THE TUMOR SUPPRESSION FUNCTION OF P21(WAF) IS CONTAINED IN ITS N-TERMINAL HALF (HALF-WAF)

The Waf-1 encoded protein, p21, mediates p53 suppression of tumor cell growth. Overexpression of p21 in the H1299 tumor cell line suppresses colony formation similar to that resulted;from p53 overexpression. In an effort to localize the tumor suppression function within the struc ture of p21 we utilized vectors constructed with systematic truncation s of p21 and tested their efficiency in suppressing tumor cell growth. We demonstrate that the N-terminal half of the p21 molecule (residues 1-80 and 1-89) shows better tumor cell growth suppression than the en tire p21 molecule whereas the C-terminal half of p21 does not show thi s effect, These results may have implications for gene therapy of canc er.