Genes affecting the expression of cytochrome c in yeast: genetic mapping and genetic interactions.
Genes affecting the expression of cytochrome c in yeast: genetic mapping and genetic interactions.
复制标题
影响酵母中细胞色素 c 表达的基因：遗传作图和遗传相互作用。
作者：
R. Rothstein;F. Sherman
影响酿酒酵母中两种异细胞色素 c 水平的四个突变基因 cyc2、cyc3、cyc8 和 cyc9 已得到表征和定位。 cyc2 和 cyc3 均降低 iso-1-细胞色素 c 和 iso-2-细胞色素 c 的量；而 cyc8 和 cyc9 则增加 iso-2-细胞色素 c 的量。 cyc2、cyc3、cyc8 和 cyc9 基因分别位于染色体 XV、I、II 和 III 上，因此彼此不连锁，并且与 CYC1（iso-1-细胞色素 c 的结构基因）和 CYC7（iso-2-细胞色素 c 的结构基因）不连锁。虽然一些 cyc3 突变体完全或几乎完全缺乏细胞色素 c，但没有一个 cyc2 突变体含有低于亲代细胞色素 c 水平的 10%，尽管超过一半的突变体含有 UAA 或 UAG 无义突变。因此，看起来好像 cyc2 基因产物的完整块仍然允许形成细胞色素 c 的残留部分。即使在 CYC7、cyc8 和 cyc9 存在的情况下，cyc2 和 cyc3 突变基因也会导致缺陷，而 CYC7、cyc8 和 cyc9 通常会导致 iso-2-细胞色素 c 过量产生。我们认为 cyc2 和 cyc3 可能与异细胞色素 c 的调节或成熟有关。除了具有高水平的 iso-2-细胞色素 c 之外，cyc8 和 cyc9 突变体还与絮状细胞和其他异常表型相关。 cyc9 突变体与 tup1 突变体具有等位基因，并具有相同的特性，包括利用外源 dTMP 的能力、特征性絮状形态、纯合二倍体缺乏孢子形成以及 α 菌株交配频率低和形状异常的细胞。不同的异常表明 cyc8 和 cyc9 不是控制 iso-2-细胞色素 c 的简单调节突变体。
The four mutant genes, cyc2, cyc3, cyc8 and cyc9, that affect the levels of the two iso-cytochromes c in the yeast Saccharomyces cerevisiae have been characterized and mapped. Both cyc2 and cyc3 lower the amount of iso-1-cytochrome c and iso-2-cytochrome c; whereas, cyc8 and cyc9 increase the amount of iso-2-cytochrome c. The cyc2, cyc3, cyc8 and cyc9 genes are located, respectively, on chromosomes XV, I, II and III, and are, therefore, unlinked to each other and unlinked to CYC1, the structural gene of iso-1-cytochrome c and to CYC7, the structural gene of iso-2-cytochrome c. While some cyc3 mutants are completely or almost completely deficient in cyotchromes c, none of the cyc2 mutants contained less than 10% of parental level of cytochrome c even though over one-half of the mutants contain UAA or UAG nonsense mutations. Thus, it appears as if a complete block of the cyc2 gene product still allows the formation of a residual fraction of cytochrome c. The cyc2 and cyc3 mutant genes cause deficiencies even in the presence of CYC7, cyc8 and cyc9, which normally cause overproduction of iso-2-cytochrome c. We suggest that cyc2 and cyc3 may be involved with the regulation or maturation of the iso-cytochromes c. In addition to having high levels of iso-2-cytochromes c, the cyc8 and cyc9 mutants are associated with flocculent cells and other abnormal phenotypes. The cyc9 mutant was shown to be allelic with the tup1 mutant and to share its properties, which include the ability to utilize exogenous dTMP, a characteristic flocculent morphology, the lack of sporulation of homozygous diploids and low frequency of mating and abnormally shaped cells of alpha strains. The diverse abnormalities suggest that cyc8 and cyc9 are not simple regulatory mutants controlling iso-2-cytochrome c.