A sequence in the rat Pit-1 gene promoter confers synergistic activation by glucocorticoids and protein kinase-C.
The 5'-flanking region of the gene for Pit-1, a pituitary-specific transcription factor, was isolated from a rat liver genomic library and sequenced. Expression of a reporter construct containing Pit-1 promoter sequences linked to the bacterial chloramphenicol acetyltransferase (CAT) gene was assessed by transient transfection in rat pituitary GH4C1 cells. Treatment of transfected cells with either dexamethasone (DEX) for 48 h or the phorbol ester 12-O-tetradecanoylphorbol 13-acetate (TPA) for the final 20 h of the 48-h posttransfection period had minimal effects on CAT expression. However, CAT activity was elevated about 20-fold when transfected cells were treated with both DEX and TPA. This apparent synergistic activation was lost when DEX treatment was also limited to the final 20 h of the 48-h posttransfection period, suggesting that a time-dependent accumulation of a DEX-induced gene product might be involved. This putative DEX-induced product appeared to be relatively stable, because synergistic activation was observed in cells treated with DEX alone for 36 h, followed by a 10-h incubation without DEX before the addition of TPA. The Pit-1 gene promoter region between -210 and -142 from the transcription start site conferred synergistic regulation by DEX and TPA when placed upstream of position -105 in the herpes viral thymidine kinase promoter.(ABSTRACT TRUNCATED AT 250 WORDS)
Department of Medicine, New York University Medical Center, New York 10016.
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MT
Jong
B M
BM
Raaka
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Samuels
D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D015500:Chloramphenicol O-Acetyltransferase / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics*; D003907:Dexamethasone / Q000494:pharmacology*; D004357:Drug Synergism; D017930:Genes, Reporter; D008969:Molecular Sequence Data; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D011493:Protein Kinase C / Q000378:metabolism*; D051381:Rats; D011993:Recombinant Fusion Proteins; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D050817:Transcription Factor Pit-1; D014157:Transcription Factors / Q000235:genetics*; D014162:Transfection
D004268:DNA-Binding Proteins; C494186:Pou1f1 protein, rat; D011993:Recombinant Fusion Proteins; D050817:Transcription Factor Pit-1; D014157:Transcription Factors; D003907:Dexamethasone; D015500:Chloramphenicol O-Acetyltransferase; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate