Partial inhibition of the proteasome enhances the activity of the myelin basic protein promoter.
We have previously shown that low concentrations of a specific proteasome inhibitor accelerate exit from the cell cycle and enhance oligodendroglial cell (OLGc) differentiation. To elucidate the mechanisms involved in this process, OLGcs of the N20.1 cell line, transfected with a reporter gene driven by the MBP promoter, were treated with proteasome inhibitors and/or inhibitors of different signaling pathways. Partial proteasome inhibition resulted in enhanced activation of the MBP promoter which involved the tyrosine kinase, PI3-Akt and PKC pathways, accompanied by an increase in the levels of p21(Cip1), p27(Kip1) and Sp1 and by a decrease in Nkx2.2. Binding of Sp1 to DNA was also increased. These results were not observed when the Sp1 binding site was mutated. We conclude that the enhanced activation of the MBP promoter induced by partial inhibition of the proteasome could be due, at least in part, to the stabilization of p27(Kip1) and Sp1.
Calatayud
C A
CA
Departamento de Química Biológica, Instituto de Química y Fisicoquímica Biológica, Universidad de Buenos Aires-CONICET, Argentina.
García
C I
CI
Paez
P M
PM
Pasquini
J M
JM
Soto
E F
EF
Pasquini
L A
LA
D000818:Animals; D015153:Blotting, Western; D002454:Cell Differentiation / Q000235:genetics*; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000378:metabolism; D024202:Electrophoretic Mobility Shift Assay; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology; D000090322:Homeobox Protein Nkx-2.2; D047468:Immunoprecipitation; D051379:Mice; D004676:Myelin Basic Protein / Q000235:genetics* / Q000378:metabolism; D009836:Oligodendroglia / Q000166:cytology* / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D011401:Promoter Regions, Genetic; D046988:Proteasome Endopeptidase Complex / Q000187:drug effects / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D016329:Sp1 Transcription Factor / Q000378:metabolism; D014162:Transfection
D050760:Cyclin-Dependent Kinase Inhibitor p27; D004791:Enzyme Inhibitors; D000090322:Homeobox Protein Nkx-2.2; D004676:Myelin Basic Protein; D019869:Phosphatidylinositol 3-Kinases; D046988:Proteasome Endopeptidase Complex; D011493:Protein Kinase C; D011505:Protein-Tyrosine Kinases; D016329:Sp1 Transcription Factor; C000715627:Nkx2-2 protein, mouse