Acts as transcriptional coactivator for TFAP2/AP-2. Enhances estrogen-dependent transactivation mediated by estrogen receptors. May function as an inhibitor of transactivation by HIF1A by disrupting HIF1A interaction with CREBBP. May be involved in regulation of gene expression during development and differentiation of blood cells, endothelial cells and mammary epithelial cells. Interacts via its C-terminal region with the CH1 domain of CREBBP and EP300. Interacts with all TFAP2/AP-2 isoforms. Expressed in most tissues examined with highest levels of expression in heart, liver, skeletal muscle and pancreas. Also expressed in bladder cell line ECV-304 and in various breast cancer cell lines. Also detected in both in situ and invasive breast tumors where its expression is down-regulated and mostly restricted to the cytoplasm of malignant epithelium. Down-regulation of expression is associated with elevated levels of HIF1A and increased tumor growth and angiogenesis. Belongs to the CITED family.