Watanabe K, Sakuraba Y, Inoue H
Department of Regulation Biology, Faculty of Science, Saitama University, Urawa, Japan.
Mol Gen Genet. 1997 Oct;256(4):436-45. doi: 10.1007/s004380050587.
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.
一种新分离出的粗糙脉孢菌突变体mus-23，被发现对多种诱变剂高度敏感，包括紫外线、甲基磺酸甲酯、4-硝基喹啉-1-氧化物、N-甲基-N'-硝基-N-亚硝基胍和叔丁基过氧化氢。该突变体最初是作为一种不能在含有组氨酸的培养基上生长的突变体分离出来的。在mus-23单倍体之间的纯合杂交中，减数分裂和孢子形成存在缺陷。mus-23基因位于LGII右臂上，在fl和trp-3之间。对mus-23与其他导致DNA修复缺陷的突变之间的上位性分析表明，mus-23基因与mei-3属于同一DNA修复组，mei-3是酿酒酵母基因RAD51的粗糙脉孢菌同源物。携带mus-23和uvs-3突变的双突变体是致死的。通过互补mus-23突变体对甲基磺酸甲酯敏感的表型克隆了mus-23基因。该基因包含一个1578 bp的开放阅读框，且不包含任何内含子。预测的mus-23基因产物的分子量为60.4 kDa。计算机分析显示，MUS23蛋白与已知参与酿酒酵母重组修复的Mre11p具有显著同源性。在用紫外线或甲基磺酸甲酯处理60分钟内，mus-23转录本水平显著增加，然后逐渐下降。文中讨论了MUS23蛋白在重组修复中的作用。
