Cyert M S, Kunisawa R, Kaim D, Thorner J
Department of Molecular and Cell Biology, University of California, Berkeley 94720.
Proc Natl Acad Sci U S A. 1991 Aug 15;88(16):7376-80. doi: 10.1073/pnas.88.16.7376.
Calcineurin, or phosphoprotein phosphatase type 2B (PP2B), is a calmodulin-regulated phosphoprotein phosphatase. We isolated a gene encoding a yeast PP2B homolog (CNA1) by screening a yeast genomic DNA library in the expression vector lambda gt11, first with 125I-labeled yeast calmodulin and then with a human cDNA encoding the catalytic (or A) subunit of calcineurin. The predicted CNA1 gene product is 54% identical to its mammalian counterpart. Using the polymerase chain reaction (PCR) with oligonucleotide primers based on sequences conserved between CNA1 and mammalian PP2B genes, we isolated a second gene, CNA2. CNA2 is identical to PP2Bw, a partial cDNA clone previously described by others as originating from rabbit brain tissue. Our findings demonstrate that a unicellular eukaryote contains phosphoprotein phosphatases of the 2B class. Haploid cells containing a single cna1 or cna2 null mutation, or both mutations, were viable. MATa cna1 cna2 double mutants were more sensitive than wild-type cells or either single mutant to growth arrest induced by the mating pheromone alpha factor and failed to resume growth during continuous exposure to alpha factor. Thus, calcineurin action antagonizes the mating-pheromone response pathway.
钙调神经磷酸酶，即2B型磷蛋白磷酸酶（PP2B），是一种受钙调蛋白调节的磷蛋白磷酸酶。我们通过在表达载体λgt11中筛选酵母基因组DNA文库来分离编码酵母PP2B同源物（CNA1）的基因，首先用125I标记的酵母钙调蛋白进行筛选，然后用编码钙调神经磷酸酶催化（或A）亚基的人cDNA进行筛选。预测的CNA1基因产物与其哺乳动物对应物有54%的同一性。利用基于CNA1和哺乳动物PP2B基因之间保守序列的寡核苷酸引物进行聚合酶链反应（PCR），我们分离出了第二个基因CNA2。CNA2与PP2Bw相同，PP2Bw是先前其他人描述的一个部分cDNA克隆，源自兔脑组织。我们的研究结果表明，单细胞真核生物含有2B类磷蛋白磷酸酶。含有单个cna1或cna2无效突变或同时含有这两种突变 的单倍体细胞是有活力的。MATa cna1 cna2双突变体比野生型细胞或任何一种单突变体对交配信息素α因子诱导的生长停滞更敏感，并且在持续暴露于α因子期间无法恢复生长。因此，钙调神经磷酸酶的作用拮抗交配信息素反应途径。
