TRF1 binds a bipartite telomeric site with extreme spatial flexibility
TRF1 binds a bipartite telomeric site with extreme spatial flexibility
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DOI：
10.1093/emboj/18.20.5735
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发表时间：
1999-10-15
期刊：
影响因子：
11.4
通讯作者：
de Lange, T
中科院分区：
文献类型：
--
作者：
Bianchi, A;Stansel, RM;de Lange, T
TRF1在端粒长度调控中起关键作用。由于长度控制被认为依赖于端粒的结构，我们研究了TRF1如何结合端粒TTAGGG重复DNA并改变其构象。尽管TRF1单体的单个myb型螺旋-转-螺旋基序可以与端粒DNA相互作用，但TRF1主要以同二聚体结合，但与二聚体TRF1结合的系统配体进化（SELEX）揭示了一个具有极端空间变异性的双端端粒识别位点。最优位点有两个5‘-YTAGGGTTR-3’半位点，不受距离和方向的限制。结合亲和力分析和DNA酶I足迹分析表明，TRF1二聚体同时与两个半位点接触，电子显微镜显示了中间DNA的环。我们提出TRF1中的一个柔性片段允许同型二聚体的两个Myb结构域与不同位置的半位点独立相互作用。这种不寻常的DNA结合模式与TRF1的结构作用直接相关。
TRF1 is a key player in telomere length regulation. Because length control was proposed to depend on the architecture of telomeres, we studied how TRF1 binds telomeric TTAGGG repeat DNA and alters its conformation. Although the single Myb-type helix-turn-helix motif of a TRF1 monomer can interact with telomeric DNA, TRF1 predominantly binds as a homodimer, Systematic Evolution of Ligands by Exponential enrichment (SELEX) with dimeric TRF1 revealed a bipartite telomeric recognition site with extreme spatial variability. Optimal sites have two copies of a 5'-YTAGGGTTR-3' half-site positioned without constraint on distance or orientation. Analysis of binding affinities and DNase I footprinting showed that both half-sites are simultaneously contacted by the TRF1 dimer, and electron microscopy revealed looping of the intervening DNA. We propose that a flexible segment in TRF1 allows the two Myb domains of the homodimer to interact independently with variably positioned half-sites. This unusual DNA binding mode is directly relevant to the proposed architectural role of TRF1.