Human RPA activates BLM's bidirectional DNA unwinding from a nick
- ShanghaiTech University, China
- Northwest A&F University, China
- Chinese Academy of Sciences, China
- Cancer Research Center of Marseille, CNRS UMR7258, Inserm U1068, France
- Ecole Normale Supérieure de Cachan, France
Abstract
BLM is a multifunctional helicase that plays critical roles in maintaining genome stability. It processes distinct DNA substrates, but not nicked DNA, during many steps in DNA replication and repair. However, how BLM prepares itself for diverse functions remains elusive. Here, using a combined single-molecule approach, we find that a high abundance of BLMs can indeed unidirectionally unwind dsDNA from a nick when an external destabilizing force is applied. Strikingly, human replication protein A (hRPA) not only ensures that limited quantities of BLMs processively unwind nicked dsDNA under a reduced force but also permits the translocation of BLMs on both intact and nicked ssDNAs, resulting in a bidirectional unwinding mode. This activation necessitates BLM targeting on the nick and the presence of free hRPAs in solution whereas direct interactions between them are dispensable. Our findings present novel DNA unwinding activities of BLM that potentially facilitate its function switching in DNA repair.
Data availability
All data generated or analysed during this study are included in the manuscript and supporting files. Source data files have been provided for Figures 1, 3, 4 and 5.
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Funding
Ministry of Science and Technology of the People's Republic of China (2016YFA0500902)
- Bo Sun
Ministry of Science and Technology of the People's Republic of China (2017YFA0106700)
- Bo Sun
The Natural Science Foundation of Shanghai (19ZR1434100)
- Bo Sun
The French National Cancer Institute (PLBIO2017-167)
- Mauro Modesti
The French National League Against Cancer (EL2028.LNCC/MaM)
- Mauro Modesti
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Copyright
© 2020, Qin et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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