NOVEL CELLULAR FACTORS INVOLVED IN REGULATION OF BRCA2-DRIVEN HOMOLOGOUS RECOMBINATION IN USTILAGO MAYDIS

Abstract

Homologous recombination (HR) is one of the most accurate mechanisms of preserving genome integrity by precise repair of double strand breaks as the most deleterious type of DNA damage. Mechanisms of HR are mostly studied in yeast which, unlike higher eukaryotes employs RAD52 as a HR mediator, instead of BRCA2. Ustilago maydis is a unicellular phytopathogen characterized by extreme radiation resistance dependent on BRCA2-driven HR. The focus of our research is to uncover novel cellular factors that regulate HR, by isolating suppressors of blm in U. maydis. We have identified 3 new factors of unknown functions, as well as Rad55 and Mph. All mutations suppress HU sensitivity of blm. Presence of truncated proteins caused by point mutations that introduce the specific premature STOP codon and complete deletions of UMAG_01566 and UMAG_01667, both lead to genotoxins sensitivity and altered growth rates on HU to a various extent. Mutation in UMAG_03150 leads to slow growth which can be suppressed by truncated UMAG_01566. Mitotic or meiotic recombination is also affected in some of the mutants. We assume that these novel factors can provide insights into HR regulation, interactions among HR participants and relations to other cellular processes.