Ž . Mutation Research 435 1999 13–21 www.elsevier.comrlocaterdnarepair Community address: www.elsevier.comrlocatermutres Minireview Rad51rRecA protein families and the associated proteins in eukaryotes Akira Shinohara a,b, ) , Tomoko Ogawa c,1 a Department of Radiation and Cellular Oncology, UniÕersity of Chicago, Chicago, IL 60637, USA b Department of Biology, Graduate School of Science, Osaka UniÕersity, Toyonaka, Osaka 560-0045, Japan c Department of Cell Genetics, National Institute of Genetics, Mishima, Shizuoka 411-8540, Japan Accepted 13 May 1999 Keywords: Recombination; DNA repair; Rad51; Rad51-binding proteins 1. Overview Searching for homologous DNA molecules, pair- ing of the molecules and exchange of the strand with one of a counterpart duplex molecule are a central process for homologous recombination. RecA pro- tein in Esherichia coli has been known to play a pivotal role in the processes. The recA gene was identified by A.J. Clark and his colleagues more than wx 30 years ago 1 and the first biochemical activities of the protein were described in 1978 by Roberts et wx wx al. 2 and Ogawa et al. 3 independently. Since then, the RecA protein has been the main focus in w x the field studying recombination 4,5 . The RecA Ž . protein binds to single-stranded DNA ssDNA in the presence of a high-energy nucleotide cofactor such as ATP and forms a typical right-handed helical ) Corresponding author. Department of Radiation and Cellular Oncology, University of Chicago, Chicago, IL 60637, USA. Tel.: q 1-773-834-3633; fax: q 1-773-702-1968: E-mail: ashinoha@midway.uchicago.edu 1 Also corresponding author. Tel.: q81-559-81-6881; fax: q81-559-81-6884; E-mail: tomogawa@lab.nig.ac.jp. filament, in which the DNA strand is extended 1.5– 1.6 times compared with B-form DNA. This struc- ture called a nucleoprotein filament or a pre-synaptic filament is essential for recombination and the repair of damaged DNA. The filament also promotes the auto-cleavage of LexA repressor protein, resulting in the de-repression of LexA-regulated genes, called SOS genes. After the finding of RecA activities, eukaryotic enzymes that have similar activity to the RecA pro- wx tein had been identified biochemically 5 , but no genes that encode the identified protein had not shown to be required for recombination and also the repair of DNA damage. In contrast, we searched the mutant that shows similar phenotypes as E. coli recA mutant among rad mutants of Saccharomyces cere- Õisiae, which are defective in the DNA repair. The RAD52 gene was a primary focus as a candidate since the rad52 mutant shows the most severe de- wx wx fects in recombination 6 , and later, RAD51 7. However, the amino acid sequence of Rad52 protein was very different from that of RecA. In 1992, two recA homologues, RAD51 and DMC1, of S. cere- w x Õisiae were identified 7,8 . The RAD51 gene was isolated to complement a radiation-sensitivity of the rad51-1 mutant, which is also defective in both 0921-8777r99r$ - see front matter q 1999 Elsevier Science B.V. All rights reserved. Ž . PII: S0921-8777 99 00033-6