Genetic analysis of the Neurospora crassa RAD14 homolog mus-43 and the RAD10 homolog mus-44 reveals that they belong to the mus-38 pathway of two nucleotide excision repair systems.
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.
Sato
Masahito
M
Faculty of Life Sciences, Toyo University, Itakura, Oura-gun, Gunma, Japan.
Niki
Takaharu
T
Tokou
Takeru
T
Suzuki
Kouhei
K
Fujimura
Makoto
M
Ichiishi
Akihiko
A
D004249:DNA Damage; D004260:DNA Repair; D004268:DNA-Binding Proteins / Q000235:genetics*; D004720:Endonucleases / Q000235:genetics*; D004843:Epistasis, Genetic; D005656:Fungal Proteins / Q000235:genetics* / Q000378:metabolism; D005800:Genes, Fungal / Q000528:radiation effects; D009153:Mutagens / Q000009:adverse effects; D009154:Mutation; D009492:Neurospora crassa / Q000235:genetics*; D014466:Ultraviolet Rays
D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D009153:Mutagens; D004720:Endonucleases