TY  - BOOK
AU  - Yodh,J.G.
AU  - Stevens,B,C
AU  - Kanagaraj,R.
AU  - Janscak,P.
AU  - Ha,T.
TI  - BLM helicase measures DNA unwound before switching strands and hRPA promotes unwinding reinitiation
N2  - 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 30-50 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, BLMunwound 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 hRPAwas necessary for unwinding reinitiation on hRPA-coated DNA. The reported activities may facilitate BLM processing of stalled replication forks and illegitimately formed recombination intermediates
UR  - https://drive.google.com/file/d/1UavaDU7DB5sXI8s7EnbtJkPXs52G-SQ-/view?usp=drivesdk
ER  -