ENZYMES INVOLVED IN DNA REPAIR AND MEIOSIS

从DNA修复和重组的研究中，很明显核酸酶 在这两个过程中发挥重要作用。 In S.酿酒酵母RAD 52 该基因是修复DNA双链断裂、有丝分裂 重组和减数分裂的成功完成。 A 72 kD 已经鉴定了核酸酶（RhoNUC）并随后纯化。 在rad 52中 突变体，RhoNuc的水平大大降低，这表明， 核酸酶在RAD 52的控制下。 编码RhoNUC的基因已经被 克隆和序列测定 OFAGE分析将编码RhoNUC的基因 （RNC 1）位于染色体Xi上。检验由以下推导出的一级序列： DNA序列显示RhoNUC是嵌合蛋白。 n-末端 该蛋白的区域与ras/rho具有高度同源性， GTP结合蛋白超家族，而C末端似乎编码 蛋白质的核酸酶部分。 这种蛋白质被命名为 RhoNUC是rho相关核酸酶。 通过利用RNC 1：：lacZ融合 在含有野生型RAD 52基因或 由于RAD 52的完全缺失，似乎RAD 52对RhoNUC的控制 是翻译后的。 RNC 1基因的过表达没有产生可观察到的 表型。 然而，携带RNC 1和RAD 52两者缺失的菌株具有 直接重复重组的接近野生型水平， 质粒上或染色体上（仅携带RAD 52缺失的菌株 表现出比野生型低约100倍的重组水平）。 根据这些观察，我们认为RhoNUC代表了一种新的 鉴定出的一类蛋白质既表现出细胞信号传导功能， G蛋白活性）和DNA代谢活性（核酸酶活性 参与重组）。

From studies of DNA repair and recombination, it is apparent that nucleases play a major role in both of these processes. In S. cerevisiae the RAD52 gene is essential for the repair of DNA double-strand breaks, mitotic recombination and for the successful completion of meiosis. A 72 kD nuclease (RhoNUC) has been identified and subsequently purified. In rad52 mutants, levels of RhoNuc are greatly decreased suggesting that this nuclease is under the control of RAD52. The gene encoding RhoNUC has been cloned and sequenced. OFAGE analysis places the gene encoding RhoNUC (RNC1) on chromosome XI. Examination of the deduced primary sequence from the DNA sequence reveals that RhoNUC is a chimeric protein. The N-terminal region of the protein shares a high degree of homology with the ras/rho superfamily of GTP binding proteins while the C-terminal appears to encode the nuclease portion of the protein. Hence, this protein has been named RhoNUC for rho-associated nuclease. By utilizing a RNC1::lacZ fusion construct in strains that either contain a wild type RAD52 gene or a complete deletion of RAD52, it appears that the control of RhoNUC by RAD52 is post-translational. Overexpression of RNC1 gene yields no observable phenotype. However, strains carrying deletions of both RNC1 and RAD52 have nearly wild-type levels of direct repeat recombination when measured either on plasmids or on the chromosome (strains carrying only a deletion of RAD52 exhibit recombination levels approximately 100-fold lower than wild-type). From these observations, we believe that RhoNUC represents a newly identified class of proteins exhibiting both a cellular signalling function (G-protein activity) and a DNA metabolic activity (nuclease activity involved in recombination).