Kelly Maire K, Jauert Peter A, Jensen Linnea E, Chan Christine L, Truong Chinh S, Kirkpatrick David T
Department of Genetics, Cell Biology and Development, University of Minnesota, Minneapolis, Minnesota 55455, USA.
Genetics. 2007 Dec;177(4):2469-79. doi: 10.1534/genetics.107.077636.
Repetitive minisatellite DNA tracts are stable in mitotic cells but unstable in meiosis, altering in repeat number and repeat composition. As relatively little is known about the factors that influence minisatellite stability, we isolated mutations that destabilize a minisatellite repeat tract in the ADE2 gene of Saccharomyces cerevisiae. One mutant class exhibited a novel color segregation phenotype, "blebbing," characterized by minisatellite instability during stationary phase. Minisatellite tract alterations in blebbing strains consist exclusively of the loss of one 20-bp repeat. Timing experiments suggest that these tract alterations occur only after cells have entered stationary phase. Two complementation groups identified in this screen have mutations in either the high-affinity zinc transporter ZRT1 or its zinc-dependent transcriptional regulator ZAP1. The Deltazrt1 mutant specifically affects the stability of minisatellite tracts; microsatellites or simple insertions in the ADE2 reading frame are not destabilized by loss of ZRT1. The Deltazrt1 blebbing phenotype is partially dependent on a functional RAD50. Zinc is known for its role as an essential cofactor in many DNA-binding proteins. We describe possible models by which zinc can influence minisatellite stability. Our findings directly implicate zinc homeostasis in the maintenance of genomic stability during stationary phase.
重复小卫星DNA序列在有丝分裂细胞中是稳定的，但在减数分裂中不稳定，其重复次数和重复组成会发生改变。由于对影响小卫星稳定性的因素了解相对较少，我们分离出了使酿酒酵母ADE2基因中的小卫星重复序列不稳定的突变。一类突变体表现出一种新的颜色分离表型，即“起泡”，其特征是在稳定期小卫星不稳定。起泡菌株中的小卫星序列改变仅包括一个20碱基对重复序列的缺失。时间实验表明，这些序列改变仅在细胞进入稳定期后才会发生。在此筛选中鉴定出的两个互补组在高亲和力锌转运蛋白ZRT1或其锌依赖性转录调节因子ZAP1中存在突变。Δzrt1突变体特异性地影响小卫星序列的稳定性；ADE2阅读框中的微卫星或简单插入不会因ZRT1的缺失而不稳定。Δzrt1起泡表型部分依赖于功能性的RAD50。锌作为许多DNA结合蛋白中的必需辅因子而闻名。我们描述了锌可能影响小卫星稳定性的模型。我们的发现直接表明锌稳态在稳定期基因组稳定性的维持中起作用。
