Saccharomyces cerevisiae Rad14 and Rad10 proteins are essential for nucleotide excision repair (NER). Rad14 is a UV-damaged DNA binding protein and Rad10 is a structure-specific endonuclease that functions in a complex with Rad1. In this study, we identified and characterized the
RAD14 and
RAD10 homolog genes in
Neurospora crassa, which we named
mus-43 and
mus-44, respectively. Disruption of
mus-43 and
mus-44 conferred sensitivity to UV and 4-nitroquinoline 1-oxide, but not to methyl methanesulfonate,
N-methyl-
N’-nitro-
N-nitrosoguanidine, camptothecin, hydroxyurea, or bleomycin. The
mus-44 mutant was more sensitive to UV than the
mus-43 mutant. Genetic analysis indicated that
mus-43 and
mus-44 are epistatic to
mus-38 which is a homolog of the
S. cerevisiae RAD1, but not to
mus-18 which belongs to a second excision repair pathway. Immunological assays demonstrated that both
mus-43 and
mus-44 retained the ability to excise UV-induced cyclobutane pyrimidine dimers and 6-4 photoproducts, but that excision ability was completely abolished in the
mus-43 mus-18 and
mus-44 mus-18 double mutants. These double mutants exhibited extremely high sensitivity to UV. In
mus-43 and
mus-44 mutants, the UV-induced mutation frequency increased compared to that of the wild-type. The
mus-44 mutants also exhibited a partial photoreactivation defect phenotype similar to
mus-38. These results suggest that both
mus-43 and
mus-44 function in the
mus-38 NER pathway, but not in the
mus-18 excision repair pathway.
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