The OPI1 gene of Saccharomyces cerevisiae, a negative regulator of phospholipid biosynthesis, encodes a protein containing polyglutamine tracts and a leucine zipper.
The OPI1 gene of Saccharomyces cerevisiae, a negative regulator of phospholipid biosynthesis, encodes a protein containing polyglutamine tracts and a leucine zipper.
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发表时间：
1991-01
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通讯作者：
M. White;J. Hirsch;S. Henry
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作者：
M. White;J. Hirsch;S. Henry
在酿酒酵母中，OPI 1基因座的隐性突变导致INO 1基因产物肌醇1-磷酸合酶的组成性去抑制表达。许多参与磷脂生物合成的其他酶也在opi 1突变体中以高去抑制水平表达。因此，OPI 1基因被认为是编码负调节子，其需要抑制编码磷脂生物合成酶的结构基因的整个子集。在这项研究中，OPI 1基因定位到染色体VIII和克隆。当转化成opi 1突变体时，克隆的DNA能够补充突变体表型并恢复对INO 1结构基因的正确调控。两个opi 1破坏等位基因的构建和随后的遗传分析的菌株携带这些等位基因证实，克隆的DNA是同源的基因组OPI 1基因座。此外，OPI 1基因被认为是非必需的生物体，因为携带无效等位基因的突变体是可行的，并表现出类似于以前分离的opi 1突变体的表型。与其他opi 1突变体相似，opi 1破坏突变体积累INO 1 mRNA组成型水平比野生型细胞中观察到的高2-3倍。对克隆的OPI 1基因进行测序，翻译开放阅读框预测了由404个氨基酸残基组成的蛋白质，分子量为40，036。预测的Opi 1蛋白含有一个明确定义的亮氨酸残基的七肽重复序列，这在其他调节蛋白中也观察到。此外，预测的蛋白质含有多聚谷氨酰胺残基的延伸，这也已被报道在酵母基因具有调节功能。化学诱变后分离的opi 1突变等位基因的测序显示，有几个是位于最大的聚谷氨酰胺残基延伸的链终止突变的结果。
In Saccharomyces cerevisiae, recessive mutations at the OPI1 locus result in constitutively derepressed expression of inositol 1-phosphate synthase, the product of the INO1 gene. Many of the other enzymes involved in phospholipid biosynthesis are also expressed at high derepressed levels in opi1 mutants. Thus, the OPI1 gene is believed to encode a negative regulator that is required to repress a whole subset of structural genes encoding for phospholipid biosynthetic enzymes. In this study, the OPI1 gene was mapped to chromosome VIII and cloned. When transformed into an opi1 mutant, the cloned DNA was capable of complementing the mutant phenotype and restoring correct regulation to the INO1 structural gene. Construction of two opi1 disruption alleles and subsequent genetic analysis of strains bearing these alleles confirmed that the cloned DNA was homologous to the genomic OPI1 locus. Furthermore, the OPI1 gene was found to be nonessential to the organism since mutants bearing the null allele were viable and exhibited a phenotype similar to that of previously isolated opi1 mutants. Similar to other opi1 mutants, the opi1 disruption mutants accumulated INO1 mRNA constitutively to a level 2-3-fold higher than that observed in wild-type cells. The cloned OPI1 gene was sequenced, and translation of the open reading frame predicted a protein composed of 404 amino acid residues with a molecular weight of 40,036. The predicted Opi1 protein contained a well defined heptad repeat of leucine residues that has been observed in other regulatory proteins. In addition, the predicted protein contained polyglutamine residue stretches which have also been reported in yeast genes having regulatory functions. Sequencing of opi1 mutant alleles, isolated after chemical mutagenesis, revealed that several were the result of a chain termination mutation located within the largest polyglutamine residue stretch.