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Harami GM, Pálinkás J, Kovács ZJ, Jezsó B, Tárnok K, Harami-Papp H, Hegedüs J, Mahmudova L, Kucsma N, Tóth S, Szakács G, Kovács M. Redox-dependent condensation and cytoplasmic granulation by human ssDNA-binding protein-1 delineate roles in oxidative stress response. iScience 2024; 27:110788. [PMID: 39286502 PMCID: PMC11403420 DOI: 10.1016/j.isci.2024.110788] [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: 05/22/2024] [Revised: 06/06/2024] [Accepted: 08/19/2024] [Indexed: 09/19/2024] Open
Abstract
Human single-stranded DNA binding protein 1 (hSSB1/NABP2/OBFC2B) plays central roles in DNA repair. Here, we show that purified hSSB1 undergoes redox-dependent liquid-liquid phase separation (LLPS) in the presence of single-stranded DNA or RNA, features that are distinct from those of LLPS by bacterial SSB. hSSB1 nucleoprotein droplets form under physiological ionic conditions in response to treatment modeling cellular oxidative stress. hSSB1's intrinsically disordered region is indispensable for LLPS, whereas all three cysteine residues of the oligonucleotide/oligosaccharide-binding fold are necessary to maintain redox-sensitive droplet formation. Proteins interacting with hSSB1 show selective enrichment inside hSSB1 droplets, suggesting tight content control and recruitment functions for the condensates. While these features appear instrumental for genome repair, we detected cytoplasmic hSSB1 condensates in various cell lines colocalizing with stress granules upon oxidative stress, implying extranuclear function in cellular stress response. Our results suggest condensation-linked roles for hSSB1, linking genome repair and cytoplasmic defense.
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Affiliation(s)
- Gábor M Harami
- ELTE-MTA "Momentum" Motor Enzymology Research Group, Department of Biochemistry, Eötvös Loránd University, Pázmány P. s. 1/c, 1117 Budapest, Hungary
| | - János Pálinkás
- ELTE-MTA "Momentum" Motor Enzymology Research Group, Department of Biochemistry, Eötvös Loránd University, Pázmány P. s. 1/c, 1117 Budapest, Hungary
| | - Zoltán J Kovács
- ELTE-MTA "Momentum" Motor Enzymology Research Group, Department of Biochemistry, Eötvös Loránd University, Pázmány P. s. 1/c, 1117 Budapest, Hungary
- HUN-REN-ELTE Motor Pharmacology Research Group, Department of Biochemistry, Eötvös Loránd University, Pázmány P. s. 1/c, 1117 Budapest, Hungary
| | - Bálint Jezsó
- ELTE-MTA "Momentum" Motor Enzymology Research Group, Department of Biochemistry, Eötvös Loránd University, Pázmány P. s. 1/c, 1117 Budapest, Hungary
| | - Krisztián Tárnok
- Department of Physiology and Neurobiology, Eötvös Loránd University, Pázmány P. s. 1/c, 1117 Budapest, Hungary
| | - Hajnalka Harami-Papp
- ELTE-MTA "Momentum" Motor Enzymology Research Group, Department of Biochemistry, Eötvös Loránd University, Pázmány P. s. 1/c, 1117 Budapest, Hungary
| | - József Hegedüs
- ELTE-MTA "Momentum" Motor Enzymology Research Group, Department of Biochemistry, Eötvös Loránd University, Pázmány P. s. 1/c, 1117 Budapest, Hungary
| | - Lamiya Mahmudova
- ELTE-MTA "Momentum" Motor Enzymology Research Group, Department of Biochemistry, Eötvös Loránd University, Pázmány P. s. 1/c, 1117 Budapest, Hungary
| | - Nóra Kucsma
- HUN-REN Institute of Molecular Life Sciences, Research Centre for Natural Sciences, Magyar Tudósok körútja 2, 1117 Budapest, Hungary
| | - Szilárd Tóth
- HUN-REN Institute of Molecular Life Sciences, Research Centre for Natural Sciences, Magyar Tudósok körútja 2, 1117 Budapest, Hungary
| | - Gergely Szakács
- HUN-REN Institute of Molecular Life Sciences, Research Centre for Natural Sciences, Magyar Tudósok körútja 2, 1117 Budapest, Hungary
- Center for Cancer Research, Medical University of Vienna, Borschkegasse 8a, 1090 Wien, Austria
| | - Mihály Kovács
- ELTE-MTA "Momentum" Motor Enzymology Research Group, Department of Biochemistry, Eötvös Loránd University, Pázmány P. s. 1/c, 1117 Budapest, Hungary
- HUN-REN-ELTE Motor Pharmacology Research Group, Department of Biochemistry, Eötvös Loránd University, Pázmány P. s. 1/c, 1117 Budapest, Hungary
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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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Schuurs ZP, Martyn AP, Soltau CP, Beard S, Shah ET, Adams MN, Croft LV, O’Byrne KJ, Richard DJ, Gandhi NS. An Exploration of Small Molecules That Bind Human Single-Stranded DNA Binding Protein 1. BIOLOGY 2023; 12:1405. [PMID: 37998004 PMCID: PMC10669474 DOI: 10.3390/biology12111405] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2023] [Revised: 10/24/2023] [Accepted: 10/30/2023] [Indexed: 11/25/2023]
Abstract
Human single-stranded DNA binding protein 1 (hSSB1) is critical to preserving genome stability, interacting with single-stranded DNA (ssDNA) through an oligonucleotide/oligosaccharide binding-fold. The depletion of hSSB1 in cell-line models leads to aberrant DNA repair and increased sensitivity to irradiation. hSSB1 is over-expressed in several types of cancers, suggesting that hSSB1 could be a novel therapeutic target in malignant disease. hSSB1 binding studies have focused on DNA; however, despite the availability of 3D structures, small molecules targeting hSSB1 have not been explored. Quinoline derivatives targeting hSSB1 were designed through a virtual fragment-based screening process, synthesizing them using AlphaLISA and EMSA to determine their affinity for hSSB1. In parallel, we further screened a structurally diverse compound library against hSSB1 using the same biochemical assays. Three compounds with nanomolar affinity for hSSB1 were identified, exhibiting cytotoxicity in an osteosarcoma cell line. To our knowledge, this is the first study to identify small molecules that modulate hSSB1 activity. Molecular dynamics simulations indicated that three of the compounds that were tested bound to the ssDNA-binding site of hSSB1, providing a framework for the further elucidation of inhibition mechanisms. These data suggest that small molecules can disrupt the interaction between hSSB1 and ssDNA, and may also affect the ability of cells to repair DNA damage. This test study of small molecules holds the potential to provide insights into fundamental biochemical questions regarding the OB-fold.
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Affiliation(s)
- Zachariah P. Schuurs
- Centre for Genomics and Personalised Health, School of Chemistry and Physics, Queensland University of Technology (QUT), Brisbane, QLD 4000, Australia; (Z.P.S.); (A.P.M.)
- Cancer and Ageing Research Program, Centre for Genomics and Personalised Health, Queensland University of Technology (QUT), Translational Research Institute (TRI), Woolloongabba, QLD 4102, Australia; (S.B.); (M.N.A.); (L.V.C.); (K.J.O.); (D.J.R.)
| | - Alexander P. Martyn
- Centre for Genomics and Personalised Health, School of Chemistry and Physics, Queensland University of Technology (QUT), Brisbane, QLD 4000, Australia; (Z.P.S.); (A.P.M.)
- Cancer and Ageing Research Program, Centre for Genomics and Personalised Health, Queensland University of Technology (QUT), Translational Research Institute (TRI), Woolloongabba, QLD 4102, Australia; (S.B.); (M.N.A.); (L.V.C.); (K.J.O.); (D.J.R.)
| | - Carl P. Soltau
- School of Chemistry and Physics, Centre for Materials Science, Queensland University of Technology, Brisbane, QLD 4000, Australia;
| | - Sam Beard
- Cancer and Ageing Research Program, Centre for Genomics and Personalised Health, Queensland University of Technology (QUT), Translational Research Institute (TRI), Woolloongabba, QLD 4102, Australia; (S.B.); (M.N.A.); (L.V.C.); (K.J.O.); (D.J.R.)
| | - Esha T. Shah
- Cancer and Ageing Research Program, Centre for Genomics and Personalised Health, Queensland University of Technology (QUT), Translational Research Institute (TRI), Woolloongabba, QLD 4102, Australia; (S.B.); (M.N.A.); (L.V.C.); (K.J.O.); (D.J.R.)
- School of Biomedical Sciences, Faculty of Health, Queensland University of Technology, Translational Research Institute, Woolloongabba, QLD 4102, Australia
| | - Mark N. Adams
- Cancer and Ageing Research Program, Centre for Genomics and Personalised Health, Queensland University of Technology (QUT), Translational Research Institute (TRI), Woolloongabba, QLD 4102, Australia; (S.B.); (M.N.A.); (L.V.C.); (K.J.O.); (D.J.R.)
- School of Biomedical Sciences, Faculty of Health, Queensland University of Technology, Translational Research Institute, Woolloongabba, QLD 4102, Australia
| | - Laura V. Croft
- Cancer and Ageing Research Program, Centre for Genomics and Personalised Health, Queensland University of Technology (QUT), Translational Research Institute (TRI), Woolloongabba, QLD 4102, Australia; (S.B.); (M.N.A.); (L.V.C.); (K.J.O.); (D.J.R.)
- School of Biomedical Sciences, Faculty of Health, Queensland University of Technology, Translational Research Institute, Woolloongabba, QLD 4102, Australia
| | - Kenneth J. O’Byrne
- Cancer and Ageing Research Program, Centre for Genomics and Personalised Health, Queensland University of Technology (QUT), Translational Research Institute (TRI), Woolloongabba, QLD 4102, Australia; (S.B.); (M.N.A.); (L.V.C.); (K.J.O.); (D.J.R.)
- Cancer Services, Princess Alexandra Hospital—Metro South Health, Woolloongabba, QLD 4102, Australia
| | - Derek J. Richard
- Cancer and Ageing Research Program, Centre for Genomics and Personalised Health, Queensland University of Technology (QUT), Translational Research Institute (TRI), Woolloongabba, QLD 4102, Australia; (S.B.); (M.N.A.); (L.V.C.); (K.J.O.); (D.J.R.)
- School of Biomedical Sciences, Faculty of Health, Queensland University of Technology, Translational Research Institute, Woolloongabba, QLD 4102, Australia
| | - Neha S. Gandhi
- Centre for Genomics and Personalised Health, School of Chemistry and Physics, Queensland University of Technology (QUT), Brisbane, QLD 4000, Australia; (Z.P.S.); (A.P.M.)
- Cancer and Ageing Research Program, Centre for Genomics and Personalised Health, Queensland University of Technology (QUT), Translational Research Institute (TRI), Woolloongabba, QLD 4102, Australia; (S.B.); (M.N.A.); (L.V.C.); (K.J.O.); (D.J.R.)
- Department of Computer Science and Engineering, Manipal Institute of Technology, Manipal Academy of Higher Education, Manipal 576104, India
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Zhang Q, Hao R, Chen H, Zhou G. SOSSB1 and SOSSB2 mutually regulate protein stability through competitive binding of SOSSA. Cell Death Discov 2023; 9:319. [PMID: 37640700 PMCID: PMC10462637 DOI: 10.1038/s41420-023-01619-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2023] [Revised: 08/08/2023] [Accepted: 08/17/2023] [Indexed: 08/31/2023] Open
Abstract
Human single-stranded DNA-binding protein homologs hSSB1 (SOSSB1) and hSSB2 (SOSSB2) make a vital impact on maintaining genome stability as the B subunits of the sensor of single-stranded DNA complex (SOSS). However, whether and how SOSSB1 and SOSSB2 modulate mutual expression is unclear. This study, demonstrated that the depletion of SOSSB1 in cells enhances the stability of the SOSSB2 protein, and conversely, SOSSB2 depletion enhances the stability of the SOSSB1 protein. The levels of SOSSB1 and SOSSB2 proteins are mutually regulated through their competitive binding with SOSSA which associates with the highly conservative OB-fold domain in SOSSB1 and SOSSB2. The destabilized SOSSB1 and SOSSB2 proteins can be degraded via the proteasome pathway. Additionally, the simultaneous loss of SOSSB1 and SOSSB2 aggravates homologous recombination (HR)-mediated DNA repair defects, enhances cellular radiosensitivity and promotes cell apoptosis. In conclusion, in this study, we showed that SOSSB1 and SOSSB2 positively regulate HR repair and the interaction between SOSSA and SOSSB1 or SOSSB2 prevents the degradation of SOSSB1 and SOSSB2 proteins via the proteasome pathway.
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Affiliation(s)
- Qi Zhang
- Graduate Collaborative Training Base of Academy of Military Sciences, Hengyang Medical School, University of South China, Hengyang City, Hunan Province, 421001, P.R. China
| | - Rongjiao Hao
- School of Life Sciences, Hebei University, Baoding City, Hebei Province, 071002, P.R. China
| | - Hongxia Chen
- State Key Laboratory of Proteomics, National Center for Protein Sciences at Beijing, Beijing Proteome Research Center, Beijing Institute of Radiation Medicine, Beijing, 100850, P.R. China.
| | - Gangqiao Zhou
- Graduate Collaborative Training Base of Academy of Military Sciences, Hengyang Medical School, University of South China, Hengyang City, Hunan Province, 421001, P.R. China.
- School of Life Sciences, Hebei University, Baoding City, Hebei Province, 071002, P.R. China.
- State Key Laboratory of Proteomics, National Center for Protein Sciences at Beijing, Beijing Proteome Research Center, Beijing Institute of Radiation Medicine, Beijing, 100850, P.R. China.
- Collaborative Innovation Center for Personalized Cancer Medicine, Center for Global Health, School of Public Health, Nanjing Medical University, Nanjing City, Jiangsu Province, 211166, P.R. China.
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El-Kamand S, Du Plessis MD, Lawson T, Cubeddu L, Gamsjaeger R. Expression, Purification, and Solution-State NMR Analysis of the Two Human Single-Stranded DNA-Binding Proteins hSSB1 (NABP2/OBFC2B) and hSSB2 (NAPB1/OBFC2A). Methods Mol Biol 2021; 2281:229-240. [PMID: 33847962 DOI: 10.1007/978-1-0716-1290-3_14] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Single-stranded DNA-binding proteins (SSBs) are essential to all living organisms as protectors and guardians of the genome. Apart from the well-characterized RPA, humans have also evolved two further SSBs, termed hSSB1 and hSSB2. Over the last few years, we have used NMR spectroscopy to determine the molecular and structural details of both hSSBs and their interactions with DNA and RNA. Here we provide a detailed overview of how to express and purify recombinant versions of these important human proteins for the purpose of detailed structural analysis by high-resolution solution-state NMR.
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Affiliation(s)
- Serene El-Kamand
- School of Science, Western Sydney University, Penrith, NSW, Australia
| | | | - Teegan Lawson
- School of Science, Western Sydney University, Penrith, NSW, Australia
| | - Liza Cubeddu
- School of Science, Western Sydney University, Penrith, NSW, Australia.
- School of Life and Environmental Sciences, University of Sydney, Sydney, NSW, Australia.
| | - Roland Gamsjaeger
- School of Science, Western Sydney University, Penrith, NSW, Australia.
- School of Life and Environmental Sciences, University of Sydney, Sydney, NSW, Australia.
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Oliveira MT, Ciesielski GL. The Essential, Ubiquitous Single-Stranded DNA-Binding Proteins. Methods Mol Biol 2021; 2281:1-21. [PMID: 33847949 DOI: 10.1007/978-1-0716-1290-3_1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Maintenance of genomes is fundamental for all living organisms. The diverse processes related to genome maintenance entail the management of various intermediate structures, which may be deleterious if unresolved. The most frequent intermediate structures that result from the melting of the DNA duplex are single-stranded (ss) DNA stretches. These are thermodynamically less stable and can spontaneously fold into secondary structures, which may obstruct a variety of genome processes. In addition, ssDNA is more prone to breaking, which may lead to the formation of deletions or DNA degradation. Single-stranded DNA-binding proteins (SSBs) bind and stabilize ssDNA, preventing the abovementioned deleterious consequences and recruiting the appropriate machinery to resolve that intermediate molecule. They are present in all forms of life and are essential for their viability, with very few exceptions. Here we present an introductory chapter to a volume of the Methods in Molecular Biology dedicated to SSBs, in which we provide a general description of SSBs from various taxa.
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Affiliation(s)
- Marcos T Oliveira
- Departamento de Tecnologia, Faculdade de Ciências Agrárias e Veterinárias, Universidade Estadual Paulista "Júlio de Mesquita Filho", Jaboticabal, SP, Brazil
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7
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Phase separation by ssDNA binding protein controlled via protein-protein and protein-DNA interactions. Proc Natl Acad Sci U S A 2020; 117:26206-26217. [PMID: 33020264 PMCID: PMC7584906 DOI: 10.1073/pnas.2000761117] [Citation(s) in RCA: 91] [Impact Index Per Article: 18.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Cells must rapidly and efficiently react to DNA damage to avoid its harmful consequences. Here we report a molecular mechanism that gives rise to a model of how bacterial cells mobilize DNA repair proteins for timely response to genomic stress and initiation of DNA repair upon exposure of single-stranded DNA. We found that bacterial single-stranded DNA binding protein (SSB), a central player in genome metabolism, can undergo dynamic phase separation under physiological conditions. SSB condensates can store a wide array of DNA repair proteins that specifically interact with SSB. However, elevated levels of single-stranded DNA during genomic stress can dissolve SSB condensates, enabling rapid mobilization of SSB and SSB-interacting proteins to sites of DNA damage. Bacterial single-stranded (ss)DNA-binding proteins (SSB) are essential for the replication and maintenance of the genome. SSBs share a conserved ssDNA-binding domain, a less conserved intrinsically disordered linker (IDL), and a highly conserved C-terminal peptide (CTP) motif that mediates a wide array of protein−protein interactions with DNA-metabolizing proteins. Here we show that the Escherichia coli SSB protein forms liquid−liquid phase-separated condensates in cellular-like conditions through multifaceted interactions involving all structural regions of the protein. SSB, ssDNA, and SSB-interacting molecules are highly concentrated within the condensates, whereas phase separation is overall regulated by the stoichiometry of SSB and ssDNA. Together with recent results on subcellular SSB localization patterns, our results point to a conserved mechanism by which bacterial cells store a pool of SSB and SSB-interacting proteins. Dynamic phase separation enables rapid mobilization of this protein pool to protect exposed ssDNA and repair genomic loci affected by DNA damage.
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8
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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: 9] [Impact Index Per Article: 1.5] [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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