title: The SOSS1 single-stranded DNA binding complex promotes DNA end resection in concert with Exo1.
abstract: The human SSB homologue 1 (hSSB1) has been shown to facilitate homologous recombination and double-strand break signalling in human cells. Here, we compare the DNA-binding properties of the SOSS1 complex, containing SSB1, with Replication Protein A (RPA), the primary single-strand DNA (ssDNA) binding complex in eukaryotes. Ensemble and single-molecule approaches show that SOSS1 binds ssDNA with lower affinity compared to RPA, and exhibits less stable interactions with DNA substrates. Nevertheless, the SOSS1 complex is uniquely capable of promoting interaction of human Exo1 with double-strand DNA ends and stimulates its activity independently of the MRN complex in vitro. Both MRN and SOSS1 also act to mitigate the inhibitory action of the Ku70/80 heterodimer on Exo1 activity in vitro. These results may explain why SOSS complexes do not localize with RPA to replication sites in human cells, yet have a strong effect on double-strand break resection and homologous recombination.
authors.affiliation: The Department of Molecular Genetics and Microbiology, The Howard Hughes Medical Institute, and Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, TX, USA.
authors.forename: Soo-Hyun
authors.initials: SH
authors.lastname: Yang
authors.forename: Ruobo
authors.initials: R
authors.lastname: Zhou
authors.forename: Judith
authors.initials: J
authors.lastname: Campbell
authors.forename: Junjie
authors.initials: J
authors.lastname: Chen
authors.forename: Taekjip
authors.initials: T
authors.lastname: Ha
authors.forename: Tanya T
authors.initials: TT
authors.lastname: Paull
mesh_terms: D034961:Antigens, Nuclear / Q000235:genetics / Q000378:metabolism; D004247:DNA / Q000378:metabolism*; D053903:DNA Breaks, Double-Stranded; D004260:DNA Repair; D045643:DNA Repair Enzymes / Q000235:genetics / Q000378:metabolism*; D004261:DNA Replication; D004277:DNA, Single-Stranded / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D005057:Eukaryotic Cells; D005090:Exodeoxyribonucleases / Q000235:genetics / Q000378:metabolism*; D031541:Fluorescence Resonance Energy Transfer; D059765:Homologous Recombination; D006801:Humans; D000072200:Ku Autoantigen; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism*; D046912:Multiprotein Complexes; D011485:Protein Binding; D055503:Protein Multimerization; D051716:Replication Protein A / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: D034961:Antigens, Nuclear; D004277:DNA, Single-Stranded; D004268:DNA-Binding Proteins; D024101:Mitochondrial Proteins; D046912:Multiprotein Complexes; C497167:RPA1 protein, human; D051716:Replication Protein A; C504091:NABP2 protein, human; D004247:DNA; C114331:EXO1 protein, human; D005090:Exodeoxyribonucleases; C000606509:Xrcc6 protein, human; D000072200:Ku Autoantigen; D045643:DNA Repair Enzymes