D-loop formation by Brh2 protein of Ustilago maydis.

TitleD-loop formation by Brh2 protein of Ustilago maydis.
Publication TypeJournal Article
Year of Publication2008
AuthorsMazloum N, Zhou Q, Holloman WK
JournalProc Natl Acad Sci U S A
Date Published2008 Jan 15
KeywordsBRCA2 Protein, DNA, DNA, Single-Stranded, DNA-Binding Proteins, Escherichia coli, Exoribonucleases, Gene Expression Regulation, Molecular Conformation, Nucleic Acid Conformation, Plasmids, Protein Binding, Protein Conformation, Rad51 Recombinase, Recombination, Genetic, Saccharomyces cerevisiae Proteins, Ustilago

Brh2, the ortholog of the BRCA2 tumor suppressor in Ustilago maydis, works hand in hand with Rad51 to promote repair of DNA by homologous recombination. Previous studies established that Brh2 can stimulate DNA strand exchange by enabling Rad51 nucleoprotein filament formation on replication protein A-coated ssDNA. But, more recently, it was noted that Brh2 has an inherent DNA annealing activity, raising the notion that it might have roles in recombination in addition to or beyond the mediator function. Here, we found that Brh2 can autonomously promote the formation of D-loops in reactions with plasmid DNA and homologous single-stranded oligonucleotides. The reaction differs from that catalyzed by Rad51 in having no requirement for cofactors or preloading phase on ssDNA. D-loop formation was most effective when Brh2 was mixed with plasmid DNA before addition of single-stranded oligomer. D-loop formation catalyzed by Rad51 was also enhanced when Brh2 was premixed with plasmid DNA. Brh2 rendered defective in Rad51 interaction by mutation in the BRC element was still capable of promoting D-loop formation. However, the mutant protein was unable to enhance the Rad51-catalyzed reaction. The results suggest a model in which Brh2 binding to plasmid DNA attracts and helps capture Rad51-coated ssDNA.

Alternate JournalProc. Natl. Acad. Sci. U.S.A.
PubMed ID18174332
PubMed Central IDPMC2206569
Grant ListGM42482 / GM / NIGMS NIH HHS / United States
GM79859 / GM / NIGMS NIH HHS / United States

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