Retinoic acid induces TGFβ-dependent autocrine fibroblast growth

To evaluate the role of murine TFIID subunit TAF4 in activation of cellular genes by all- trans retinoic acid (T-RA), we have characterized the T-RA response of taf4 lox /− and taf4 −/− embryonic fibroblasts. T-RA regulates almost 1000 genes in taf4 lox /− cells, but less than 300 in taf4 −/− cells showing that TAF4 is required for T-RA regulation of most, but not all cellular genes. We further show that T-RA-treated taf4 lox /− cells exhibit transforming growth factor (TGF) β -dependent autocrine growth and identify a set of genes regulated by loss of TAF4 and by T-RA corresponding to key mediators of the TGF β signalling pathway. T-RA rapidly and potently induces expression of connective tissue growth factor (CTGF) via a conserved DR2 type response element in its proximal promoter leading to serum-free autocrine growth. These results highlight the role of TAF4 as a cofactor in the cellular response to T-RA and identify the genetic programme of a novel cross talk between the T-RA and TGF β pathways that leads to deregulated cell growth.