Cyclic AMP response element-binding protein and the catalytic subunit of protein kinase A are present in F9 embryonal carcinoma cells but are unable to activate the somatostatin promoter.
The cyclic AMP (cAMP) response elements (CREs) of the somatostatin and vasoactive intestinal peptide (VIP) promoters contain binding sites for CRE-binding protein (CREB) that are essential for cAMP-regulated transcription. Using F9 embryonal carcinoma cells, we show that the somatostatin and VIP promoters exhibit a differentiation-dependent cAMP response, demonstrating that these promoters are regulated by transcription factors that become active during differentiation. Lack of cAMP responsiveness of the somatostatin promoter in undifferentiated cells is not due to the absence of known positive-acting factors (the catalytic subunit of protein kinase A [cPKA] and CREB) or a general inhibition of protein kinase A activity. Since overexpression of exogenous cPKA and CREB is sufficient to activate the somatostatin promoter in undifferentiated cells, these findings suggest that a negative factor(s) represses endogenous cPKA and CREB. In contrast to their effects on somatostatin, exogenous CREB and cPKA do not activate the VIP promoter. Thus, despite coregulation during differentiation and the ability to bind CREB, the somatostatin and VIP promoters are not coordinately activated by CREB in undifferentiated F9 cells.
Gene Activation Laboratory, Imperial Cancer Research Fund, Clare Hall Laboratories, South Mimms, Hertfordshire, United Kingdom.
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N
Masson
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M
Ellis
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S
Goodbourn
K A
KA
Lee
D001483:Base Sequence; D015153:Blotting, Western; D002384:Catalysis; D002454:Cell Differentiation; D017362:Cyclic AMP Response Element-Binding Protein; D004247:DNA; D004268:DNA-Binding Proteins / Q000378:metabolism*; D054278:Embryonal Carcinoma Stem Cells; D005786:Gene Expression Regulation; D008969:Molecular Sequence Data; D014411:Neoplastic Stem Cells; D011401:Promoter Regions, Genetic; D011494:Protein Kinases / Q000737:chemistry / Q000378:metabolism*; D013004:Somatostatin / Q000235:genetics*; D014407:Tumor Cells, Cultured; D014660:Vasoactive Intestinal Peptide / Q000235:genetics
D017362:Cyclic AMP Response Element-Binding Protein; D004268:DNA-Binding Proteins; D014660:Vasoactive Intestinal Peptide; D013004:Somatostatin; D004247:DNA; D011494:Protein Kinases