1. Transcriptional activation of hTERT through the NF-kappaB pathway in HTLV-I-transformed cells.
- Author
-
Sinha-Datta U, Horikawa I, Michishita E, Datta A, Sigler-Nicot JC, Brown M, Kazanji M, Barrett JC, and Nicot C
- Subjects
- Cell Line, Transformed, Cells, Cultured, Chromatin genetics, Chromatin metabolism, DNA-Binding Proteins, Gene Products, tax genetics, Humans, Leukemia-Lymphoma, Adult T-Cell enzymology, Leukemia-Lymphoma, Adult T-Cell genetics, Leukemia-Lymphoma, Adult T-Cell virology, Lymphocyte Activation drug effects, Models, Genetic, Promoter Regions, Genetic genetics, Proto-Oncogene Proteins c-myc metabolism, RNA, Messenger genetics, RNA, Messenger metabolism, Sp1 Transcription Factor metabolism, T-Lymphocytes cytology, T-Lymphocytes drug effects, T-Lymphocytes metabolism, T-Lymphocytes virology, Telomerase metabolism, Gene Products, tax metabolism, Human T-lymphotropic virus 1 physiology, NF-kappa B metabolism, Telomerase genetics, Transcription, Genetic genetics, Transcriptional Activation genetics
- Abstract
In immortal cells, the existence of a mechanism for the maintenance of telomere length is critical. In most cases this is achieved by the reactivation of telomerase, a cellular reverse transcriptase that prevents telomere shortening. Here we report that the telomerase gene (hTERT) promoter is up-regulated during transmission of human T-cell lymphotropic virus type-I (HTLV-I) to primary T cells in vitro and in ex vivo adult T-cell leukemia/lymphoma (ATLL) samples, but not asymptomatic carriers. Although Tax impaired induction of human telomerase reverse transcriptase (hTERT) mRNA in response to mitogenic stimulation, transduction of Tax into primary lymphocytes was sufficient to activate and maintain telomerase expression and telomere length when cultured in the absence of any exogenous stimulation. Transient transfection assays revealed that Tax stimulates the hTERT promoter through the nuclear factor kappaB (NF-kappaB) pathway. Consistently, Tax mutants inactive for NF-kappaB activation could not activate the hTERT or sustain telomere length in transduced primary lymphocytes. Analysis of the hTERT promoter occupancy in vivo using chromatin immunoprecipitation assays suggested that an increased binding of c-Myc and Sp1 is involved in the NF-kappaB-mediated activation of the hTERT promoter. This study establishes the role of Tax in regulation of telomerase expression, which may cooperate with other functions of Tax to promote HTLV-I-associated adult T-cell leukemia.
- Published
- 2004
- Full Text
- View/download PDF