Individual protein-binding domains of the insulin gene enhancer positively activate beta-cell-specific transcription

A beta-cell-specific enhancer is located in the 5'-flanking DNA of the rat insulin 1 gene. Two homologous 8-base-pair sequences in the enhancer (IEB1 and IEB2) significantly stimulated transcription from a heterologous promoter (two- to fourfold) in a cell-specific fashion. When the elements were combined or duplicated, more than 50% of the activity of the intact enhancer was obtained. These two cis-acting elements appear to play a dominant role in the positive control of beta-cell-specific transcription of the insulin gene.