Tissue‐specific binding of a nuclear factor to the insulin gene promoter

Using a DNA‐binding gel mobility shift assay, a protein‐DNA complex was detected using the rat II insulin promoter and a nuclear extract from rat insulinoma cells. This complex was detected using extracts from other insulin‐producing cell lines but was not found using nuclear extracts from non‐insulin‐producing pancreatic cell lines or other cell types. Binding of the tissue‐specific protein to the labelled promoter fragment was effectively competed by both rat and human insulin genes but not by the SV40 TATA box. This protein‐DNA interaction may be involved in tissue‐specific regulation of insulin gene expression.