DIFFERENTIAL ACTIVITY OF A VARIANT FORM OF THE HUMAN ID-1 PROTEIN GENERATED BY ALTERNATIVE SPLICING

Members of the Id family of helix-loop-helix proteins are ubiquitously expressed and dimerize with members of the class A and class B basic helix-loop-helix proteins. Due to the absence of a basic region, Id pr oteins act as dominant-negative antagonists of basic helix-loop-helix transcription factors, which regulate cell growth and differentiation in diverse cell types. Recent findings suggest that the functions of I d proteins are well regulated at both the transcriptional level and th e posttranscriptional level. We show here that the alternative splicin g variant of human Id-1 protein possesses a different binding specific ity for basic helix-loop-helix transcription factors and is expressed in a cell cycle-dependent manner. Therefore, alternative splicing of I d-1 could provide a post-transcriptional mechanism to regulate Id-1 fu nction. (C) 1998 Federation of European Biochemical Societies.