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GENETICS, GENOMICS, AND MOLECULAR EVOLUTION

A Homolog of ScRAD5 Is Involved in DNA Repair and Homologous Recombination in Arabidopsis^1,[W]

Botanical Institute II, University Karlsruhe, D–76128 Karlsruhe, Germany

Rad5 is the key component in the Rad5-dependent error-free branch of postreplication repair in yeast (Saccharomyces cerevisiae). Rad5 is a member of the Snf2 ATPase/helicase family, possessing as a characteristic feature, a RING-finger domain embedded in the Snf2-helicase domain and a HIRAN domain. Yeast mutants are sensitive to DNA-damaging agents and reveal differences in homologous recombination. By sequence comparisons we were able to identify two homologs (AtRAD5a and AtRAD5b) in the Arabidopsis thaliana genome, sharing about 30% identity and 45% similarity to yeast Rad5. AtRad5a and AtRad5b have the same kind of domain organization with a higher degree of similarity to each other than to ScRad5. Surprisingly, both genes differ in function: whereas two independent mutants of Atrad5a are hypersensitive to the cross-linking agents mitomycin C and cis-platin and to a lesser extent to the methylating agent, methyl methane sulfonate, the Atrad5b mutants did not exhibit any sensitivity to all DNA-damaging agents tested. An Atrad5a/Atrad5b double mutant resembles the sensitivity phenotype of the Atrad5a single mutants. Moreover, in contrast to Atrad5b, the two Atrad5a mutants are deficient in homologous recombination after treatment with the double-strand break-inducing agent bleomycin. Our results suggest that the RAD5-dependent error-free branch of postreplication repair is conserved between yeast and plants, and that AtRad5a might be functionally homologous to ScRad5.

² Present address: Institute for Clinical Neurobiology, University of Wuerzburg, Josef-Schneiderstr. 11, 97080 Wuerzburg, Germany.

³ Present address: Institute of Biology and Genetics, Freie Universitaet Berlin, Arnimallee 7, 14195 Berlin, Germany.

The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: Holger Puchta (holger.puchta{at}bio.uka.de).

^[W] The online version of this article contains Web-only data.

www.plantphysiol.org/cgi/doi/10.1104/pp.108.116806

^* Corresponding author; e-mail holger.puchta{at}bio.uka.de.

Received January 28, 2008; accepted February 25, 2008; published February 29, 2008.