title: Telomerase is controlled by protein kinase Calpha in human breast cancer cells.
abstract: Telomerase, a specialized RNA-directed DNA polymerase that extends telomeres of eukaryotic chromosomes, is repressed in human somatic tissues and becomes activated during tumor progression in most human cancers. To date, little is known about how telomerase is activated and controlled in cancer, although activation is thought to be involved in cancer cell immortalization. Here, we report that human telomerase-associated protein 1 (hTEP1) and the telomerase catalytic subunit (human telomerase reverse transcriptase (hTERT)) are phosphoproteins and that their phosphorylation is a prerequisite for the activation of telomerase in intact human breast cancer cells. Identified by hTEP1 peptide affinity chromatography, protein kinase Calpha mediates the phosphorylation of hTEP1 and hTERT and induces a marked increase in telomerase activity. Thus, phosphorylation of hTEP1 and hTERT by protein kinase Calpha represents an essential step in the generation of a functional telomerase complex in the initiation and maintenance of telomerase activity in human cancer.
authors.affiliation: Molecular Signaling Laboratory, Baker Medical Research Institute, Commercial Road, Prahran, Victoria 3181, Australia.
authors.forename: H
authors.initials: H
authors.lastname: Li
authors.forename: L
authors.initials: L
authors.lastname: Zhao
authors.forename: Z
authors.initials: Z
authors.lastname: Yang
authors.forename: J W
authors.initials: JW
authors.lastname: Funder
authors.forename: J P
authors.initials: JP
authors.lastname: Liu
mesh_terms: D000595:Amino Acid Sequence; D001943:Breast Neoplasms / Q000201:enzymology* / Q000473:pathology; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism*; D008969:Molecular Sequence Data; D010766:Phosphorylation; D011233:Precipitin Tests; D011493:Protein Kinase C / Q000378:metabolism*; D051571:Protein Kinase C-alpha; D019098:Telomerase / Q000378:metabolism*; D014407:Tumor Cells, Cultured
chemical_list: D007527:Isoenzymes; C496628:PRKCA protein, human; D011493:Protein Kinase C; D051571:Protein Kinase C-alpha; D019098:Telomerase