Apoptotic endonuclease EndoG inhibits telomerase activity and induces malignant transformation of human CD4+ T cells
- 130 Downloads
Telomerase activity is regulated by an alternative splicing of mRNA of the telomerase catalytic subunit hTERT (human telomerase reverse transcriptase). Increased expression of the inactive spliced hTERT results in inhibition of telomerase activity. Little is known about the mechanism of hTERT mRNA alternative splicing. This study was aimed at determining the effect of an apoptotic endonuclease G (EndoG) on alternative splicing of hTERT and telomerase activity in CD4+ human T lymphocytes. Overexpression of EndoG in CD4+ T cells downregulated the expression of the active fulllength hTERT variant and upregulated the inactive alternatively spliced variant. Reduction of full-length hTERT levels caused downregulation of the telomerase activity, critical telomere shortening during cell division that converted cells into the replicative senescence state, activation of apoptosis, and finally cell death. Some cells survive and undergo a malignant transformation. Transformed cells feature increased telomerase activity and proliferative potential compared to the original CD4+ T cells. These cells have phenotype of T lymphoblastic leukemia cells and can form tumors and cause death in experimental mice.
KeywordsEndoG telomerase hTERT alternative splicing malignant transformation
green fluorescent protein
human telomerase reverse transcriptase
mean fluorescence intensity
telomeric repeats amplification protocol
Unable to display preview. Download preview PDF.
- 4.Saeboe-Larssen, S., Fossberg, E., and Gaudernack, G. (2006) Characterization of novel alternative splicing sites in human telomerase reverse transcriptase (hTERT): analysis of expression and mutual correlation in mRNA isoforms from normal and tumor tissues, BMC Mol. Biol., 7, 26.CrossRefPubMedPubMedCentralGoogle Scholar
- 5.Ulaner, G. A., Hu, J. F., Vu, T. H., Oruganti, H., Giudice, L. C., and Hoffman, A. R. (2000) Regulation of telomerase by alternate splicing of human telomerase reverse transcriptase (hTERT) in normal and neoplastic ovary, endometrium and myometrium, Int. J. Cancer, 85, 330–335.CrossRefPubMedGoogle Scholar
- 7.Listerman, I., Sun, J., Gazzaniga, F. S., Lukas, J. L., and Blackburn, E. H. (2013) The major reverse transcriptaseincompetent splice variant of the human telomerase protein inhibits telomerase activity but protects from apoptosis, Cancer Res., 73, 2817–2828.CrossRefPubMedPubMedCentralGoogle Scholar
- 13.Marian, C. O., Cho, S. K., McEllin, B. M., Maher, E. A., Hatanpaa, K. J., and Madden, C. J. (2010) The telomerase antagonist, imetelstat, efficiently targets glioblastoma tumor-initiating cells leading to decreased proliferation and tumor growth, Clin. Cancer Res., 16, 154–163.Google Scholar
- 24.Cawthon, R. M. (2002) Telomere measurement by quantitative PCR, Nucleic Acids Res., e47.Google Scholar
- 27.Zhdanov, D. D., Vasina, D. A., Orlova, V. S., Gotovtseva, V. Y., Bibikova, M. V., Pokrovsky, V. S., Pokrovskaya, M. V., Aleksandrova, S. S., and Sokolov, N. N. (2016) Apoptotic endonuclease EndoG induces alternative splicing of telomerase catalytic subunit hTERT and death of tumor cells, Biomed. Chem., 62, 239–250.Google Scholar
- 29.Counter, C. M., Gupta, J., Harley, C. B., Leber, B., and Bacchetti, S. (1995) Telomerase activity in normal leukocytes and in hematologic malignancies, Blood, 85, 23152320.Google Scholar