Glassner B J, Mortimer R K
Department of Molecular and Cellular Biology, University of California, Berkeley 94720.
Radiat Res. 1994 Jul;139(1):24-33.
Considerable homology has recently been noted between the proteins encoded by the RAD5, RAD16 and RAD54 genes of Saccharomyces cerevisiae. These genes are members of the RAD6, RAD3 and RAD50 epistasis groups, respectively, which correspond to the three major DNA repair pathways in yeast. These proteins also share homology with other eucaryotic proteins, including those encoded by SNF2 and MOT1 of yeast, brahma and lodestar of Drosophila and the human ERCC6 gene. The homology shares features with known helicases, suggesting a newly identified helicase subfamily. We have constructed a series of congenic single-, double- and triple-deletion mutants involving RAD5, RAD16 and RAD54 to examine the interactions between these genes. Each deletion mutation alone has only a moderate effect on survival after exposure to UV radiation. Each pairwise-double mutant exhibits marked synergism. The triple-deletion mutant displays further synergism. These results confirm the assignment of the RAD54 gene to the RAD50 epistasis group and suggest that the RAD16 gene play a larger role in DNA repair after exposure to UV radiation than has been suggested previously. Additionally, the proteins encoded by RAD5, RAD16 and RAD54 may compete for the same substrate after damage induced by UV radiation, possibly at an early step in their respective pathways.
最近发现酿酒酵母的RAD5、RAD16和RAD54基因所编码的蛋白质之间存在相当程度的同源性。这些基因分别是RAD6、RAD3和RAD50上位性群的成员，它们对应于酵母中的三种主要DNA修复途径。这些蛋白质还与其他真核生物蛋白质具有同源性，包括酵母的SNF2和MOT1、果蝇的brahma和lodestar以及人类ERCC6基因所编码的蛋白质。这种同源性与已知的解旋酶具有共同特征，提示存在一个新鉴定的解旋酶亚家族。我们构建了一系列涉及RAD5、RAD16和RAD54的同基因单缺失、双缺失和三缺失突变体，以研究这些基因之间的相互作用。单独的每个缺失突变对紫外线照射后的存活率只有中等程度的影响。每对双突变体都表现出明显的协同作用。三缺失突变体表现出进一步的协同作用。这些结果证实了RAD54基因属于RAD50上位性群，并表明RAD16基因在紫外线照射后的DNA修复中发挥的作用比之前认为的更大。此外，RAD5、RAD16和RAD54所编码的蛋白质可能在紫外线诱导的损伤后竞争相同的底物，可能在其各自途径的早期阶段。
