Fig. 7. Effect of Pax6 protein on activity of the P53 promoter. Pax6 protein (3 µg of pPax6) does not positively regulate activity of the human P53 promoter in transiently transfected SAOS2 cells, but upon overexpression (16 µg pPax6, indicated by ++) does inhibit the P53 promoter activity. By contrast, Pax6-5a shows no significant effect. Normalized luciferase activity in the presence or absence of functional pRb is indicated; error bars indicate s.d. The luciferase activity of the `empty' vector pCMV without pRb was given an arbitrary value of 100. Note that pRB slightly increases the Pax6 inhibitory effect on P53.