Multiple elements regulate phosphoenolpyruvate carboxykinase gene expression in hepatoma hybrid cells.
The phosphoenolpyruvate carboxykinase (PEPCK) gene is highly expressed in cultured rat hepatoma cells, but extinguished in hepatoma x fibroblast hybrids. Extinction of PEPCK gene expression in hybrids is a polygenic process that involves several fibroblast loci, only one of which (tissue-specific extinguisher-1, TSE1) has been characterized to date. To identify sequence elements of the PEPCK gene that are involved both in TSE1-mediated extinction and in TSE1-independent processes, we assayed expression of chimeric PEPCK transgenes in transiently and stably transfected hybrid cells. We report that TSE1 responsiveness mapped to the PEPCK CRE (cAMP response element), as shown previously for the tyrosine aminotransferase gene. This was expected from the recent identification of the TSE1 gene product as a regulatory subunit of protein kinase A. However, none of the transgenes we assayed were responsive to TSE1-independent extinction mechanisms, suggesting that these controls require DNA sequences and/or chromatin structures that were not present in the transfected reporters. The implications of these findings are discussed.
Schafer
A J
AJ
Department of Molecular Medicine, Fred Hutchinson Cancer Research Center, Seattle, Washington 98104.
Fournier
R E
RE
D000818:Animals; D001483:Base Sequence; D006528:Carcinoma, Hepatocellular; D017362:Cyclic AMP Response Element-Binding Protein / Q000235:genetics; D054756:Cyclic AMP-Dependent Protein Kinase RIalpha Subunit; D017868:Cyclic AMP-Dependent Protein Kinases; D004247:DNA / Q000235:genetics; D015971:Gene Expression Regulation, Enzymologic; D006801:Humans; D006822:Hybrid Cells; D008099:Liver / Q000166:cytology / Q000378:metabolism; D008969:Molecular Sequence Data; D010729:Phosphoenolpyruvate Carboxykinase (GTP) / Q000235:genetics*; D011401:Promoter Regions, Genetic; D011506:Proteins / Q000502:physiology; D051381:Rats; D014162:Transfection
D017362:Cyclic AMP Response Element-Binding Protein; D054756:Cyclic AMP-Dependent Protein Kinase RIalpha Subunit; C517834:PRKAR1A protein, human; C517836:Prkar1a protein, rat; D011506:Proteins; D004247:DNA; D017868:Cyclic AMP-Dependent Protein Kinases; D010729:Phosphoenolpyruvate Carboxykinase (GTP)