Regulation of rat insulin 1 gene expression: Evidence for negative regulation in nonpancreatic cells

U. Nir, M. D. Walker, W. J. Rutter

Research output: Contribution to journalArticlepeer-review

98 Scopus citations

Abstract

Two cis-acting elements, the enhancer and the promoter, independently contribute to the cell-specific expression of the rat insulin 1 gene. The activities of these elements are presumably mediated by trans-acting factors. We have performed intracellular competition experiments that suggest the presence of a negative factor(s) that represses the enhancer activity in cells that do not express the insulin gene. In these experiments fibroblast cells (COS-7) were transfected with two plasmids: a test plasmid containing the gene for chloramphenicol acetyltransferase under the control of the thymidine kinase promoter and the insulin enhancer; and a competitor plasmid containing insulin enhancer sequencies and the simian virus 40 origin of replication to permit its replication in the recipient cells. The presence of the competitor plasmid led to a 5- to 6-fold increase in chloramphenicol acetyltransferase activity as compared with the activity detected when insulin enhancer was absent from either the competitor or the test plasmid. A 5-fold increase in chloramphenicol acetyltransferase activity was also seen when the rat amylase enhancer was present on the competitor plasmid; in contrast the simian virus 40 enhancer exerted no effect. Efficient derepression required additional sequences downstream from those essential for enhancer activity. We propose that the activity of the rat insulin 1 enhancer is modulated by a negative trans-acting factor(s) that is active in cells not expressing insulin but is overridden by the dominant positive trans-acting factor(s) present in insulin-producing cells.

Original languageEnglish
Pages (from-to)3180-3184
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Volume83
Issue number10
DOIs
StatePublished - May 1986
Externally publishedYes

Funding

FundersFunder number
National Institute of General Medical SciencesR01GM028520

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