Moreover, a cancer-derived ATF3 mutant (R88G) devoid of ubiquitination failed to prevent p53 from MDM2-mediated degradation and thus was unable to activate the tumor suppressor.
The results show that: (i) the p53 mutants H115N and S116M are thermally more stable than wild-type p53; (ii) H115N but not S116M is capable of rescuing the DNA binding of one of the most frequent p53 mutants in cancer, R248Q, as shown by binding of R248Q/H115N to gadd45 (the promoter of a gene involved in cell-cycle arrest); (iii) the double mutant R248Q/H115N is more stable than wild-type p53; (iv) the effect of H115N as a second-site suppressor to restore DNA-binding activity is specific to R248Q, but not to R248W; (v) molecular-dynamics simulations indicate that R248Q/H115N has a conformation similar to wild-type p53, which is distinct from that of R248Q.
To elucidate the nature of the gain of function, we introduced the most common p53 cancer mutations (R248W and R273H) independently into the humanized p53 knock-in (HUPKI) allele in mice.