Interference and synergism of glucocorticoid receptor and octamer factors.

Abstract

We have analysed the interplay of glucocorticoid receptor (GR) and the lymphocyte‐specific factor Oct‐2A with transient co‐transfection assays. Our data confirm our previously described observation that GR and the apparently unrelated factors belonging to the Octamer family can synergize when permitted to bind in cis. However, when GR binding sites are not present in the reporter genes, we observe that the action of the cloned factor Oct‐2A expressed in HeLa cells is strongly inhibited in the presence of active GR molecules. We can demonstrate that this GR‐mediated inhibition of Oct‐2A action is neither due to competitive binding to DNA target sites nor to a reduction of DNA binding competent Oct‐2A in the transfected cells. We observe that the phenomenon is not reciprocal, since co‐expression of Oct‐2A does not inhibit GR‐dependent transcription activation. Furthermore, we provide evidence that the observed GR‐Oct‐2A interference may be dependent on the type of cell line hosting the co‐transfected molecules. We consider it likely that the GR‐mediated inhibition is due to the exhaustion of some rate‐limiting co‐activators.

Down‐regulation of the protein kinase A pathway by activators of protein kinase C and intracellular Ca2+ in fibroblast cells

“…Therefore it seems that these and PKAactivated transcription factors do not compete for DNA binding sites or co-factors, as it has been shown in other systems [13,24]. This result also shows that AP-1 and JUNB do not activate another activity which blocks the PKA pathway.…”

Specific DNA Binding of Stat5, but Not of Glucocorticoid Receptor, Is Required for Their Functional Cooperation in the Regulation of Gene Transcription

“…The expression vectors for MGF-Stat5 (pXM-MGF), m-Stat5a (pXM-Stat5a), m-Stat5b (pXM-Stat5b), the mutated MGF-Stat5 Y694F (pXM-MGF Y694F), the deleted MGF-Stat5⌬750 (pXM-MGF⌬750), and the long form of the Prl R (pcDNAI-PrlR) have been described previously (19,50,73). The human GR expression vector pRSVhGR␣, the constructs encoding the deleted versions of the GRs pSTC 407-795 and pSTC 3-556, and the mutations in the DNA binding domain of the GR (C476W/R479Q and D4X) have also been described previously (18,79). The GR in which the DNA binding domain was replaced with that of the estrogen receptor (GR-ERcas) has been described previously (40).…”

“…To confirm this conclusion, we utilized a number of GR variants which lack the ability to specifically bind to the GRE in cotransfection assays. Two of these mutants, hGR (C476W/R479Q) and hGR (N454D/A458T/R460D/D462C), contain specific amino acid substitutions in the DNA binding domain (18,79). A third variant, in which the specific GRE 1 to 4) or the mouse homologs m-Stat5a (Stat5a) (lanes 5 to 8) or m-Stat5b (Stat5b) (lanes 9 to 12) and the prolactin receptor (Prl R), the GR, the ␤-casein-luciferase reporter gene (␤-casein-luc), and an expression plasmid encoding ␤-galactosidase.…”

Modulation of HLA-G Antigens Expression by Human Cytomegalovirus: Specific Induction in Activated Macrophages Harboring Human Cytomegalovirus Infection

“…In transfected cells expressing IE-pp86 alone, the viral gene was inserted in the pMam-neo plasmid under the control of the dexamethasone-inducible Moloney murine tumor virus-long terminal repeat promoter. This vector was cotransfected with the pCT-TK-GR3-795 plasmid expressing a glucocorticoid receptor (27). U-373 MG astrocytoma cells transfected with empty vector expressing the G418 resistance gene were used as negative controls.…”