Proteasome-dependent degradation of Est1p regulates the cell cycle-restricted assembly of telomerase in Saccharomyces cerevisiae
Proteasome-dependent degradation of Est1p regulates the cell cycle-restricted assembly of telomerase in Saccharomyces cerevisiae
复制标题
DOI：
10.1038/nsmb1125
复制
发表时间：
2006-08-01
影响因子：
16.8
通讯作者：
Friedman, Katherine L.
中科院分区：
文献类型：
--
作者：
Osterhage, Jennifer L.;Talley, Jennell M.;Friedman, Katherine L.
Telomerase counteracts loss of terminal sequences incurred during DNA replication. In S. cerevisiae, telomerase contains an RNA template (TLC1), a reverse transcriptase (Est2p) and at least two regulatory proteins (Est1p and Est3p). Whereas Est2p is constitutively telomere bound, Est1p associates in late S phase, coincident with telomere lengthening. Here we directly demonstrate by coimmunoprecipitation that the composition of telomerase varies during the cell cycle. The absence of Est1p and Est3p from the complex during G1 phase can be attributed to proteasome-dependent degradation of Est1p. Stabilization of Est1p during G1 phase promotes telomerase assembly, revealing a previously uncharacterized role for Est1p in the recruitment of Est3p to the telomerase complex. Though catalytically active, complexes assembled during G1 cannot lengthen telomeres. We conclude that telomerase assembly during G1 phase is regulated by Est1p stability, but assembly is insufficient to activate telomerase at telomeres.
