在紫外线照射的酿酒酵母中,Swi2/Snf2家族成员Rad26的过表达增加了转录偶联修复以及非转录链的修复。

In UV-irradiated Saccharomyces cerevisiae, overexpression of Swi2/Snf2 family member Rad26 increases transcription-coupled repair and repair of the non-transcribed strand.

作者信息

Bucheli Miriam, Sweder Kevin

机构信息

Program in Microbiology and Molecular Genetics, Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey, NJ, USA.

出版信息

Mol Microbiol. 2004 Jun;52(6):1653-63. doi: 10.1111/j.1365-2958.2004.04081.x.

Abstract

Nucleotide excision repair (NER) in eukaryotes is a pathway conserved from yeast to humans that removes many bulky chemical adducts and UV-induced photoproducts from DNA in a relatively error-free manner. In addition to the recognition and excision of DNA damage throughout the genome (GGR), there exists a mechanism, transcription-coupled nucleotide excision repair (TCR), for recognizing some types of DNA damage in the transcribed strand of genes in Escherichia coli, yeast and mammalian cells. An obstacle in the repair of the transcribed strand of active genes is the RNA polymerase complex stalled at sites of DNA damage. The stalled RNA polymerase complex may then mediate recruitment of repair proteins to damage in the transcribed strand. Proteins enabling TCR are the Cockayne syndrome B (CSB) protein in humans and its yeast homologue Rad26. Both CSB and Rad26 belong to the Swi2/Snf2 family of DNA-dependent ATPases, which change DNA accessibility to proteins by altering chromatin structure. To address how Rad26 functions in yeast repair, we used the genetic approach of overexpressing Rad26 and examined phenotypic changes, i.e. changes in NER. We found that repair of both the transcribed and the non-transcribed strands is increased. In addition, overexpression of Rad26 partially bypasses the requirement for Rad7 in GGR, specifically in the repair of non-transcribed sequences. As TCR takes place in very localized regions of DNA (i.e. within genes) in wild-type cells, we propose that overexpression of recombinant Rad26 increases accessibility of the damaged DNA in chromatin for interaction with repair proteins.

摘要

真核生物中的核苷酸切除修复(NER)是一条从酵母到人类都保守的途径,它能以相对无差错的方式从DNA中去除许多大分子化学加合物和紫外线诱导的光产物。除了识别和切除全基因组中的DNA损伤(GGR)外,在大肠杆菌、酵母和哺乳动物细胞中还存在一种机制,即转录偶联核苷酸切除修复(TCR),用于识别基因转录链中的某些类型的DNA损伤。修复活跃基因转录链的一个障碍是RNA聚合酶复合物在DNA损伤位点处停滞。停滞的RNA聚合酶复合物随后可能介导修复蛋白募集到转录链中的损伤处。参与TCR的蛋白质在人类中是科凯恩综合征B(CSB)蛋白,在酵母中是其同源物Rad26。CSB和Rad26都属于依赖DNA的ATP酶的Swi2/Snf2家族,它们通过改变染色质结构来改变DNA对蛋白质的可及性。为了研究Rad26在酵母修复中的功能,我们采用了过表达Rad26的遗传学方法,并检查了表型变化,即NER的变化。我们发现转录链和非转录链的修复都增加了。此外,Rad26的过表达部分绕过了GGR中对Rad7的需求,特别是在非转录序列的修复中。由于TCR在野生型细胞的DNA非常局部的区域(即基因内)发生,我们提出重组Rad26的过表达增加了染色质中受损DNA与修复蛋白相互作用的可及性。

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