The engagement of CD4 surface antigen in the HEL haemopoietic cell line up-regulates the transforming growth factor-beta1 (TGF-beta1) promoter activity.
In order to investigate the effect of CD4 engagement on the transforming growth factor beta1 (TGF-beta1) promoter activity in haemopoietic progenitors, HEL cells were transiently transfected with a plasmid vector containing -453/+11 nucleotides of the TGF-beta1 promoter fused with the bacterial chloramphenicol acetyltransferase (CAT) gene and then treated with various agonists. Both cross-linked CD4mAb and envelope gp120 were able to significantly up-regulate CAT activity with respect to the levels of activation observed in HEL cells treated with cross-linked CD8 mAb or p24. By using deletion mutants of the TGFbeta1 promoter, we found that the minimal DNA sequence still responsive to cross-linked CD4 mAb or gp120 was located between nucleotides -453/-323 of the TGF-beta1 promoter, which contains two activating protein 1 (AP1) binding sites. In electromobility shift assays (EMSA) we could demonstrate that CD4 engagement of HEL cells induced a significant increase of AP1 binding activity at the nuclear level. Furthermore, the steady-state mRNA of endogenous TGF-beta1 showed a small but reproducible increase when HEL cells were treated with cross-linked CD4mAb or gp120. Altogether, these findings suggest that the engagement of CD4 in HEL cells modulates TGF-beta1 expression, acting predominantly at the transcriptional level.
Gibellini
D
D
Institute of Microbiology, University of Bologna, Italy.
Celeghini
C
C
Panaya
R
R
Secchiero
P
P
Capitani
S
S
La Placa
M
M
Zauli
G
G
D015152:Blotting, Northern; D015704:CD4 Antigens / Q000378:metabolism*; D002460:Cell Line; D015500:Chloramphenicol O-Acetyltransferase / Q000378:metabolism*; D017353:Gene Deletion; D006412:Hematopoietic Stem Cells / Q000378:metabolism*; D006801:Humans; D009154:Mutation; D016211:Transforming Growth Factor alpha / Q000378:metabolism*; D015854:Up-Regulation
D015704:CD4 Antigens; D016211:Transforming Growth Factor alpha; D015500:Chloramphenicol O-Acetyltransferase