Two isoforms of plant RAD23 complement a UV-sensitive rad23 mutant in yeast

DNA repair by nucleotide excision (NER) has been demonstrated in plant cells at the biochemical level but until now none of the molecular components of the plant NER complex has been identified. In this paper, the cloning and characterization of two isoforms of RAD23 from carrot (Daucus carota L.) are reported. It has been suggested that RAD23 in yeast is an assembly factor of the NER complex required for transcription-coupled repair as well as efficient overall genome repair. A functional assay demonstrated that both plant homologues complement the UV-sensitive phenotype of a rad23 deletion mutant of yeast. This result suggests that homologous polypeptides may catalyse NER in plants and yeast and, possibly, by a similar mechanism.