Telomeric overhang length determines structural dynamics and accessibility to telomerase and ALT-associated proteins.
Telomeric overhang length determines structural dynamics and accessibility to telomerase and ALT-associated proteins.
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DOI：
10.1016/j.str.2014.03.013
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发表时间：
2014-06-10
期刊：
影响因子：
--
通讯作者：
Myong S
中科院分区：
文献类型：
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作者：
Hwang H;Kreig A;Calvert J;Lormand J;Kwon Y;Daley JM;Sung P;Opresko PL;Myong S
人端粒3′端富含G的单链DNA可以自折叠成G-四倍体（G-quaduplex，GQ）。然而，通过端粒酶或基于重组的端粒替代延长（ALT）机制的端粒延长需要在突出端上加载蛋白质。使用单分子荧光光谱，我们发现，延长端粒突出端也增加了结构构象之间的动态交换率。与四个重复相比，具有五至七个TTAGGG重复的突出端显示出更大的动力学和对端粒酶结合和活性的可及性，以及ALT相关蛋白RAD 51、WRN和BLM的加载。虽然八个重复序列是高度动态的，但它们可以折叠成两个GQ，这限制了蛋白质的可及性。相比之下，端粒特异性蛋白POT 1的独特之处在于它的结合不依赖于重复数。我们的研究结果表明，端粒突出端的长度和动力学可能有助于通过端粒酶作用和ALT机制调节端粒延伸。
The G-rich single stranded DNA at the 3′ end of human telomeres can self-fold into G-quaduplex (GQ). However, telomere lengthening by telomerase or the recombination-based alternative lengthening of telomere (ALT) mechanism requires protein loading on the overhang. Using single molecule fluorescence spectroscopy we discovered that lengthening the telomeric overhang also increased the rate of dynamic exchanges between structural conformations. Overhangs with five to seven TTAGGG repeats, compared to four repeats, showed much greater dynamics and accessibility to telomerase binding and activity, and loading of the ALT-associated proteins RAD51, WRN and BLM. Although the eight repeats are highly dynamic, they can fold into two GQs, which limited protein accessibility. In contrast, the telomere-specific protein, POT1 is unique in that it binds independently of repeat number. Our results suggest that the telomeric overhang length and dynamics may contribute to the regulation of telomere extension via telomerase action and the ALT mechanism.