The function of ENSG00000140577 (CRTC3, CREB regulated transcription coactivator 3) is as follows. 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). {ECO:0000269|PubMed:14506290, ECO:0000269|PubMed:15454081, ECO:0000269|PubMed:15466468, ECO:0000269|PubMed:16817901, ECO:0000269|PubMed:16980408, ECO:0000269|PubMed:17210223, ECO:0000269|PubMed:17644518}.