Positive and negative regulation of gene expression by insulin and glucagon: The model of L-type pyruvate kinase gene

• Published in: Biochimie Vol. 73; no. 1; pp. 41 - 45
• Main Authors: Raymondjean, M., Voulont, S., Cognet, M., Decaux, J.F., Puzenat, N., Bergot, M.O., Kahn, A.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Paris Elsevier Masson SAS 1991; Elsevier
• Subjects: Animals; Biological and medical sciences; Cell physiology; chromatin structure; cis-acting DNA elements; DNA-Binding Proteins - metabolism; Eating - physiology; Fasting - physiology; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation, Enzymologic; Glucagon - physiology; Hormonal regulation; Humans; Insulin - physiology; Molecular and cellular biology; protein-DNA interactions; Pyruvate Kinase - genetics; Regulatory Sequences, Nucleic Acid; tissue specific activation; chromatin structure; protein-DNA interactions; cis-acting DNA elements; tissue specific activation; Pancreatic hormone; Glucagon; Pyruvate kinase; Transcription; Liver; Peptide hormone; Tissue specificity; Molecular interaction; Glucose; Insulin; Protein hormone; Gene; Hormonal regulation; Trans acting regulatory factor; Regulatory sequence; Mechanism of action
• ISSN: 0300-9084; 1638-6183
• DOI: 10.1016/0300-9084(91)90072-9

L-type pyruvate kinase gene regulation is an excellent model of gene control by hormones and diet. In vivo and ex vivo experiments allowed us to established that thyroid hormones and glucocorticoids act on pyruvate kinase gene expression at the post-transcriptional level. In contrast, glucose and insulin together stimulate transcription of this gene while glucagon inhibits it. Insulin or glucose are individually inefficient and glucagon-dependent transcriptional inhibition seems to be dominant in insulin + glucose-dependent activation. A 14-kbp fragment encompassing the entire pyruvate kinase gene and 3.2-kbp of 5′ flanking sequences is expressed in transgenic mice exactly like the endogenous gene; the 3.2-kbp usptream region is sufficient to confer this tissue-specific and hormone/diet-regulated expression to reporter genes. In vivo, DNAse I hypersensitivity analysis revealed the presence of 3 liver-specific groups of hypersensitive sites (HSS). The proximal sites, between + 1 and −183 bp with respect to the start site of transcription, were, in addition, transcription-dependent. The nature and functional role of proteins binding to this proximal upstream sequence were analyzed by in vitro binding and cell free transcription experiments. The existence of more upstream cis-acting elements was investigated by transient transfection assays using differentiated hepatoma cell lines and hepatocytes in primary culture. These experiments permitted the detection of an extinguisher active in hepatoma Hep G 2 cells but not in hepatocytes, and of an activating element which could correspond to a distal HSS. Unfortunately, this investigation has not yet allowed us to determine with accuracy the DNA elements responsible for response to diet and hormones.