Abstract:Genome analyses suggested that archaea could possess a eukaryotictype nucleotide excision repair (NER) pathway because they encode homologs of several eukaryotic NER proteins.To investigate the archaeal nucleotide excision repair pathway in vivo,the genes encoding the potential NER helicases in the genome of the hyperthermophilic crenarchaeon Sulfolobus islandicus were deleted via a gene knockout strategy and deletion mutants of the xpb1 and xpb2 genes were isolated,indicating that they were not essential to the survival of S. islandicus.Phenotypic analysis of deletion mutants showed that the xpb1 mutant was only slightly sensitive to 4NQO,as compared with the wildtype strain REY15A,while the xpb2 mutant showed no sensitivity to 4NQO.It is the first genetic study of the crenarchaeon NER pathway.