BMP signaling is responsible for serum-induced Id2 expression

► Serum induction of Id2 gene expression is suppressed by inhibition of BMP signaling. ► Smads binding sites are important for serum-induced activation of the Id2 promoter. ► Smad1/5/8 and Smad4 bind to the Id2 promoter in a serum-dependent manner. ► Smad1 is critical for serum-induced Id2 expression.