Developmental regulation of beta-globin gene switching.

A chicken erythroid cell-specific enhancer is located in the intergenic region between the adult beta- and embryonic epsilon-globin genes. In this paper we show that the beta-globin enhancer stimulates transcription of both genes. epsilon-Globin is, however, inappropriately regulated since it is expressed in both embryonic and adult red blood cells. Appropriate stage-specific regulation is observed for both genes when they are present on one plasmid. By analysis of deletion and substitution mutants, we conclude that beta-globin tissue- and developmental stage-specific regulation is mediated by interaction of the beta-globin enhancer with a positive regulatory element within the adult beta-globin promoter, the developmental stage selector element (SSE).