Structure and Products of Sporulation Genes in Saccharomyces Cerevisiae

对含有基因座SPOT 7的5.2Kb DNA片段进行测序。一个1039个氨基酸的开放阅读框被鉴定为可能的基因产物（SPOT 7A）。检测到约3.3Kb大小的mRNA。突变体的温度敏感性和基因破坏表明，基因SPOT 7A是生长所必需的。在非允许温度37 ° C下，分裂细胞停滞在细胞周期的M期。在与SPOT 7A基因的3'端编码区重叠的相对链上，通过几种β-半乳糖苷酶融合物的构建，定位了另一个基因SPOT 7 B。SPOT 7 B编码含有36个氨基酸的肽。它只在二倍体细胞的孢子形成培养基中表达。表达发生在减数分裂前DNA合成开始的类似时间。SPOT 7 B的表达在其他几种Spo^-突变体中受到影响，这些突变体在孢子形成的不同早期和晚期被阻断。液泡膜的二维电泳结果表明，SPOT 7A基因产物是液泡膜蛋白的组成部分。用紫外线照射一个同宗配合二倍体菌株的孢子，分离出孢子形成缺陷突变体的染色体DNA。MT 98 a-3D的脉冲场凝胶电泳分析。MT 98 a-3D菌株的III号染色体的DNA大小为450 Kb，而突变体的DNA大小在350 Kb至530 Kb之间变化。在突变体的其他染色体DNA中没有观察到大小的变化。几个实验室储备菌株的染色体III的DNA大小的分析表明，所有的菌株检查，除了MT 98 a-3D，具有约350 KB。染色体III的DNA大小的变化被证明是由紫外线照射孢子携带的450 Kb染色体III的DNA诱导。

A 5.2 Kb DNA fragment containing the gene locus SPOT7 was sequenced. An open reading frame of 1039 amino acids was identified as the possible gene product (SPOT7A). A mRNA of about 3.3 Kb size was detected. The temperature-sensitivity of the mutant and a gene disruption showed that the gene SPOT7A is essential for growth. At the non-permissive temperature 37^ﾟC dividing cells arrest in the M-phase of the cell cycle. On the opposite strand overlapping with the 3' conding region of the SPOT7A gene another gene, SPOT7B, was located by the cnstruction of several beta-galactosidase fusions. SPOT7B codes for a peptide containing 36 amino acids. It is exclusively expressed in sporulation medium in diploid cells. The expression occurs at a similar time when premeiotic DNA synthesis starts. The expression of SPOT7B is affected in several other Spo^- mutants which are blocked at various early and late stages of sporulation. Two dimensional electrophoreis of vacuolar membrane showed that gene products of SPOT7A was a component of vacuolar membrane proteins. The chromosomal DNAs of sporulation-deficient mutants, which were isolated by the ultraviolet-loght irradiation on spores of a homothallic diploid strain. MT98a-3D, of Saccharomyces cerevisiae, were analyzed by a pulsed-field gel electrophoresis. While the DNA size of chromosome III of the strain MT98a-3D was 450 Kb, DNA sizes of mutants varied from 350 Kb to 530 Kb. No variation in a size was observed in other chromosomal DNAs of mutants. An analysis of the DNA size of chromosome III of several laboratory-stock strains showed that all strains examined, except MT98a-3D, possessed about 350 KB. The variation in DNA size of chromosome III was shown to be induced by the ultraviolet-light irradiation on spores carrying the 450 Kb chromosome III DNA.