The Bloom's syndrome helicase promotes the annealing of complementary single-stranded DNA.
The product of the gene mutated in Bloom's syndrome, BLM, is a 3'-5' DNA helicase belonging to the highly conserved RecQ family. In addition to a conventional DNA strand separation activity, BLM catalyzes both the disruption of non-B-form DNA, such as G-quadruplexes, and the branch migration of Holliday junctions. Here, we have characterized a new activity for BLM: the promotion of single-stranded DNA (ssDNA) annealing. This activity does not require Mg(2+), is inhibited by ssDNA binding proteins and ATP, and is dependent on DNA length. Through analysis of various truncation mutants of BLM, we show that the C-terminal domain is essential for strand annealing and identify a 60 amino acid stretch of this domain as being important for both ssDNA binding and strand annealing. We present a model in which the ssDNA annealing activity of BLM facilitates its role in the processing of DNA intermediates that arise during repair of damaged replication forks.
Cheok
Chit Fang
CF
Cancer Research UK Laboratories, Weatherall Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital Oxford OX3 9DS, UK.
Wu
Leonard
L
Garcia
Patrick L
PL
Janscak
Pavel
P
Hickson
Ian D
ID
D000251:Adenosine Triphosphatases / Q000737:chemistry / Q000378:metabolism*; D004265:DNA Helicases / Q000737:chemistry / Q000378:metabolism*; D004260:DNA Repair; D004277:DNA, Single-Stranded / Q000737:chemistry / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism; D008957:Models, Genetic; D017434:Protein Structure, Tertiary; D053484:RecQ Helicases
D004277:DNA, Single-Stranded; D004268:DNA-Binding Proteins; D000251:Adenosine Triphosphatases; C097151:Bloom syndrome protein; D004265:DNA Helicases; D053484:RecQ Helicases