Topoisomerase 1 and Single-Strand Break Repair Modulate Transcription-Induced CAG Repeat Contraction in Human Cells
Topoisomerase 1 and Single-Strand Break Repair Modulate Transcription-Induced CAG Repeat Contraction in Human Cells
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DOI：
10.1128/mcb.05158-11
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发表时间：
2011-08-01
影响因子：
5.3
通讯作者：
Wilson, John H.
中科院分区：
文献类型：
--
作者：
Hubert, Leroy, Jr.;Lin, Yunfu;Wilson, John H.
扩展的三核苷酸重复是导致许多神经退行性疾病的原因，例如亨廷顿病和1型强直性肌营养不良。生殖细胞系和人类患者体细胞组织中重复不稳定的机制尚不清楚。使用基于人类细胞中 CAG 重复序列收缩的选择测定，我们以中等高通量测定筛选了 Prestwick 化学文库，并鉴定了 18 种新型重复收缩诱导剂。这些化合物的一个子集靶向参与与转录相关的 DNA 超螺旋管理的途径。使用小分子抑制剂和小干扰 RNA (siRNA) 介导的敲低的进一步分析表明，拓扑异构酶 1 (TOP1)、酪氨酰 DNA 磷酸二酯酶 1 (TDP1) 和单链断裂修复 (SSBR) 参与调节转录依赖性 CAG 重复收缩。 TOP1-TDP1-SSBR 通路通常起到抑制重复不稳定性的作用，因为干扰它会刺激重复收缩。我们进一步表明，当 TOP1-TDP1-SSBR 途径受到损害时，重复收缩的增加是通过转录偶联的核苷酸切除修复引起的，这是先前确定的转录诱导的重复不稳定的原因。这些研究拓宽了转录诱导的 CAG 重复不稳定性相关途径的范围，并开始定义它们之间的相互关系。
Expanded trinucleotide repeats are responsible for a number of neurodegenerative diseases, such as Huntington disease and myotonic dystrophy type 1. The mechanisms that underlie repeat instability in the germ line and in the somatic tissues of human patients are undefined. Using a selection assay based on contraction of CAG repeat tracts in human cells, we screened the Prestwick chemical library in a moderately high-throughput assay and identified 18 novel inducers of repeat contraction. A subset of these compounds targeted pathways involved in the management of DNA supercoiling associated with transcription. Further analyses using both small molecule inhibitors and small interfering RNA (siRNA)-mediated knockdowns demonstrated the involvement of topoisomerase 1 (TOP1), tyrosyl-DNA phosphodiesterase 1 (TDP1), and single-strand break repair (SSBR) in modulating transcription-dependent CAG repeat contractions. The TOP1-TDP1-SSBR pathway normally functions to suppress repeat instability, since interfering with it stimulated repeat contractions. We further showed that the increase in repeat contractions when the TOP1-TDP1-SSBR pathway is compromised arises via transcription-coupled nucleotide excision repair, a previously identified contributor to transcription-induced repeat instability. These studies broaden the scope of pathways involved in transcription-induced CAG repeat instability and begin to define their interrelationships.