Premium
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
Author(s) -
Turgeman Hava,
Aboud Mordechai
Publication year - 1998
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(98)00513-4
Subject(s) - transactivation , jurkat cells , transfection , long terminal repeat , protein kinase a , microbiology and biotechnology , cell culture , biology , gene expression , kinase , t cell , gene , biochemistry , immunology , genetics , immune system
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 ‐[2‐( p ‐bromocinnamylamine)ethyl]‐5‐ isoquinolinsulfonamide (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.