Hennessy K M, Lee A, Chen E, Botstein D
Department of Genetics, Stanford University, California 94305.
Genes Dev. 1991 Jun;5(6):958-69. doi: 10.1101/gad.5.6.958.
Mutations in the cell-division-cycle genes CDC46 and CDC47 were originally isolated as suppressors of mutations in two other cell-division-cycle genes (CDC45 and CDC54). We found several combinations of mutations in these genes that result in allele-specific suppression and synthetic lethality, confirming that this set of genes forms a group of genetically interacting components. Here, we show that the other genes, like CDC46, are all involved in an early step of DNA replication, possibly initiation of DNA synthesis. Mutants defective in each of the four genes exhibit high rates of mitotic chromosome loss and recombination. The mutants appear also to accumulate chromosome damage that can be detected by a novel chromosome electrophoresis assay. Conditional mutants in this group, under fully nonpermissive conditions, show cell-cycle arrest at the beginning of DNA synthesis; under less stringent conditions, some arrest later, in S-phase. The DNA sequence of the CDC46 gene indicates that the protein is a member of a new family of genes apparently required for DNA initiation, with family members now identified in Saccharomyces cerevisiae, Schizosaccharomyces pombe, and mouse cells.
细胞分裂周期基因CDC46和CDC47中的突变最初是作为另外两个细胞分裂周期基因（CDC45和CDC54）中突变的抑制子被分离出来的。我们发现这些基因中的几种突变组合会导致等位基因特异性抑制和合成致死性，证实这一组基因构成了一组遗传相互作用的成分。在这里，我们表明其他基因，如CDC46，都参与了DNA复制的早期步骤，可能是DNA合成的起始。这四个基因中每个基因有缺陷的突变体都表现出有丝分裂染色体丢失和重组的高发生率。这些突变体似乎也会积累染色体损伤，这可以通过一种新的染色体电泳分析检测到。这一组中的条件突变体在完全非允许条件下，在DNA合成开始时显示细胞周期停滞；在不太严格的条件下，一些突变体在S期后期停滞。CDC46基因的DNA序列表明，该蛋白质是一个显然对DNA起始所需的新基因家族的成员，现在在酿酒酵母、粟酒裂殖酵母和小鼠细胞中都已鉴定出该家族成员。
