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Datta S, Patel M, Sathyaseelan C, Ghosh C, Mudgal A, Patel D, Rathinavelan T, Singh U. G-quadruplex landscape and its regulation revealed by a new antibody capture method. Oncotarget 2024; 15:175-198. [PMID: 38484151 PMCID: PMC10939474 DOI: 10.18632/oncotarget.28564] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2023] [Accepted: 02/12/2024] [Indexed: 03/17/2024] Open
Abstract
Our understanding of DNA G-quadruplexes (G4s) from in vitro studies has been complemented by genome-wide G4 landscapes from cultured cells. Conventionally, the formation of G4s is accepted to depend on G-repeats such that they form tetrads. However, genome-wide G4s characterized through high-throughput sequencing suggest that these structures form at a large number of regions with no such canonical G4-forming signatures. Many G4-binding proteins have been described with no evidence for any protein that binds to and stabilizes G4s. It remains unknown what fraction of G4s formed in human cells are protein-bound. The G4-chromatin immunoprecipitation (G4-ChIP) method hitherto employed to describe G4 landscapes preferentially reports G4s that get crosslinked to proteins in their proximity. Our current understanding of the G4 landscape is biased against representation of G4s which escape crosslinking as they are not stabilized by protein-binding and presumably transient. We report a protocol that captures G4s from the cells efficiently without any bias as well as eliminates the detection of G4s formed artifactually on crosslinked sheared chromatin post-fixation. We discover that G4s form sparingly at SINEs. An application of this method shows that depletion of a repeat-binding protein CGGBP1 enhances net G4 capture at CGGBP1-dependent CTCF-binding sites and regions of sharp interstrand G/C-skew transitions. Thus, we present an improved method for G4 landscape determination and by applying it we show that sequence property-specific constraints of the nuclear environment mitigate G4 formation.
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Affiliation(s)
- Subhamoy Datta
- HoMeCell Lab, Discipline of Biological Engineering, Indian Institute of Technology Gandhinagar, Gandhinagar, Gujarat 382355, India
| | - Manthan Patel
- Centre for Genomics and Child Health, Blizard Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London E1 2AT, UK
| | - Chakkarai Sathyaseelan
- Department of Biotechnology, Indian Institute of Technology Hyderabad, Kandi Campus, Telangana 502285, India
| | - Chandrama Ghosh
- Azrieli Faculty of Medicine, Bar-Ilan University, Henrietta Szold 8A, Safed 1311502, Israel
| | - Akanksha Mudgal
- Department of Biopharmacy, Medical University of Lublin, Lublin 20059, Poland
| | - Divyesh Patel
- Research Programs Unit, Applied Tumor Genomics Program, Faculty of Medicine, University of Helsinki, Biomedicum, Helsinki 00290, Finland
| | | | - Umashankar Singh
- HoMeCell Lab, Discipline of Biological Engineering, Indian Institute of Technology Gandhinagar, Gandhinagar, Gujarat 382355, India
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2
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Patel M, Patel D, Datta S, Singh U. An immunochemistry-based screen for chemical inhibitors of DNA-protein interactions and its application to human CGGBP1. BMC Cancer 2020; 20:1016. [PMID: 33081720 PMCID: PMC7576722 DOI: 10.1186/s12885-020-07526-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2020] [Accepted: 10/14/2020] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND Inhibition of DNA-binding of proteins by small-molecule chemicals holds immense potential in manipulating the activities of DNA-binding proteins. Such a chemical inhibition of DNA-binding of proteins can be used to modulate processes such as replication, transcription, DNA repair and maintenance of epigenetic states. This prospect is currently challenged with the absence of robust and generic protocols to identify DNA-protein interactions. Additionally, much of the current approaches to designing inhibitors requires structural information of the target proteins. METHODS We have developed a simple dot blot and immunodetection-based assay to screen chemical libraries for inhibitors of DNA-protein interactions. The assay has been applied to a library of 1685 FDA-approved chemicals to discover inhibitors of CGGBP1, a multifunctional DNA-binding protein with no known structure. Additional in vitro and in cellulo assays have been performed to verify and supplement the findings of the screen. RESULTS Our primary screen has identified multiple inhibitors of direct or indirect interactions between CGGBP1 and genomic DNA. Of these, one inhibitor, Givinostat, was found to inhibit direct DNA-binding of CGGBP1 in the secondary screen using purified recombinant protein as the target. DNA and chromatin immunoprecipitation assays reinforced the findings of the screen that Givinostat inhibits CGGBP1-DNA binding. CONCLUSIONS The assay we have described successfully identifies verifiable inhibitors of DNA-binding of protein; in this example, the human CGGBP1. This assay is customizable for a wide range of targets for which primary antibodies are available. It works with different sources of the target protein, cell lysates or purified recombinant preparations and does not require special equipment, DNA modifications or protein structural data. This assay is scalable and highly adaptable with the potential to discover inhibitors of transcription factors with implications in cancer biology.
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Affiliation(s)
- Manthan Patel
- HoMeCell Lab, Biological Engineering, Indian Institute of Technology Gandhinagar, Gandhinagar, Gujarat, 382355, India
| | - Divyesh Patel
- HoMeCell Lab, Biological Engineering, Indian Institute of Technology Gandhinagar, Gandhinagar, Gujarat, 382355, India
| | - Subhamoy Datta
- HoMeCell Lab, Biological Engineering, Indian Institute of Technology Gandhinagar, Gandhinagar, Gujarat, 382355, India
| | - Umashankar Singh
- HoMeCell Lab, Biological Engineering, Indian Institute of Technology Gandhinagar, Gandhinagar, Gujarat, 382355, India.
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3
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Patel M, Patel D, Datta S, Singh U. CGGBP1-regulated cytosine methylation at CTCF-binding motifs resists stochasticity. BMC Genet 2020; 21:84. [PMID: 32727353 PMCID: PMC7392725 DOI: 10.1186/s12863-020-00894-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2020] [Accepted: 07/23/2020] [Indexed: 12/03/2022] Open
Abstract
Background The human CGGBP1 binds to GC-rich regions and interspersed repeats, maintains homeostasis of stochastic cytosine methylation and determines DNA-binding of CTCF. Interdependence between regulation of cytosine methylation and CTCF occupancy by CGGBP1 remains unknown. Results By analyzing methylated DNA-sequencing data obtained from CGGBP1-depleted cells, we report that some transcription factor-binding sites, including CTCF, resist stochastic changes in cytosine methylation. By analysing CTCF-binding sites we show that cytosine methylation changes at CTCF motifs caused by CGGBP1 depletion resist stochastic changes. These CTCF-binding sites are positioned at locations where the spread of cytosine methylation in cis depends on the levels of CGGBP1. Conclusion Our findings suggest that CTCF occupancy and functions are determined by CGGBP1-regulated cytosine methylation patterns.
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Affiliation(s)
- Manthan Patel
- HoMeCell Lab, Biological Engineering, Indian Institute of Technology Gandhinagar, Palaj, Gandhinagar, 382355, Gujarat, India
| | - Divyesh Patel
- HoMeCell Lab, Biological Engineering, Indian Institute of Technology Gandhinagar, Palaj, Gandhinagar, 382355, Gujarat, India
| | - Subhamoy Datta
- HoMeCell Lab, Biological Engineering, Indian Institute of Technology Gandhinagar, Palaj, Gandhinagar, 382355, Gujarat, India
| | - Umashankar Singh
- HoMeCell Lab, Biological Engineering, Indian Institute of Technology Gandhinagar, Palaj, Gandhinagar, 382355, Gujarat, India.
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4
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Patel D, Patel M, Datta S, Singh U. CGGBP1 regulates CTCF occupancy at repeats. Epigenetics Chromatin 2019; 12:57. [PMID: 31547883 PMCID: PMC6757366 DOI: 10.1186/s13072-019-0305-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2019] [Accepted: 09/12/2019] [Indexed: 12/27/2022] Open
Abstract
Background CGGBP1 is a repeat-binding protein with diverse functions in the regulation of gene expression, cytosine methylation, repeat silencing and genomic integrity. CGGBP1 has also been identified as a cooperator of histone-modifying enzymes and as a component of CTCF-containing complexes that regulate the enhancer–promoter looping. CGGBP1–CTCF cross talk in chromatin regulation has been hitherto unknown. Results Here, we report that the occupancy of CTCF at repeats depends on CGGBP1. Using ChIP-sequencing for CTCF, we describe its occupancy at repetitive DNA. Our results show that endogenous level of CGGBP1 ensures CTCF occupancy preferentially on repeats over canonical CTCF motifs. By combining CTCF ChIP-sequencing results with ChIP sequencing for three different kinds of histone modifications (H3K4me3, H3K9me3 and H3K27me3), we show that the CGGBP1-dependent repeat-rich CTCF-binding sites regulate histone marks in flanking regions. Conclusion CGGBP1 affects the pattern of CTCF occupancy. Our results posit CGGBP1 as a regulator of CTCF and its binding sites in interspersed repeats.
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Affiliation(s)
- Divyesh Patel
- HoMeCell Lab, Biological Engineering, Indian Institute of Technology Gandhinagar, Gandhinagar, Gujarat, 382355, India
| | - Manthan Patel
- HoMeCell Lab, Biological Engineering, Indian Institute of Technology Gandhinagar, Gandhinagar, Gujarat, 382355, India
| | - Subhamoy Datta
- HoMeCell Lab, Biological Engineering, Indian Institute of Technology Gandhinagar, Gandhinagar, Gujarat, 382355, India
| | - Umashankar Singh
- HoMeCell Lab, Biological Engineering, Indian Institute of Technology Gandhinagar, Gandhinagar, Gujarat, 382355, India.
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5
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Agarwal P, Enroth S, Teichmann M, Jernberg Wiklund H, Smit A, Westermark B, Singh U. Growth signals employ CGGBP1 to suppress transcription of Alu-SINEs. Cell Cycle 2017; 15:1558-71. [PMID: 25483050 PMCID: PMC4934077 DOI: 10.4161/15384101.2014.967094] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
CGGBP1 (CGG triplet repeat-binding protein 1) regulates cell proliferation, stress response, cytokinesis, telomeric integrity and transcription. It could affect these processes by modulating target gene expression under different conditions. Identification of CGGBP1-target genes and their regulation could reveal how a transcription regulator affects such diverse cellular processes. Here we describe the mechanisms of differential gene expression regulation by CGGBP1 in quiescent or growing cells. By studying global gene expression patterns and genome-wide DNA-binding patterns of CGGBP1, we show that a possible mechanism through which it affects the expression of RNA Pol II-transcribed genes in trans depends on Alu RNA. We also show that it regulates Alu transcription in cis by binding to Alu promoter. Our results also indicate that potential phosphorylation of CGGBP1 upon growth stimulation facilitates its nuclear retention, Alu-binding and dislodging of RNA Pol III therefrom. These findings provide insights into how Alu transcription is regulated in response to growth signals.
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Affiliation(s)
- Prasoon Agarwal
- a Department of Immunology, Genetics and Pathology, Rudbeck Laboratory , Uppsala University , Uppsala , Sweden
| | - Stefan Enroth
- a Department of Immunology, Genetics and Pathology, Rudbeck Laboratory , Uppsala University , Uppsala , Sweden
| | - Martin Teichmann
- b University of Bordeaux, IECB , ARNA laboratory, Equipe Labellisée Contre le Cancer , Pessac , France
| | - Helena Jernberg Wiklund
- a Department of Immunology, Genetics and Pathology, Rudbeck Laboratory , Uppsala University , Uppsala , Sweden
| | - Arian Smit
- c Institute for Systems Biology , Seattle , WA , USA
| | - Bengt Westermark
- a Department of Immunology, Genetics and Pathology, Rudbeck Laboratory , Uppsala University , Uppsala , Sweden
| | - Umashankar Singh
- a Department of Immunology, Genetics and Pathology, Rudbeck Laboratory , Uppsala University , Uppsala , Sweden
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Kapeli K, Pratt GA, Vu AQ, Hutt KR, Martinez FJ, Sundararaman B, Batra R, Freese P, Lambert NJ, Huelga SC, Chun SJ, Liang TY, Chang J, Donohue JP, Shiue L, Zhang J, Zhu H, Cambi F, Kasarskis E, Hoon S, Ares M, Burge CB, Ravits J, Rigo F, Yeo GW. Distinct and shared functions of ALS-associated proteins TDP-43, FUS and TAF15 revealed by multisystem analyses. Nat Commun 2016; 7:12143. [PMID: 27378374 PMCID: PMC4935974 DOI: 10.1038/ncomms12143] [Citation(s) in RCA: 109] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2015] [Accepted: 06/03/2016] [Indexed: 12/12/2022] Open
Abstract
The RNA-binding protein (RBP) TAF15 is implicated in amyotrophic lateral sclerosis (ALS). To compare TAF15 function to that of two ALS-associated RBPs, FUS and TDP-43, we integrate CLIP-seq and RNA Bind-N-Seq technologies, and show that TAF15 binds to ∼4,900 RNAs enriched for GGUA motifs in adult mouse brains. TAF15 and FUS exhibit similar binding patterns in introns, are enriched in 3' untranslated regions and alter genes distinct from TDP-43. However, unlike FUS and TDP-43, TAF15 has a minimal role in alternative splicing. In human neural progenitors, TAF15 and FUS affect turnover of their RNA targets. In human stem cell-derived motor neurons, the RNA profile associated with concomitant loss of both TAF15 and FUS resembles that observed in the presence of the ALS-associated mutation FUS R521G, but contrasts with late-stage sporadic ALS patients. Taken together, our findings reveal convergent and divergent roles for FUS, TAF15 and TDP-43 in RNA metabolism.
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Affiliation(s)
- Katannya Kapeli
- Department of Cellular and Molecular Medicine, University of California at San Diego, La Jolla, California 92093, USA.,Stem Cell Program and Institute for Genomic Medicine, University of California at San Diego, La Jolla, California 92093, USA.,Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117549, Singapore
| | - Gabriel A Pratt
- Department of Cellular and Molecular Medicine, University of California at San Diego, La Jolla, California 92093, USA.,Stem Cell Program and Institute for Genomic Medicine, University of California at San Diego, La Jolla, California 92093, USA.,Department of Bioinformatics and Systems Biology, University of California at San Diego, La Jolla, California 92093, USA
| | - Anthony Q Vu
- Department of Cellular and Molecular Medicine, University of California at San Diego, La Jolla, California 92093, USA.,Stem Cell Program and Institute for Genomic Medicine, University of California at San Diego, La Jolla, California 92093, USA
| | - Kasey R Hutt
- Department of Cellular and Molecular Medicine, University of California at San Diego, La Jolla, California 92093, USA.,Stem Cell Program and Institute for Genomic Medicine, University of California at San Diego, La Jolla, California 92093, USA
| | - Fernando J Martinez
- Department of Cellular and Molecular Medicine, University of California at San Diego, La Jolla, California 92093, USA.,Stem Cell Program and Institute for Genomic Medicine, University of California at San Diego, La Jolla, California 92093, USA
| | - Balaji Sundararaman
- Department of Cellular and Molecular Medicine, University of California at San Diego, La Jolla, California 92093, USA.,Stem Cell Program and Institute for Genomic Medicine, University of California at San Diego, La Jolla, California 92093, USA
| | - Ranjan Batra
- Department of Cellular and Molecular Medicine, University of California at San Diego, La Jolla, California 92093, USA.,Stem Cell Program and Institute for Genomic Medicine, University of California at San Diego, La Jolla, California 92093, USA.,Department of Neurosciences, University of California at San Diego, La Jolla, California 92093, USA
| | - Peter Freese
- Department of Biology, MIT, Cambridge, Massachusetts 02142, USA
| | | | - Stephanie C Huelga
- Department of Cellular and Molecular Medicine, University of California at San Diego, La Jolla, California 92093, USA.,Stem Cell Program and Institute for Genomic Medicine, University of California at San Diego, La Jolla, California 92093, USA.,Department of Bioinformatics and Systems Biology, University of California at San Diego, La Jolla, California 92093, USA
| | - Seung J Chun
- Ionis Pharmaceuticals, Carlsbad, California 92010, USA
| | - Tiffany Y Liang
- Department of Cellular and Molecular Medicine, University of California at San Diego, La Jolla, California 92093, USA.,Stem Cell Program and Institute for Genomic Medicine, University of California at San Diego, La Jolla, California 92093, USA
| | - Jeremy Chang
- Department of Cellular and Molecular Medicine, University of California at San Diego, La Jolla, California 92093, USA.,Stem Cell Program and Institute for Genomic Medicine, University of California at San Diego, La Jolla, California 92093, USA
| | - John P Donohue
- Department of Molecular, Cell and Developmental Biology, Sinsheimer Labs, University of California, Santa Cruz, California 95064, USA
| | - Lily Shiue
- Department of Molecular, Cell and Developmental Biology, Sinsheimer Labs, University of California, Santa Cruz, California 95064, USA
| | - Jiayu Zhang
- Department of Molecular and Cellular Biochemistry, College of Medicine, University of Kentucky, Lexington, Kentucky 40536, USA
| | - Haining Zhu
- Department of Molecular and Cellular Biochemistry, College of Medicine, University of Kentucky, Lexington, Kentucky 40536, USA
| | - Franca Cambi
- Department of Neurology, University of Kentucky, Lexington, Kentucky 40536, USA
| | - Edward Kasarskis
- Department of Neurology, University of Kentucky, Lexington, Kentucky 40536, USA
| | - Shawn Hoon
- Molecular Engineering Laboratory, A*STAR, Singapore 138673, Singapore
| | - Manuel Ares
- Department of Molecular, Cell and Developmental Biology, Sinsheimer Labs, University of California, Santa Cruz, California 95064, USA
| | | | - John Ravits
- Department of Neurosciences, University of California at San Diego, La Jolla, California 92093, USA
| | - Frank Rigo
- Ionis Pharmaceuticals, Carlsbad, California 92010, USA
| | - Gene W Yeo
- Department of Cellular and Molecular Medicine, University of California at San Diego, La Jolla, California 92093, USA.,Stem Cell Program and Institute for Genomic Medicine, University of California at San Diego, La Jolla, California 92093, USA.,Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117549, Singapore.,Department of Bioinformatics and Systems Biology, University of California at San Diego, La Jolla, California 92093, USA.,Molecular Engineering Laboratory, A*STAR, Singapore 138673, Singapore
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7
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Defining the role of the CGGBP1 protein in FMR1 gene expression. Eur J Hum Genet 2015; 24:697-703. [PMID: 26306647 DOI: 10.1038/ejhg.2015.182] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2015] [Revised: 06/13/2015] [Accepted: 07/21/2015] [Indexed: 02/06/2023] Open
Abstract
Fragile X syndrome is the most common heritable form of intellectual disability and is caused by the expansion over 200 repeats and subsequent methylation of the CGG triplets at the 5' UTR of the FMR1 gene, leading to its silencing. The epigenetic and molecular mechanisms responsible for FMR1 gene silencing are not fully clarified. To identify structure-specific proteins that could recruit components of the silencing machinery we investigated the role of CGGBP1 in FMR1 gene transcription. CGGBP1 is a highly conserved protein that binds specifically to unmethylated CGG tracts. Its role on FMR1 transcription is yet to be defined. Sequencing analysis and expression studies through quantitative PCR of CGGBP1 were performed in cell lines with different allele expansions: wild type, premutation, methylated full mutation and unmethylated full mutation, demonstrating no differences between them. ChIP assays clearly demonstrated that CGGBP1 binds to unmethylated CGG triplets of the FMR1 gene, but not to methylated CGGs. We also observed that CGGBP1 binding to the FMR1 locus was restored after pharmacological demethylation, with 5-azadC, of alleles, carriers of methylated full mutation, suggesting a possible role for CGGBP1 in FMR1 expression. CGGBP1 silencing with shRNAs (reaching ~98% of CGGBP1-mRNA depletion) did not affect FMR1 transcription and CGG expansion stability in expanded alleles. Although the strong binding to the CGG tract could suggest a relevant role of CGGBP1 on FMR1 gene expression, our results demonstrate that CGGBP1 has no direct effect on FMR1 transcription and CGG repeat stability.
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8
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Agarwal P, Collier P, Fritz MHY, Benes V, Wiklund HJ, Westermark B, Singh U. CGGBP1 mitigates cytosine methylation at repetitive DNA sequences. BMC Genomics 2015; 16:390. [PMID: 25981527 PMCID: PMC4432828 DOI: 10.1186/s12864-015-1593-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2014] [Accepted: 04/28/2015] [Indexed: 11/24/2022] Open
Abstract
Background CGGBP1 is a repetitive DNA-binding transcription regulator with target sites at CpG-rich sequences such as CGG repeats and Alu-SINEs and L1-LINEs. The role of CGGBP1 as a possible mediator of CpG methylation however remains unknown. At CpG-rich sequences cytosine methylation is a major mechanism of transcriptional repression. Concordantly, gene-rich regions typically carry lower levels of CpG methylation than the repetitive elements. It is well known that at interspersed repeats Alu-SINEs and L1-LINEs high levels of CpG methylation constitute a transcriptional silencing and retrotransposon inactivating mechanism. Results Here, we have studied genome-wide CpG methylation with or without CGGBP1-depletion. By high throughput sequencing of bisulfite-treated genomic DNA we have identified CGGBP1 to be a negative regulator of CpG methylation at repetitive DNA sequences. In addition, we have studied CpG methylation alterations on Alu and L1 retrotransposons in CGGBP1-depleted cells using a novel bisulfite-treatment and high throughput sequencing approach. Conclusions The results clearly show that CGGBP1 is a possible bidirectional regulator of CpG methylation at Alus, and acts as a repressor of methylation at L1 retrotransposons. Electronic supplementary material The online version of this article (doi:10.1186/s12864-015-1593-2) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Prasoon Agarwal
- Department of Immunology, Genetics and Pathology, Uppsala University, Science for Life Laboratory, Rudbeck Laboratory, Dag Hammarskjölds Väg 20, Uppsala, 75185, Sweden.
| | - Paul Collier
- EMBL, Core Facilities and Services, Meyerhofsstrasse 1, Heidelberg, D-69117, Germany.
| | - Markus Hsi-Yang Fritz
- EMBL, Core Facilities and Services, Meyerhofsstrasse 1, Heidelberg, D-69117, Germany.
| | - Vladimir Benes
- EMBL, Core Facilities and Services, Meyerhofsstrasse 1, Heidelberg, D-69117, Germany.
| | - Helena Jernberg Wiklund
- Department of Immunology, Genetics and Pathology, Uppsala University, Science for Life Laboratory, Rudbeck Laboratory, Dag Hammarskjölds Väg 20, Uppsala, 75185, Sweden.
| | - Bengt Westermark
- Department of Immunology, Genetics and Pathology, Uppsala University, Science for Life Laboratory, Rudbeck Laboratory, Dag Hammarskjölds Väg 20, Uppsala, 75185, Sweden.
| | - Umashankar Singh
- Department of Immunology, Genetics and Pathology, Uppsala University, Science for Life Laboratory, Rudbeck Laboratory, Dag Hammarskjölds Väg 20, Uppsala, 75185, Sweden.
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Yudkin DV, Lemskaya NA, Grischenko IV, Dolskiy AA. Chromatin changes caused by expansion of CGG repeats in fmr1 gene. Mol Biol 2015. [DOI: 10.1134/s0026893315010197] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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10
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Abstract
The human genome contains multiple stretches of CGG trinucleotide repeats, which act as transcription- and translation-regulatory elements but at the same time form secondary structures that impede replication and give rise to sites of chromosome fragility. Proteins binding to such DNA elements may be involved in divergent cellular processes such as transcription, DNA damage, and epigenetic state of the chromatin. We review here the work done on CGG repeats and associated proteins with special focus on a factor called CGGBP1. CGGBP1 presents with an interesting example of factors that do not have any single dedicated function, but participate indispensably in multiple processes. Both experimental results and data from cancer genome sequencing have revealed that any alteration in CGGBP1 that compromises its function is not tolerated by normal or cancer cells alike. Based upon a large amount of published data, information from databases, and unpublished results, we decipher in this review how CGGBP1 is a classic example of the 'one factor, divergent functions' paradigm of cytoprotection. By taking cues from the studies on CGGBP1, more such factors can be discovered for a better understanding of the evolution of mechanisms of cellular survival.
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Affiliation(s)
- Umashankar Singh
- Biological Sciences and Engineering, Indian Institute of Technology, Gandhinagar, Gujarat, India
- Correspondence: Umashankar Singh, Biological Sciences and Engineering, Indian Institute of Technology, Gandhinagar, Gujarat, India.
| | - Bengt Westermark
- Department of Immunology, Genetics and Pathology, Science for Life Laboratory, Rudbeck Laboratory, Uppsala University, Sweden
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11
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Singh U, Maturi V, Jones RE, Paulsson Y, Baird DM, Westermark B. CGGBP1 phosphorylation constitutes a telomere-protection signal. Cell Cycle 2013; 13:96-105. [PMID: 24196442 PMCID: PMC3925742 DOI: 10.4161/cc.26813] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The shelterin proteins are required for telomere integrity. Shelterin dysfunction can lead to initiation of unwarranted DNA damage and repair pathways at chromosomal termini. Interestingly, many shelterin accessory proteins are involved in DNA damage signaling and repair. We demonstrate here that in normal human fibroblasts, telomeric ends are protected by phosphorylation of CGG triplet repeat-binding protein 1 (CGGBP1) at serine 164 (S164). We show that serine 164 is a major phosphorylation site on CGGBP1 with important functions. We provide evidence that one of the kinases that can phosphorylate S164 CGGBP1 is ATR. Overexpression of S164A phospho-deficient CGGBP1 exerted a dominant-negative effect, causing telomeric dysfunction, accelerated telomere shortening, enhanced fusion of telomeres, and crisis. However, overexpression of wild-type or phospho-mimicking S164E CGGBP1 did not cause these effects. This telomere damage was associated with reduced binding of the shelterin protein POT1 to telomeric DNA. Our results suggest that CGGBP1 phosphorylation at S164 is a novel telomere protection signal, which can affect telomere-protective function of the shelterin complex.
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Affiliation(s)
- Umashankar Singh
- Department of Immunology, Genetics, and Pathology; Uppsala University; Tumor Biology; Rudbeck Laboratory; Uppsala, Sweden
| | - Varun Maturi
- Department of Immunology, Genetics, and Pathology; Uppsala University; Tumor Biology; Rudbeck Laboratory; Uppsala, Sweden; Ludwig Institute for Cancer Research; Science for Life Laboratory; Uppsala University; Biomedical Center; Uppsala, Sweden
| | - Rhiannon E Jones
- Department of Pathology; School of Medicine; Cardiff University; Cardiff, UK
| | - Ylva Paulsson
- Department of Immunology, Genetics, and Pathology; Uppsala University; Tumor Biology; Rudbeck Laboratory; Uppsala, Sweden
| | - Duncan M Baird
- Department of Pathology; School of Medicine; Cardiff University; Cardiff, UK
| | - Bengt Westermark
- Department of Immunology, Genetics, and Pathology; Uppsala University; Tumor Biology; Rudbeck Laboratory; Uppsala, Sweden
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12
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Singh U, Roswall P, Uhrbom L, Westermark B. CGGBP1 regulates cell cycle in cancer cells. BMC Mol Biol 2011; 12:28. [PMID: 21733196 PMCID: PMC3142506 DOI: 10.1186/1471-2199-12-28] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2011] [Accepted: 07/07/2011] [Indexed: 12/31/2022] Open
Abstract
Background CGGBP1 is a CGG-triplet repeat binding protein, which affects transcription from CGG-triplet-rich promoters such as the FMR1 gene and the ribosomal RNA gene clusters. Earlier, we reported some previously unknown functions of CGGBP1 in gene expression during heat shock stress response. Recently we had found CGGBP1 to be a cell cycle regulatory midbody protein required for normal cytokinetic abscission in normal human fibroblasts, which have all the cell cycle regulatory mechanisms intact. Results In this study we explored the role of CGGBP1 in the cell cycle in various cancer cell lines. CGGBP1 depletion by RNA interference in tumor-derived cells caused an increase in the cell population at G0/G1 phase and reduced the number of cells in the S phase. CGGBP1 depletion also increased the expression of cell cycle regulatory genes CDKN1A and GAS1, associated with reductions in histone H3 lysine 9 trimethylation in their promoters. By combining RNA interference and genetic mutations, we found that the role of CGGBP1 in cell cycle involves multiple mechanisms, as single deficiencies of CDKN1A, GAS1 as well as TP53, INK4A or ARF failed to rescue the G0/G1 arrest caused by CGGBP1 depletion. Conclusions Our results show that CGGBP1 expression is important for cell cycle progression through multiple parallel mechanisms including the regulation of CDKN1A and GAS1 levels.
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Affiliation(s)
- Umashankar Singh
- Department of Immunology, Genetics and Pathology, Rudbeck Laboratory, Uppsala University, 751 85 Uppsala, Sweden.
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13
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Singh U, Westermark B. CGGBP1 is a nuclear and midbody protein regulating abscission. Exp Cell Res 2010; 317:143-50. [PMID: 20832400 DOI: 10.1016/j.yexcr.2010.08.019] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2010] [Revised: 08/09/2010] [Accepted: 08/29/2010] [Indexed: 01/20/2023]
Abstract
Abscission marks the completion of cell division and its failure is associated with delayed cytokinesis and even tetraploidization. Aberrant abscission and consequential ploidy changes can underlie various diseases including cancer. Midbody, a transient structure formed in the intercellular bridge during telophase, contains several proteins including Aurora kinase B (AURKB), which participate in abscission. We report here an unexpected expression pattern and function of the transcription repressor protein CGG triplet repeat-binding protein 1 (CGGBP1), in normal human fibroblasts. We show that CGGBP1, a chromatin-associated protein, trans-localizes to spindle midzone and midbodies in a manner similar to that of AURKB. CGGBP1 depletion resulted in a cell cycle block at G2, characterized by failure of cells to undergo mitosis and also reduced entry into S phase. Consistent with its presence in the midbodies, live microscopy showed that CGGBP1 deficiency caused mitotic failure at abscission resulting in tetraploidy, which could be rescued by CGGBP1 overexpression. These results show that CGGBP1 is a bona fide midbody protein required for normal abscission and mitosis in general.
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Affiliation(s)
- Umashankar Singh
- Department of Genetics and Pathology, Uppsala University, Uppsala, Sweden.
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14
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Orlov SV, Kuteykin-Teplyakov KB, Ignatovich IA, Dizhe EB, Mirgorodskaya OA, Grishin AV, Guzhova OB, Prokhortchouk EB, Guliy PV, Perevozchikov AP. Novel repressor of the human FMR1 gene - identification of p56 human (GCC)(n)-binding protein as a Krüppel-like transcription factor ZF5. FEBS J 2007; 274:4848-62. [PMID: 17714511 DOI: 10.1111/j.1742-4658.2007.06006.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
A series of relatively short (GCC)(n) triplet repeats (n = 3-30) located within regulatory regions of many mammalian genes may be considered as putative cis-acting transcriptional elements (GCC-elements). Fragile X-mental retardation syndrome is caused by an expansion of (GCC)(n) triplet repeats within the 5'-untranslated region of the human fragile X-mental retardation 1 (FMR1) gene. The present study aimed to characterize a novel human (GCC)(n)-binding protein and investigate its possible role in the regulation of the FMR1 gene. A novel human (GCC)(n)-binding protein, p56, was isolated and identified as a Krüppel-like transcription factor, ZF5, by MALDI-TOF analysis. The capacity of ZF5 to specifically interact with (GCC)(n) triplet repeats was confirmed by the electrophoretic mobility shift assay with purified recombinant ZF5 protein. In cotransfection experiments, ZF5 overexpression repressed activity of the GCC-element containing mouse ribosomal protein L32 gene promoter. Moreover, RNA interference assay results showed that endogenous ZF5 acts as a repressor of the human FMR1 gene. Thus, these data identify a new class of ZF5 targets, a subset of genes containing GCC-elements in their regulatory regions, and raise the question of whether transcription factor ZF5 is implicated in the pathogenesis of fragile X syndrome.
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Affiliation(s)
- Sergey V Orlov
- Department of Biochemistry, Institute of Experimental Medicine, Russian Academy of Medical Sciences, St Petersburg, Russia.
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15
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Rizzolio F, Sala C, Alboresi S, Bione S, Gilli S, Goegan M, Pramparo T, Zuffardi O, Toniolo D. Epigenetic control of the critical region for premature ovarian failure on autosomal genes translocated to the X chromosome: a hypothesis. Hum Genet 2007; 121:441-50. [PMID: 17265046 DOI: 10.1007/s00439-007-0329-z] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2006] [Accepted: 01/08/2007] [Indexed: 11/28/2022]
Abstract
Chromosomal rearrangements in Xq are frequently associated to premature ovarian failure (POF) and have contributed to define a POF "critical region" from Xq13.3 to Xq26. Search for X-linked genes responsible for the phenotype has been elusive as most rearrangements did not interrupt genes and many were mapped to gene deserts. We now report that ovary-expressed genes flanked autosomal breakpoints in four POF cases analyzed whose X chromosome breakpoints interrupted a gene poor region in Xq21, where no ovary-expressed candidate genes could be found. We also show that the global down regulation in the oocyte and up regulation in the ovary of X-linked genes compared to the autosomes is mainly due to genes in the POF "critical region". We thus propose that POF, in X;autosome balanced translocations, may not only be caused by haploinsufficiency, but also by a oocyte-specific position effect on autosomal genes, dependent on dosage compensation mechanisms operating on the active X chromosome in mammals.
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Affiliation(s)
- Flavio Rizzolio
- Department of Molecular Biology and Functional Genomics, San Raffaele Scientific Institute, Milan, Italy
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16
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Doerfler W. De novo methylation, long-term promoter silencing, methylation patterns in the human genome, and consequences of foreign DNA insertion. Curr Top Microbiol Immunol 2006; 301:125-75. [PMID: 16570847 DOI: 10.1007/3-540-31390-7_5] [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: 03/02/2023]
Abstract
This chapter presents a personal account of the work on DNA methylation in viral and mammalian systems performed in the author's laboratory in the course of the past 30 years. The text does not attempt to give a complete and meticulous account of the work accomplished in many other laboratories; in that sense it is not a review of the field in a conventional sense. Since the author is also one of the editors of this series of Current Topics in Immunology and Microbiology on DNA methylation, to which contributions by many of our colleagues in this field have been invited, the author's conscience is alleviated that he has not cited many of the relevant and excellent reports by others. The choice of viral model systems in molecular biology is well founded. Over many decades, viruses have proved their invaluable and pioneering role as tools in molecular genetics. When our interest turned to the demonstration of genome-wide patterns of DNA methylation, we focused mainly on the human genome. The following topics in DNA methylation will be treated in detail: (1) The de novo methylation of integrated foreign genomes; (2) the long-term gene silencing effect of sequence-specific promoter methylation and its reversal; (3) the properties and specificity of patterns of DNA methylation in the human genome and their possible relations to pathogenesis; (4) the long-range global effects on cellular DNA methylation and transcriptional profiles as a consequence of foreign DNA insertion into an established genome; (5) the patterns of DNA methylation can be considered part of a cellular defense mechanism against foreign or repetitive DNA; which role has food-ingested DNA played in the elaboration of this mechanism? The interest in problems related to DNA methylation has spread-like the mechanism itself-into many neighboring fields. The nature of the transcriptional programs orchestrating embryonal and fetal development, chromatin structure, genetic imprinting, genetic disease, X chromosome inactivation, and tumor biology are but a few of the areas of research that have incorporated studies on the importance of the hitherto somewhat neglected fifth nucleotide in many genomes. Even the fly researchers now have to cope with the presence of this nucleotide, in however small quantities it exists in the genome of their model organism, at least during embryonal development. The bulk of the experimental work accomplished in the author's laboratory has been shouldered by many very motivated undergraduate and graduate students and by a number of talented postdoctoral researchers. Their contributions are reflected in the list of references in this chapter. We have also had the good luck to receive funding through a number or organizations as acknowledged.
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Affiliation(s)
- W Doerfler
- Institut für Genetik, Universität zu Köln, Germany.
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17
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Doerfler W. On the biological significance of DNA methylation. BIOCHEMISTRY (MOSCOW) 2005; 70:505-24. [PMID: 15948705 DOI: 10.1007/s10541-005-0145-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
This chapter presents a personal account of the work on DNA methylation in viral and mammalian systems performed in the author's laboratory in the course of the past thirty years. The text does not attempt to give a complete and meticulous account of the many relevant and excellent reports published by many other laboratories, so it is not a review of the field in a conventional sense. The choice of viral model systems in molecular biology is well founded. Over many decades, viruses have proven their invaluable and pioneering role as tools in molecular genetics. When our interest turned to the demonstration of genome-wide patterns of DNA methylation, we focused mainly on the human genome. The following topics in DNA methylation will be treated in detail: (i) the de novo methylation of integrated foreign genomes; (ii) the long-term gene silencing effect of sequence-specific promoter methylation and its reversal; (iii) the properties and specificity of patterns of DNA methylation in the human genome and their possible relations to pathogenesis; (iv) the long-range global effects on cellular DNA methylation and transcriptional profiles as a consequence of foreign DNA insertion into an established genome; (v) the patterns of DNA methylation can be considered part of a cellular defense mechanism against foreign or repetitive DNA; what role has food-ingested DNA played in the elaboration of this mechanism?
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Affiliation(s)
- W Doerfler
- Institut für Genetik, Universität zu Köln, 50674 Köln, Germany.
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18
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Lim JH, Booker AB, Fallon JR. Regulating fragile X gene transcription in the brain and beyond. J Cell Physiol 2005; 205:170-5. [PMID: 15895397 DOI: 10.1002/jcp.20401] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The past several years have seen remarkable growth in our understanding of the molecular processes underlying fragile X syndrome (FXS). Many studies have provided new insights into the regulation of Fmr1 gene expression and the potential function of its protein product. It is now known that the promoter elements modulating Fmr1 transcription involve a complex array of both cis and trans factors. Moreover, recent studies of epigenetic modification of chromatin have provided novel clues to unlocking the mysteries behind the regulation of Fmr1 expression. Here, we review the latest findings on the regulation of Fmr1 transcription.
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Affiliation(s)
- Jae H Lim
- Department of Neuroscience, Brown University, Providence, Rhode Island 02912, USA
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19
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Naumann F, Remus R, Schmitz B, Doerfler W. Gene structure and expression of the 5'-(CGG)(n)-3'-binding protein (CGGBP1). Genomics 2004; 83:106-18. [PMID: 14667814 DOI: 10.1016/s0888-7543(03)00212-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The human nuclear 5'-(CGG)(n)-3'-binding protein (CGGBP1) influences the expression of the fragile X mental retardation (FMR1) gene by specifically interacting with the 5'-(CGG)(n>5)-3' repeat in its 5' untranslated region. Here, we show that CGGBP1 binds to 5'-(CGG)(n)-3' repeats with n>or=5 and to interrupted repeats. The genomic and mRNA organization of the human and murine CGGBP1 genes was studied and the human gene was mapped to chromosome 3p. Due to alternative polyadenylation, mRNAs of 1.2 and 4.5 kb are transcribed at varying ratios in human and murine cells and in embryonic, fetal, and adult tissues. The human and the murine genes, including promoters and large parts of the untranslated regions, are highly conserved. A sequence of 235 nucleotides 5' upstream of CGGBP1 is essential for promoter activity in transfection experiments. Complete in vitro methylation inactivates the promoter, which is unmethylated in human cells as shown by bisulfite genomic sequencing.
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MESH Headings
- Alternative Splicing
- Animals
- Base Sequence
- Blotting, Northern
- Chromosome Mapping
- Chromosomes, Human, Pair 3/genetics
- DNA/chemistry
- DNA/genetics
- DNA Methylation
- DNA-Binding Proteins/genetics
- DNA-Binding Proteins/metabolism
- Female
- Gene Expression Profiling
- Gene Expression Regulation, Developmental
- Genes/genetics
- HeLa Cells
- Humans
- In Situ Hybridization, Fluorescence
- Luciferases/genetics
- Luciferases/metabolism
- Male
- Mice
- Mice, Inbred C57BL
- Molecular Sequence Data
- NIH 3T3 Cells
- Nuclear Proteins/genetics
- Nuclear Proteins/metabolism
- Open Reading Frames/genetics
- Poly A/genetics
- Promoter Regions, Genetic/genetics
- Protein Binding
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Recombinant Fusion Proteins/genetics
- Recombinant Fusion Proteins/metabolism
- Sequence Alignment
- Sequence Analysis, DNA
- Sequence Homology, Nucleic Acid
- Transfection
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20
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Abstract
The FMR1 gene is involved in three different syndromes, the Fragile X syndrome, premature ovarian failure (POF) and the Fragile X-associated tremor/ataxia syndrome (FXTAS) at older age. Fragile X syndrome is caused by an expanded CGG repeat above 200 units in the FMR1 gene resulting in the absence of the FMR1 mRNA and protein. The FMR1 protein is proposed to act as a regulator of mRNA transport and/or translation that plays a role in synaptic maturation and function. POF and FXTAS are found in individuals with an expanded repeat between 50 and 200 CGGs and are associated with increased FMR1 mRNA levels. The presence of elevated FMR1 mRNA in all patients suggests that these syndromes may represent a gain-of-function effect from the elevated message levels. The level of FMR1 mRNA is in fragile balance and is therefore critical for normal functioning.
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Affiliation(s)
- Ben A Oostra
- Department of Clinical Genetics, Erasmus MC, The Netherlands.
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21
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Cleary JD, Pearson CE. The contribution of cis-elements to disease-associated repeat instability: clinical and experimental evidence. Cytogenet Genome Res 2003; 100:25-55. [PMID: 14526163 DOI: 10.1159/000072837] [Citation(s) in RCA: 116] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2002] [Accepted: 02/11/2003] [Indexed: 11/19/2022] Open
Abstract
Alterations in the length (instability) of gene-specific microsatellites and minisatellites are associated with at least 35 human diseases. This review will discuss the various cis-elements that contribute to repeat instability, primarily through examination of the most abundant disease-associated repetitive element, trinucleotide repeats. For the purpose of this review, we define cis-elements to include the sequence of the repeat units, the length and purity of the repeat tracts, the sequences flanking the repeat, as well as the surrounding epigenetic environment, including DNA methylation and chromatin structure. Gender-, tissue-, developmental- and locus-specific cis-elements in conjunction with trans-factors may facilitate instability through the processes of DNA replication, repair and/or recombination. Here we review the available human data that supports the involvement of cis-elements in repeat instability with limited reference to model systems. In diverse tissues at different developmental times and at specific loci, repetitive elements display variable levels of instability, suggesting vastly different mechanisms may be responsible for repeat instability amongst the disease loci and between various tissues.
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Affiliation(s)
- J D Cleary
- Program of Genetics and Genomic Biology, The Hospital for Sick Children, and Department of Molecular and Medical Genetics, University of Toronto, Toronto, Ontario, Canada
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22
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Chandler SP, Kansagra P, Hirst MC. Fragile X (CGG)n repeats induce a transcriptional repression in cis upon a linked promoter: evidence for a chromatin mediated effect. BMC Mol Biol 2003; 4:3. [PMID: 12659659 PMCID: PMC153536 DOI: 10.1186/1471-2199-4-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2003] [Accepted: 03/21/2003] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Expansion of an unstable (CGG)n repeat to over 200 triplets within the promoter region of the human FMR1 gene leads to extensive local methylation and transcription silencing, resulting in the loss of FMRP protein and the development of the clinical features of fragile X syndrome. The causative link between (CGG)n expansion, methylation and gene silencing is unknown, although gene silencing is associated with extensive changes to local chromatin architecture. RESULTS In order to determine the direct effects of increased repeat length on gene transcription in a chromatin context, we have examined the influence of FMR1 (CGG)n repeats upon transcription from the HSV thymidine kinase promoter in the Xenopus laevis oocyte. We observe a reduction in mRNA production directly associated with increasing repeat length, with a 90% reduction in mRNA production from arrays over 100 repeats in length. Using a kinetic approach, we show that this transcriptional repression is concomitant with chromatin maturation and, using in vitro transcription, we show that chromatin formation is a fundamental part of the repressive pathway mediated by (CGG)n repeats. Using Trichostatin A, a histone deacetylase inhibitor, we show reactivation of the silenced promoter. CONCLUSIONS Thus, isolated fragile X associated (CGG)n repeat arrays can exert a modifying and transcriptionally repressive influence over adjacent promoters and this repressive phenomenon is, in part, mediated by histone deacetylation.
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Affiliation(s)
- Simon P Chandler
- Sangamo BioSciences, 501 Canal Blvd. Ste A100, Point Richmond Tech Center II, Richmond, CA 94804, USA
- formerly at Lab. Epigenetics & Chromatin, Institute of Biomolecular & Biomedical Sciences, St. Michaels Bldg, University of Portsmouth, Southsea, Hampshire, PO1 2DT, UK
| | - Pushpa Kansagra
- Genome Instability Group, Department of Biological Sciences, The Open University, Walton Hall, Milton Keynes, MK7 6AA UK
| | - Mark C Hirst
- Genome Instability Group, Department of Biological Sciences, The Open University, Walton Hall, Milton Keynes, MK7 6AA UK
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23
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Abstract
Fragile X syndrome is the most common cause of mental retardation known to be inherited. The syndrome results from the suppressed expression of a single protein, the fragile X mental retardation protein (FMRP). Understanding the function and regulation of FMRP can, therefore, offer insights into both the pathophysiology of fragile X syndrome and the molecular mechanisms of learning and memory. We provide an overview of current concepts of how FMRP functions in the nervous system, with special emphasis on recent evidence that FMRP has a role in metabotropic glutamate receptor-activated protein translation and synaptic plasticity.
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Affiliation(s)
- Peter K Todd
- Department of Pathology, Medical Scientist and Neuroscience Training Program, University of Wisconsin, 600 Highland Drive, Madison, WI 53792, USA
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24
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Latha KS, Anitha S, Rao KSJ, Viswamitra MA. Molecular understanding of aluminum-induced topological changes in (CCG)12 triplet repeats: relevance to neurological disorders. BIOCHIMICA ET BIOPHYSICA ACTA 2002; 1588:56-64. [PMID: 12379314 DOI: 10.1016/s0925-4439(02)00133-3] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Recent studies have shown that gene mutations are involved in the pathology of neurological disorders. CCG repeats cause genetic instability and are localized at the 5' end of the non-coding regions of the FMR1 gene in fragile X syndrome. Our studies for the first time showed that aluminum (Al) levels were elevated in the serum samples of fragile X syndrome and also provide evidence for the interaction of aluminum with (CCG)12-repeats. Circular dichroism spectroscopic studies of (CCG)12 indicated B-DNA conformation and in the presence of Al (10(-5) M) CCG repeats attained Z-DNA conformation. Further spectroscopic studies, which included melting profiles, ethidium bromide binding patterns and interaction of Z-DNA specific polyclonal antibodies confirmed the Z-conformation in (CCG)12-repeats in the presence of Al (10(-5) M). It is interesting to mention that Al-induced Z-conformation is stable even after the total removal of Al from CCG by desferoximine, a chelating drug. This is the first report to proof the role of Al in modulating the DNA (CCG repeats) topology and this information provides a clue about the possible involvement of Al at a molecular level in neurological/neurodegenerative disorders.
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Affiliation(s)
- Kallur Siddaramaiah Latha
- Centre for Human Genetics, Institute of Biotechnology, G-05, Discoverer, ITPL, Whitefield Road, Bangalore, India
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25
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Nichol K, Pearson CE. CpG methylation modifies the genetic stability of cloned repeat sequences. Genome Res 2002; 12:1246-56. [PMID: 12176932 PMCID: PMC186631 DOI: 10.1101/gr.74502] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
The genetic stability of tandemly repeated DNAs is affected by repeat sequence, tract length, tract purity, and replication direction. Alterations in DNA methylation status are thought to influence many processes of mutagenesis. By use of bacterial and primate cell systems, we have determined the effect of CpG methylation on the genetic stability of cloned di-, tri-, penta- and minisatellite repeated DNA sequences. Depending on the repeat sequence, methylation can significantly enhance or reduce its genetic stability. This effect was evident when repeat tracts were replicated from either direction. Unexpectedly, methylation of adjacent sequences altered the stability of contiguous repeat sequences void of methylatable sites. Of the seven repeat sequences investigated, methylation stabilized five, destabilized one, and had no effect on another. Thus, although methylation generally stabilized repeat tracts, its influence depended on the sequence of the repeat. The current results lend support to the notion that the biological consequences of CpG methylation may be affected through local alterations of DNA structure as well as through direct protein-DNA interactions. In vivo CpG methylation in bacteria may have technical applications for the isolation and stable propagation of DNA sequences that have been recalcitrant to isolation and/or analyses because of their extreme instability.
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Affiliation(s)
- Kerrie Nichol
- Program of Genetics and Genomic Biology, The Hospital for Sick Children, Toronto, Ontario, Canada M5G 1X8
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26
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Pietrobono R, Pomponi MG, Tabolacci E, Oostra B, Chiurazzi P, Neri G. Quantitative analysis of DNA demethylation and transcriptional reactivation of the FMR1 gene in fragile X cells treated with 5-azadeoxycytidine. Nucleic Acids Res 2002; 30:3278-85. [PMID: 12136110 PMCID: PMC135754 DOI: 10.1093/nar/gkf434] [Citation(s) in RCA: 91] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
In fragile X syndrome, hypermethylation of the expanded CGG repeat and of the upstream promoter leads to transcriptional silencing of the FMR1 gene. Absence of the FMR1 protein results in mental retardation. We previously proved that treatment with 5-azadeoxycytidine (5-azadC) of fragile X cell lines results in reactivation of the FMR1 gene. We now show that this treatment causes passive demethylation of the FMR1 gene promoter. We employed the bisulfite-sequencing technique to detect the methylation status of individual CpG sites in the entire promoter region, upstream of the CGG repeat. Lymphoblastoid cell lines of fragile X males with full mutations of different sizes were tested before and after treatment with 5-azadC at various time points. We observed that individual cells are either completely unmethylated or not, with few relevant exceptions. We also investigated the extent of methylation in the full mutation (CGG repeat) itself by Southern blot analysis after digestion with methylation-sensitive enzymes Fnu4HI and McrBC and found that the CGG repeat remains at least partially methylated in many cells with a demethylated promoter. This may explain the quantitative discrepancy between the large extent of promoter demethylation and the limited levels of FMR1 transcriptional reactivation estimated by quantitative real-time fluorescent RT-PCR analysis.
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Affiliation(s)
- Roberta Pietrobono
- Istituto di Genetica Medica, Università Cattolica, and Centro Ricerche per la Disabilità Mentale e Motoria, Associazione Anni Verdi, Largo F. Vito 1, 00168 Rome, Italy
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27
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Grabczyk E, Kumari D, Usdin K. Fragile X syndrome and Friedreich's ataxia: two different paradigms for repeat induced transcript insufficiency. Brain Res Bull 2001; 56:367-73. [PMID: 11719274 DOI: 10.1016/s0361-9230(01)00572-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
DNA repeat expansion is the genetic basis for a growing number of neurological disorders. While the largest subset of these diseases results in an increase in the length of a polyglutamine tract in the protein encoded by the affected gene, the most common form of inherited mental retardation, fragile X syndrome, and the most common inherited ataxia, Friedreich's ataxia, are both caused by expansions that are transcribed but not translated. These expansions both decrease expression of the gene in which the expanded repeat is located, but they do so by quite different mechanisms. In fragile X syndrome, CGG. CCG expansion in the 5' untranslated region of the FMR1 gene leads to hypermethylation of the repeats and the adjacent CpG-rich promoter. Methylation prevents the binding of the transcription factor alpha-Pal/NRF-1, and may indirectly affect the binding of other factors via the formation of transcriptionally silent chromatin. In Friedreich's ataxia, GAA. TTC expansion in an intron of the FRDA gene reduces expression by interfering with transcription elongation. The model that best describes the available data is transcription-driven formation of a transient purine. purine. pyrimidine DNA triplex behind an advancing RNA polymerase. This structure lassoes the RNA polymerase that caused it, trapping the enzyme on the template.
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Affiliation(s)
- E Grabczyk
- Section on Genomic Structure and Function, Laboratory of Molecular and Cellular Biology, National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892-0830, USA
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28
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Abstract
Taxonomic features of fragile X syndrome (FXS) associated with the fragile X mutation have evolved over several decades. Males are more severely impacted cognitively than females, but both show declines in IQ scores as they age. Although many males with FXS exhibit autistic-like features, autism does not occur more frequently in males with FXS than among males with mental retardation (MR). FXS is caused by inactivation of the FMR1 gene located on Xq27.3. FMRP, the protein produced by FMR1, has been detected in most organs and in brain. In cells, it is located primarily in cytoplasm and contains motifs found in RNA-binding proteins. The FMRP N-terminal contains a functional nuclear localization signal which permits the protein to shuttle between cytoplasm and nucleus. FMR1 knockout mice show subtle behavioral and visual-spatial difficulties. Analysis of their brain tissue suggests absence of FMRP impairs synaptic maturation. Individuals with the fragile premutation produce FMRP, and the phenotype associated with the premutation has been controversial. However, there seems to be a higher incidence of premature ovarian failure in women with the premutation than is found in the general female population. This may be related to unusual increases in mRNA levels in premutation carriers.
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Affiliation(s)
- B Bardoni
- Institute of Medical Genetics at the Pavia Faculty of Medicine, Italy
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Mäueler W, Bassili G, Hardt C, Keyl HG, Epplen JT. A complex containing at least one zinc dependent HeLa nuclear protein binds to the intronic (gaa)(n) block of the frataxin gene. Gene 2001; 270:131-43. [PMID: 11404010 DOI: 10.1016/s0378-1119(01)00487-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
We analyzed HeLa nuclear proteins binding to the (gaa)(n) harbouring intron 1 of nine frataxin alleles and characterized the structures of the repeats. Fragments with blocks longer than (gaa)(9) form spontaneously different intramolecular H-y topoisomeres in linear state. The observed triplexes depend on the length of the repeat. Interruption of the perfectly repeated (gaa)(n) block entails two structural regions. At least two HeLa nuclear proteins bind to the (gaa)(n) fragments resulting in a distinct major retarded complex as revealed by EMSA. One of these proteins is zinc dependent. Importantly, the fragment harbouring (gan)(121) binds additional proteins. Protein binding appears to be locus specific, and the binding affinity was found to be not random. The affinities of the different target fragments varied by a factor of four. Binding affinities of the fragments were not obviously correlated to differences in the composition of the repeats. DNase I footprinting revealed only weakly protected binding regions, but multiple HS sites in the repeat regions of the fragments. These findings and the fact, that DNA conformers observed in EMSA and electron microscopical experiments bind proteins, lead to the assumption that the proteins recognize, both, B-DNA and triple helical structures, but with different affinity. Possible functions of the proteins are discussed in the context of transformation of triple helical structures into B-DNA and the pathogenesis of FRDA.
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Affiliation(s)
- W Mäueler
- Department of Molecular Human Genetics, Ruhr-Universität, 44780, Bochum, Germany.
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Kumari D, Usdin K. Interaction of the transcription factors USF1, USF2, and alpha -Pal/Nrf-1 with the FMR1 promoter. Implications for Fragile X mental retardation syndrome. J Biol Chem 2001; 276:4357-64. [PMID: 11058604 DOI: 10.1074/jbc.m009629200] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Hypermethylation of the FMR1 promoter reduces its transcriptional activity, resulting in the mental retardation and macroorchidism characteristic of Fragile X syndrome. How exactly methylation causes transcriptional silencing is not known but is relevant if current attempts to reactivate the gene are to be successful. Understanding the effect of methylation requires a better understanding of the factors responsible for FMR1 gene expression. To this end we have identified five evolutionarily conserved transcription factor binding sites in this promoter and shown that four of them are important for transcriptional activity in neuronally derived cells. We have also shown that USF1, USF2, and alpha-Pal/Nrf-1 are the major transcription factors that bind the promoter in brain and testis extracts and suggest that elevated levels of these factors account in part for elevated FMR1 expression in these organs. We also show that methylation abolishes alpha-Pal/Nrf-1 binding to the promoter and affects binding of USF1 and USF2 to a lesser degree. Methylation may therefore inhibit FMR1 transcription not only by recruiting histone deacetylases but also by blocking transcription factor binding. This suggests that for efficient reactivation of the FMR1 promoter, significant demethylation must occur and that current approaches to gene reactivation using histone deacetylase inhibitors alone may therefore have limited effect.
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Affiliation(s)
- D Kumari
- Section on Genomic Structure and Function, Laboratory of Molecular and Cellular Biology, NIDDK, National Institutes of Health, Bethesda, Maryland 20892-0830, USA
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Uliel L, Weisman-Shomer P, Oren-Jazan H, Newcomb T, Loeb LA, Fry M. Human Ku antigen tightly binds and stabilizes a tetrahelical form of the Fragile X syndrome d(CGG)n expanded sequence. J Biol Chem 2000; 275:33134-41. [PMID: 10924524 DOI: 10.1074/jbc.m005542200] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Hairpin and tetrahelical structures of a d(CGG)(n) sequence in the FMR1 gene have been implicated in its expansion in fragile X syndrome. The identification of tetraplex d(CGG)(n) destabilizing proteins (Fry, M., and Loeb, L. A.(1999) J. Biol. Chem. 274, 12797-12803; Weisman-Shomer, P., Naot, Y., and Fry, M. (2000) J. Biol. Chem. 275, 2231-2238) suggested that proteins might modulate d(CGG)(n) folding and aggregation. We assayed human TK-6 lymphoblastoid cell extracts for d(CGG)(8) oligomer binding proteins. The principal binding protein was identified as Ku antigen by its partial amino acid sequence and antigenicity. The purified 88/75-kDa heterodimeric Ku bound with similar affinities (K(d) approximately 1. 8-10.2 x 10(-9) mol/liter) to double-stranded d(CGG)(8).d(CCG)(8), hairpin d(CGG)(8), single-stranded d(CII)(8), or tetraplex structures of telomeric or IgG switch region sequences. However, Ku associated more tightly with bimolecular G'2 tetraplex d(CGG)(8) (K(d) approximately 0.35 x 10(-9) mol/liter). Binding to Ku protected G'2 d(CGG)(8) against nuclease digestion and impeded its unwinding by the tetraplex destabilizing protein qTBP42. Stabilization of d(CGG)(n) tetraplex domains in FMR1 by Ku or other proteins might promote d(CGG) expansion and FMR1 silencing.
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Affiliation(s)
- L Uliel
- Unit of Biochemistry, The Bruce Rappaport Faculty of Medicine, Technion, Israel Institute of Technology, Haifa 31096, Israel
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