title: Cell cycle-dependent modulation of telomerase activity in tumor cells.
abstract: Telomerase is a ribonucleoprotein complex that is thought to add telomeric repeats onto the ends of chromosomes during the replicative phase of the cell cycle. We tested this hypothesis by arresting human tumor cell lines at different stages of the cell cycle. Induction of quiescence by serum deprivation did not affect telomerase activity. Cells arrested at the G1/S phase of the cell cycle showed similar levels of telomerase to asynchronous cultures; progression through the S phase was associated with increased telomerase activity. The highest level of telomerase activity was detected in S-phase cells. In contrast, cells arrested at G2/M phase of the cell cycle were almost devoid of telomerase activity. Diverse cell cycle blockers, including transforming growth factor beta1 and cytotoxic agents, also caused inhibition of telomerase activity. These results establish a direct link between telomerase activity and progression through the cell cycle.
authors.affiliation: Division of Oncology, Roche Research Center, Hoffman-La Roche, Inc., Nutley, NJ 07110, USA.
authors.forename: X
authors.initials: X
authors.lastname: Zhu
authors.forename: R
authors.initials: R
authors.lastname: Kumar
authors.forename: M
authors.initials: M
authors.lastname: Mandal
authors.forename: N
authors.initials: N
authors.lastname: Sharma
authors.forename: H W
authors.initials: HW
authors.lastname: Sharma
authors.forename: U
authors.initials: U
authors.lastname: Dhingra
authors.forename: J A
authors.initials: JA
authors.lastname: Sokoloski
authors.forename: R
authors.initials: R
authors.lastname: Hsiao
authors.forename: R
authors.initials: R
authors.lastname: Narayanan
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology; D002453:Cell Cycle; D006801:Humans; D019098:Telomerase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D016212:Transforming Growth Factor beta / Q000494:pharmacology; D014407:Tumor Cells, Cultured
chemical_list: D000970:Antineoplastic Agents; D016212:Transforming Growth Factor beta; D019098:Telomerase