Second-end capture in DNA double-strand break repair promoted by Brh2 protein of Ustilago maydis.
Brh2 plays a central role in the homologous recombination system of Ustilago maydis, mediating delivery of Rad51 to single-stranded DNA. Here we report that Brh2 can pair the displaced strand of a D loop with a complementary single-stranded DNA to form a duplexed, or double, D loop. The reaction emulates the second-end capture step envisioned in models of DNA double-strand break repair. This second-end capture reaction promoted by Brh2 proceeds efficiently when performed in the presence of Rad51 under conditions that block annealing by Rad52, or when the second single-stranded DNA substrate is replaced by double-stranded DNA. In a coupled reaction that requires extension of the D loop more than 200 nt by DNA synthesis in order to reveal a complementary region, Brh2 was also able to promote second-end capture and thus model a synthesis-dependent strand-annealing mechanism.
Mazloum
Nayef
N
Department of Microbiology and Immunology, Weill Cornell Medical College, New York, NY 10021, USA.
Holloman
William K
WK
D053903:DNA Breaks, Double-Stranded; D004260:DNA Repair / Q000502:physiology*; D004271:DNA, Fungal / Q000235:genetics / Q000378:metabolism*; D004277:DNA, Single-Stranded / Q000235:genetics / Q000378:metabolism; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D008957:Models, Genetic; D011995:Recombination, Genetic / Q000502:physiology*; D014588:Ustilago / Q000378:metabolism*
D004271:DNA, Fungal; D004277:DNA, Single-Stranded; D005656:Fungal Proteins