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.
Highlights
In most eukaryotes, telomerase is responsible for the synthesis and maintenance of telomeric DNA that together with proteins forms a protective cap known as telomeres for eukaryotic linear chromosomes [1,2,3,4,5,6,7,8,9,10]
To establish if telomerase is directly regulated by protein phosphorylation and which protein kinase(s) are involved in the process, we have made use of affinity chromatography with a synthetic peptide corresponding to the N-terminal sequence of human telomeraseassociated protein 1 (hTEP1) and produced polyclonal antibodies against hTEP1 and hTERT to isolate telomerase and its potentially responsible protein kinase(s) involved in the regulation of telomerase activity
To further explore the mechanisms of regulation of telomerase activity by protein phosphorylation, telomerase was partially purified by hTEP1 peptide affinity chromatography, and protein kinase(s) potentially interacting with the hTEP1 peptide were analyzed by immunoblotting
Summary
Telomerase is responsible for the synthesis and maintenance of telomeric DNA that together with proteins forms a protective cap known as telomeres for eukaryotic linear chromosomes [1,2,3,4,5,6,7,8,9,10]. Our data show that protein kinase C␣ (PKC␣) is selectively eluted from the hTEP1 peptide affinity column and mediates phosphorylation of hTEP1 and hTERT in intact human breast cancer cells.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
