Tanaka K, Matsumoto K, Toh-E A
Department of Fermentation Technology, Hiroshima University, Japan.
Mol Cell Biol. 1989 Feb;9(2):757-68. doi: 10.1128/mcb.9.2.757-768.1989.
A mutation in the gene IRA1 (formerly called PPD1) was originally characterized as a deficiency of a phosphoprotein phosphatase. The IRA1 gene has been cloned and sequenced. A large open reading frame (8,817 base pairs) which can encode a protein of 2,938 amino acids was found. Northern (RNA) blot analysis detected a message of about 10 kilobases, and nuclease S1 protection demonstrated mRNA start points at 97 and 98 base pairs upstream from the putative initiator ATG codon. Disruption of the IRA1 gene resulted in sensitivity to nitrogen starvation and heat shock. Diploids homozygous for the disrupted IRA1 gene were deficient in sporulation. Disruption of the IRA1 gene suppressed the lethality of the cdc25 mutation but did not suppress the lethality of either the ras1 ras2 or the cyr1 mutations. Deficiency of the phosphoprotein phosphatase was not reproducible in the disruption mutant of the IRA1 gene. Moreover, the ira1 mutant showed an increased level of cyclic AMP. Our results suggest that the IRA1 protein inhibits the function of the RAS proteins in a fashion antagonistic to the function of the CDC25 protein in the RAS-cyclic AMP pathway in Saccharomyces cerevisiae.
IRA1基因（以前称为PPD1）中的一种突变最初被表征为一种磷蛋白磷酸酶的缺陷。IRA1基因已被克隆和测序。发现了一个大的开放阅读框（8817个碱基对），它可以编码一个由2938个氨基酸组成的蛋白质。Northern（RNA）印迹分析检测到一条约10千碱基的信息，核酸酶S1保护显示mRNA起始点位于假定起始ATG密码子上游97和98个碱基对处。IRA1基因的破坏导致对氮饥饿和热休克敏感。IRA1基因破坏的纯合二倍体在孢子形成方面存在缺陷。IRA1基因的破坏抑制了cdc25突变的致死性，但没有抑制ras1 ras2或cyr1突变的致死性。在IRA1基因的破坏突变体中，磷蛋白磷酸酶的缺陷无法重现。此外，ira1突变体显示出环磷酸腺苷水平的升高。我们的结果表明，IRA1蛋白以一种与酿酒酵母RAS-环磷酸腺苷途径中CDC25蛋白功能拮抗的方式抑制RAS蛋白的功能。
