Counter C M, Meyerson M, Eaton E N, Weinberg R A
Whitehead Institute for Biomedical Research and Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02142, USA.
Proc Natl Acad Sci U S A. 1997 Aug 19;94(17):9202-7. doi: 10.1073/pnas.94.17.9202.
Telomerase is an RNA-directed DNA polymerase, composed of RNA and protein subunits, that replicates the telomere ends of linear eukaryotic chromosomes. Using a genetic strategy described here, we identify the product of the EST2 gene, Est2p, as a subunit of telomerase in the yeast Saccharomyces cerevisiae. Est2p is required for enzyme catalysis, as mutations in EST2 were found to result in the absence of telomerase activity. Immunochemical experiments show that Est2p is an integral subunit of the telomerase enzyme. Critical catalytic residues present in RNA-directed DNA polymerases are conserved in Est2p; mutation of one such residue abolishes telomerase activity, suggesting a direct catalytic role for Est2p.
端粒酶是一种由RNA和蛋白质亚基组成的RNA指导的DNA聚合酶，它复制线性真核染色体的端粒末端。利用本文所述的遗传策略，我们确定了EST2基因的产物Est2p是酿酒酵母中端粒酶的一个亚基。Est2p是酶催化所必需的，因为发现EST2中的突变会导致端粒酶活性缺失。免疫化学实验表明，Est2p是端粒酶的一个组成亚基。RNA指导的DNA聚合酶中存在的关键催化残基在Est2p中是保守的；其中一个这样的残基发生突变会消除端粒酶活性，这表明Est2p具有直接的催化作用。
