DNA damoge checkpoint control in yeast

在真核生物中，ATM和ATR家族蛋白在DNA损伤和复制检查点控制中起关键作用。这些蛋白质的特征在于与磷脂酰肌醇（PI）3-激酶相关的激酶结构域，但具有使蛋白质磷酸化的能力。在芽殖酵母中，ATR家族蛋白Mec 1/Esr 1对于检查点反应和细胞生长是必不可少的。我们已经分离出PIE 1基因在atwo-hybrid屏幕与Mec 1相互作用的蛋白质，并显示PIE 1与Mec 1在体内物理相互作用。与MEC 1一样，PIE 1对细胞生长至关重要，PIE 1基因的缺失会导致DNA损伤和复制阻断检查点的缺陷，类似于在mec 1突变体中观察到的缺陷。在DNA损伤和复制阻断后，在pie 1细胞中的Rad 53过度磷酸化也减少，如在mec 1细胞中所发现的。Pie 1表现出有限的同源性裂变酵母Rad 26形成一个与ATR家族蛋白Rad 3的复合物。Pie 1中与Rad 26同源的区域的突变导致与Pie 1突变的表型相似的表型。Mec 1蛋白激酶活性似乎对检查点反应和细胞生长至关重要。然而，Mec 1激酶活性不受Pie 1突变的影响，这表明Pie 1调节Mec 1激酶活性以外的一些重要功能。因此，Pie 1在结构和功能上与Rad 26相关，并与Mec 1相互作用以控制检查点和细胞增殖。

In eukaryotes, the ATM and ATR family proteins play a critical role in the DNA damage and replication checkpoint controls. These proteins are characterized by a kinase domain related to the phosphatidylinositol (PI) 3-kinase, but have the ability to phosphorylate proteins. In budding yeast, the ATR family protein Mec1/Esr1 is essential for checkpoint responses and cell growth. We have isolated the PIE1 gene in atwo-hybrid screen for proteins that interact with Mec1 and show that Pie1 interacts physically with Mec1 in vivo. Like MEC1, PIE1 is essential for cell growth, and deletion of the PIE1 gene causes defects in the DNA damage and replication block checkpoints similar to those observed in mec1 mutants. Rad53 hyperphosphorylation following DNA damage and replication block is also decreased in pie1 cells as found in mec1 cells. Pie1 exhibits a limited homology to fission yeast Rad26 which forms a complex with the ATR family protein Rad3. Mutaion of the region in Pie1 homologous to Rad26 results in a phenotype similar to that of the pie1 mutation. Mec1 protein kinase activity appears to be essential for checkpoint responses and cell growth. However, Mec1 kinase activity is unaffected by the pie1 mutation, suggesting that Pie1 regulates some essential funtion other than Mec1 kinase activity. Thus, Pie1 is structurally and functionally related to Rad26, and interacts with Mec1 to control checkpoints and cell proliferation.