We found that the expression of cyclin A and p21 waf1 molecules was primarily modulated by TGFb1 treatment while the expression of other regulatory components, like cyclins D, cyclin E, cdk2, cdk4, and cdk6 or p15 ink4b, p16ink4a, and p27kip1 was not significantly affected. The binding activity of CREB - 1 and ATF - 2 to the CRE region of the cyclin A promoter was almost completely abolished due to the treatment. Moreover, CREB-1 was dephosphorylated due to the treatment as revealed by immunoblotting.
