COMMON THEMES IN THE FUNCTION OF TRANSCRIPTION AND SPLICING ENHANCERS

Regulation of both transcription and RNA splicing requires enhancer el ements, that is, cis-acting DNA or RNA sequences that promote the acti vities of linked promoters or splice sites, respectively. Both types o f enhancer associate with regulatory proteins to form multicomponent e nhancer complexes that recruit the necessary enzymatic machinery to pr omoter or splice site recognition sequences. This recruitment occurs a s a result of direct interactions between regulatory proteins in the e nhancer complexes and components of the basic enzymatic machineries. R ecent 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 cooperat ive assembly.