Evidence that protein kinase A activity is required for the basal and tax-stimulated transcriptional activity of human T-cell leukemia virus type-I long terminal repeat.
The present study was undertaken to investigate the role of protein kinase A (PKA) in the control of human T-cell leukemia virus type-I (HTLV-I) long terminal repeat (LTR) expression, since this issue is still controversial. For this purpose we employed two human T-cell lines; the Jurkat cells in which long exposure to diBu-cAMP severely down-regulated the catalytic subunit of PKA (PKA-C), and H-9 cells in which such exposure markedly increased PKA-C level. Transient transfection assays revealed that addition of diBu-cAMP 1 h before or after transfection profoundly increased HTLV-I LTR directed CAT expression and synergistically enhanced its stimulation by the viral transactivator tax gene product in both cell lines. However longer exposure to diBu-cAMP before transfection reduced LTR-CAT expression to below its basal level and completely abolished its stimulation by tax in Jurkat cells, and this diBu-cAMP inhibitory effect could be abrogated by co-transfection of a PKA-C expressing vector. By contrast, in H-9 cells, this long exposure to diBu-cAMP continued enhancing LTR-CAT expression and its tax-mediated transactivation, and this stimulatory effect of diBu-cAMP could be diminished by the PKA-specific inhibitor N-12-(p-bromocinnamylamine)ethyll-5-isoquinolinsulfonamid e (H-89). Notably, in the absence of diBu-cAMP treatment H-89 reduced LTR-CAT expression to below its basal level and prevented its stimulation by tax in both cell lines. Together these findings indicate not only that cAMP-activated PKA stimulates HTLV-I LTR expression and its transactivation by tax, but even in the absence of PKA activating signals the basal HTLV-I LTR expression as well as its stimulation by tax are both dependent on a basal PKA activity.
Turgeman
H
H
Department of Microbiology and Immunology, Faculty of Health Sciences, Ben Gurion University of the Negev, Beer Sheva, Israel.
Aboud
M
M
D003994:Bucladesine / Q000494:pharmacology*; D015500:Chloramphenicol O-Acetyltransferase / Q000096:biosynthesis; D017868:Cyclic AMP-Dependent Protein Kinases / Q000096:biosynthesis / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D016356:Gene Products, tax / Q000096:biosynthesis / Q000378:metabolism*; D017930:Genes, Reporter; D016355:Genes, pX; D015368:Human T-lymphotropic virus 1 / Q000235:genetics* / Q000378:metabolism*; D006801:Humans; D019169:Jurkat Cells; D007700:Kinetics; D046911:Macromolecular Substances; D011994:Recombinant Proteins / Q000096:biosynthesis; D014158:Transcription, Genetic; D014162:Transfection
D016356:Gene Products, tax; D046911:Macromolecular Substances; D011994:Recombinant Proteins; D003994:Bucladesine; D015500:Chloramphenicol O-Acetyltransferase; D017868:Cyclic AMP-Dependent Protein Kinases