Common themes in the function of transcription enhancers

Regulation of both transcription and RNA splicing requires enhancer elements, that is, &-acting DNA or RNA sequences that promote the activities of linked promoters or splice sites, respectively. Both types of enhancer associate with regulatory proteins to form multicomponent enhancer complexes that recruit the necessary enzymatic machinery to promoter or splice site recognition sequences. This recruitment occurs as a result of direct interactions between regulatory proteins in the enhancer complexes and components of the basic enzymatic machineries. Recent advances suggest that the high degree of regulatory specificity observed for both transcription and splicing is due, in large part, to the multicomponent nature of enhancer complexes and to their cooperative assembly.