hnRNP A1 associates with telomere ends and stimulates telomerase activity
hnRNP A1 associates with telomere ends and stimulates telomerase activity
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DOI：
10.1261/rna.58806
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发表时间：
2006-06-01
期刊：
影响因子：
4.5
通讯作者：
Krainer, Adrian R.
中科院分区：
文献类型：
--
作者：
Zhang, Qing-Shuo;Manche, Lisa;Krainer, Adrian R.
端粒酶是一种核糖核蛋白酶复合物，它对一个完整的RNA模板进行反向转录，从而在端粒的3'端添加短的DNA重复序列。DNA底物中的g -四重体结构可以阻断端粒酶的延伸。我们已经发现hnRNP A1 -先前与端粒长度调节有关-结合单链和结构化的人类端粒重复序列，在后者的情况下，它破坏了它们的高阶结构。通过体外端粒酶测定，我们发现293人胚胎肾细胞提取物中hnRNP A/B蛋白的缺失显著降低了端粒酶活性，添加纯化的重组hnRNP A1后，端粒酶活性完全恢复。这一发现表明，hnRNP A1作为端粒酶全酶的辅助因子，如果不是必需的。我们进一步证明，使用染色质免疫沉淀，hnRNP A1在体内与人类端粒相关。我们提出hnRNP A1通过在每个易位步骤中形成的g -四重体或G-G发夹结构的解绕来刺激端粒延长。
Telomerase is a ribonucleoprotein enzyme complex that reverse-transcribes an integral RNA template to add short DNA repeats to the 3'-ends of telomeres. G-quadruplex structure in a DNA substrate can block its extension by telomerase. We have found that hnRNP A1 - which was previously implicated in telomere length regulation - binds to both single-stranded and structured human telomeric repeats, and in the latter case, it disrupts their higher-order structure. Using an in vitro telomerase assay, we observed that depletion of hnRNP A/B proteins from 293 human embryonic kidney cell extracts dramatically reduced telomerase activity, which was fully recovered upon addition of purified recombinant hnRNP A1. This finding suggests that hnRNP A1 functions as an auxiliary, if not essential, factor of telomerase holoenzyme. We further show, using chromatin immunoprecipitation, that hnRNP A1 associates with human telomeres in vivo. We propose that hnRNP A1 stimulates telomere elongation through unwinding of a G-quadruplex or G-G hairpin structure formed at each translocation step.