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Published January 9, 2013 | public
Journal Article

The SOSS1 single-stranded DNA binding complex promotes DNA end resection in concert with Exo1


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.

Additional Information

© 2013 European Molecular Biology Organization. Received: 23 May 2012; accepted: 5 November 2012; published online: 23 November 2012. These studies were supported by grants from the National Institutes of Health (CA094008 to TTP; GM100196 to JC; RR025341 and GM065367 to TH), the National Science Foundation (0822613 to TH), CDMRP (W81XWH-09-1-0041 to JC), and the Cancer Prevention and Research Institute of Texas (RP110465 to TTP and JC). We thank Paul Modrich, Ian Hickson, Marc Wold, and Dale Ramsden for expression constructs. Author contributions: S-HY performed experiments, evaluated the data, and helped in the writing of the manuscript. RZ performed experiments and evaluated the data. JC and JC provided essential reagents and contributed to the evaluation of the data. TH evaluated the data and edited the manuscript. TP planned experiments, evaluated the data, and wrote and edited the manuscript.

Additional details

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