期刊
EMBO JOURNAL
卷 28, 期 4, 页码 405-416出版社
WILEY
DOI: 10.1038/emboj.2008.298
关键词
Bloom syndrome; FRET; helicase; hRPA; single molecule
资金
- National Institutes of Health [GM065367]
- National Science Foundation [0822613]
- University of Illinois at Urbana-Champaign School of Molecular and Cellular Biology
- The Swiss National Science Foundation
Bloom syndrome (BS) is a rare genetic disorder characterized by genomic instability and a high predisposition to cancer. The gene defective in BS, BLM, encodes a member of the RecQ family of 3'-5' DNA helicases, and is proposed to function in recombinational repair during DNA replication. Here, we have utilized single-molecule fluorescence resonance energy transfer microscopy to examine the behaviour of BLMon forked DNA substrates. Strikingly, BLM unwound individual DNA molecules in a repetitive manner, unwinding a short length of duplex DNA followed by rapid reannealing and reinitiation of unwinding in several successions. Our results show that a monomeric BLM can 'measure' how many base pairs it has unwound, and once it has unwound a critical length, it reverses the unwinding reaction through strand switching and translocating on the opposing strand. Repetitive unwinding persisted even in the presence of hRPA, and interaction between wild-type BLM and hRPA was necessary for unwinding reinitiation on hRPA-coated DNA. The reported activities may facilitate BLM processing of stalled replication forks and illegitimately formed recombination intermediates.
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