Tounekti Kaouther, Aouida Mustapha, Leduc Anick, Poschmann Jeremie, Yang Xiaoming, Belhadj Omrane, Ramotar Dindial
Laboratoire de Biochimie et de Biotechnologie, Faculte des Sciences de Tunis, Université Tunis El-Manar, Tunis, Tunisia.
Environ Mol Mutagen. 2006 Dec;47(9):707-17. doi: 10.1002/em.20260.
The Saccharomyces cerevisiae SPT10 protein possesses a DNA-binding domain that is fused to a putative histone acetyltransferase domain. It binds specifically to upstream-activating sequence elements in the core histone promoters and plays a direct role in histone gene regulation. SPT10 is also required for cell-cycle-specific K56 acetylation at histone genes, allowing the recruitment of the nucleosome remodeling factor Snf5 and subsequent regulation of gene transcription. We reisolated the SPT10 gene in a functional genome-wide screen designed to identify haploid yeast mutants that are hypersensitive to the antitumor drug bleomycin, which acts by damaging DNA. In addition to bleomycin, we show that spt10Delta mutants are also hypersensitive to a limited set of genotoxic agents that create DNA strand breaks, but not to 254-nm ultraviolet light or 4-nitroquinoline-1-oxide, which generate helix distortion. The hypersensitivities of the spt10Delta mutant to the genotoxic agents are rescued by a single copy plasmid carrying the SPT10 gene. We further showed that spt10Delta mutants displayed a modest twofold increase spontaneous mutant frequency, as compared to the parent. Following exposure to bleomycin, these mutants accumulate unrepaired lesions, e.g., DNA strand breaks with blocked 3'-ends in the chromosomal DNA. This defect is not due to the altered expression level or the enzymatic activities of a key DNA repair enzyme, APN1, which is known to repair DNA strand breaks with blocked ends. We propose that SPT10 mediates repair of a subset of DNA lesions by acetylating histones to promote recruitment of DNA repair enzymes.
酿酒酵母SPT10蛋白拥有一个与假定的组蛋白乙酰转移酶结构域融合的DNA结合结构域。它特异性结合核心组蛋白启动子中的上游激活序列元件，并在组蛋白基因调控中发挥直接作用。SPT10对于组蛋白基因上细胞周期特异性的K56乙酰化也是必需的，这使得核小体重塑因子Snf5能够被招募并随后调控基因转录。我们在一个全基因组功能筛选中重新分离出了SPT10基因，该筛选旨在鉴定对通过损伤DNA起作用的抗肿瘤药物博来霉素敏感的单倍体酵母突变体。除了博来霉素，我们还表明spt10Δ突变体对一组有限的产生DNA链断裂的基因毒性试剂也敏感，但对产生螺旋扭曲的254纳米紫外线或4-硝基喹啉-1-氧化物不敏感。携带SPT10基因的单拷贝质粒可挽救spt10Δ突变体对基因毒性试剂的敏感性。我们进一步表明，与亲本相比，spt10Δ突变体的自发突变频率适度增加了两倍。暴露于博来霉素后，这些突变体积累了未修复的损伤，例如染色体DNA中3'-末端被阻断的DNA链断裂。这种缺陷并不是由于关键DNA修复酶APN1的表达水平改变或酶活性改变，已知APN1可修复末端被阻断的DNA链断裂。我们提出，SPT10通过乙酰化组蛋白以促进DNA修复酶的招募来介导一部分DNA损伤的修复。
