title: Rec2 interplay with both Brh2 and Rad51 balances recombinational repair in Ustilago maydis.
abstract: Rec2 is the single Rad51 paralog in Ustilago maydis. Here, we find that Rec2 is required for radiation-induced Rad51 nuclear focus formation but that Rec2 foci form independently of Rad51 and Brh2. Brh2 foci also form in the absence of Rad51 and Rec2. By coprecipitation from cleared extracts prepared from Escherichia coli cells expressing the proteins, we found that Rec2 interacts physically not only with Rad51 and itself but also with Brh2. Transgenic expression of Brh2 in rec2 mutants can effectively restore radiation resistance, but the frequencies of spontaneous Rad51 focus formation and allelic recombination are elevated. The Dss1-independent Brh2-RPA70 fusion protein is also active in restoring radiation sensitivity of rec2 but is hyperactive to an extreme degree in allelic recombination and in suppressing the meiotic block of rec2. However, the high frequency of chromosome missegregation in meiotic products is an indicator of a corrupted process. The results demonstrate that the importance of Rec2 function is not only in stimulating recombination activity but also in ensuring that recombination is properly controlled.
authors.affiliation: Department of Microbiology and Immunology, Hearst Microbiology Research Center, Box 62, Cornell University Weill Medical College, 1300 York Avenue, New York, New York 10021, USA.
authors.forename: Milorad
authors.initials: M
authors.lastname: Kojic
authors.forename: Qingwen
authors.initials: Q
authors.lastname: Zhou
authors.forename: Michael
authors.initials: M
authors.lastname: Lisby
authors.forename: William K
authors.initials: WK
authors.lastname: Holloman
mesh_terms: D024682:BRCA2 Protein / Q000235:genetics; D002869:Chromosome Aberrations; D004260:DNA Repair / Q000502:physiology*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D005656:Fungal Proteins / Q000235:genetics / Q000502:physiology*; D008540:Meiosis; D009154:Mutation; D011485:Protein Binding; D051135:Rad51 Recombinase / Q000235:genetics / Q000502:physiology*; D011836:Radiation Tolerance; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D011995:Recombination, Genetic; D014588:Ustilago / Q000235:genetics / Q000502:physiology* / Q000528:radiation effects*
chemical_list: D024682:BRCA2 Protein; D005656:Fungal Proteins; C088888:REC2 protein, Ustilago maydis; D011994:Recombinant Proteins; D051135:Rad51 Recombinase