GABP mediates insulin-increased prolactin gene transcription.
The insulin-response element from the prolactin gene is identical to the Ets-binding site, and dominant-negative Ets protein inhibits insulin-increased prolactin gene expression. Immunoblotting identified the Ets-related transcription factor GABP in nuclear extracts from GH cells. Expression of GABP alpha and GABP beta 1 squelches insulin-increased prolactin gene expression. GABP alpha and GABP beta 1 bind the insulin-response element of the prolactin promoter, and anti-GABP alpha and anti-GABP beta 1 antibodies supershift a species seen with nuclear extracts from GH cells. GABP alpha immunoprecipitated from insulin-treated, 32P-labeled GH cells was phosphorylated 3-fold more than GABP alpha from control cells. There was no increase in phosphorylation of GABP beta in response to insulin. Mitogen-activated protein (MAP) kinase activity is increased 10-fold in insulin-treated GH4 cells. MAP kinase immunoprecipitated from control cells does not phosphorylate GABP alpha while MAP kinase immunoprecipitated from insulin-treated cells shows substantial phosphorylation of GABP alpha. These studies suggest that GABP mediates insulin-increased transcription of the prolactin gene. GABP may be regulated by MAP kinase phosphorylation.
Ouyang
L
L
Department of Medicine, New York University Medical Center, New York, USA.
Jacob
K K
KK
Stanley
F M
FM
D001483:Base Sequence; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000378:metabolism*; D051268:GA-Binding Protein Transcription Factor; D007328:Insulin / Q000494:pharmacology*; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides; D010766:Phosphorylation; D011233:Precipitin Tests; D011388:Prolactin / Q000235:genetics*; D011401:Promoter Regions, Genetic; D011494:Protein Kinases / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic
D004268:DNA-Binding Proteins; D051268:GA-Binding Protein Transcription Factor; D007328:Insulin; D009838:Oligodeoxyribonucleotides; D014157:Transcription Factors; D011388:Prolactin; D011494:Protein Kinases