1
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Zaharias S, Zhang Z, Davis K, Fargason T, Cashman D, Yu T, Zhang J. Intrinsically disordered electronegative clusters improve stability and binding specificity of RNA-binding proteins. J Biol Chem 2021; 297:100945. [PMID: 34246632 PMCID: PMC8348266 DOI: 10.1016/j.jbc.2021.100945] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2021] [Revised: 06/28/2021] [Accepted: 07/07/2021] [Indexed: 11/25/2022] Open
Abstract
RNA-binding proteins play crucial roles in various cellular functions and contain abundant disordered protein regions. The disordered regions in RNA-binding proteins are rich in repetitive sequences, such as poly-K/R, poly-N/Q, poly-A, and poly-G residues. Our bioinformatic analysis identified a largely neglected repetitive sequence family we define as electronegative clusters (ENCs) that contain acidic residues and/or phosphorylation sites. The abundance and length of ENCs exceed other known repetitive sequences. Despite their abundance, the functions of ENCs in RNA-binding proteins are still elusive. To investigate the impacts of ENCs on protein stability, RNA-binding affinity, and specificity, we selected one RNA-binding protein, the ribosomal biogenesis factor 15 (Nop15), as a model. We found that the Nop15 ENC increases protein stability and inhibits nonspecific RNA binding, but minimally interferes with specific RNA binding. To investigate the effect of ENCs on sequence specificity of RNA binding, we grafted an ENC to another RNA-binding protein, Ser/Arg-rich splicing factor 3. Using RNA Bind-n-Seq, we found that the engineered ENC inhibits disparate RNA motifs differently, instead of weakening all RNA motifs to the same extent. The motif site directly involved in electrostatic interaction is more susceptible to the ENC inhibition. These results suggest that one of functions of ENCs is to regulate RNA binding via electrostatic interaction. This is consistent with our finding that ENCs are also overrepresented in DNA-binding proteins, whereas underrepresented in halophiles, in which nonspecific nucleic acid binding is inhibited by high concentrations of salts.
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Affiliation(s)
- Steve Zaharias
- Department of Chemistry, College of Arts and Sciences, University of Alabama at Birmingham, Birmingham, Alabama, USA
| | - Zihan Zhang
- Department of Chemistry, College of Arts and Sciences, University of Alabama at Birmingham, Birmingham, Alabama, USA
| | - Kenneth Davis
- Department of Chemistry, College of Arts and Sciences, University of Alabama at Birmingham, Birmingham, Alabama, USA
| | - Talia Fargason
- Department of Chemistry, College of Arts and Sciences, University of Alabama at Birmingham, Birmingham, Alabama, USA
| | - Derek Cashman
- Department of Chemistry, Tennessee Technological University, Cookeville, Tennessee, USA
| | - Tao Yu
- Department of Chemistry, University of North Dakota, Grand Forks, North Dakota, USA
| | - Jun Zhang
- Department of Chemistry, College of Arts and Sciences, University of Alabama at Birmingham, Birmingham, Alabama, USA.
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2
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Sun Y, Aik WS, Yang XC, Marzluff WF, Dominski Z, Tong L. Reconstitution and biochemical assays of an active human histone pre-mRNA 3'-end processing machinery. Methods Enzymol 2021; 655:291-324. [PMID: 34183127 DOI: 10.1016/bs.mie.2021.03.021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
In animal cells, replication-dependent histone pre-mRNAs are processed at the 3'-end by an endonucleolytic cleavage carried out by the U7 snRNP, a machinery that contains the U7 snRNA and many protein subunits. Studies on the composition of this machinery and understanding of its role in 3'-end processing were greatly facilitated by the development of an in vitro system utilizing nuclear extracts from mammalian cells 35 years ago and later from Drosophila cells. Most recently, recombinant expression and purification of the components of the machinery have enabled the full reconstitution of an active machinery and its complex with a model pre-mRNA substrate, using 13 proteins and 2 RNAs, and the determination of the structure of this active machinery. This chapter presents protocols for preparing nuclear extracts containing endogenous processing machinery, for assembling semi-recombinant and fully reconstituted machineries, and for histone pre-mRNA 3'-end processing assays with these samples.
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Affiliation(s)
- Yadong Sun
- Department of Biological Sciences, Columbia University, New York, NY, United States
| | - Wei Shen Aik
- Department of Biological Sciences, Columbia University, New York, NY, United States
| | - Xiao-Cui Yang
- Integrative Program for Biological and Genome Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC, United States
| | - William F Marzluff
- Integrative Program for Biological and Genome Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC, United States; Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC, United States
| | - Zbigniew Dominski
- Integrative Program for Biological and Genome Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC, United States; Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC, United States.
| | - Liang Tong
- Department of Biological Sciences, Columbia University, New York, NY, United States.
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3
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Potter-Birriel JM, Gonsalvez GB, Marzluff WF. A region of SLBP outside the mRNA-processing domain is essential for deposition of histone mRNA into the Drosophila egg. J Cell Sci 2021; 134:jcs251728. [PMID: 33408246 PMCID: PMC7888719 DOI: 10.1242/jcs.251728] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2020] [Accepted: 12/21/2020] [Indexed: 01/01/2023] Open
Abstract
Replication-dependent histone mRNAs are the only cellular mRNAs that are not polyadenylated, ending in a stemloop instead of a polyA tail, and are normally regulated coordinately with DNA replication. Stemloop-binding protein (SLBP) binds the 3' end of histone mRNA, and is required for processing and translation. During Drosophila oogenesis, large amounts of histone mRNAs and proteins are deposited in the developing oocyte. The maternally deposited histone mRNA is synthesized in stage 10B oocytes after the nurse cells complete endoreduplication. We report that in wild-type stage 10B oocytes, the histone locus bodies (HLBs), formed on the histone genes, produce histone mRNAs in the absence of phosphorylation of Mxc, which is normally required for histone gene expression in S-phase cells. Two mutants of SLBP, one with reduced expression and another with a 10-amino-acid deletion, fail to deposit sufficient histone mRNA in the oocyte, and do not transcribe the histone genes in stage 10B. Mutations in a putative SLBP nuclear localization sequence overlapping the deletion phenocopy the deletion. We conclude that a high concentration of SLBP in the nucleus of stage 10B oocytes is essential for histone gene transcription.This article has an associated First Person interview with the first author of the paper.
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Affiliation(s)
- Jennifer Michelle Potter-Birriel
- Curriculum in Genetics and Molecular Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- Interdisciplinary Program in Biological and Genome Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Graydon B Gonsalvez
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta University, Augusta, GA 30912 , USA
| | - William F Marzluff
- Curriculum in Genetics and Molecular Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- Interdisciplinary Program in Biological and Genome Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
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4
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Yang XC, Sun Y, Aik WS, Marzluff WF, Tong L, Dominski Z. Studies with recombinant U7 snRNP demonstrate that CPSF73 is both an endonuclease and a 5'-3' exonuclease. RNA (NEW YORK, N.Y.) 2020; 26:1345-1359. [PMID: 32554553 PMCID: PMC7491329 DOI: 10.1261/rna.076273.120] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2020] [Accepted: 05/26/2020] [Indexed: 05/24/2023]
Abstract
Metazoan replication-dependent histone pre-mRNAs are cleaved at the 3' end by U7 snRNP, an RNA-guided endonuclease that contains U7 snRNA, seven proteins of the Sm ring, FLASH, and four polyadenylation factors: symplekin, CPSF73, CPSF100, and CstF64. A fully recombinant U7 snRNP was recently reconstituted from all 13 components for functional and structural studies and shown to accurately cleave histone pre-mRNAs. Here, we analyzed the activity of recombinant U7 snRNP in more detail. We demonstrate that in addition to cleaving histone pre-mRNAs endonucleolytically, reconstituted U7 snRNP acts as a 5'-3' exonuclease that degrades the downstream product generated from histone pre-mRNAs as a result of the endonucleolytic cleavage. Surprisingly, recombinant U7 snRNP also acts as an endonuclease on single-stranded DNA substrates. All these activities depend on the ability of U7 snRNA to base-pair with the substrate and on the presence of the amino-terminal domain (NTD) of symplekin in either cis or trans, and are abolished by mutations within the catalytic center of CPSF73, or by binding of the NTD to the SSU72 phosphatase of RNA polymerase II. Altogether, our results demonstrate that recombinant U7 snRNP functionally mimics its endogenous counterpart and provide evidence that CPSF73 is both an endonuclease and a 5'-3' exonuclease, consistent with the activity of other members of the β-CASP family. Our results also raise the intriguing possibility that CPSF73 may be involved in some aspects of DNA metabolism in vivo.
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Affiliation(s)
- Xiao-Cui Yang
- Integrative Program for Biological and Genome Sciences, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
| | - Yadong Sun
- Department of Biological Sciences, Columbia University, New York, New York 10027, USA
| | - Wei Shen Aik
- Department of Biological Sciences, Columbia University, New York, New York 10027, USA
| | - William F Marzluff
- Integrative Program for Biological and Genome Sciences, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
| | - Liang Tong
- Department of Biological Sciences, Columbia University, New York, New York 10027, USA
| | - Zbigniew Dominski
- Integrative Program for Biological and Genome Sciences, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
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5
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Bucholc K, Aik WS, Yang XC, Wang K, Zhou ZH, Dadlez M, Marzluff WF, Tong L, Dominski Z. Composition and processing activity of a semi-recombinant holo U7 snRNP. Nucleic Acids Res 2020; 48:1508-1530. [PMID: 31819999 PMCID: PMC7026596 DOI: 10.1093/nar/gkz1148] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2019] [Revised: 10/29/2019] [Accepted: 11/25/2019] [Indexed: 11/14/2022] Open
Abstract
In animal cells, replication-dependent histone pre-mRNAs are cleaved at the 3' end by U7 snRNP consisting of two core components: a ∼60-nucleotide U7 snRNA and a ring of seven proteins, with Lsm10 and Lsm11 replacing the spliceosomal SmD1 and SmD2. Lsm11 interacts with FLASH and together they recruit the endonuclease CPSF73 and other polyadenylation factors, forming catalytically active holo U7 snRNP. Here, we assembled core U7 snRNP bound to FLASH from recombinant components and analyzed its appearance by electron microscopy and ability to support histone pre-mRNA processing in the presence of polyadenylation factors from nuclear extracts. We demonstrate that semi-recombinant holo U7 snRNP reconstituted in this manner has the same composition and functional properties as endogenous U7 snRNP, and accurately cleaves histone pre-mRNAs in a reconstituted in vitro processing reaction. We also demonstrate that the U7-specific Sm ring assembles efficiently in vitro on a spliceosomal Sm site but the engineered U7 snRNP is functionally impaired. This approach offers a unique opportunity to study the importance of various regions in the Sm proteins and U7 snRNA in 3' end processing of histone pre-mRNAs.
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Affiliation(s)
- Katarzyna Bucholc
- Integrative Program for Biological and Genome Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.,Department of Biophysics, Institute of Biochemistry and Biophysics, Polish Academy of Sciences, 02-106 Warsaw, Poland
| | - Wei Shen Aik
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA
| | - Xiao-Cui Yang
- Integrative Program for Biological and Genome Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Kaituo Wang
- California NanoSystems Institute, University of California Los Angeles, Los Angeles, CA 90095, USA
| | - Z Hong Zhou
- California NanoSystems Institute, University of California Los Angeles, Los Angeles, CA 90095, USA
| | - Michał Dadlez
- Department of Biophysics, Institute of Biochemistry and Biophysics, Polish Academy of Sciences, 02-106 Warsaw, Poland.,Institute of Genetics and Biotechnology, Warsaw University, 02-106 Warsaw, Poland
| | - William F Marzluff
- Integrative Program for Biological and Genome Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.,Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Liang Tong
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA
| | - Zbigniew Dominski
- Integrative Program for Biological and Genome Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.,Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
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6
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Chari S, Wilky H, Govindan J, Amodeo AA. Histone concentration regulates the cell cycle and transcription in early development. Development 2019; 146:dev.177402. [PMID: 31511251 DOI: 10.1242/dev.177402] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2019] [Accepted: 08/28/2019] [Indexed: 12/12/2022]
Abstract
The early embryos of many animals, including flies, fish and frogs, have unusually rapid cell cycles and delayed onset of transcription. These divisions are dependent on maternally supplied RNAs and proteins including histones. Previous work suggests that the pool size of maternally provided histones can alter the timing of zygotic genome activation (ZGA) in frogs and fish. Here, we examine the effects of under- and overexpression of maternal histones in Drosophila embryogenesis. Decreasing histone concentration advances zygotic transcription, cell cycle elongation, Chk1 activation and gastrulation. Conversely, increasing histone concentration delays transcription and results in an additional nuclear cycle before gastrulation. Numerous zygotic transcripts are sensitive to histone concentration, and the promoters of histone-sensitive genes are associated with specific chromatin features linked to increased histone turnover. These include enrichment of the pioneer transcription factor Zelda, and lack of SIN3A and associated histone deacetylases. Our findings uncover a crucial regulatory role for histone concentrations in ZGA of Drosophila.
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Affiliation(s)
- Sudarshan Chari
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA
| | - Henry Wilky
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA
| | - Jayalakshmi Govindan
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA
| | - Amanda A Amodeo
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA
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7
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Skrajna A, Yang XC, Dadlez M, Marzluff WF, Dominski Z. Protein composition of catalytically active U7-dependent processing complexes assembled on histone pre-mRNA containing biotin and a photo-cleavable linker. Nucleic Acids Res 2019. [PMID: 29529248 PMCID: PMC5961079 DOI: 10.1093/nar/gky133] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
3′ end cleavage of metazoan replication-dependent histone pre-mRNAs requires the multi-subunit holo-U7 snRNP and the stem–loop binding protein (SLBP). The exact composition of the U7 snRNP and details of SLBP function in processing remain unclear. To identify components of the U7 snRNP in an unbiased manner, we developed a novel approach for purifying processing complexes from Drosophila and mouse nuclear extracts. In this method, catalytically active processing complexes are assembled in vitro on a cleavage-resistant histone pre-mRNA containing biotin and a photo-sensitive linker, and eluted from streptavidin beads by UV irradiation for direct analysis by mass spectrometry. In the purified processing complexes, Drosophila and mouse U7 snRNP have a remarkably similar composition, always being associated with CPSF73, CPSF100, symplekin and CstF64. Many other proteins previously implicated in the U7-dependent processing are not present. Drosophila U7 snRNP bound to histone pre-mRNA in the absence of SLBP contains the same subset of polyadenylation factors but is catalytically inactive and addition of recombinant SLBP is sufficient to trigger cleavage. This result suggests that Drosophila SLBP promotes a structural rearrangement of the processing complex, resulting in juxtaposition of the CPSF73 endonuclease with the cleavage site in the pre-mRNA substrate.
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Affiliation(s)
- Aleksandra Skrajna
- Integrative Program for Biological and Genome Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.,Department of Biophysics, Institute of Biochemistry and Biophysics, Polish Academy of Sciences, 02-106 Warsaw, Poland
| | - Xiao-Cui Yang
- Integrative Program for Biological and Genome Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Michal Dadlez
- Department of Biophysics, Institute of Biochemistry and Biophysics, Polish Academy of Sciences, 02-106 Warsaw, Poland
| | - William F Marzluff
- Integrative Program for Biological and Genome Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.,Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Zbigniew Dominski
- Integrative Program for Biological and Genome Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.,Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
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8
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Biochemical Fractionation of Time-Resolved Drosophila Embryos Reveals Similar Transcriptomic Alterations in Replication Checkpoint and Histone mRNA Processing Mutants. J Mol Biol 2017; 429:3264-3279. [DOI: 10.1016/j.jmb.2017.01.022] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Revised: 01/28/2017] [Accepted: 01/30/2017] [Indexed: 11/22/2022]
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9
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Alexiadis A, Delidakis C, Kalantidis K. Snipper, an Eri1 homologue, affects histone mRNA abundance and is crucial for normal Drosophila melanogaster development. FEBS Lett 2017. [PMID: 28626879 DOI: 10.1002/1873-3468.12719] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The conserved 3'-5' RNA exonuclease ERI1 is implicated in RNA interference inhibition, 5.8S rRNA maturation and histone mRNA maturation and turnover. The single ERI1 homologue in Drosophila melanogaster Snipper (Snp) is a 3'-5' exonuclease, but its in vivo function remains elusive. Here, we report Snp requirement for normal Drosophila development, since its perturbation leads to larval arrest and tissue-specific downregulation results in abnormal tissue development. Additionally, Snp directly interacts with histone mRNA, and its depletion results in drastic reduction in histone transcript levels. We propose that Snp protects the 3'-ends of histone mRNAs and upon its absence, histone transcripts are readily degraded. This in turn may lead to cell cycle delay or arrest, causing growth arrest and developmental perturbations.
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Affiliation(s)
- Anastasios Alexiadis
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas, Heraklion, Greece.,Department of Biology, University of Crete, Heraklion, Greece
| | - Christos Delidakis
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas, Heraklion, Greece.,Department of Biology, University of Crete, Heraklion, Greece
| | - Kriton Kalantidis
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas, Heraklion, Greece.,Department of Biology, University of Crete, Heraklion, Greece
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10
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Skrajna A, Yang XC, Bucholc K, Zhang J, Hall TMT, Dadlez M, Marzluff WF, Dominski Z. U7 snRNP is recruited to histone pre-mRNA in a FLASH-dependent manner by two separate regions of the stem-loop binding protein. RNA (NEW YORK, N.Y.) 2017; 23:938-951. [PMID: 28289156 PMCID: PMC5435866 DOI: 10.1261/rna.060806.117] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/16/2017] [Accepted: 03/09/2017] [Indexed: 05/07/2023]
Abstract
Cleavage of histone pre-mRNAs at the 3' end requires stem-loop binding protein (SLBP) and U7 snRNP that consists of U7 snRNA and a unique Sm ring containing two U7-specific proteins: Lsm10 and Lsm11. Lsm11 interacts with FLASH and together they bring a subset of polyadenylation factors to U7 snRNP, including the CPSF73 endonuclease that cleaves histone pre-mRNA. SLBP binds to a conserved stem-loop structure upstream of the cleavage site and acts by promoting an interaction between the U7 snRNP and a sequence element located downstream from the cleavage site. We show that both human and Drosophila SLBPs stabilize U7 snRNP on histone pre-mRNA via two regions that are not directly involved in recognizing the stem-loop structure: helix B of the RNA binding domain and the C-terminal region that follows the RNA binding domain. Stabilization of U7 snRNP binding to histone pre-mRNA by SLBP requires FLASH but not the polyadenylation factors. Thus, FLASH plays two roles in 3' end processing of histone pre-mRNAs: It interacts with Lsm11 to form a docking platform for the polyadenylation factors, and it cooperates with SLBP to recruit U7 snRNP to histone pre-mRNA.
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Affiliation(s)
- Aleksandra Skrajna
- Integrative Program for Biological and Genome Sciences, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
- Department of Biophysics, Institute of Biochemistry and Biophysics, Polish Academy of Sciences, 02-106 Warsaw, Poland
| | - Xiao-Cui Yang
- Integrative Program for Biological and Genome Sciences, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
| | - Katarzyna Bucholc
- Department of Biophysics, Institute of Biochemistry and Biophysics, Polish Academy of Sciences, 02-106 Warsaw, Poland
| | - Jun Zhang
- Epigenetics and Stem Cell Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina 27709, USA
| | - Traci M Tanaka Hall
- Epigenetics and Stem Cell Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina 27709, USA
| | - Michał Dadlez
- Department of Biophysics, Institute of Biochemistry and Biophysics, Polish Academy of Sciences, 02-106 Warsaw, Poland
| | - William F Marzluff
- Integrative Program for Biological and Genome Sciences, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
| | - Zbigniew Dominski
- Integrative Program for Biological and Genome Sciences, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
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11
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Lampert F, Brodersen MML, Peter M. Guard the guardian: A CRL4 ligase stands watch over histone production. Nucleus 2017; 8:134-143. [PMID: 28072566 DOI: 10.1080/19491034.2016.1276143] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Histones are evolutionarily conserved proteins that together with DNA constitute eukaryotic chromatin in a defined stoichiometry. Core histones are dynamic scaffolding proteins that undergo a myriad of post-translational modifications, which selectively engage chromosome condensation, replication, transcription and DNA damage repair. Cullin4-RING ubiquitin E3 ligases are known to hold pivotal roles in a wide spectrum of chromatin biology ranging from chromatin remodeling and transcriptional repression, to sensing of cytotoxic DNA lesions. Our recent work uncovers an unexpected function of a CRL4 ligase upstream of these processes in promoting histone biogenesis. The CRL4WDR23 ligase directly controls the activity of the stem-loop binding protein (SLBP), which orchestrates elemental steps of canonical histone transcript metabolism. We demonstrate that non-proteolytic ubiquitination of SLBP ensures sufficient histone reservoirs during DNA replication and is vital for genome integrity and cellular fitness.
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Affiliation(s)
| | - Mia M L Brodersen
- a Institute of Biochemistry, ETH Zurich , Zürich , Switzerland.,b nspm. ltd. , Meggen , Switzerland
| | - Matthias Peter
- a Institute of Biochemistry, ETH Zurich , Zürich , Switzerland
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12
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Abstract
Ribonucleoprotein complexes involved in pre-mRNA splicing and mRNA decay are often regulated by phosphorylation of RNA-binding proteins. Cells use phosphorylation-dependent signaling pathways to turn on and off gene expression. Not much is known about how phosphorylation-dependent signals transmitted by exogenous factors or cell cycle checkpoints regulate RNA-mediated gene expression at the atomic level. Several human diseases are linked to an altered phosphorylation state of an RNA binding protein. Understanding the structural response to the phosphorylation "signal" and its effect on ribonucleoprotein assembly provides mechanistic understanding, as well as new information for the design of novel drugs. In this review, I highlight recent structural studies that reveal the mechanisms by which phosphorylation can regulate protein-protein and protein-RNA interactions in ribonucleoprotein complexes.
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Affiliation(s)
- Roopa Thapar
- BioSciences
at Rice, Biochemistry
and Cell Biology, Rice University, Houston, Texas 77251-1892, United States
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13
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Thapar R. Structure-specific nucleic acid recognition by L-motifs and their diverse roles in expression and regulation of the genome. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2015; 1849:677-87. [PMID: 25748361 DOI: 10.1016/j.bbagrm.2015.02.006] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2014] [Revised: 02/05/2015] [Accepted: 02/24/2015] [Indexed: 01/08/2023]
Abstract
The high-mobility group (HMG) domain containing proteins regulate transcription, DNA replication and recombination. They adopt L-shaped folds and are structure-specific DNA binding motifs. Here, I define the L-motif super-family that consists of DNA-binding HMG-box proteins and the L-motif of the histone mRNA binding domain of stem-loop binding protein (SLBP). The SLBP L-motif and HMG-box domains adopt similar L-shaped folds with three α-helices and two or three small hydrophobic cores that stabilize the overall fold, but have very different and distinct modes of nucleic acid recognition. A comparison of the structure, dynamics, protein-protein and nucleic acid interactions, and regulation by PTMs of the SLBP and the HMG-box L-motifs reveals the versatile and diverse modes by which L-motifs utilize their surfaces for structure-specific recognition of nucleic acids to regulate gene expression.
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Affiliation(s)
- Roopa Thapar
- BioSciences at Rice-Biochemistry and Cell Biology, Rice University, Houston, TX 77251-1892, USA.
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14
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Thapar R. Contribution of protein phosphorylation to binding-induced folding of the SLBP-histone mRNA complex probed by phosphorus-31 NMR. FEBS Open Bio 2014; 4:853-7. [PMID: 25379382 PMCID: PMC4215118 DOI: 10.1016/j.fob.2014.10.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2014] [Revised: 10/02/2014] [Accepted: 10/03/2014] [Indexed: 11/30/2022] Open
Abstract
SLBP is an intrinsically disordered protein (IDP) in the absence of RNA. A phosphothreonine in the SLBP RNA-binding domain stabilizes the SLBP–histone mRNA complex. This phosphate exhibits torsional strain as revealed by its 31P NMR chemical shift. Phosphates can play structural roles in stabilizing tertiary structure in IDPs. 31P NMR can be a good spectroscopic probe for folding of phosphorylated IDPs.
Phosphorus-31 (31P) NMR can be used to characterize the structure and dynamics of phosphorylated proteins. Here, I use 31P NMR to report on the chemical nature of a phosphothreonine that lies in the RNA binding domain of SLBP (stem-loop binding protein). SLBP is an intrinsically disordered protein and phosphorylation at this threonine promotes the assembly of the SLBP–RNA complex. The data show that the 31P chemical shift can be a good spectroscopic probe for phosphate-coupled folding and binding processes in intrinsically disordered proteins, particularly where the phosphate exhibits torsional strain and is involved in a network of hydrogen-bonding interactions.
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Affiliation(s)
- Roopa Thapar
- Department of Biochemistry and Biophysics and Program in Molecular Biology and Biotechnology, University of North Carolina, Chapel Hill, NC 27599, USA
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15
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Molecular mechanisms for the regulation of histone mRNA stem-loop-binding protein by phosphorylation. Proc Natl Acad Sci U S A 2014; 111:E2937-46. [PMID: 25002523 DOI: 10.1073/pnas.1406381111] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Replication-dependent histone mRNAs end with a conserved stem loop that is recognized by stem-loop-binding protein (SLBP). The minimal RNA-processing domain of SLBP is phosphorylated at an internal threonine, and Drosophila SLBP (dSLBP) also is phosphorylated at four serines in its 18-aa C-terminal tail. We show that phosphorylation of dSLBP increases RNA-binding affinity dramatically, and we use structural and biophysical analyses of dSLBP and a crystal structure of human SLBP phosphorylated on the internal threonine to understand the striking improvement in RNA binding. Together these results suggest that, although the C-terminal tail of dSLBP does not contact the RNA, phosphorylation of the tail promotes SLBP conformations competent for RNA binding and thereby appears to reduce the entropic penalty for the association. Increased negative charge in this C-terminal tail balances positively charged residues, allowing a more compact ensemble of structures in the absence of RNA.
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16
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Iampietro C, Bergalet J, Wang X, Cody NAL, Chin A, Lefebvre FA, Douziech M, Krause HM, Lécuyer E. Developmentally regulated elimination of damaged nuclei involves a Chk2-dependent mechanism of mRNA nuclear retention. Dev Cell 2014; 29:468-81. [PMID: 24835465 DOI: 10.1016/j.devcel.2014.03.025] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2013] [Revised: 12/18/2013] [Accepted: 03/31/2014] [Indexed: 11/25/2022]
Abstract
The faithful execution of embryogenesis relies on the ability of organisms to respond to genotoxic stress and to eliminate defective cells that could otherwise compromise viability. In syncytial-stage Drosophila embryos, nuclei with excessive DNA damage undergo programmed elimination through an as-yet poorly understood process of nuclear fallout at the midblastula transition. We show that this involves a Chk2-dependent mechanism of mRNA nuclear retention that is induced by DNA damage and prevents the translation of specific zygotic mRNAs encoding key mitotic, cytoskeletal, and nuclear proteins required to maintain nuclear viability. For histone messages, we show that nuclear retention involves Chk2-mediated inactivation of the Drosophila stem loop binding protein (SLBP), the levels of which are specifically depleted in damaged nuclei following Chk2 phosphorylation, an event that contributes to nuclear fallout. These results reveal a layer of regulation within the DNA damage surveillance systems that safeguard genome integrity in eukaryotes.
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Affiliation(s)
- Carole Iampietro
- Institut de Recherches Cliniques de Montréal (IRCM), Montréal, QC H2W 1R7, Canada
| | - Julie Bergalet
- Institut de Recherches Cliniques de Montréal (IRCM), Montréal, QC H2W 1R7, Canada
| | - Xiaofeng Wang
- Institut de Recherches Cliniques de Montréal (IRCM), Montréal, QC H2W 1R7, Canada
| | - Neal A L Cody
- Institut de Recherches Cliniques de Montréal (IRCM), Montréal, QC H2W 1R7, Canada
| | - Ashley Chin
- Institut de Recherches Cliniques de Montréal (IRCM), Montréal, QC H2W 1R7, Canada
| | - Fabio Alexis Lefebvre
- Institut de Recherches Cliniques de Montréal (IRCM), Montréal, QC H2W 1R7, Canada; Département de Biochimie, Université de Montréal, Montréal, QC H3T 1J4, Canada
| | - Mélanie Douziech
- Institut de Recherches Cliniques de Montréal (IRCM), Montréal, QC H2W 1R7, Canada
| | - Henry M Krause
- Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Toronto, ON M5S 3E1, Canada
| | - Eric Lécuyer
- Institut de Recherches Cliniques de Montréal (IRCM), Montréal, QC H2W 1R7, Canada; Département de Biochimie, Université de Montréal, Montréal, QC H3T 1J4, Canada; Division of Experimental Medicine, McGill University, Montréal, QC H3A 1A3, Canada.
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17
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Sabath I, Skrajna A, Yang XC, Dadlez M, Marzluff WF, Dominski Z. 3'-End processing of histone pre-mRNAs in Drosophila: U7 snRNP is associated with FLASH and polyadenylation factors. RNA (NEW YORK, N.Y.) 2013; 19:1726-44. [PMID: 24145821 PMCID: PMC3884669 DOI: 10.1261/rna.040360.113] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
3'-End cleavage of animal replication-dependent histone pre-mRNAs is controlled by the U7 snRNP. Lsm11, the largest component of the U7-specific Sm ring, interacts with FLASH, and in mammalian nuclear extracts these two proteins form a platform that recruits the CPSF73 endonuclease and other polyadenylation factors to the U7 snRNP. FLASH is limiting, and the majority of the U7 snRNP in mammalian extracts exists as a core particle consisting of the U7 snRNA and the Sm ring. Here, we purified the U7 snRNP from Drosophila nuclear extracts and characterized its composition by mass spectrometry. In contrast to the mammalian U7 snRNP, a significant fraction of the Drosophila U7 snRNP contains endogenous FLASH and at least six subunits of the polyadenylation machinery: symplekin, CPSF73, CPSF100, CPSF160, WDR33, and CstF64. The same composite U7 snRNP is recruited to histone pre-mRNA for 3'-end processing. We identified a motif in Drosophila FLASH that is essential for the recruitment of the polyadenylation complex to the U7 snRNP and analyzed the role of other factors, including SLBP and Ars2, in 3'-end processing of Drosophila histone pre-mRNAs. SLBP that binds the upstream stem-loop structure likely recruits a yet-unidentified essential component(s) to the processing machinery. In contrast, Ars2, a protein previously shown to interact with FLASH in mammalian cells, is dispensable for processing in Drosophila. Our studies also demonstrate that Drosophila symplekin and three factors involved in cleavage and polyadenylation-CPSF, CstF, and CF Im-are present in Drosophila nuclear extracts in a stable supercomplex.
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Affiliation(s)
- Ivan Sabath
- Department of Biochemistry and Biophysics, Program in Molecular Biology and Biotechnology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
| | - Aleksandra Skrajna
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, 00-901 Warsaw, Poland
| | - Xiao-cui Yang
- Department of Biochemistry and Biophysics, Program in Molecular Biology and Biotechnology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
| | - Michał Dadlez
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, 00-901 Warsaw, Poland
- Institute of Genetics and Biotechnology, Warsaw University, 02-106 Warsaw, Poland
| | - William F. Marzluff
- Department of Biochemistry and Biophysics, Program in Molecular Biology and Biotechnology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
| | - Zbigniew Dominski
- Department of Biochemistry and Biophysics, Program in Molecular Biology and Biotechnology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
- Corresponding authorE-mail
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18
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Dominski Z, Carpousis AJ, Clouet-d'Orval B. Emergence of the β-CASP ribonucleases: highly conserved and ubiquitous metallo-enzymes involved in messenger RNA maturation and degradation. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2013; 1829:532-51. [PMID: 23403287 DOI: 10.1016/j.bbagrm.2013.01.010] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2012] [Revised: 01/18/2013] [Accepted: 01/22/2013] [Indexed: 01/05/2023]
Abstract
The β-CASP ribonucleases, which are found in the three domains of life, have in common a core of 460 residues containing seven conserved sequence motifs involved in the tight binding of two catalytic zinc ions. A hallmark of these enzymes is their ability to catalyze both endo- and exo-ribonucleolytic degradation. Exo-ribonucleolytic degradation proceeds in the 5' to 3' direction and is sensitive to the phosphorylation state of the 5' end of a transcript. Recent phylogenomic analyses have shown that the β-CASP ribonucleases can be partitioned into two major subdivisions that correspond to orthologs of eukaryal CPSF73 and bacterial RNase J. We discuss the known functions of the CPSF73 and RNase J orthologs, their association into complexes, and their structure as it relates to mechanism of action. Eukaryal CPSF73 is part of a large multiprotein complex that is involved in the maturation of the 3' end of RNA Polymerase II transcripts and the polyadenylation of messenger RNA. RNase J1 and J2 are paralogs in Bacillus subtilis that are involved in the degradation of messenger RNA and the maturation of non-coding RNA. RNase J1 and J2 co-purify as a heteromeric complex and there is recent evidence that they interact with other enzymes to form a bacterial RNA degradosome. Finally, we speculate on the evolutionary origin of β-CASP ribonucleases and on their functions in Archaea. Orthologs of CPSF73 with endo- and exo-ribonuclease activity are strictly conserved throughout the archaea suggesting a role for these enzymes in the maturation and/or degradation of messenger RNA. This article is part of a Special Issue entitled: RNA Decay mechanisms.
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Affiliation(s)
- Zbigniew Dominski
- Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, NC, USA
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19
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Bansal N, Zhang M, Bhaskar A, Itotia P, Lee E, Shlyakhtenko LS, Lam TT, Fritz A, Berezney R, Lyubchenko YL, Stafford WF, Thapar R. Assembly of the SLIP1-SLBP complex on histone mRNA requires heterodimerization and sequential binding of SLBP followed by SLIP1. Biochemistry 2013; 52:520-36. [PMID: 23286197 DOI: 10.1021/bi301074r] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The SLIP1-SLBP complex activates translation of replication-dependent histone mRNAs. In this report, we describe how the activity of the SLIP1-SLBP complex is modulated by phosphorylation and oligomerization. Biophysical characterization of the free proteins shows that whereas SLIP1 is a homodimer that does not bind RNA, human SLBP is an intrinsically disordered protein that is phosphorylated at 23 Ser/Thr sites when expressed in a eukaryotic expression system such as baculovirus. The bacterially expressed unphosphorylated SLIP1-SLBP complex forms a 2:2 high-affinity (K(D) < 0.9 nM) heterotetramer that is also incapable of binding histone mRNA. In contrast, phosphorylated SLBP from baculovirus has a weak affinity (K(D) ~3 μM) for SLIP1. Sequential binding of phosphorylated SLBP to the histone mRNA stem-loop motif followed by association with SLIP1 is required to form an "active" ternary complex. Phosphorylation of SLBP at Thr171 promotes dissociation of the heterotetramer to the SLIP1-SLBP heterodimer. Using alanine scanning mutagenesis, we demonstrate that the binding site on SLIP1 for SLBP lies close to the dimer interface. A single-point mutant near the SLIP1 homodimer interface abolished interaction with SLBP in vitro and reduced the abundance of histone mRNA in vivo. On the basis of these biophysical studies, we propose that oligomerization and SLBP phosphorylation may regulate the SLBP-SLIP1 complex in vivo. SLIP1 may act to sequester SLBP in vivo, protecting it from proteolytic degradation as an inactive heterotetramer, or alternatively, formation of the SLIP1-SLBP heterotetramer may facilitate removal of SLBP from the histone mRNA prior to histone mRNA degradation.
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Affiliation(s)
- Nitin Bansal
- Hauptman-Woodward Medical Research Institute, 700 Ellicott Street, Buffalo, NY 14203, USA
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20
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Krishnan N, Lam TT, Fritz A, Rempinski D, O'Loughlin K, Minderman H, Berezney R, Marzluff WF, Thapar R. The prolyl isomerase Pin1 targets stem-loop binding protein (SLBP) to dissociate the SLBP-histone mRNA complex linking histone mRNA decay with SLBP ubiquitination. Mol Cell Biol 2012; 32:4306-22. [PMID: 22907757 PMCID: PMC3486140 DOI: 10.1128/mcb.00382-12] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2012] [Accepted: 08/13/2012] [Indexed: 01/04/2023] Open
Abstract
Histone mRNAs are rapidly degraded at the end of S phase, and a 26-nucleotide stem-loop in the 3' untranslated region is a key determinant of histone mRNA stability. This sequence is the binding site for stem-loop binding protein (SLBP), which helps to recruit components of the RNA degradation machinery to the histone mRNA 3' end. SLBP is the only protein whose expression is cell cycle regulated during S phase and whose degradation is temporally correlated with histone mRNA degradation. Here we report that chemical inhibition of the prolyl isomerase Pin1 or downregulation of Pin1 by small interfering RNA (siRNA) increases the mRNA stability of all five core histone mRNAs and the stability of SLBP. Pin1 regulates SLBP polyubiquitination via the Ser20/Ser23 phosphodegron in the N terminus. siRNA knockdown of Pin1 results in accumulation of SLBP in the nucleus. We show that Pin1 can act along with protein phosphatase 2A (PP2A) in vitro to dephosphorylate a phosphothreonine in a conserved TPNK sequence in the SLBP RNA binding domain, thereby dissociating SLBP from the histone mRNA hairpin. Our data suggest that Pin1 and PP2A act to coordinate the degradation of SLBP by the ubiquitin proteasome system and the exosome-mediated degradation of the histone mRNA by regulating complex dissociation.
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Affiliation(s)
| | - TuKiet T. Lam
- W. M. Keck Foundation Biotechnology Resource Laboratory, Yale University, New Haven, Connecticut, USA
| | - Andrew Fritz
- Department of Biological Sciences, SUNY at Buffalo, Buffalo, New York, USA
| | | | - Kieran O'Loughlin
- Department of Flow and Image Cytometry, Roswell Park Cancer Institute, Buffalo, New York, USA
| | - Hans Minderman
- Department of Flow and Image Cytometry, Roswell Park Cancer Institute, Buffalo, New York, USA
| | - Ronald Berezney
- Department of Biological Sciences, SUNY at Buffalo, Buffalo, New York, USA
| | - William F. Marzluff
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - Roopa Thapar
- Hauptman Woodward Medical Research Institute
- Department of Structural Biology, SUNY at Buffalo, Buffalo, New York, USA
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21
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Zhang M, Lam TT, Tonelli M, Marzluff WF, Thapar R. Interaction of the histone mRNA hairpin with stem-loop binding protein (SLBP) and regulation of the SLBP-RNA complex by phosphorylation and proline isomerization. Biochemistry 2012; 51:3215-31. [PMID: 22439849 DOI: 10.1021/bi2018255] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
In metazoans, the majority of histone proteins are generated from replication-dependent histone mRNAs. These mRNAs are unique in that they are not polyadenylated but have a stem-loop structure in their 3' untranslated region. An early event in 3' end formation of histone mRNAs is the binding of stem-loop binding protein (SLBP) to the stem-loop structure. Here we provide insight into the mechanism by which SLBP contacts the histone mRNA. There are two binding sites in the SLBP RNA binding domain for the histone mRNA hairpin. The first binding site (Glu129-Val158) consists of a helix-turn-helix motif that likely recognizes the unpaired uridines in the loop of the histone hairpin and, upon binding, destabilizes the first G-C base pair at the base of the stem. The second binding site lies between residues Arg180 and Pro200, which appears to recognize the second G-C base pair from the base of the stem and possibly regions flanking the stem-loop structure. We show that the SLBP-histone mRNA complex is regulated by threonine phosphorylation and proline isomerization in a conserved TPNK sequence that lies between the two binding sites. Threonine phosphorylation increases the affinity of SLBP for histone mRNA by slowing the off rate for complex dissociation, whereas the adjacent proline acts as a critical hinge that may orient the second binding site for formation of a stable SLBP-histone mRNA complex. The nuclear magnetic resonance and kinetic studies presented here provide a framework for understanding how SLBP recognizes histone mRNA and highlight possible structural roles of phosphorylation and proline isomerization in RNA binding proteins in remodeling ribonucleoprotein complexes.
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Affiliation(s)
- Minyou Zhang
- Hauptman-Woodward Medical Research Institute, Buffalo, New York 14203, United States
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22
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Roca X, Karginov FV. RNA biology in a test tube--an overview of in vitro systems/assays. WILEY INTERDISCIPLINARY REVIEWS-RNA 2012; 3:509-27. [PMID: 22447682 DOI: 10.1002/wrna.1115] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
In vitro systems have provided a wealth of information in the field of RNA biology, as they constitute a superior and sometimes the unique approach to address many important questions. Such cell-free methods can be sorted by the degree of complexity of the preparation of enzymatic and/or regulatory activity. Progress in the study of pre-mRNA processing has largely relied on traditional in vitro methods, as these reactions have been recapitulated in cell-free systems. The pre-mRNA capping, editing, and cleavage/polyadenylation reactions have even been reconstituted using purified components, and the enzymes responsible for catalysis have been characterized by such techniques. In vitro splicing using nuclear or cytoplasmic extracts has yielded clues on spliceosome assembly, kinetics, and mechanisms of splicing and has been essential to elucidate the function of splicing factors. Coupled systems have been important to functionally connect distinct processes, like transcription and splicing. Extract preparation has also been adapted to cells from a variety of tissues and species, revealing general versus species-specific mechanisms. Cell-free assays have also been applied to newly discovered pathways such as those involving small RNAs, including microRNAs (miRNAs), small interfering RNAs (siRNAs), and Piwi-interacting RNAs (piRNAs). The first two pathways have been well characterized largely by in vitro methods, which need to be developed for piRNAs. Finally, new techniques, such as single-molecule studies, are continuously being established, providing new and important insights into the field. Thus, in vitro approaches have been, are, and will continue being at the forefront of RNA research.
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Affiliation(s)
- Xavier Roca
- Division of Molecular Genetics & Cell Biology, School of Biological Sciences, Nanyang Technological University, Singapore, Singapore.
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23
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Cyr AB, Nimmakayalu M, Longmuir SQ, Patil SR, Keppler-Noreuil KM, Shchelochkov OA. A novel 4p16.3 microduplication distal to WHSC1 and WHSC2 characterized by oligonucleotide array with new phenotypic features. Am J Med Genet A 2011; 155A:2224-8. [PMID: 21815251 DOI: 10.1002/ajmg.a.34120] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2011] [Accepted: 04/27/2011] [Indexed: 01/19/2023]
Abstract
Larger imbalances on chromosome 4p in the form of deletions associated with Wolf-Hirschhorn syndrome (WHS) and duplications of chromosome 4p have a defined clinical phenotype. The critical region for both these clinical disorders has been narrowed based on the genotype-phenotype correlations. However, cryptic rearrangements in this region have been reported infrequently. We report on a male patient with a microduplication of chromosome 4p, who presents with findings of macrocephaly, irregular iris pigmentation-heterochromia, and preserved linear growth in addition to overlapping features of trisomy 4p such as seizures, delayed psychomotor development, and dysmorphic features including prominent glabella, low-set ears, and short neck. Using a high-density oligonucleotide microarray, we have identified a novel submicroscopic duplication involving dosage sensitive genes TACC3, FGFR3, and LETM1. The microduplication did not involve WHSC1 and WHSC2 which are considered in the critical region for WHS and trisomy 4p. This patient's presentation and genomic findings help further delineate clinical significance of re-arrangements in the 4p16 region without the involvement of WHS critical region.
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Affiliation(s)
- Andrew B Cyr
- Division of Medical Genetics, Department of Pediatrics, University of Iowa Hospitals and Clinics, Iowa City, Iowa, USA
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24
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Dominski Z. The hunt for the 3' endonuclease. WILEY INTERDISCIPLINARY REVIEWS-RNA 2010; 1:325-40. [PMID: 21935893 DOI: 10.1002/wrna.33] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Pre-mRNAs are typically processed at the 3(') end by cleavage/polyadenylation. This is a two-step processing reaction initiated by endonucleolytic cleavage of pre-mRNAs downstream of the AAUAAA sequence or its variant, followed by extension of the newly generated 3(') end with a poly(A) tail. In metazoans, replication-dependent histone transcripts are cleaved by a different 3(') end processing mechanism that depends on the U7 small nuclear ribonucleoprotein and the polyadenylation step is omitted. Each of the two mechanisms occurs in a macromolecular assembly that primarily functions to juxtapose the scissile bond with the 3(') endonuclease. Remarkably, despite characterizing a number of processing factors, the identity of this most critical component remained elusive until recently. For cleavage coupled to polyadenylation, much needed help was offered by bioinformatics, which pointed to CPSF-73, a known processing factor required for both cleavage and polyadenylation, as the possible 3(') endonuclease. In silico structural analysis indicated that this protein is a member of the large metallo-β-lactamase family of hydrolytic enzymes and belongs to the β-CASP subfamily that includes several RNA and DNA-specific nucleases. Subsequent experimental studies supported the notion that CPSF-73 does function as the endonuclease in the formation of polyadenylated mRNAs, but some controversy still remains as a different cleavage and polyadenylation specificity factor (CPSF) subunit, CPSF-30, displays an endonuclease activity in vitro while recombinant CPSF-73 is inactive. Unexpectedly, CPSF-73 as the 3(') endonuclease in cleavage coupled to polyadenylation found a strong ally in U7-dependent processing of histone pre-mRNAs, which was shown to utilize the same protein as the cleaving enzyme. It thus seems likely that these two processing reactions evolved from a common mechanism, with CPSF-73 as the endonuclease.
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Affiliation(s)
- Zbigniew Dominski
- Department of Biochemistry and Biophysics and Program in Molecular Biology and Biotechnology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
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25
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Farber LJ, Kort EJ, Wang P, Chen J, Teh BT. The tumor suppressor parafibromin is required for posttranscriptional processing of histone mRNA. Mol Carcinog 2010; 49:215-23. [PMID: 19908240 DOI: 10.1002/mc.20591] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Parafibromin, encoded by the gene HRPT2, is a tumor suppressor protein associated with the RNA polymerase II-associated complex, Paf1 complex. HRPT2 mutations were first identified in patients with the multiple endocrine neoplasia syndrome, hyperparathyroidism-jaw tumor (HPT-JT) syndrome, and have also been found in sporadic parathyroid and renal tumors. However, the mechanisms by which parafibromin suppresses tumor formation remain unknown. In this study, we identify a novel role of parafibromin in the regulation of replication-dependent histones. Both in vitro and in vivo analyses reveal a posttranscriptional role of parafibromin in histone mRNA processing. Downregulation of parafibromin through RNA interference or in vivo mutations lead to uncleaved histone mRNA with polyadenylated tails. These results indicate that parafibromin regulates the 3' processing of histone RNA, an essential component of the cell cycle.
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Affiliation(s)
- Leslie J Farber
- Laboratory of Cancer Genetics, Van Andel Research Institute, Grand Rapids, Michigan 49503, USA
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26
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Phosphorylation of threonine 61 by cyclin a/Cdk1 triggers degradation of stem-loop binding protein at the end of S phase. Mol Cell Biol 2008; 28:4469-79. [PMID: 18490441 DOI: 10.1128/mcb.01416-07] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Histone mRNA levels are cell cycle regulated, and a major regulatory mechanism is restriction of stem-loop binding protein (SLBP) to S phase. Degradation of SLBP at the end of S phase results in cessation of histone mRNA biosynthesis, preventing accumulation of histone mRNA until SLBP is synthesized just before entry into the next S phase. Degradation of SLBP requires an SFTTP (58 to 62) and KRKL (95 to 98) sequence, which is a putative cyclin binding site. A fusion protein with the 58-amino-acid sequence of SLBP (amino acids 51 to 108) fused to glutathione S-transferase (GST) is sufficient to mimic SLBP degradation at late S phase. Using GST-SLBP fusion proteins as a substrate, we show that cyclin A/Cdk1 phosphorylates Thr61. Furthermore, knockdown of Cdk1 by RNA interference stabilizes SLBP at the end of S phase. Phosphorylation of Thr61 is necessary for subsequent phosphorylation of Thr60 by CK2 in vitro. Inhibitors of CK2 also prevent degradation of SLBP at the end of S phase. Thus, phosphorylation of Thr61 by cyclin A/Cdk1 primes phosphorylation of Thr60 by CK2 and is responsible for initiating SLBP degradation. We conclude that the increase in cyclin A/Cdk1 activity at the end of S phase triggers degradation of SLBP at S/G(2).
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27
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Dominski Z, Marzluff WF. Formation of the 3' end of histone mRNA: getting closer to the end. Gene 2007; 396:373-90. [PMID: 17531405 PMCID: PMC2888136 DOI: 10.1016/j.gene.2007.04.021] [Citation(s) in RCA: 136] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2007] [Accepted: 04/09/2007] [Indexed: 11/17/2022]
Abstract
Nearly all eukaryotic mRNAs end with a poly(A) tail that is added to their 3' end by the ubiquitous cleavage/polyadenylation machinery. The only known exceptions to this rule are metazoan replication-dependent histone mRNAs, which end with a highly conserved stem-loop structure. This distinct 3' end is generated by specialized 3' end processing machinery that cleaves histone pre-mRNAs 4-5 nucleotides downstream of the stem-loop and consists of the U7 small nuclear RNP (snRNP) and number of protein factors. Recently, the U7 snRNP has been shown to contain a unique Sm core that differs from that of the spliceosomal snRNPs, and an essential heat labile processing factor has been identified as symplekin. In addition, cross-linking studies have pinpointed CPSF-73 as the endonuclease, which catalyzes the cleavage reaction. Thus, many of the critical components of the 3' end processing machinery are now identified. Strikingly, this machinery is not as unique as initially thought but contains at least two factors involved in cleavage/polyadenylation, suggesting that the two mechanisms have a common evolutionary origin. The greatest challenge that lies ahead is to determine how all these factors interact with each other to form a catalytically competent processing complex capable of cleaving histone pre-mRNAs.
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Affiliation(s)
- Zbigniew Dominski
- Program in Molecular Biology and Biotechnology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
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28
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Borchers CH, Thapar R, Petrotchenko EV, Torres MP, Speir JP, Easterling M, Dominski Z, Marzluff WF. Combined top-down and bottom-up proteomics identifies a phosphorylation site in stem-loop-binding proteins that contributes to high-affinity RNA binding. Proc Natl Acad Sci U S A 2006; 103:3094-9. [PMID: 16492733 PMCID: PMC1413926 DOI: 10.1073/pnas.0511289103] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2005] [Indexed: 11/18/2022] Open
Abstract
The stem-loop-binding protein (SLBP) is involved in multiple aspects of histone mRNA metabolism. To characterize the modification status and sites of SLBP, we combined mass spectrometric bottom-up (analysis of peptides) and top-down (analysis of intact proteins) proteomic approaches. Drosophilia SLBP is heavily phosphorylated, containing up to seven phosphoryl groups. Accurate M(r) determination by Fourier transform ion cyclotron resonance (FTICR)-MS and FTICR-MS top-down experiments using a variety of dissociation techniques show there is removal of the initiator methionine and acetylation of the N terminus in the baculovirus-expressed protein, and that T230 is stoichiometrically phosphorylated. T230 is highly conserved; we have determined that this site is also completely phosphorylated in baculovirus-expressed mammalian SLBP and extensively phosphorylated in both Drosophila and mammalian cultured cells. Removal of the phosphoryl group from T230 by either dephosphorylation or mutation results in a 7-fold reduction in the affinity of SLBP for the stem-loop RNA.
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Affiliation(s)
| | - Roopa Thapar
- *Department of Biochemistry and Biophysics and
- Program in Molecular Biology and Biotechnology, University of North Carolina, Chapel Hill, NC 27599; and
| | | | | | | | | | - Zbigniew Dominski
- *Department of Biochemistry and Biophysics and
- Program in Molecular Biology and Biotechnology, University of North Carolina, Chapel Hill, NC 27599; and
| | - William F. Marzluff
- *Department of Biochemistry and Biophysics and
- Program in Molecular Biology and Biotechnology, University of North Carolina, Chapel Hill, NC 27599; and
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29
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Dominski Z, Yang XC, Purdy M, Marzluff WF. Differences and similarities between Drosophila and mammalian 3' end processing of histone pre-mRNAs. RNA (NEW YORK, N.Y.) 2005; 11:1835-47. [PMID: 16251385 PMCID: PMC1370872 DOI: 10.1261/rna.2179305] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
We used nuclear extracts from Drosophila Kc cells to characterize 3' end processing of Drosophila histone pre-mRNAs. Drosophila SLBP plays a critical role in recruiting the U 7 snRNP to the pre-mRNA and is essential for processing all five Drosophila histone pre-mRNAs. The Drosophila processing machinery strongly prefers cleavage after a fourth nucleotide following the stem-loop and favors an adenosine over pyrimidines in this position. Increasing the distance between the stem-loop and the HDE does not result in a corresponding shift of the cleavage site, suggesting that in Drosophila processing the U 7 snRNP does not function as a molecular ruler. Instead, SLBP directs the cleavage site close to the stem-loop. The upstream cleavage product generated in Drosophila nuclear extracts contains a 3' OH, and the downstream cleavage product is degraded by a nuclease dependent on the U 7 snRNP, suggesting that the cleavage factor has been conserved between Drosophila and mammalian processing. A 2'O-methyl oligonucleotide complementary to the first 17 nt of the Drosophila U 7 snRNA was not able to deplete the U 7 snRNP from Drosophila nuclear extracts, suggesting that the 5' end of the Drosophila U 7 snRNA is inaccessible. This oligonucleotide selectively inhibited processing of only two Drosophila pre-mRNAs and had no effect on processing of the other three pre-mRNAs. Together, these studies demonstrate that although Drosophila and mammalian histone pre-mRNA processing share common features, there are also significant differences, likely reflecting divergence in the mechanism of 3' end processing between vertebrates and invertebrates.
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Affiliation(s)
- Zbigniew Dominski
- Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, NC 27599, USA.
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30
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Torres MP, Thapar R, Marzluff WF, Borchers CH. Phosphatase-Directed Phosphorylation-Site Determination: A Synthesis of Methods for the Detection and Identification of Phosphopeptides. J Proteome Res 2005; 4:1628-35. [PMID: 16212415 DOI: 10.1021/pr050129d] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Phosphopeptides can be difficult to detect and sequence by mass spectrometry (MS) due to low ionization efficiency and suppression effects in the MS mode, and insufficient fragmentation in the tandem MS (MS/MS) mode, respectively. To address this problem, we have developed a technique called Phosphatase-directed Phosphorylation-site Determination (PPD), which combines on-target phosphatase reactions, MALDI MS/MS of IMAC beads on target, and hypothesis-driven MS (HD-MS). In this method, on-target dephosphorylation experiments are conducted on IMAC-bound phosphopeptides, because dephosphorylated peptides have, in general, higher MS sensitivities than the corresponding phosphopeptides. The detected dephosphorylated peptides are sequenced by MS/MS, which identifies the potentially phosphorylated peptide and the total number of Ser, Thr, or Tyr residues that could hypothetically be phosphorylated within that peptide. On the basis of this information, a mass list containing every possible phosphorylation state of each observed peptide (where 1 HPO(3) = 80 Da) is used to direct MALDI-MS/MS on the phosphorylated peptides bound to IMAC beads at each theoretical mass from the list. If the peptide is present, the resulting MS/MS spectrum reveals the exact site(s) of phosphorylation in the peptide. We have demonstrated the applicability of PPD to the detection of in vivo phosphorylation sites on the Drosophila Stem Loop Binding Protein (dSLBP), and the complementarity of this new technique to conventional MS phosphorylation site mapping methods, since the phosphorylation sites in dSLBP could not be detected by other methods.
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Affiliation(s)
- Matthew P Torres
- Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, NC 27599, USA
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31
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Warren EN, Jiang J, Parker CE, Borchers CH. Absolute quantitation of cancer-related proteins using an MS-based peptide chip. Biotechniques 2005; Suppl:7-11. [PMID: 16528910 DOI: 10.2144/05386su01] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
New technologies are needed that can diagnose cancer more rapidly and accurately. These technologies must also have the ability to identify the particular cellular abnormalities contributing to the malignancy, thus directing the appropriate treatments. Such technologies should permit absolute quantitation of specific tumor biomarkers and their level of posttranslational modifications. Quantitative molecular profiling of cancer signaling networks would provide a more detailed understanding of the contribution of protein expression and posttranslational modification levels to tumorigenesis. We have developed a unique approach for absolute quantitation of protein expression that integrates affinity capture of proteolytic peptides with mass spectrometry and thus provides detection, identification, and quantitation of their cognate proteins. We have previously shown the high sensitivity and specificity of this approach. Here we demonstrate the absolute quantitation of a model peptide using our technology. We have used this approach to capture epitope-containing peptides from proteolytically digested target proteins, including p53, epidermal growth factor receptor (EGFR), and prostate-specific antigen (PSA). Our technology can easily be extended to the absolute quantitation of protein modification levels, in addition to the determination of protein expression levels, and can be readily adapted for use in a microarray format. This method offers an improved approach to protein chip technology that should prove useful for clinical diagnosis and drug development applications.
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Affiliation(s)
- Erin N Warren
- University of North Carolina Medical School, Chapel Hill, NC 27599, USA
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32
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Berger A, Stierkorb E, Nickenig G. The role of the AUUUUA hexamer for the posttranscriptional regulation of the AT1 receptor mRNA stability. Biochem Biophys Res Commun 2005; 330:805-12. [PMID: 15809068 DOI: 10.1016/j.bbrc.2005.03.043] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2005] [Indexed: 10/25/2022]
Abstract
AT1 receptor expression is mainly regulated posttranscriptionally involving modulation of RNA stability which is dependent on protein binding to the cognate sequence bases 2179-2195 within the 3' untranslated region of the AT1 receptor RNA. This region contains an AUUUUA hexamer which forms part of a stem-loop structure. To clarify the significance of the AUUUUA hexamer for AT1 receptor mRNA regulation, mutations were introduced inside, up- or downstream of it. In vitro decay assays, transfection experiments, and UV-light mRNA protein crosslink assays could demonstrate that mutations within the AUUUUA hexamer disrupted AT1 receptor mRNA degradation as well as the binding of polysomal proteins. In contrast, modification in the neighboring sequence had no effect on mRNA turnover or protein binding. Computer modelling revealed that the AUUUUA hexamer is important for the formation of a stem-loop structure which in turn is relevant for mRNA-protein interactions. These findings indicate that the AUUUUA hexamer is essential for the posttranscriptional modulation of the AT1 receptor mRNA expression.
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Affiliation(s)
- Anja Berger
- Klinik und Poliklinik, Innere Medizin III, Universität des Saarlandes, 66421 Homburg, Saarland, Germany
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33
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Jaeger S, Barends S, Giegé R, Eriani G, Martin F. Expression of metazoan replication-dependent histone genes. Biochimie 2005; 87:827-34. [PMID: 16164992 DOI: 10.1016/j.biochi.2005.03.012] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2004] [Revised: 02/24/2005] [Accepted: 03/18/2005] [Indexed: 11/18/2022]
Abstract
Histone proteins are essential components of eukaryotic chromosomes. In metazoans, they are produced from the so-called replication-dependent histone genes. The biogenesis of histones is tightly coupled to DNA replication in a stoichiometric manner because an excess of histones is highly toxic for the cell. Therefore, a strict cell cycle-regulation of critical factors required for histone expression ensures exclusive S-phase expression. This review focuses on the molecular mechanisms responsible for such a fine expression regulation. Among these, a large part will be dedicated to post-transcriptional events occurring on histone mRNA, like histone mRNA 3' end processing, nucleo-cytoplasmic mRNA export, translation and mRNA degradation. Many factors are involved, including an RNA-binding protein called HBP, also called SLBP (for hairpin- or stem-loop-binding protein) that binds to a conserved hairpin located in the 3' UTR part of histone mRNA. HBP plays a pivotal role in the expression of histone genes since it is necessary for most of the steps of histone mRNA metabolism in the cell. Moreover, the strict S-phase expression pattern of histones is achieved through a fine cell cycle-regulation of HBP. A large part of the discussion will be centered on the critical role of HBP in histone biogenesis.
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Affiliation(s)
- Sophie Jaeger
- Département Mécanismes et Macromolécules de la Synthèse Protéique et Cristallogenèse, UPR 9002, Institut de Biologie Moléculaire et Cellulaire du CNRS, 15, rue René Descartes, 67084 Strasbourg cedex, France
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34
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Dominski Z, Yang XC, Purdy M, Wagner EJ, Marzluff WF. A CPSF-73 homologue is required for cell cycle progression but not cell growth and interacts with a protein having features of CPSF-100. Mol Cell Biol 2005; 25:1489-500. [PMID: 15684398 PMCID: PMC548002 DOI: 10.1128/mcb.25.4.1489-1500.2005] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Formation of the mature 3' ends of the vast majority of cellular mRNAs occurs through cleavage and polyadenylation and requires a cleavage and polyadenylation specificity factor (CPSF) containing, among other proteins, CPSF-73 and CPSF-100. These two proteins belong to a superfamily of zinc-dependent beta-lactamase fold proteins with catalytic specificity for a wide range of substrates including nucleic acids. CPSF-73 contains a zinc-binding histidine motif involved in catalysis in other members of the beta-lactamase superfamily, whereas CPSF-100 has substitutions within the histidine motif and thus is unlikely to be catalytically active. Here we describe two previously unknown human proteins, designated RC-68 and RC-74, which are related to CPSF-73 and CPSF-100 and which form a complex in HeLa and mouse cells. RC-68 contains the intact histidine motif, and hence it might be a functional counterpart of CPSF-73, whereas RC-74 lacks this motif, thus resembling CPSF-100. In HeLa cells RC-68 is present in both the cytoplasm and the nucleus whereas RC-74 is exclusively nuclear. RC-74 does not interact with CPSF-73, and neither RC-68 nor RC-74 is found in a complex with CPSF-160, indicating that these two proteins form a separate entity independent of the CPSF complex and are likely involved in a pre-mRNA processing event other than cleavage and polyadenylation of the vast majority of cellular pre-mRNAs. RNA interference-mediated depletion of RC-68 arrests HeLa cells early in G(1) phase, but surprisingly the arrested cells continue growing and reach the size typical of G(2) cells. RC-68 is highly conserved from plants to humans and may function in conjunction with RC-74 in the 3' end processing of a distinct subset of cellular pre-mRNAs encoding proteins required for G(1) progression and entry into S phase.
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Affiliation(s)
- Zbigniew Dominski
- Program in Molecular Biology and Biotechnology, CB #3280, University of North Carolina, Chapel Hill, NC 27599.
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35
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Erkmann JA, Sànchez R, Treichel N, Marzluff WF, Kutay U. Nuclear export of metazoan replication-dependent histone mRNAs is dependent on RNA length and is mediated by TAP. RNA (NEW YORK, N.Y.) 2005; 11:45-58. [PMID: 15611298 PMCID: PMC1370690 DOI: 10.1261/rna.7189205] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2004] [Accepted: 10/25/2004] [Indexed: 05/23/2023]
Abstract
Replication-dependent histone mRNAs are the only metazoan mRNAs that are not polyadenylated, ending instead in a conserved stem-loop sequence. Histone pre-mRNAs lack introns and are processed in the nucleus by a single cleavage step, which produces the mature 3' end of the mRNA. We have systematically examined the requirements for the nuclear export of a mouse histone mRNA using the Xenopus oocyte system. Histone mRNAs were efficiently exported when injected as mature mRNAs, demonstrating that the process of 3' end cleavage is not required for export factor binding. Export also does not depend on the stem-loop binding protein (SLBP) since mutations of the stem-loop that prevent SLBP binding and competition with a stem-loop RNA did not affect export. Only the length of the region upstream of the stem-loop, but not its sequence, was important for efficient export. Histone mRNA export was blocked by competition with constitutive transport element (CTE) RNA, indicating that the mRNA export receptor TAP is involved in histone mRNA export. Consistent with this observation, depletion of TAP from Drosophila cells by RNAi resulted in the restriction of mature histone mRNAs to the nucleus.
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Affiliation(s)
- Judith A Erkmann
- Program in Molecular Biology and Biotechnology, University of North Carolina, Chapel Hill, NC 27599, USA
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36
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Lanzotti DJ, Kupsco JM, Marzluff WF, Duronio RJ. string(cdc25) and cyclin E are required for patterned histone expression at different stages of Drosophila embryonic development. Dev Biol 2004; 274:82-93. [PMID: 15355790 DOI: 10.1016/j.ydbio.2004.06.019] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2003] [Revised: 05/26/2004] [Accepted: 06/01/2004] [Indexed: 10/26/2022]
Abstract
Metazoan replication-dependent histone mRNAs accumulate to high levels during S phase as a result of an increase in the rate of histone gene transcription, pre-mRNA processing, and mRNA stability at the G1-S transition. However, relatively little is known about the contribution of these processes to histone expression in the cell cycles of early development, which often lack a G1 phase. In post-blastoderm Drosophila embryos, zygotic expression of the stg(cdc25) phosphatase in G2 activates cyclin/cdc2 kinases and triggers mitosis. Here we show that histone transcription initiates in late G2 of cycle 14 in response to stg(cdc25) and in anticipation of S phase of the next cycle, which occurs immediately following mitosis. Mutation of stg(cdc25) arrests cells in G2 and prevents histone transcription. Expression of a mutant form of Cdc2 that bypasses the requirement for stg(cdc25) activates histone transcription during G2 in stg(cdc25) mutant embryos. Thus, in these embryonic cycles, histone transcription is controlled by the principal G2-M regulators, string(cdc25), and cdc2 kinase, rather than solely by regulators of the G1-S transition. After the introduction of G1-S control midway through embryogenesis, histone expression depends on DNA replication and the function of cyclin E, and no longer requires stg(cdc25). Thus, during the altered cell cycles of early animal development, different cell cycle mechanisms are employed to ensure that the production of histones accompanies DNA synthesis.
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Affiliation(s)
- David J Lanzotti
- Curriculum in Genetics and Molecular Biology, University of North Carolina, Chapel Hill, NC 27599, USA
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37
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Lanzotti DJ, Kupsco JM, Yang XC, Dominski Z, Marzluff WF, Duronio RJ. Drosophila stem-loop binding protein intracellular localization is mediated by phosphorylation and is required for cell cycle-regulated histone mRNA expression. Mol Biol Cell 2004; 15:1112-23. [PMID: 14999087 PMCID: PMC363087 DOI: 10.1091/mbc.e03-09-0649] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Stem-loop binding protein (SLBP) is an essential component of the histone pre-mRNA processing machinery. SLBP protein expression was examined during Drosophila development by using transgenes expressing hemagglutinin (HA) epitope-tagged proteins expressed from the endogenous Slbp promoter. Full-length HA-dSLBP complemented a Slbp null mutation, demonstrating that it was fully functional. dSLBP protein accumulates throughout the cell cycle, in contrast to the observed restriction of mammalian SLBP to S phase. dSLBP is located in both nucleus and cytoplasm in replicating cells, but it becomes predominantly nuclear during G2. dSLBP is present in mitotic cells and is down-regulated in G1 when cells exit the cell cycle. We determined whether mutation at previously identified phosphorylation sites, T120 and T230, affected the ability of the protein to restore viability and histone mRNA processing to dSLBP null mutants. The T120A SLBP restored viability and histone pre-mRNA processing. However, the T230A mutant, located in a conserved TPNK sequence in the RNA binding domain, did not restore viability and histone mRNA processing in vivo, although it had full activity in histone mRNA processing in vitro. The T230A protein is concentrated in the cytoplasm, suggesting that it is defective in nuclear targeting, and accounting for its failure to function in histone pre-mRNA processing in vivo.
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Affiliation(s)
- David J Lanzotti
- Department of Biology, University of North Carolina, Chapel Hill, North Carolina 27599, USA
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38
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Jaeger S, Eriani G, Martin F. Critical residues for RNA discrimination of the histone hairpin binding protein (HBP) investigated by the yeast three-hybrid system. FEBS Lett 2004; 556:265-70. [PMID: 14706861 DOI: 10.1016/s0014-5793(03)01433-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The histone hairpin binding protein (HBP, also called SLBP, which stands for stem-loop binding protein) binds specifically to a highly conserved hairpin structure located in the 3' UTR of the cell-cycle-dependent histone mRNAs. HBP consists of a minimal central RNA binding domain (RBD) flanked by an N- and C-terminal domain. The yeast three-hybrid system has been used to investigate the critical residues of the human HBP involved in the binding of its target hairpin structure. By means of negative selections followed by positive selections, we isolated mutant HBP species. Our results indicate tight relationships between the RBD and the N- and C-terminal domains.
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Affiliation(s)
- Sophie Jaeger
- Institut de Biologie Moléculaire et Cellulaire, UPR No. 9002 du CNRS, 15 rue René Descartes, 67084 Cedex, Strasbourg, France
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39
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Azzouz TN, Schumperli D. Evolutionary conservation of the U7 small nuclear ribonucleoprotein in Drosophila melanogaster. RNA (NEW YORK, N.Y.) 2003; 9:1532-41. [PMID: 14624008 PMCID: PMC1370506 DOI: 10.1261/rna.5143303] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2003] [Accepted: 09/04/2003] [Indexed: 05/21/2023]
Abstract
The U7 snRNP involved in histone RNA 3' end processing is related to but biochemically distinct from spliceosomal snRNPs. In vertebrates, the Sm core structure assembling around the noncanonical Sm-binding sequence of U7 snRNA contains only five of the seven standard Sm proteins. The missing Sm D1 and D2 subunits are replaced by U7-specific Sm-like proteins Lsm10 and Lsm11, at least the latter of which is important for histone RNA processing. So far, it was unknown if this special U7 snRNP composition is conserved in invertebrates. Here we describe several putative invertebrate Lsm10 and Lsm11 orthologs that display low but clear sequence similarity to their vertebrate counterparts. Immunoprecipitation studies in Drosophila S2 cells indicate that the Drosophila Lsm10 and Lsm11 orthologs (dLsm10 and dLsm11) associate with each other and with Sm B, but not with Sm D1 and D2. Moreover, dLsm11 associates with the recently characterized Drosophila U7 snRNA and, indirectly, with histone H3 pre-mRNA. Furthermore, dLsm10 and dLsm11 can assemble into U7 snRNPs in mammalian cells. These experiments demonstrate a strong evolutionary conservation of the unique U7 snRNP composition, despite a high degree of primary sequence divergence of its constituents. Therefore, Drosophila appears to be a suitable system for further genetic studies of the cell biology of U7 snRNPs.
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Affiliation(s)
- Teldja N Azzouz
- Institute of Cell Biology, University of Bern, 3012 Bern, Switzerland
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40
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Mazumder B, Sampath P, Seshadri V, Maitra RK, DiCorleto PE, Fox PL. Regulated release of L13a from the 60S ribosomal subunit as a mechanism of transcript-specific translational control. Cell 2003; 115:187-98. [PMID: 14567916 DOI: 10.1016/s0092-8674(03)00773-6] [Citation(s) in RCA: 253] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Transcript-specific translational control is generally directed by binding of trans-acting proteins to structural elements in the untranslated region (UTR) of the target mRNA. Here, we elucidate a translational silencing mechanism involving regulated release of an integral ribosomal protein and subsequent binding to its target mRNA. Human ribosomal protein L13a was identified as a candidate interferon-Gamma-Activated Inhibitor of Translation (GAIT) of ceruloplasmin (Cp) mRNA by a genetic screen for Cp 3'-UTR binding proteins. In vitro activity of L13a was shown by inhibition of target mRNA translation by recombinant protein. In response to interferon-gamma in vivo, the entire cellular pool of L13a was phosphorylated and released from the 60S ribosomal subunit. Released L13a specifically bound the 3'-UTR GAIT element of Cp mRNA and silenced translation. We propose a model in which the ribosome functions not only as a protein synthesis machine, but also as a depot for regulatory proteins that modulate translation.
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Affiliation(s)
- Barsanjit Mazumder
- Department of Cell Biology, Lerner Research Institute, Cleveland Clinic Foundation, 9500 Euclid Avenue, Cleveland, OH 44195, USA
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41
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Dominski Z, Yang XC, Purdy M, Marzluff WF. Cloning and characterization of the Drosophila U7 small nuclear RNA. Proc Natl Acad Sci U S A 2003; 100:9422-7. [PMID: 12872004 PMCID: PMC170934 DOI: 10.1073/pnas.1533509100] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Base pairing between the 5' end of U7 small nuclear RNA (snRNA) and the histone downstream element (HDE) in replication-dependent histone pre-mRNAs is the key event in 3'-end processing that leads to generation of mature histone mRNAs. We have cloned the Drosophila U7 snRNA and demonstrated that it is required for histone pre-mRNA 3'-end processing in a Drosophila nuclear extract. The 71-nt Drosophila U7 snRNA is encoded by a single gene that is embedded in the direct orientation in an intron of the Eip63E gene. The U7 snRNA gene contains conserved promoter elements typical of other Drosophila snRNA genes, and the coding sequence is followed by a 3' box indicating that the Drosophila U7 snRNA gene is an independent transcription unit. Drosophila U7 snRNA contains a trimethyl-guanosine cap at the 5' end and a putative Sm-binding site similar to the unique Sm-binding site found in other U7 snRNAs. Drosophila U7 snRNA is approximately 10 nt longer than mammalian U7 snRNAs because of an extended 5' sequence and has only a limited potential to form a stem-loop structure near the 3' end. The extended 5' end of Drosophila U7 snRNA can base pair with the HDE in all five Drosophila histone pre-mRNAs. Blocking the 5' end of the U7 snRNA with a complementary oligonucleotide specifically blocks processing of a Drosophila histone pre-mRNA. Changes in the HDE that abolish or decrease processing efficiency result in a reduced ability to recruit U7 snRNA to the pre-mRNA.
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Affiliation(s)
- Zbigniew Dominski
- Department of Biochemistry and Biophysics and Program in Molecular Biology and Biotechnology, University of North Carolina, Chapel Hill, NC 27599, USA.
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42
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Adamson TE, Price DH. Cotranscriptional processing of Drosophila histone mRNAs. Mol Cell Biol 2003; 23:4046-55. [PMID: 12773550 PMCID: PMC156150 DOI: 10.1128/mcb.23.12.4046-4055.2003] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2002] [Revised: 02/06/2003] [Accepted: 03/21/2003] [Indexed: 11/20/2022] Open
Abstract
The 3' ends of metazoan histone mRNAs are generated by specialized processing machinery that cleaves downstream of a conserved stem-loop structure. To examine how this reaction might be influenced by transcription, we used a Drosophila melanogaster in vitro system that supports both processes. In this system the complete synthesis of histone mRNA, including transcription initiation and elongation, followed by 3' end formation, occurred at a physiologically significant rate. Processing of free transcripts was efficient and occurred with a t(1/2) of less than 1 min. Divalent cations were not required, but nucleoside triphosphates (NTPs) stimulated the rate of cleavage slightly. Isolated elongation complexes encountered a strong arrest site downstream of the mature histone H4 3' end. In the presence of NTPs, transcripts in these arrested complexes were processed at a rate similar to that of free RNA. Removal of NTPs dramatically reduced this rate, potentially due to concealment of the U7 snRNP binding element. The arrest site was found to be a conserved feature located 32 to 35 nucleotides downstream of the processing site on the H4, H2b, and H3 genes. The significance of the newly discovered arrest sites to our understanding of the coupling between transcription and RNA processing on the one hand and histone gene expression on the other is discussed.
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Affiliation(s)
- Todd E Adamson
- Department of Biochemistry, University of Iowa, Iowa City, Iowa 52242, USA
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43
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Medlin JE, Uguen P, Taylor A, Bentley DL, Murphy S. The C-terminal domain of pol II and a DRB-sensitive kinase are required for 3' processing of U2 snRNA. EMBO J 2003; 22:925-34. [PMID: 12574128 PMCID: PMC145437 DOI: 10.1093/emboj/cdg077] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The human snRNA genes transcribed by RNA polymerase II (e.g. U1 and U2) have a characteristic TATA-less promoter containing an essential proximal sequence element. Formation of the 3' end of these non-polyadenylated RNAs requires a specialized 3' box element whose function is promoter specific. Here we show that truncation of the C-terminal domain (CTD) of RNA polymerase II and treatment of cells with CTD kinase inhibitors, including DRB (5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole), causes a dramatic reduction in proper 3' end formation of U2 transcripts. Activation of 3' box recognition by the phosphorylated CTD would be consistent with the role of phospho-CTD in mRNA processing. CTD kinase inhibitors, however, have little effect on initiation or elongation of transcription of the U2 genes, whereas elongation of transcription of the beta-actin gene is severely affected. This result highlights differences in transcription of snRNA and mRNA genes.
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Affiliation(s)
| | | | | | - David L. Bentley
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK and
Department of Biochemistry and Molecular Genetics, University of Colorado Health Sciences Center, B121, 4200 East 9th Avenue, Denver, CO 80262, USA Corresponding author e-mail:
| | - Shona Murphy
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK and
Department of Biochemistry and Molecular Genetics, University of Colorado Health Sciences Center, B121, 4200 East 9th Avenue, Denver, CO 80262, USA Corresponding author e-mail:
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