The transcriptional enhancer factor-1 (TEF-1) family of transcription factors regulate tissue-specific gene expression in muscle and placenta. The mechanism whereby TEF-1 confers tissue specificity depends largely on the interaction of TEF-1 with tissue-specific cofactors. Transcription cofactor Vgl-3 (vestigial-like protein 3), also known as colon carcinoma related protein, is a 326 amino acid nuclear protein that may act as a specific coactivator for the mammalian transcription elongation factors. Both Vgl-1 and Vgl-3 are enriched in placenta, whereas Vgl-2 is expressed in differentiating somites and branchial arches during embryogenesis and is skeletal-muscle specific in adult tissues. There are two isoforms of Vgl-3 that are produced as a result of alternative splicing events.