Single-molecule visualization of human BLM helicase as it acts upon double- and single-stranded DNA substrates

Chaoyou Xue, James M. Daley, Xiaoyu Xue, Justin Steinfeld, Youngho Kwon, Patrick Sung, Eric C. Greene

Research output: Contribution to journalArticle

3 Scopus citations

Abstract

Bloom helicase (BLM) and its orthologs are essential for the maintenance of genome integrity. BLM defects represent the underlying cause of Bloom Syndrome, a rare genetic disorder that is marked by strong cancer predisposition. BLM deficient cells accumulate extensive chromosomal aberrations stemming from dysfunctions in homologous recombination (HR). BLM participates in several HR stages and helps dismantle potentially harmful HR intermediates. However, much remains to be learned about the molecular mechanisms of these BLM-mediated regulatory effects. Here, we use DNA curtains to directly visualize the activity of BLM helicase on single molecules of DNA. Our data show that BLM is a robust helicase capable of rapidly (∼70-80 base pairs per second) unwinding extensive tracts (∼8-10 kilobases) of double-stranded DNA (dsDNA). Importantly, we find no evidence for BLM activity on single-stranded DNA (ssDNA) that is bound by replication protein A (RPA). Likewise, our results show that BLM can neither associate with nor translocate on ssDNA that is bound by the recombinase protein RAD51. Moreover, our data reveal that the presence of RAD51 also blocks BLM translocation on dsDNA substrates. We discuss our findings within the context of potential regulator roles for BLM helicase during DNA replication and repair.

Original languageEnglish (US)
Pages (from-to)11225-11237
Number of pages13
JournalNucleic acids research
Volume47
Issue number21
DOIs
StatePublished - Dec 2 2019

ASJC Scopus subject areas

  • Genetics

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