The product of this gene belongs to the family of basic helix-loop-helix leucine zipper (bHLH-Zip) transcription factors. These factors form heterodimers with Mad proteins and play a role in proliferation, determination and differentiation. This gene product may act to diversify Mad family function by its restricted association with a subset of the Mad family of transcriptional repressors, namely, Mad1 and Mad4. Alternatively spliced transcript variants encoding different isoforms have been identified for this gene. [provided by RefSeq, Jul 2008].