Akt protein kinase enhances human telomerase acitvity through phosphorylation of telomerase reverse transcriptase subunit

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Title
Akt protein kinase enhances human telomerase acitvity through phosphorylation of telomerase reverse transcriptase subunit
Author(s)
Sang Sun Kang; Taeg Un Kwon; Do Yoon Kwon; Su Il Do
Bibliographic Citation
Journal of Biological Chemistry, vol. 274, no. 19, pp. 13085-13090
Publication Year
1999
Abstract
With the amino acid sequences of all reported Akt kinase physiological substrates, the possible Akt kinase substrate specificity has been suggested. The serine/threonine residue to be phosphorylated in these proteins is placed within stretches of amino acids with homology, and the arginine residues on the -5 and -3 positions and a hydrophobic amino acid on the +2 position are conserved relative to those of serine/threonine residues (XXRXRXXS/TXX). We noticed two putative Akt kinase phosphorylation sites (220GARRRGGSAS229) and (817AVRIRGKSYV826) in human telomerase reverse transcriptase (hTERT) subunit. To demonstrate that hTERT is an Akt kinase substrate protein, we performed the nonradioactive protein kinase assay with the fluorescein hTERT peptide (817AVRIRGKSYV826). We observed the phosphorylation of hTERT peptide by the human melanoma cell lysate or the activated recombinant Akt kinase proteins in vitro. With the treatment of the growth factor deprivation or okadaic acid, we also observed the up-regulation of both hTERT peptide phosphorylation and the telomerase activity. We noticed that Wortmannin down-regulates hTERT peptide phosphorylation and telomerase activity together. In addition, we observed the enhancement of telomerase activity with the pretreatment of Akt kinase in vitro. Thus, these observations suggest that Akt kinase enhances human telomerase activity through phosphorylation of hTERT subunit as one of its substrate proteins.
ISSN
0021-9258
Publisher
Amer Soc Biochemistry Molecular Biology Inc
DOI
http://dx.doi.org/10.1074/jbc.274.19.13085
Type
Article
Appears in Collections:
1. Journal Articles > Journal Articles
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