The Anaphase Promoting Complex Contributes to the Degradation of the S. cerevisiae Telomerase Recruitment Subunit Est1p
The Anaphase Promoting Complex Contributes to the Degradation of the S. cerevisiae Telomerase Recruitment Subunit Est1p
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DOI：
10.1371/journal.pone.0055055
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发表时间：
2013-01-25
期刊：
影响因子：
3.7
通讯作者：
Friedman, Katherine L.
中科院分区：
文献类型：
--
作者：
Ferguson, Jenifer L.;Chao, William Chong Hang;Friedman, Katherine L.
端粒酶是一种多亚基酶，它将端粒重复序列逆转录到线性真核细胞染色体的末端，因此对基因组稳定性至关重要。S.酿酒酵母端粒酶活性受细胞周期调控;端粒在G1期不延长。先前的研究表明，Est 1蛋白水平在G1期较低，阻止端粒酶复合物组装。然而，靶向Est 1 p降解的途径仍然没有表征。在这里，我们表明，Est 1 p的稳定性，通过细胞周期反映了Clb 2 p，一个已知的目标后期促进复合物（APC）。事实上，Est 1 p通过APC的必需和非必需组分中的突变而稳定。推定的破坏盒（D-box）的突变，该地区被证明是重要的识别已知的APC基板，稳定Est 1 p，这表明Est 1 p很可能是直接降解的APC为目标。然而，我们没有检测到降解或泛素化的重组Est 1 p的APC在体外，这表明要么重组蛋白缺乏必要的翻译后修饰和/或构象，或APC影响Est 1 p降解的间接机制。总之，这些研究揭示了酵母端粒酶组装的调控，并证明了端粒维持和细胞周期调控途径之间的新联系。
Telomerase is a multi-subunit enzyme that reverse transcribes telomere repeats onto the ends of linear eukaryotic chromosomes and is therefore critical for genome stability. S. cerevisiae telomerase activity is cell-cycle regulated; telomeres are not elongated during G1 phase. Previous work has shown that Est1 protein levels are low during G1 phase, preventing telomerase complex assembly. However, the pathway targeting Est1p for degradation remained uncharacterized. Here, we show that Est1p stability through the cell cycle mirrors that of Clb2p, a known target of the Anaphase Promoting Complex (APC). Indeed, Est1p is stabilized by mutations in both essential and non-essential components of the APC. Mutations of putative Destruction boxes (D-boxes), regions shown to be important for recognition of known APC substrates, stabilize Est1p, suggesting that Est1p is likely to be targeted for degradation directly by the APC. However, we do not detect degradation or ubiquitination of recombinant Est1p by the APC in vitro, suggesting either that the recombinant protein lacks necessary post-translational modification and/or conformation, or that the APC affects Est1p degradation by an indirect mechanism. Together, these studies shed light on the regulation of yeast telomerase assembly and demonstrate a new connection between telomere maintenance and cell cycle regulation pathways.