Human MSH2 binds to trinucleotide repeat DNA structures associated with neurodegenerative diseases
Human MSH2 binds to trinucleotide repeat DNA structures associated with neurodegenerative diseases
复制标题
DOI：
10.1093/hmg/6.7.1117
复制
发表时间：
1997-07-01
影响因子：
3.5
通讯作者：
Sinden, RR
中科院分区：
文献类型：
--
作者：
Pearson, CE;Ewel, A;Sinden, RR
三核苷酸重复序列的扩增与几种神经退行性疾病有关。这种扩增的机制尚不清楚，但可能涉及到三核苷酸重复序列的相邻而非完美互补序列成对的滑链结构。在这里，我们研究了人类错配修复蛋白MSH2与由三联体重复序列形成的滑链结构的相互作用，以解决MSH2在三核苷酸扩增中的可能作用。我们检测了包含疾病相关长度（CTG）(n).(CAG)(n)三重重复序列的肌强直性营养不良基因座的基因组克隆。我们通过退火互补DNA链构建了两种类型的滑链结构，其中包含：(i)相同数目的三核苷酸重复序列（同源双链滑移结构或S-DNA）或（ii）不同数目的重复序列（异双链滑移中间体或SI-DNA），具有过量CTG或CAG重复序列的SI-DNA在结构上是不同的，可以通过电泳分离和单独研究。使用带移实验，MSH2被证明以结构特异性的方式与S-DNA和SI-DNA结合，MSH2的亲和力随着重复序列的长度而增加。此外，MSH2优先结合环状CAG重复序列，暗示MSH2识别中的链不对称。我们的结果与MSH2可能通过其在修复和/或重组中的作用参与三核苷酸重复扩增的观点一致。
The expansion of trinucleotide repeat sequences is associated with several neurodegenerative diseases. The mechanism of this expansion is unknown but may involve slipped-strand structures where adjacent rather than perfect complementary sequences of a trinucleotide repeat become paired, Here, we have studied the interaction of the human mismatch repair protein MSH2 with slipped-strand structures formed from a triplet repeat sequence in order to address the possible role of MSH2 in trinucleotide expansion, Genomic clones of the myotonic dystrophy locus containing disease-relevant lengths of (CTG)(n).(CAG)(n) triplet repeats were examined, We have constructed two types of slipped-strand structures by annealing complementary strands of DNA containing: (i) equal numbers of trinucleotide repeats (homoduplex slipped structures or S-DNA) or (ii) different numbers of repeats (heteroduplex slipped intermediates or SI-DNA), SI-DNAs having an excess of either CTG or CAG repeats were structurally distinct and could be separated electrophoretically and studied individually, Using a band-shift assay, the MSH2 was shown to bind to both S-DNA and SI-DNA in a structure-specific manner, The affinity of MSH2 increased with the length of the repeat sequence, Furthermore, MSH2 bound preferentially to looped-out CAG repeat sequences, implicating a strand asymmetry in MSH2 recognition. Our results are consistent with the idea that MSH2 may participate in trinucleotide repeat expansion Via its role in repair and/or recombination.