Genetic and molecular characterization of Neurospora crassa mus-23: a gene involved in recombinational repair.
A newly isolated mutant, mus-23, of Neurospora crassa was found to be highly sensitive to a wide variety of mutagens, including UV light, methyl methanesulfonate, 4-nitroquinoline 1-oxide, N-methyl-N'-nitro-N-nitrosoguanidine and tert-butyl hydroperoxide. This mutant was originally isolated as a mutant that could not grow on medium containing histidine. Meiosis and sporulation were defective in homozygous crosses between mus-23 haploids. The mus-23 gene is located on the right arm of LGII, between fl and trp-3. Analyses of epistasis between mus-23 and other mutations that cause defects in DNA repair indicated that the mus-23 gene belongs to the same DNA repair group as mei-3, which is the Neurospora homolog of the Saccharomyces cerevisiae gene RAD51. The double mutant carrying mus-23 and uvs-3 mutations was lethal. The mus-23 gene was cloned by complementation of the MMS-sensitive phenotype of the mus-23 mutant. The gene contained an open reading frame of 1578 bp and did not contain any introns. The molecular weight of the predicted mus-23 gene product was 60.4 kDa. Computer analyses revealed that the MUS23 protein has significant homology to Mre11p, which is known to be involved in recombinational repair in S. cerevisiae. The level of mus-23 transcripts increased significantly within 60 min of treatment with UV or MMS and then gradually decreased. The role of MUS23 protein in recombinational repair is discussed.
Watanabe
K
K
Department of Regulation Biology, Faculty of Science, Saitama University, Urawa, Japan.
Sakuraba
Y
Y
Inoue
H
H
D000595:Amino Acid Sequence; D001483:Base Sequence; D003001:Cloning, Molecular; D004260:DNA Repair; D004271:DNA, Fungal; D004843:Epistasis, Genetic; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D015966:Gene Expression Regulation, Fungal; D005800:Genes, Fungal; D008969:Molecular Sequence Data; D009153:Mutagens / Q000494:pharmacology; D009154:Mutation; D009492:Neurospora crassa / Q000187:drug effects / Q000235:genetics* / Q000528:radiation effects; D011995:Recombination, Genetic; D017386:Sequence Homology, Amino Acid
D004271:DNA, Fungal; D005656:Fungal Proteins; C109530:MUS-23 protein, Neurospora crassa; D009153:Mutagens