Miyake S, Yamashita S
Department of Biochemistry, Toho University School of Medicine, Tokyo, Japan.
Genes Cells. 1998 Mar;3(3):157-66. doi: 10.1046/j.1365-2443.1998.00177.x.
The replication licensing factor limits DNA replication to once in a cell cycle and is thought to contain MCM proteins as its component parts. Six MCM subtypes have been identified in various species. These MCM proteins are thought to bind each other to make a heteromeric complex. The Nda4 protein of Schizosaccharomyces pombe is one of the MCM proteins and is involved in DNA replication.
The suppressor mutant of nda4 was isolated and the mutant gene was named sna41. The sna41-912 mutant demonstrated the ts phenotype, with an elongated cell shape at the restrictive temperature. Cells with 1C DNA content accumulated 2 h after shifting up to the restrictive temperature. This result suggests that sna41 is also involved in DNA replication. The sna41 genomic clone was isolated by a complementation of the ts phenotype of the mutant strain and was sequenced. The sna41 gene encodes a protein of 638 amino acids, which has low homology with CDC45 in S. cerevisiae. The gene disruption analysis showed that sna41 gene is essential for viability.
The S. pombe sna41 mutation suppresses the nda4-108 mutation. Sna41 is involved in DNA replication and may play some roles in the regulation of DNA replication by the MCM proteins.
复制许可因子将DNA复制限制在一个细胞周期内进行一次，并且被认为包含MCM蛋白作为其组成部分。在各种物种中已鉴定出六种MCM亚型。这些MCM蛋白被认为相互结合形成异源复合物。粟酒裂殖酵母的Nda4蛋白是MCM蛋白之一，参与DNA复制。
分离出nda4的抑制突变体，并将突变基因命名为sna41。sna41-912突变体表现出温度敏感型（ts）表型，在限制温度下细胞形状拉长。在转移到限制温度2小时后，积累了1C DNA含量的细胞。该结果表明sna41也参与DNA复制。通过对突变菌株的ts表型进行互补分离出sna41基因组克隆并进行测序。sna41基因编码一种638个氨基酸的蛋白质，与酿酒酵母中的CDC45具有低同源性。基因敲除分析表明sna41基因对生存力至关重要。
粟酒裂殖酵母sna41突变抑制nda4-108突变。Sna41参与DNA复制，可能在MCM蛋白对DNA复制的调控中发挥某些作用。
