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Kovács ZJ, Harami GM, Pálinkás J, Kuljanishvili N, Hegedüs J, Harami‐Papp H, Mahmudova L, Khamisi L, Szakács G, Kovács M. DNA-dependent phase separation by human SSB2 (NABP1/OBFC2A) protein points to adaptations to eukaryotic genome repair processes. Protein Sci 2024; 33:e4959. [PMID: 38511671 PMCID: PMC10955726 DOI: 10.1002/pro.4959] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2023] [Revised: 02/04/2024] [Accepted: 02/21/2024] [Indexed: 03/22/2024]
Abstract
Single-stranded DNA binding proteins (SSBs) are ubiquitous across all domains of life and play essential roles via stabilizing and protecting single-stranded (ss) DNA as well as organizing multiprotein complexes during DNA replication, recombination, and repair. Two mammalian SSB paralogs (hSSB1 and hSSB2 in humans) were recently identified and shown to be involved in various genome maintenance processes. Following our recent discovery of the liquid-liquid phase separation (LLPS) propensity of Escherichia coli (Ec) SSB, here we show that hSSB2 also forms LLPS condensates under physiologically relevant ionic conditions. Similar to that seen for EcSSB, we demonstrate the essential contribution of hSSB2's C-terminal intrinsically disordered region (IDR) to condensate formation, and the selective enrichment of various genome metabolic proteins in hSSB2 condensates. However, in contrast to EcSSB-driven LLPS that is inhibited by ssDNA binding, hSSB2 phase separation requires single-stranded nucleic acid binding, and is especially facilitated by ssDNA. Our results reveal an evolutionarily conserved role for SSB-mediated LLPS in the spatiotemporal organization of genome maintenance complexes. At the same time, differential LLPS features of EcSSB and hSSB2 point to functional adaptations to prokaryotic versus eukaryotic genome metabolic contexts.
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Affiliation(s)
- Zoltán J. Kovács
- ELTE‐MTA “Momentum” Motor Enzymology Research Group, Department of BiochemistryEötvös Loránd UniversityBudapestHungary
- HUN‐REN–ELTE Motor Pharmacology Research Group, Department of BiochemistryEötvös Loránd UniversityBudapestHungary
| | - Gábor M. Harami
- ELTE‐MTA “Momentum” Motor Enzymology Research Group, Department of BiochemistryEötvös Loránd UniversityBudapestHungary
| | - János Pálinkás
- ELTE‐MTA “Momentum” Motor Enzymology Research Group, Department of BiochemistryEötvös Loránd UniversityBudapestHungary
| | - Natalie Kuljanishvili
- ELTE‐MTA “Momentum” Motor Enzymology Research Group, Department of BiochemistryEötvös Loránd UniversityBudapestHungary
| | - József Hegedüs
- ELTE‐MTA “Momentum” Motor Enzymology Research Group, Department of BiochemistryEötvös Loránd UniversityBudapestHungary
| | - Hajnalka Harami‐Papp
- ELTE‐MTA “Momentum” Motor Enzymology Research Group, Department of BiochemistryEötvös Loránd UniversityBudapestHungary
| | - Lamiya Mahmudova
- ELTE‐MTA “Momentum” Motor Enzymology Research Group, Department of BiochemistryEötvös Loránd UniversityBudapestHungary
| | - Lana Khamisi
- ELTE‐MTA “Momentum” Motor Enzymology Research Group, Department of BiochemistryEötvös Loránd UniversityBudapestHungary
| | - Gergely Szakács
- HUN‐REN Institute of Molecular Life Sciences, Research Centre for Natural Sciences, Hungarian Academy of SciencesBudapestHungary
- Center for Cancer ResearchMedical University of ViennaWienAustria
| | - Mihály Kovács
- ELTE‐MTA “Momentum” Motor Enzymology Research Group, Department of BiochemistryEötvös Loránd UniversityBudapestHungary
- HUN‐REN–ELTE Motor Pharmacology Research Group, Department of BiochemistryEötvös Loránd UniversityBudapestHungary
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2
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Adams MN, Croft LV, Urquhart A, Saleem MAM, Rockstroh A, Duijf PHG, Thomas PB, Ferguson GP, Najib IM, Shah ET, Bolderson E, Nagaraj S, Williams ED, Nelson CC, O'Byrne KJ, Richard DJ. hSSB1 (NABP2/OBFC2B) modulates the DNA damage and androgen-induced transcriptional response in prostate cancer. Prostate 2023; 83:628-640. [PMID: 36811381 PMCID: PMC10953336 DOI: 10.1002/pros.24496] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/28/2022] [Revised: 12/21/2022] [Accepted: 01/23/2023] [Indexed: 02/24/2023]
Abstract
BACKGROUND Activation and regulation of androgen receptor (AR) signaling and the DNA damage response impact the prostate cancer (PCa) treatment modalities of androgen deprivation therapy (ADT) and radiotherapy. Here, we have evaluated a role for human single-strand binding protein 1 (hSSB1/NABP2) in modulation of the cellular response to androgens and ionizing radiation (IR). hSSB1 has defined roles in transcription and maintenance of genome stability, yet little is known about this protein in PCa. METHODS We correlated hSSB1 with measures of genomic instability across available PCa cases from The Cancer Genome Atlas (TCGA). Microarray and subsequent pathway and transcription factor enrichment analysis were performed on LNCaP and DU145 prostate cancer cells. RESULTS Our data demonstrate that hSSB1 expression in PCa correlates with measures of genomic instability including multigene signatures and genomic scars that are reflective of defects in the repair of DNA double-strand breaks via homologous recombination. In response to IR-induced DNA damage, we demonstrate that hSSB1 regulates cellular pathways that control cell cycle progression and the associated checkpoints. In keeping with a role for hSSB1 in transcription, our analysis revealed that hSSB1 negatively modulates p53 and RNA polymerase II transcription in PCa. Of relevance to PCa pathology, our findings highlight a transcriptional role for hSSB1 in regulating the androgen response. We identified that AR function is predicted to be impacted by hSSB1 depletion, whereby this protein is required to modulate AR gene activity in PCa. CONCLUSIONS Our findings point to a key role for hSSB1 in mediating the cellular response to androgen and DNA damage via modulation of transcription. Exploiting hSSB1 in PCa might yield benefits as a strategy to ensure a durable response to ADT and/or radiotherapy and improved patient outcomes.
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Affiliation(s)
- Mark N. Adams
- School of Biomedical Sciences, Faculty of Health, Translational Research InstituteQueensland University of TechnologyWoolloongabbaQueenslandAustralia
| | - Laura V. Croft
- School of Biomedical Sciences, Faculty of Health, Translational Research InstituteQueensland University of TechnologyWoolloongabbaQueenslandAustralia
| | - Aaron Urquhart
- School of Biomedical Sciences, Faculty of Health, Translational Research InstituteQueensland University of TechnologyWoolloongabbaQueenslandAustralia
| | | | - Anja Rockstroh
- School of Biomedical Sciences, Faculty of Health, Translational Research InstituteQueensland University of TechnologyWoolloongabbaQueenslandAustralia
| | - Pascal H. G. Duijf
- School of Biomedical Sciences, Faculty of Health, Translational Research InstituteQueensland University of TechnologyWoolloongabbaQueenslandAustralia
- Centre for Data ScienceQueensland University of TechnologyBrisbaneQueenslandAustralia
- Institute of Clinical MedicineUniversity of OsloOsloNorway
- Department of Medical GeneticsOslo University HospitalOsloNorway
- Diamantina InstituteThe University of QueenslandBrisbaneQueenslandAustralia
| | - Patrick B. Thomas
- School of Biomedical Sciences, Faculty of Health, Translational Research InstituteQueensland University of TechnologyWoolloongabbaQueenslandAustralia
- Queensland Bladder Cancer InitiativeWoolloongabbaQueenslandAustralia
- Australian Prostate Cancer Research Centre – QueenslandBrisbaneQueenslandAustralia
| | - Genevieve P. Ferguson
- School of Biomedical Sciences, Faculty of Health, Translational Research InstituteQueensland University of TechnologyWoolloongabbaQueenslandAustralia
| | - Idris Mohd Najib
- School of Biomedical Sciences, Faculty of Health, Translational Research InstituteQueensland University of TechnologyWoolloongabbaQueenslandAustralia
| | - Esha T. Shah
- School of Biomedical Sciences, Faculty of Health, Translational Research InstituteQueensland University of TechnologyWoolloongabbaQueenslandAustralia
| | - Emma Bolderson
- School of Biomedical Sciences, Faculty of Health, Translational Research InstituteQueensland University of TechnologyWoolloongabbaQueenslandAustralia
| | - Shivashankar Nagaraj
- School of Biomedical Sciences, Faculty of Health, Translational Research InstituteQueensland University of TechnologyWoolloongabbaQueenslandAustralia
| | - Elizabeth D. Williams
- School of Biomedical Sciences, Faculty of Health, Translational Research InstituteQueensland University of TechnologyWoolloongabbaQueenslandAustralia
- Queensland Bladder Cancer InitiativeWoolloongabbaQueenslandAustralia
- Australian Prostate Cancer Research Centre – QueenslandBrisbaneQueenslandAustralia
| | - Colleen C. Nelson
- School of Biomedical Sciences, Faculty of Health, Translational Research InstituteQueensland University of TechnologyWoolloongabbaQueenslandAustralia
- Australian Prostate Cancer Research Centre – QueenslandBrisbaneQueenslandAustralia
| | - Kenneth J. O'Byrne
- School of Biomedical Sciences, Faculty of Health, Translational Research InstituteQueensland University of TechnologyWoolloongabbaQueenslandAustralia
- Australian Prostate Cancer Research Centre – QueenslandBrisbaneQueenslandAustralia
- Cancer ServicesPrincess Alexandra HospitalWoolloongabbaQueenslandAustralia
| | - Derek J. Richard
- School of Biomedical Sciences, Faculty of Health, Translational Research InstituteQueensland University of TechnologyWoolloongabbaQueenslandAustralia
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hSSB2 (NABP1) is required for the recruitment of RPA during the cellular response to DNA UV damage. Sci Rep 2021; 11:20256. [PMID: 34642383 PMCID: PMC8511049 DOI: 10.1038/s41598-021-99355-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2021] [Accepted: 09/15/2021] [Indexed: 11/17/2022] Open
Abstract
Maintenance of genomic stability is critical to prevent diseases such as cancer. As such, eukaryotic cells have multiple pathways to efficiently detect, signal and repair DNA damage. One common form of exogenous DNA damage comes from ultraviolet B (UVB) radiation. UVB generates cyclobutane pyrimidine dimers (CPD) that must be rapidly detected and repaired to maintain the genetic code. The nucleotide excision repair (NER) pathway is the main repair system for this type of DNA damage. Here, we determined the role of the human Single-Stranded DNA Binding protein 2, hSSB2, in the response to UVB exposure. We demonstrate that hSSB2 levels increase in vitro and in vivo after UVB irradiation and that hSSB2 rapidly binds to chromatin. Depletion of hSSB2 results in significantly decreased Replication Protein A (RPA32) phosphorylation and impaired RPA32 localisation to the site of UV-induced DNA damage. Delayed recruitment of NER protein Xeroderma Pigmentosum group C (XPC) was also observed, leading to increased cellular sensitivity to UVB. Finally, hSSB2 was shown to have affinity for single-strand DNA containing a single CPD and for duplex DNA with a two-base mismatch mimicking a CPD moiety. Altogether our data demonstrate that hSSB2 is involved in the cellular response to UV exposure.
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Fernandez A, O’Leary C, O’Byrne KJ, Burgess J, Richard DJ, Suraweera A. Epigenetic Mechanisms in DNA Double Strand Break Repair: A Clinical Review. Front Mol Biosci 2021; 8:685440. [PMID: 34307454 PMCID: PMC8292790 DOI: 10.3389/fmolb.2021.685440] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Accepted: 06/24/2021] [Indexed: 12/14/2022] Open
Abstract
Upon the induction of DNA damage, the chromatin structure unwinds to allow access to enzymes to catalyse the repair. The regulation of the winding and unwinding of chromatin occurs via epigenetic modifications, which can alter gene expression without changing the DNA sequence. Epigenetic mechanisms such as histone acetylation and DNA methylation are known to be reversible and have been indicated to play different roles in the repair of DNA. More importantly, the inhibition of such mechanisms has been reported to play a role in the repair of double strand breaks, the most detrimental type of DNA damage. This occurs by manipulating the chromatin structure and the expression of essential proteins that are critical for homologous recombination and non-homologous end joining repair pathways. Inhibitors of histone deacetylases and DNA methyltransferases have demonstrated efficacy in the clinic and represent a promising approach for cancer therapy. The aims of this review are to summarise the role of histone deacetylase and DNA methyltransferase inhibitors involved in DNA double strand break repair and explore their current and future independent use in combination with other DNA repair inhibitors or pre-existing therapies in the clinic.
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Affiliation(s)
- Alejandra Fernandez
- Centre for Genomics and Personalised Health, School of Biomedical Sciences and Translational Research Institute, Queensland University of Technology (QUT), Brisbane, QLD, Australia
| | - Connor O’Leary
- Centre for Genomics and Personalised Health, School of Biomedical Sciences and Translational Research Institute, Queensland University of Technology (QUT), Brisbane, QLD, Australia
- Princess Alexandra Hospital, Woolloongabba, QLD, Australia
| | - Kenneth J O’Byrne
- Centre for Genomics and Personalised Health, School of Biomedical Sciences and Translational Research Institute, Queensland University of Technology (QUT), Brisbane, QLD, Australia
- Princess Alexandra Hospital, Woolloongabba, QLD, Australia
| | - Joshua Burgess
- Centre for Genomics and Personalised Health, School of Biomedical Sciences and Translational Research Institute, Queensland University of Technology (QUT), Brisbane, QLD, Australia
- Princess Alexandra Hospital, Woolloongabba, QLD, Australia
| | - Derek J Richard
- Centre for Genomics and Personalised Health, School of Biomedical Sciences and Translational Research Institute, Queensland University of Technology (QUT), Brisbane, QLD, Australia
- Princess Alexandra Hospital, Woolloongabba, QLD, Australia
| | - Amila Suraweera
- Centre for Genomics and Personalised Health, School of Biomedical Sciences and Translational Research Institute, Queensland University of Technology (QUT), Brisbane, QLD, Australia
- Princess Alexandra Hospital, Woolloongabba, QLD, Australia
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Pavani RS, Elias MC. Following Trypanosoma cruzi RPA-DNA Interaction Using Fluorescent In Situ Hybridization Coupled with Immunofluorescence (FISH/IF). Methods Mol Biol 2021; 2281:209-215. [PMID: 33847960 DOI: 10.1007/978-1-0716-1290-3_12] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Fluorescent in situ hybridization coupled with immunofluorescence (FISH/IF) is an assay that has been widely used to study DNA-protein interactions. The technique is based on the use of a fluorescent nucleic acid probe and fluorescent antibodies to reveal the localization of a DNA sequence and a specific protein in the cell. The interaction can be inferred by the quantification of the co-localization between the protein and the DNA. Here, we describe a detailed FISH/IF methodology that our group used to study RPA-telomere interaction in the pathogenic protozoa parasite Trypanosoma cruzi.
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Affiliation(s)
- Raphael S Pavani
- Laboratório de Ciclo Celular and Center of Toxins, Immune Response and Cell Signaling (CeTICS), Instituto Butantan, São Paulo, SP, Brazil
| | - Maria Carolina Elias
- Laboratório de Ciclo Celular and Center of Toxins, Immune Response and Cell Signaling (CeTICS), Instituto Butantan, São Paulo, SP, Brazil.
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6
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Lochhead PA, Tucker JA, Tatum NJ, Wang J, Oxley D, Kidger AM, Johnson VP, Cassidy MA, Gray NS, Noble MEM, Cook SJ. Paradoxical activation of the protein kinase-transcription factor ERK5 by ERK5 kinase inhibitors. Nat Commun 2020; 11:1383. [PMID: 32170057 PMCID: PMC7069993 DOI: 10.1038/s41467-020-15031-3] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2018] [Accepted: 02/11/2020] [Indexed: 12/20/2022] Open
Abstract
The dual protein kinase-transcription factor, ERK5, is an emerging drug target in cancer and inflammation, and small-molecule ERK5 kinase inhibitors have been developed. However, selective ERK5 kinase inhibitors fail to recapitulate ERK5 genetic ablation phenotypes, suggesting kinase-independent functions for ERK5. Here we show that ERK5 kinase inhibitors cause paradoxical activation of ERK5 transcriptional activity mediated through its unique C-terminal transcriptional activation domain (TAD). Using the ERK5 kinase inhibitor, Compound 26 (ERK5-IN-1), as a paradigm, we have developed kinase-active, drug-resistant mutants of ERK5. With these mutants, we show that induction of ERK5 transcriptional activity requires direct binding of the inhibitor to the kinase domain. This in turn promotes conformational changes in the kinase domain that result in nuclear translocation of ERK5 and stimulation of gene transcription. This shows that both the ERK5 kinase and TAD must be considered when assessing the role of ERK5 and the effectiveness of anti-ERK5 therapeutics.
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Affiliation(s)
- Pamela A Lochhead
- Signalling Laboratory, The Babraham Institute, Babraham Research Campus, Cambridge, CB22 3AT, UK.
| | - Julie A Tucker
- York Biomedical Research Institute and Department of Biology, University of York, York, YO10 5DD, UK
| | - Natalie J Tatum
- CRUK Newcastle Drug Discovery Unit, Newcastle University Centre for Cancer, Newcastle University, Newcastle, NE2 4HH, UK
| | - Jinhua Wang
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA, 02215, USA
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, 02115, USA
| | - David Oxley
- Signalling Laboratory, The Babraham Institute, Babraham Research Campus, Cambridge, CB22 3AT, UK
| | - Andrew M Kidger
- Signalling Laboratory, The Babraham Institute, Babraham Research Campus, Cambridge, CB22 3AT, UK
| | - Victoria P Johnson
- Signalling Laboratory, The Babraham Institute, Babraham Research Campus, Cambridge, CB22 3AT, UK
- Institute of Cancer Research, Chester Beatty Laboratories, 237 Fulham Road, London, SW3 6JB, UK
| | - Megan A Cassidy
- Signalling Laboratory, The Babraham Institute, Babraham Research Campus, Cambridge, CB22 3AT, UK
| | - Nathanael S Gray
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA, 02215, USA
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, 02115, USA
| | - Martin E M Noble
- CRUK Newcastle Drug Discovery Unit, Newcastle University Centre for Cancer, Newcastle University, Newcastle, NE2 4HH, UK
| | - Simon J Cook
- Signalling Laboratory, The Babraham Institute, Babraham Research Campus, Cambridge, CB22 3AT, UK.
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Lawson T, El-Kamand S, Boucher D, Duong DC, Kariawasam R, Bonvin AMJJ, Richard DJ, Gamsjaeger R, Cubeddu L. The structural details of the interaction of single-stranded DNA binding protein hSSB2 (NABP1/OBFC2A) with UV-damaged DNA. Proteins 2019; 88:319-326. [PMID: 31443132 DOI: 10.1002/prot.25806] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2019] [Revised: 08/02/2019] [Accepted: 08/19/2019] [Indexed: 12/17/2022]
Abstract
Single-stranded DNA-binding proteins (SSBs) are required for all known DNA metabolic events such as DNA replication, recombination and repair. While a wealth of structural and functional data is available on the essential human SSB, hSSB1 (NABP2/OBFC2B), the close homolog hSSB2 (NABP1/OBFC2A) remains relatively uncharacterized. Both SSBs possess a well-structured OB (oligonucleotide/oligosaccharide-binding) domain that is able to recognize single-stranded DNA (ssDNA) followed by a flexible carboxyl-tail implicated in the interaction with other proteins. Despite the high sequence similarity of the OB domain, several recent studies have revealed distinct functional differences between hSSB1 and hSSB2. In this study, we show that hSSB2 is able to recognize cyclobutane pyrimidine dimers (CPD) that form in cellular DNA as a consequence of UV damage. Using a combination of biolayer interferometry and NMR, we determine the molecular details of the binding of the OB domain of hSSB2 to CPD-containing ssDNA, confirming the role of four key aromatic residues in hSSB2 (W59, Y78, W82, and Y89) that are also conserved in hSSB1. Our structural data thus demonstrate that ssDNA recognition by the OB fold of hSSB2 is highly similar to hSSB1, indicating that one SSB may be able to replace the other in any initial ssDNA binding event. However, any subsequent recruitment of other repair proteins most likely depends on the divergent carboxyl-tail and as such is likely to be different between hSSB1 and hSSB2.
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Affiliation(s)
- Teegan Lawson
- School of Science and Health, Western Sydney University, Penrith, New South Wales, Australia
| | - Serene El-Kamand
- School of Science and Health, Western Sydney University, Penrith, New South Wales, Australia
| | - Didier Boucher
- Cancer and Ageing Research Program, Institute of Health and Biomedical Innovation, Translational Research Institute, Queensland University of Technology, Woolloongabba, Queensland, Australia
| | - Duc Cong Duong
- School of Science and Health, Western Sydney University, Penrith, New South Wales, Australia
| | - Ruvini Kariawasam
- School of Science and Health, Western Sydney University, Penrith, New South Wales, Australia
| | - Alexandre M J J Bonvin
- Bijvoet Center for Biomolecular Research, Faculty of Science - Chemistry, Utrecht University, Utrecht, The Netherlands
| | - Derek J Richard
- Cancer and Ageing Research Program, Institute of Health and Biomedical Innovation, Translational Research Institute, Queensland University of Technology, Woolloongabba, Queensland, Australia
| | - Roland Gamsjaeger
- School of Science and Health, Western Sydney University, Penrith, New South Wales, Australia.,School of Life and Environmental Sciences, University of Sydney, Sydney, New South Wales, Australia
| | - Liza Cubeddu
- School of Science and Health, Western Sydney University, Penrith, New South Wales, Australia.,School of Life and Environmental Sciences, University of Sydney, Sydney, New South Wales, Australia
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8
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Kariawasam R, Knight M, Gamsjaeger R, Cubeddu L. Backbone 1H, 13C and 15N resonance assignments of the OB domain of the single stranded DNA-binding protein hSSB2 (NABP1/OBFC2A) and chemical shift mapping of the DNA-binding interface. BIOMOLECULAR NMR ASSIGNMENTS 2018; 12:107-111. [PMID: 29063999 DOI: 10.1007/s12104-017-9789-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/31/2017] [Accepted: 10/20/2017] [Indexed: 06/07/2023]
Abstract
Single stranded DNA-binding proteins (SSBs) are essential for the maintenance of genome integrity and are required in in all known cellular organisms. Over the last 10 years, the role of two new human SSBs, hSSB1 (NABP2/OBFC2B) and hSSB2 (NABP1/OBFC2A), has been described and characterised in various important DNA repair processes. Both these proteins are made up of a conserved oligonucleotide-binding (OB) fold that is responsible for ssDNA recognition as well a unique flexible carboxy-terminal extension involved in protein-protein interactions. Due to their similar domain organisation, hSSB1 and hSSB2 have been found to display some overlapping functions. However, several studies have also revealed cell- and tissue-specific roles for these two proteins, most likely due to small but significant differences in the protein sequence of the OB domains. While the molecular details of ssDNA binding by hSSB1 has been studied extensively, comparatively little is known about hSSB2. In this study, we use NMR solution-state backbone resonance assignments of the OB domain of hSSB2 to map the ssDNA interaction interface. Our data reveal that ssDNA binding by hSSB2 is driven by four key aromatic residues in analogy to hSSB1, however, some significant differences in the chemical shift perturbations are observed, reflecting differences in ssDNA recognition. Future studies will aim at determining the structural basis of these differences and thus help to gain a more comprehensive understanding of the functional divergences that these novel hSSBs display in the context of genome maintenance.
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Affiliation(s)
- Ruvini Kariawasam
- School of Science and Health, Western Sydney University, Penrith, NSW, 2751, Australia
| | - Maddison Knight
- School of Science and Health, Western Sydney University, Penrith, NSW, 2751, Australia
| | - Roland Gamsjaeger
- School of Science and Health, Western Sydney University, Penrith, NSW, 2751, Australia.
- School of Life and Environmental Sciences, University of Sydney, Sydney, NSW, 2006, Australia.
| | - Liza Cubeddu
- School of Science and Health, Western Sydney University, Penrith, NSW, 2751, Australia.
- School of Life and Environmental Sciences, University of Sydney, Sydney, NSW, 2006, Australia.
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