DeZwaan Diane C, Freeman Brian C
Department of Cell and Developmental Biology, University of Illinois, 601 South Goodwin Avenue, Urbana, IL 61801, USA.
Proc Natl Acad Sci U S A. 2009 Oct 13;106(41):17337-42. doi: 10.1073/pnas.0905703106. Epub 2009 Sep 24.
The first telomerase cofactor identified was the budding yeast protein Est1, which is conserved through humans. While it is evident that Est1 is required for telomere DNA maintenance, understanding its mechanistic contributions to telomerase regulation has been limited. In vitro, the primary effect of Est1 is to activate telomerase-mediated DNA extension. Although Est1 displayed specific DNA and RNA binding, neither activity contributed significantly to telomerase stimulation. Rather Est1 mediated telomerase upregulation through direct contacts with the reverse transcriptase subunit. In addition to intrinsic Est1 functions, we found that Est1 cooperatively activated telomerase in conjunction with Cdc13 and that the combinatorial effect was dependent upon a known salt-bridge interaction between Est1 (K444) and Cdc13 (E252). Our studies provide insights into the molecular events used to control the enzymatic activity of the telomerase holoenzyme.
首个被鉴定出的端粒酶辅助因子是芽殖酵母蛋白Est1，该蛋白在人类中具有保守性。虽然很明显Est1是端粒DNA维持所必需的，但对其在端粒酶调控中的机制性贡献的了解一直有限。在体外，Est1的主要作用是激活端粒酶介导的DNA延伸。尽管Est1表现出特异性的DNA和RNA结合能力，但这两种活性对端粒酶刺激的贡献都不大。相反，Est1通过与逆转录酶亚基的直接接触介导端粒酶上调。除了Est1的内在功能外，我们发现Est1与Cdc13协同激活端粒酶，并且这种组合效应依赖于Est1（K444）和Cdc13（E252）之间已知的盐桥相互作用。我们的研究为用于控制端粒酶全酶酶活性的分子事件提供了见解。
