Identification of a Novel HumanRAD51Homolog,RAD51B

The highly conservedSaccharomyces cerevisiaeRAD51 protein functions in both mitotic and meiotic homologous recombination and in double-strand break repair. Screening of the public cDNA sequence database forRAD51-like genes led to the identification of a partial sequence from a breast tissue library present in the I.M.A.G.E. (Integrated Molecular Analysis of Genes and their Expression) collection. An extended 1764-bp cDNA clone encoding an open reading frame of 350 amino acids was isolated. This clone showed significant amino acid identity with other human RAD51 homologs. The new homolog, namedRAD51B,was mapped to human chromosome 14q23–q24.2 using a panel of human–hamster somatic cell hybrids and fluorescencein situhybridization. Northern blot analysis demonstrated thatRAD51BmRNA is widely expressed and most abundant in tissues active in recombination. Functions associated with known RAD51 homologs suggest a role for RAD51B in meiotic recombination and/or recombinational repair.