Effects of the heterogeneous nuclear ribonucleoprotein U (hnRNP U/SAF-A) on glucocorticoid-dependent transcription in vivo.
The glucocorticoid receptor (GR) is a ligand dependent transcription factor, which regulates the transcription of multiple hormone-dependent genes. The transcriptional regulation by GR takes place by interaction of GR with the basal transcription machinery and by recruiting glucocorticoid receptor interacting proteins (GRIPs). Previously we identified hnRNP U/SAF-A as a factor interfering with GR-dependent transcription by repressing glucocorticoid induced activation. To gain insight into the mechanisms that govern this interference, we have now investigated the transcription of GR-dependent reporter genes in Ltk(-) cells transiently transfected with a variety of hnRNP U constructs. We demonstrate that a hnRNP U construct lacking the GR-binding domain acts as a dominant negative factor that now enhances GR-driven transcription. In addition, hnRNP U repression of glucocorticoid induced transcription was found to be dependent on the amount of cotransfected GR, where a high amount of GR leads to ligand-inducible repression of GR-dependent reporter gene activity by hnRNP U, whereas low amounts of GR showed nearly no effect. The relative concentrations of GR, hnRNP U and DNA-binding sites for GR are important for the effect of hnRNP U on transcription, suggesting a model where hnRNP-U acts as a storage site for intranuclear GR.
Eggert
H
H
Institut für Genetik der Justus-Liebig-Universität, Heinrich-Buff-Ring 58-62, D-35392 Giessen, Germany.
Schulz
M
M
Fackelmayer
F O
FO
Renkawitz
R
R
Eggert
M
M
D001665:Binding Sites; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D002469:Cell Separation; D015500:Chloramphenicol O-Acetyltransferase / Q000378:metabolism; D005057:Eukaryotic Cells / Q000378:metabolism; D005434:Flow Cytometry; D005799:Genes, Dominant; D017930:Genes, Reporter; D005938:Glucocorticoids / Q000378:metabolism*; D034722:Heterogeneous-Nuclear Ribonucleoprotein U; D034441:Heterogeneous-Nuclear Ribonucleoproteins; D006801:Humans; D008024:Ligands; D008957:Models, Genetic; D009154:Mutation; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012319:RNA Polymerase II / Q000378:metabolism; D012261:Ribonucleoproteins / Q000494:pharmacology*; D014158:Transcription, Genetic; D014162:Transfection
D005938:Glucocorticoids; D034722:Heterogeneous-Nuclear Ribonucleoprotein U; D034441:Heterogeneous-Nuclear Ribonucleoproteins; D008024:Ligands; D012261:Ribonucleoproteins; D015500:Chloramphenicol O-Acetyltransferase; D012319:RNA Polymerase II