The yeast Pif1p helicase removes telomerase from telomeric DNA
The yeast Pif1p helicase removes telomerase from telomeric DNA
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DOI：
10.1038/nature04091
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发表时间：
2005-11-03
期刊：
影响因子：
64.8
通讯作者：
Zakian, VA
中科院分区：
文献类型：
--
作者：
Boulé, JB;Vega, LR;Zakian, VA
端粒是真核生物染色体的物理末端。遗传学研究已经确定，面包酵母Pif1p DNA解旋酶是端粒酶的负调节剂，端粒酶是维持端粒DNA的专门逆转录酶，但这种抑制的生物化学基础尚不清楚。在这里，我们表明，在体外，Pif1p降低端粒酶的持续合成能力，并释放端粒寡核苷酸端粒酶。释放的端粒酶是酶活性的，因为它能够延长挑战寡核苷酸。在体内，Pif1p的过度表达减少了端粒酶与端粒的结合，而Pif1p的耗竭细胞增加了端粒结合的Est1p的水平，Est1p是端粒酶活性时存在于端粒上的端粒酶亚基。我们建议，Pif1p解旋酶活性限制端粒酶的行动，在体内和体外置换活性端粒酶的DNA末端。
Telomeres are the physical ends of eukaryotic chromosomes. Genetic studies have established that the baker's yeast Pif1p DNA helicase is a negative regulator of telomerase, the specialized reverse transcriptase that maintains telomeric DNA, but the biochemical basis for this inhibition was unknown. Here we show that in vitro, Pif1p reduces the processivity of telomerase and releases telomerase from telomeric oligonucleotides. The released telomerase is enzymatically active because it is able to lengthen a challenger oligonucleotide. In vivo, overexpression of Pif1p reduces telomerase association with telomeres, whereas depleting cells of Pif1p increases the levels of telomere-bound Est1p, a telomerase subunit that is present on the telomere when telomerase is active. We propose that Pif1p helicase activity limits telomerase action both in vivo and in vitro by displacing active telomerase from DNA ends.