Transcriptional regulation of the interleukin 2 gene by glucocorticoid hormones. Role of steroid receptor and antigen-responsive 5'-flanking sequences.
Dexamethasone treatment of the Jurkat T77 cell clone inhibited the enhancing effect of 12-O-tetradecanoylporbol-13-acetate (TPA) and the calcium ionophore A23187 on the interleukin 2 (IL2) mRNA levels and gene transcription from intact nuclei. Dexamethasone treatment of Jurkat T77 cells inhibited the TPA/A23187-dependent activation of the transcription from the transfected pIL2CAT, containing 600 base pairs of the genomic sequences upstream of the coding region of IL2 gene, including the TPA/calcium responsive cis-regulatory elements and promoter sequences, driving the expression of the chloramphenicol acetyltransferase (CAT) gene. Transfection of either Jurkat T77 cell clone or glucocorticoid-resistant Jurkat cells with a human glucocorticoid receptor cDNA under the transcriptional control of the Rous sarcoma virus long terminal repeat (LTR) (pRShGR alpha) significantly increased or induced, respectively, the dexamethasone-mediated inhibition of the TPA/A23187-dependent expression of pIL2-CAT as well as the enhancing effect on the expression of the cotransfected CAT gene under the control of the mouse mammary tumor virus LTR, as a marker of glucocorticoid receptor action. This suggests a role for the glucocorticoid receptor in mediating the dexamethasone action on IL2 gene expression. To study the cis-regulatory sequence specificity of the dexamethasone-induced interference with the TPA/A23187-mediated T cell activating signals, we studied the effect of the hormone on the regulatory elements contained in the Rous sarcoma virus and human T lymphotropic virus 1 long terminal repeats and the SV40 promoter, which are known to be transcriptionally enhanced by those activating agents. Dexamethasone was unable to interfere with the TPA/A23187-mediated enhancement of these cis-regulatory elements, suggesting that the hormone effect is specific for IL-2 gene sequences. Our data suggest that the dexamethasone-mediated transcriptional inhibition of the IL2 gene is mediated by an interference with the protein kinase C and calcium-mediated trans-activation of the antigen-responsive and T cell-specific elements lying in the 5'-flanking region of the gene.
Vacca
A
A
Department of Experimental Medicine, University La Sapienza, Rome, Italy.
Martinotti
S
S
Screpanti
I
I
Maroder
M
M
Felli
M P
MP
Farina
A R
AR
Gismondi
A
A
Santoni
A
A
Frati
L
L
Gulino
A
A
D000818:Animals; D001358:Avian Sarcoma Viruses / Q000235:genetics; D000001:Calcimycin / Q000494:pharmacology; D002467:Cell Nucleus / Q000378:metabolism; D015500:Chloramphenicol O-Acetyltransferase / Q000235:genetics; D004274:DNA, Recombinant; D003907:Dexamethasone / Q000494:pharmacology*; D005786:Gene Expression Regulation / Q000187:drug effects*; D015368:Human T-lymphotropic virus 1 / Q000235:genetics; D006801:Humans; D006922:Hylobates; D007376:Interleukin-2 / Q000235:genetics*; D008324:Mammary Tumor Virus, Mouse / Q000235:genetics; D051379:Mice; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000378:metabolism; D011965:Receptors, Glucocorticoid / Q000502:physiology; D012045:Regulatory Sequences, Nucleic Acid; D012091:Repetitive Sequences, Nucleic Acid; D013539:Simian virus 40 / Q000235:genetics; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014158:Transcription, Genetic / Q000187:drug effects*; D014162:Transfection; D014407:Tumor Cells, Cultured
D004274:DNA, Recombinant; D007376:Interleukin-2; D012333:RNA, Messenger; D011965:Receptors, Glucocorticoid; D000001:Calcimycin; D003907:Dexamethasone; D015500:Chloramphenicol O-Acetyltransferase; D013755:Tetradecanoylphorbol Acetate