An endocrine-specific element is an integral component of an exocrine-specific pancreatic enhancer.

We have analyzed the function of individual elements of the elastase I transcriptional enhancer in transgenic animals. This pancreas-specific enhancer comprises three functional elements, one of which (the B element) plays a dual role. Within the context of the enhancer, the B element contributes to appropriate acinar cell expression. However, when separated from the other enhancer components, the B element selectively directs transcription in islet cells of transgenic animals. This islet-specific activity is normally suppressed by an upstream repressor domain. The B element binds a novel islet-specific factor, and similar B-like elements are present in other pancreatic genes, both exocrine and endocrine specific. We suggest that a principal role of this transcriptional element and its associated factors is to activate many pancreatic genes as part of the program of pancreatic determination prior to the divergence of the acinar and islet cell lineages.