The Arabidopsis UVH1 Gene Is a Homolog of the Yeast Repair Endonuclease RAD1

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Abstract
Ultraviolet radiation induces DNA damage products, largely in the form of pyrimidine dimers, that are both toxic and mutagenic. In most organisms, including Arabidopsis, these lesions are repaired both through a dimer-specific photoreactivation mechanism and through a less efficient light-independent mechanism. Several mutants defective in this “dark repair” pathway have been previously described. The mechanism of this repair has not been elucidated, but is thought to be homologous to the nucleotide excision repair mechanisms found in other eukaryotes. Here we report the complementation of the Arabidopsisuvh1 dark repair mutant with the Arabidopsis homolog of the yeast nucleotide excision repair gene RAD1, which encodes one of the subunits of the 5′-repair endonuclease. Theuvh1-2 mutant allele carries a glycine→aspartate amino acid change that has been previously identified to produce a null allele of RAD1 in yeast. Although Arabidopsis homologs of genes involved in nucleotide excision repair are readily identified by searching the genomic database, it has not been established that these homologs are actually required for dark repair in plants. The complementation of the Arabidopsisuvh1 mutation with the Arabidopsis RAD1homolog clearly demonstrates that the mechanism of nucleotide excision repair is conserved among the plant, animal, and fungal kingdoms.