Coe J G, Murray L E, Dawes I W
School of Biochemistry and Molecular Genetics, University of New South Wales, Sydney, Australia.
Mol Gen Genet. 1994 Sep 28;244(6):661-72. doi: 10.1007/BF00282757.
Promoters that control gene expression in Saccharomyces cerevisiae only in a sporulation-specific manner have previously been isolated from a genomic yeast DNA library fused to a promoterless Escherichia coli lacZ gene. Two novel sporulation-specific genes, SPS18 and SPS19, were isolated using this technique. These genes are divergently controlled by the same promoter but with SPS18 expressed at four times the level of SPS19. Deletion analysis has shown that the promoter elements that exert sporulation control on each of the genes overlap, having a common 25 bp sequence located within the intergenic region. SPS18 encodes a 34-KDa protein of 300 amino acids that contains a putative zinc-binding domain and a region of highly basic residues that could target the protein to the nucleus. SPS19 encodes a 31-KDa protein of 295 amino acids, which has a peroxisomal targeting signal (SKL) at its C terminus; this protein belongs to the family of non-metallo short-chain alcohol dehydrogenases. A null mutation deleting the intergenic promoter prevented expression of both genes, and when homozygous in diploids, reduced the extent of sporulation four-fold; the spores that did form were viable, but failed to become resistant to ether, and were more sensitive to lytic enzymes. This phenotype reflects a defect in spore wall maturation, indicating that the product of at least one of the genes functions during the process of spore wall formation. Therefore these genes belong to the class of late sporulation-specific genes that are sequentially activated during the process of meiosis and spore formation.
以前已经从与无启动子的大肠杆菌lacZ基因融合的基因组酵母DNA文库中分离出仅以孢子形成特异性方式控制酿酒酵母基因表达的启动子。利用该技术分离出两个新的孢子形成特异性基因SPS18和SPS19。这些基因由同一个启动子反向控制，但SPS18的表达水平是SPS19的四倍。缺失分析表明，对每个基因施加孢子形成控制的启动子元件重叠，在基因间区域内有一个共同的25 bp序列。SPS18编码一个由300个氨基酸组成的34 kDa蛋白质，该蛋白质含有一个假定的锌结合结构域和一个可将该蛋白质靶向细胞核的高碱性残基区域。SPS19编码一个由295个氨基酸组成的31 kDa蛋白质，其C末端有一个过氧化物酶体靶向信号（SKL）；该蛋白质属于非金属短链醇脱氢酶家族。缺失基因间启动子的无效突变阻止了两个基因的表达，当在二倍体中纯合时，孢子形成的程度降低了四倍；形成的孢子是有活力的，但对乙醚没有抗性，并且对裂解酶更敏感。这种表型反映了孢子壁成熟的缺陷，表明至少其中一个基因的产物在孢子壁形成过程中起作用。因此，这些基因属于在减数分裂和孢子形成过程中被顺序激活的晚期孢子形成特异性基因类别。
