tokens: In the present study , we demonstrated that BMP-2 activated the mouse p21 ( CIP1/WAF1 ) promoter in HS-72 cells , and that a 29-base pair ( b ) region of the promoter ( -1928/-1900 relative to the TATA box ) , conserved between mice and humans , was responsive to BMP-2 as well as expression of Smad1 , Smad4 , and constitutively active mutants of BMP type I receptors .