Cloning of mouse Cited4, a member of the CITED family p300/CBP-binding transcriptional coactivators: induced expression in mammary epithelial cells.

The CITED family proteins bind to CBP/p300 transcriptional integrators through their conserved C-terminal acidic domain and function as coactivators. The 21-kDa mouse Cited4 protein, a novel member of the CITED family, interacted with CBP/p300 as well as isoforms of the TFAP2 transcription factor, coactivating TFAP2-dependent transcription. The cited4 gene consisted of only a single exon located on chromosome 4 at 56.5-56.8 cM flanked by marker genes kcnq4 and scml1. Expression of Cited4 protein was strong and selective in embryonic hematopoietic tissues and endothelial cells. In adult animals, Cited4 showed strong milk cycle-dependent induction in pregnant and lactating mammary epithelial cells. Strong induction of Cited4 expression was also observed in SCp2 mouse mammary epithelial cells during their prolactin-dependent in vitro differentiation. These results implied possible roles for Cited4 in regulation of gene expression during development and differentiation of blood cells, endothelial cells, and mammary epithelial cells.