Transcriptional coactivator for CREB1 which activates transcription through both consensus and variant cAMP response element (CRE) sites. Acts as a coactivator, in the SIK/TORC signaling pathway, being active when dephosphorylated and acts independently of CREB1 'Ser-133' phosphorylation. Enhances the interaction of CREB1 with TAF4. Regulates the expression of specific CREB-activated genes such as the steroidogenic gene, StAR. Potent coactivator of PPARGC1A and inducer of mitochondrial biogenesis in muscle cells. Also coactivator for TAX activation of the human T-cell leukemia virus type 1 (HTLV-1) long terminal repeats (LTR). Binding, as a tetramer, through its N-terminal region, with the bZIP domain of CREB1 enhances recruitment of TAF4 to the promoter. 'Arg-314' in the bZIP domain of CREB1 is essential for this interaction. Interaction with HTLV-1 TAX enhances its transcriptional activity. Interacts, via the N- terminal with the ankyrin repeats of BCL3, to form a complex with CREB1 on CRE and TxRE responsive elements and represses HTLV-1 LTR-mediated transcription. Predominantly expressed in B and T lymphocytes. Highest levels in lung. Also expressed in brain, colon, heart, kidney, ovary, and prostate. Weak expression in liver, pancreas, muscle, small intestine, spleen and stomach. Belongs to the TORC family. 2 isoforms of the human protein are produced by alternative splicing. Note: This description may include information from UniProtKB.
Protein type: Transcription, coactivator/corepressor