The Srs2 helicase activity is stimulated by Rad51 filaments on dsDNA: implications for crossover incidence during mitotic recombination.
Saccharomyces cerevisiae Srs2 helicase was shown to displace Rad51 in vitro upon translocation on single-stranded DNA. This activity is sufficient to account for its antirecombination effect and for the elimination of otherwise dead-end recombination intermediates. Roles for the helicase activity are yet unknown. Because cells lacking Srs2 show increased incidence of mitotic crossovers, it was postulated that Srs2 promotes synthesis-dependent strand annealing (SDSA) by unwinding the elongating invading strand from the donor strand. We report here that synthetic DNA structures that mimic D loops are good substrates for the Srs2 helicase activity, that Srs2 translocates on RPA-coated ssDNA, and, furthermore, that the helicase activity is largely stimulated by the presence of Rad51 nucleoprotein filaments on double-stranded DNA. These properties strongly support the idea that Srs2 actively prevents crossovers by promoting SDSA.
Dupaigne
Pauline
P
Laboratorie de Microscopie Moléculaire et Cellulaire, UMR 8126, Interactions Moléculaires et Cancer CNRS-Université Paris Sud-Institut de Cancérologie Gustave Roussy, Villejuif, France.
Le Breton
Cyrille
C
Fabre
Francis
F
Gangloff
Serge
S
Le Cam
Eric
E
Veaute
Xavier
X
D003434:Crossing Over, Genetic / Q000502:physiology*; D004265:DNA Helicases / Q000235:genetics / Q000378:metabolism*; D004271:DNA, Fungal / Q000235:genetics / Q000378:metabolism*; D004277:DNA, Single-Stranded / Q000235:genetics / Q000378:metabolism*; D008938:Mitosis / Q000502:physiology; D051135:Rad51 Recombinase / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*
D004271:DNA, Fungal; D004277:DNA, Single-Stranded; D029701:Saccharomyces cerevisiae Proteins; C061376:SRS2 protein, S cerevisiae; C495151:RAD51 protein, S cerevisiae; D051135:Rad51 Recombinase; D004265:DNA Helicases