proteins contribute to the modulation of translation in development. This review discusses examples of translational control and their relevance for developmental regulation.
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Affiliation(s)
- C H de Moor
- Department of Molecular Genetics and Microbiology, University of Massachusetts Medical School, Worcester 01655, USA
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38
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Welk JF, Charlesworth A, Smith GD, MacNicol AM. Identification and characterization of the gene encoding human cytoplasmic polyadenylation element binding protein. Gene 2001; 263:113-20. [PMID: 11223249 DOI: 10.1016/s0378-1119(00)00588-6] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The maturation of human oocytes occurs in the absence of gene transcription. In model organisms, such as Drosophila, Xenopus, and the mouse, oocyte maturation and early pattern formation is mediated through the regulated translation of maternally derived mRNAs. The maturation-dependent stimulation of maternal mRNA translation is correlated with increases in poly(A) tail length, controlled through a process termed cytoplasmic polyadenylation. However, this mechanism of mRNA translational control has not been characterized in humans. In this study we report the cloning of a human cytoplasmic polyadenylation element binding (hCPEB) protein with sequence-specific RNA binding activity. Our data demonstrate that alternative splicing generates hCPEB mRNAs that encode proteins with a conserved C-terminal RNA binding domain but with different N-terminal regulatory domains. The hCPEB mRNA is expressed in the brain and heart as well as in immature oocytes, consistent with the hypothesis that cytoplasmic polyadenylation may regulate the translation of human mRNAs in both oocytes and somatic cells.
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Affiliation(s)
- J F Welk
- Department of Medicine, University of Chicago, 5841 S. Maryland Avenue, Chicago, IL 60637, USA
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39
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Jin SW, Kimble J, Ellis RE. Regulation of cell fate in Caenorhabditis elegans by a novel cytoplasmic polyadenylation element binding protein. Dev Biol 2001; 229:537-53. [PMID: 11150246 DOI: 10.1006/dbio.2000.9993] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The fog-1 gene of Caenorhabditis elegans specifies that germ cells differentiate as sperm rather than as oocytes. We cloned fog-1 through a combination of transformation rescue experiments, RNA-mediated inactivation, and mutant analyses. Our results show that fog-1 produces two transcripts, both of which are found in germ cells but not in the soma. Furthermore, two deletion mutants alter these transcripts and are likely to eliminate fog-1 activity. The larger transcript is expressed under the control of sex-determination genes, is necessary for fog-1 activity, and is sufficient to rescue a fog-1 mutant. This transcript encodes a novel member of the CPEB family of RNA-binding proteins. Because CPEB proteins in Xenopus and Drosophila regulate gene expression at the level of translation, we propose that FOG-1 controls germ cell fates by regulating the translation of specific messenger RNAs.
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Affiliation(s)
- S W Jin
- Department of Biology, University of Michigan, Ann Arbor, Michigan, 48109
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40
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Charlesworth A, Welk J, MacNicol AM. The temporal control of Wee1 mRNA translation during Xenopus oocyte maturation is regulated by cytoplasmic polyadenylation elements within the 3'-untranslated region. Dev Biol 2000; 227:706-19. [PMID: 11071785 DOI: 10.1006/dbio.2000.9922] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The Wee1 protein tyrosine kinase is a key regulator of cell cycle progression. Wee1 activity is necessary for the control of the first embryonic cell cycle following the fertilization of meiotically mature Xenopus oocytes. Wee1 mRNA is present in immature oocytes, but Wee1 protein does not accumulate in immature oocytes or during the early stages of progesterone-stimulated maturation. This delay in Wee1 translation is critical since premature Wee1 protein accumulation has been shown to inhibit oocyte maturation. In this study we provide evidence that Wee1 protein accumulation is regulated at the level of mRNA translation. This translational control is directed by sequences within the Wee1 mRNA 3'-untranslated region (3' UTR). Specifically, cytoplasmic polyadenylation element (CPE) sequences within the Wee1 3' UTR are necessary for full translational repression in immature oocytes. Our data further indicate that while CPE-independent mechanisms may regulate the levels of Wee1 protein accumulation during progesterone-stimulated oocyte maturation, the timing of Wee1 mRNA translational induction is directed through a CPE-dependent mechanism.
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Affiliation(s)
- A Charlesworth
- Department of Medicine, Committee on Developmental Biology, Ben May Institute for Cancer Research, The University of Chicago, 5841 S. Maryland Avenue, Chicago, Illinois 60637, USA
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41
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Luitjens C, Gallegos M, Kraemer B, Kimble J, Wickens M. CPEB proteins control two key steps in spermatogenesis in C. elegans. Genes Dev 2000; 14:2596-609. [PMID: 11040214 PMCID: PMC316992 DOI: 10.1101/gad.831700] [Citation(s) in RCA: 118] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Cytoplasmic polyadenylation element binding (CPEB) proteins bind to and regulate the translation of specific mRNAs. CPEBs from Xenopus, Drosophila, and Spisula participate in oogenesis. In this report, we examine the biological roles of all identifiable CPEB homologs in a single organism, Caenorhabditis elegans. We find four homologs in the C. elegans genome: cbp-1, cpb-2, cpb-3, and fog-1. Surprisingly, two homologs, CPB-1 and FOG-1, have key functions in spermatogenesis and are dispensable for oogenesis. CPB-2 and CPB-3 also appear not to be required for oogenesis. CPB-1 is essential for progression through meiosis: cpb-1(RNAi) spermatocytes fail to undergo the meiotic cell divisions. CPB-1 protein is present in the germ line just prior to overt spermatogenesis; once sperm differentiation begins, CPB-1 disappears. CPB-1 physically interacts with FBF, another RNA-binding protein and 3' UTR regulator. In addition to its role in controlling the sperm/oocyte switch, we find that FBF also appears to be required for spermatogenesis, consistent with its interaction with CPEB. A second CPEB homolog, FOG-1, is required for specification of the sperm fate. The fog-1 gene produces fog-1(L) and fog-1(S) transcripts. The fog-1(L) RNA is enriched in animals making sperm and is predicted to encode a larger protein; fog-1(S) RNA is enriched in animals making oocytes and is predicted to encode a smaller protein. The relative abundance of the two mRNAs is controlled temporally during germ-line development and by the sex determination pathway in a fashion that suggests that the fog-1(L) species encodes the active form. In sum, our results demonstrate that, in C. elegans, two CPEB proteins have distinct functions in the germ line, both in spermatogenesis: FOG-1 specifies the sperm cell fate and CPB-1 executes that decision.
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Affiliation(s)
- C Luitjens
- Program in Cell and Molecular Biology, University of Wisconsin, Madison, Wisconsin 53706, USA
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42
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de Melo Neto OP, Walker JA, Martins de Sa CM, Standart N. Levels of free PABP are limited by newly polyadenylated mRNA in early Spisula embryogenesis. Nucleic Acids Res 2000; 28:3346-53. [PMID: 10954604 PMCID: PMC110693 DOI: 10.1093/nar/28.17.3346] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
The poly(A) tail of eukaryotic mRNAs regulates translation and RNA stability through an association with the poly(A)-binding protein (PABP). The role of PABP in selective polyadenylation/deadenylation and translational recruitment/repression of maternal mRNAs that occurs in early development is not fully understood. Here, we report studies including UV-crosslinking and immunoblotting assays to characterise PABP in the early developmental stages of the clam Spisula solidissima. A single, 70 kDa PABP, whose sequence is highly homologous to vertebrate, yeast and plant PABPs, is detected in oocytes. The levels of clam PABP are constant in early embryogenesis, although its ability to crosslink labelled poly(A) is 'masked' shortly after fertilisation and remains so until the larval stage. Full RNA-binding potential of PABP in embryo lysates was achieved by brief denaturation with guanidinium hydrochloride followed by dilution for binding and crosslinking or by controlled treatment of lysates with Ca(2+)-dependent micrococcal nuclease. Masking of PABP, which accompanies cytoplasmic polyadenylation in maturing oocytes and in in vitro activated oocyte lysates, is very likely due to an association with mRNAs that bear new PABP target binding sites and thus prevent protein binding to the labelled A-rich probe. Functional implications of these findings as well as the potential application of this unmasking method to other RNA-binding proteins is discussed.
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Affiliation(s)
- O P de Melo Neto
- Department of Biochemistry, University of Cambridge, 80 Tennis Court Road, Cambridge CB2 1GA, UK
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43
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Huynh JR, St Johnston D. The role of BicD, egl, orb and the microtubules in the restriction of meiosis to the Drosophila oocyte. Development 2000; 127:2785-94. [PMID: 10851125 DOI: 10.1242/dev.127.13.2785] [Citation(s) in RCA: 85] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The oocyte is the only cell in Drosophila that goes through meiosis with meiotic recombination, but several germ cells in a 16-cell cyst enter meiosis and form synaptonemal complexes (SC) before one cell is selected to become the oocyte. Using an antibody that recognises a component of the SC or the synapsed chromosomes, we have analysed how meiosis becomes restricted to one cell, in relation to the other events in oocyte determination. Although BicD and egl mutants both cause the development of cysts with no oocyte, they have opposite effects on the behaviour of the SC: none of the cells in the cyst form SC in BicD null mutants, whereas all of the cells do in egl and orb mutants. Furthermore, unlike all cytoplasmic markers for the oocyte, the SC still becomes restricted to one cell when the microtubules are depolymerised, even though the BicD/Egl complex is not localised. These results lead us to propose a model in which BicD, Egl and Orb control entry into meiosis by regulating translation.
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Affiliation(s)
- J R Huynh
- The Wellcome/CRC Institute and the Department of Genetics, University of Cambridge, Tennis Court Rd, Cambridge, CB2 1QR, UK
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44
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Wang W, Caldwell MC, Lin S, Furneaux H, Gorospe M. HuR regulates cyclin A and cyclin B1 mRNA stability during cell proliferation. EMBO J 2000; 19:2340-50. [PMID: 10811625 PMCID: PMC384372 DOI: 10.1093/emboj/19.10.2340] [Citation(s) in RCA: 361] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Colorectal carcinoma RKO cells expressing reduced levels of the RNA-binding protein HuR (ASHuR) displayed markedly reduced growth. In synchronous RKO populations, HuR was almost exclusively nuclear during early G(1), increasing in the cytoplasm during late G(1), S and G(2). The expression and half-life of mRNAs encoding cyclins A and B1 similarly increased during S and G(2), then declined, indicating that mRNA stabilization contributed to their cell cycle-regulated expression. In gel-shift assays using radiolabeled cyclin RNA transcripts and RKO protein extracts, only those transcripts corresponding to the 3'-untranslated regions of cyclins A and B1 formed RNA-protein complexes in a cell cycle-dependent fashion. HuR directly bound mRNAs encoding cyclins A and B1, as anti-HuR antibodies supershifted such RNA-protein complexes. Importantly, the expression and half-life of mRNAs encoding cyclins A and B1 were reduced in ASHuR RKO cells. Our results indicate that HuR may play a critical role in cell proliferation, at least in part by mediating cell cycle-dependent stabilization of mRNAs encoding cyclins A and B1.
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Affiliation(s)
- W Wang
- Laboratory of Biological Chemistry, NIA, NIH, Baltimore, MD 21224, USA
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45
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Barkoff AF, Dickson KS, Gray NK, Wickens M. Translational control of cyclin B1 mRNA during meiotic maturation: coordinated repression and cytoplasmic polyadenylation. Dev Biol 2000; 220:97-109. [PMID: 10720434 DOI: 10.1006/dbio.2000.9613] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Translational control is prominent during meiotic maturation and early development. In this report, we investigate a mode of translational repression in Xenopus laevis oocytes, focusing on the mRNA encoding cyclin B1. Translation of cyclin B1 mRNA is relatively inactive in the oocyte and increases dramatically during meiotic maturation. We show, by injection of synthetic mRNAs, that the cis-acting sequences responsible for repression of cyclin B1 mRNA reside within its 3'UTR. Repression can be saturated by increasing the concentration of reporter mRNA injected, suggesting that the cyclin B1 3'UTR sequences provide a binding site for a trans-acting repressor. The sequences that direct repression overlap and include cytoplasmic polyadenylation elements (CPEs), sequences known to promote cytoplasmic polyadenylation. However, the presence of a CPE per se appears insufficient to cause repression, as other mRNAs that contain CPEs are not translationally repressed. We demonstrate that relief of repression and cytoplasmic polyadenylation are intimately linked. Repressing elements do not override the stimulatory effect of a long poly(A) tail, and polyadenylation of cyclin B1 mRNA is required for its translational recruitment. Our results suggest that translational recruitment of endogenous cyclin B1 mRNA is a collaborative effect of derepression and poly(A) addition. We discuss several molecular mechanisms that might underlie this collaboration.
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Affiliation(s)
- A F Barkoff
- Department of Biochemistry, University of Wisconsin, 433 Babcock Drive, Madison, Wisconsin 53706, USA
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46
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Stebbins-Boaz B, Cao Q, de Moor CH, Mendez R, Richter JD. Maskin is a CPEB-associated factor that transiently interacts with elF-4E. Mol Cell 1999; 4:1017-27. [PMID: 10635326 DOI: 10.1016/s1097-2765(00)80230-0] [Citation(s) in RCA: 276] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
In Xenopus, the CPE is a bifunctional 3' UTR sequence that maintains maternal mRNA in a dormant state in oocytes and activates polyadenylation-induced translation during oocyte maturation. Here, we report that CPEB, which binds the CPE and stimulates polyadenylation, interacts with a new factor we term maskin. Maskin contains a peptide sequence that is conserved among elF-4E-binding proteins. Affinity chromatography demonstrates that CPEB, maskin, and elF-4E reside in a complex in oocytes, and yeast two-hybrid analyses indicate that CPEB and maskin bind directly, as do maskin and elF-4E. While CPEB and maskin remain together during oocyte maturation, the maskin-elF-4E interaction is substantially reduced. The dissolution of this complex may result in the binding of elF-4E to elF-4G and the translational activation of CPE-containing mRNAs.
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Affiliation(s)
- B Stebbins-Boaz
- Department of Molecular Genetics and Microbiology, University of Massachusetts Medical School, Worcester 01655, USA
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47
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Chang JS, Tan L, Schedl P. The Drosophila CPEB homolog, orb, is required for oskar protein expression in oocytes. Dev Biol 1999; 215:91-106. [PMID: 10525352 DOI: 10.1006/dbio.1999.9444] [Citation(s) in RCA: 129] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The establishment of polarity axes in the Drosophila egg and embryo depends upon the localization and on-site expression of maternal mRNAs. The critical step in the targeting of posterior determinants is the localization of oskar (osk) mRNA to the pole and its on-site translation. Osk protein then recruits other posterior group gene products involved in the formation of pole plasm and in the localization and regulation of the posterior determinant, nanos. Here we have investigated the role of the Drosophila CPEB homolog, the orb gene, in the osk mRNA localization pathway. We demonstrate that the expression of Osk protein is dependent upon the orb gene. In strong orb mutants, Osk protein expression is undetectable, while in the hypomorphic mutant, orb(mel), little or no on-site expression of Osk protein at the posterior pole is observed. The defects in Osk protein accumulation in orb mutant ovaries are correlated with a reduction in the length of the osk poly(A) tails. We show that osk mRNA is in immunoprecipitable complexes with Orb protein in ovaries and that the osk 3' UTR can be UV cross-linked to Orb protein in ovarian extracts. These data suggest that Orb is required to activate the translation of osk mRNA and at that this may be accomplished by a mechanism similar to that used by the Xenopus CPEB protein to control translation of "masked" mRNAs.
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Affiliation(s)
- J S Chang
- Department of Molecular Biology, Princeton University, Washington Road, Princeton, New Jersey, 08544, USA
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48
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Culp PA, Musci TJ. c-mos and cdc2 cooperate in the translational activation of fibroblast growth factor receptor-1 during Xenopus oocyte maturation. Mol Biol Cell 1999; 10:3567-81. [PMID: 10564256 PMCID: PMC25638 DOI: 10.1091/mbc.10.11.3567] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
During oocyte maturation in Xenopus, previously quiescent maternal mRNAs are translationally activated at specific times. We hypothesized that the translational recruitment of individual messages is triggered by particular cellular events and investigated the potential for known effectors of the meiotic cell cycle to activate the translation of the FGF receptor-1 (XFGFR) maternal mRNA. We found that both c-mos and cdc2 activate the translation of XFGFR. However, although oocytes matured by injection of recombinant cdc2/cyclin B translate normal levels of XFGFR protein, c-mos depletion reduces the level of XFGFR protein induced by cdc2/cyclin B injection. In oocytes blocked for cdc2 activity, injection of mos RNA induced low levels of XFGFR protein, independent of MAPK activity. Through the use of injected reporter RNAs, we show that the XFGFR 3' untranslated region inhibitory element is completely derepressed by cdc2 alone. In addition, we identified a new inhibitory element through which both mos and cdc2 activate translation. We found that cdc2 derepresses translation in the absence of polyadenylation, whereas mos requires poly(A) extension to activate XFGFR translation. Our results demonstrate that mos and cdc2, in addition to functioning as key regulators of the meiotic cell cycle, cooperate in the translational activation of a specific maternal mRNA during oocyte maturation.
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Affiliation(s)
- P A Culp
- Department of Obstetrics, Gynecology, and Reproductive Sciences, University of California School of Medicine, San Francisco, California 94143-0556, USA
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49
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Preiss T, Hentze MW. From factors to mechanisms: translation and translational control in eukaryotes. Curr Opin Genet Dev 1999; 9:515-21. [PMID: 10508691 DOI: 10.1016/s0959-437x(99)00005-2] [Citation(s) in RCA: 118] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Biochemical and genetic studies are revealing a network of interactions between eukaryotic translation initiation factors, further refining or redefining perceptions of their function. The notion of translated mRNA as a 'closed-loop' has gained support from the identification of physical and functional interactions between the two mRNA ends and their associated factors. Translational control mechanisms are beginning to unravel in sufficient detail to pinpoint the affected step in the initiation pathway.
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Affiliation(s)
- T Preiss
- Gene Expression Programme European Molecular Biology Laboratory Meyerhofstrasse 1, D-69117, Heidelberg, Germany.
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50
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Ralle T, Gremmels D, Stick R. Translational control of nuclear lamin B1 mRNA during oogenesis and early development of Xenopus. Mech Dev 1999; 84:89-101. [PMID: 10473123 DOI: 10.1016/s0925-4773(99)00078-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Cytoplasmic polyadenylation of specific mRNAs is commonly correlated with their translational activation during development. A canonical nuclear polyadenylation element AAUAAA (NPE) and cytoplasmic polyadenylation element(s) (CPE) are necessary and sufficient for polyadenylation during egg maturation. We have characterized cis-acting sequences of Xenopus nuclear lamin B1 mRNA that mediate translational regulation. By injection of synthetic RNAs into oocytes we show that the two CPE-like elements found in the 3'-untranslated region of B1 mRNA act as translational repressors in oocytes. The same CPEs in conjunction with the NPE confer transient polyadenylation and translational activation during egg maturation. Poly(A) length determination of the endogenous lamin B1 mRNA reveals a gradual increase of poly(A) tail length in early development up to mid-blastula, and a shortening of poly(A) tails during gastrulation and neurulation. The same kinetic and extent of polyadenylation and poly(A) tail shortening is observed with synthetic RNAs injected into fertilized eggs. Polyadenylation and translational activation of these RNAs is independent of the two CPEs and a NPE during early development. While translational regulation of lamin B1 mRNA functions in parts via established mechanisms, the pattern of polyadenylation and deadenylation during early development points to a novel mode of translational regulation.
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Affiliation(s)
- T Ralle
- Institut für Biochemie und Molekulare Zellbiologie, Abteilung für Entwicklungsbiochemie, Universität Göttingen, Germany
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