C-terminal regions of the human telomerase catalytic subunit essential for in vivo enzyme activity
C-terminal regions of the human telomerase catalytic subunit essential for in vivo enzyme activity
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DOI：
10.1128/mcb.22.17.6234-6246.2002
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发表时间：
2002-09-01
影响因子：
5.3
通讯作者：
Counter, CM
中科院分区：
文献类型：
--
作者：
Banik, SSR;Guo, CH;Counter, CM
大多数人类癌细胞被认为通过非法激活编码端粒酶催化亚基的基因hTERT获得了超出正常体细胞能力的分裂能力。虽然端粒酶逆转录酶（TERT）在大多数真核生物中是保守的，但越来越多的证据表明，人类蛋白质的C末端可能具有高等真核生物特有的功能。为了寻找负责这些功能的结构域，我们测定了一组串联取代突变，包括体外和体内功能的人TERT的该区域。我们发现了四组突变，这些突变使端粒酶的生物化学和生物学功能失活，它们被对酶活性几乎没有影响或没有影响的突变分开。我们还确定了一个区域，突变产生催化活性，但生物惰性蛋白质。这C-末端区域，解离端粒酶（C-DAT）的活动似乎不参与核定位或蛋白质多聚化。相反，似乎C-DAT区域参与催化活性酶组装后的体内端粒合成步骤。有趣的是，所有描述的区域都位于酵母中细胞活力的一部分TERT中，这表明C末端在高等真核生物中具有不同的作用。
Most human cancer cells are thought to acquire the ability to divide beyond the capacity of normal somatic cells through illegitimately activating the gene hTERT, which encodes the catalytic subunit of telomerase. While telomerase reverse transcriptase (TERT) is conserved in most eukaryotes, mounting evidence suggests that the C terminus of the human protein may have functions unique to higher eukaryotes. To search for domains responsible for such functions, we assayed a panel of tandem substitution mutations encompassing this region of human TERT for in vitro and in vivo functionality. We found four clusters of mutations that inactivated the biochemical and biological functions of telomerase, separated by mutations that had little or no effect on enzyme activity. We also identified a region where mutations generate catalytically active but biologically inert proteins. This C-terminal region that dissociates activities of telomerase (C-DAT) does not appear to be involved in nuclear localization or protein multimerization. Instead, it appears that the C-DAT region is involved in a step of in vivo telomere synthesis after the assembly of a catalytically active enzyme. Intriguingly, all of the described regions reside in a portion of TERT that is dispensable for cellular viability in yeast, arguing for a divergent role of the C terminus in higher eukaryotes.