Homologous Recombination, but Not DNA Repair, Is Reduced in Vertebrate Cells Deficient in RAD52 |
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| Authors: | Yuko Yamaguchi-Iwai Eiichiro Sonoda Jean-Marie Buerstedde Olga Bezzubova Ciaran Morrison Minoru Takata Akira Shinohara and Shunichi Takeda |
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| Institution: | Bayer-chair Department of Molecular Immunology and Allergology, Faculty of Medicine, Kyoto University, Konoe Yoshida, Sakyo-ku, Kyoto 606-8501,1. and Department of Biology, Faculty of Science, Osaka University, Toyonaka, Osaka 560-0043,3. Japan, and Basel Institute for Immunology, CH-4005 Basel, Switzerland2. |
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| Abstract: | Rad52 plays a pivotal role in double-strand break (DSB) repair and genetic recombination in Saccharomyces cerevisiae, where mutation of this gene leads to extreme X-ray sensitivity and defective recombination. Yeast Rad51 and Rad52 interact, as do their human homologues, which stimulates Rad51-mediated DNA strand exchange in vitro, suggesting that Rad51 and Rad52 act cooperatively. To define the role of Rad52 in vertebrates, we generated RAD52−/− mutants of the chicken B-cell line DT40. Surprisingly, RAD52−/− cells were not hypersensitive to DNA damages induced by γ-irradiation, methyl methanesulfonate, or cis-platinum(II)diammine dichloride (cisplatin). Intrachromosomal recombination, measured by immunoglobulin gene conversion, and radiation-induced Rad51 nuclear focus formation, which is a putative intermediate step during recombinational repair, occurred as frequently in RAD52−/− cells as in wild-type cells. Targeted integration frequencies, however, were consistently reduced in RAD52−/− cells, showing a clear role for Rad52 in genetic recombination. These findings reveal striking differences between S. cerevisiae and vertebrates in the functions of RAD51 and RAD52. |
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