Function, oligomerization, and conformation of tumor-associated p53 proteins with mutated C-terminus

Mutations that affect the oligomerization domain (OD) of the p53 tumor supp ressor may be of particular interest because of the remarkable contradictio n between the conservation of the OD and its relative functional resistance to amino acid substitutions, and because of recent hints that cellular pro tein factors may interact with the OD. Both point to the possibility that t his domain fulfills tasks beyond oligomerization. We report that the tumor- associated mutants 330H, 334V, and 337C are defective for homo-oligomerizat ion by th ree criteria. Accordingly, 330H and 337C failed to bind to a p53 recognition motif in gel-shift assays and to stimulate reporter genes effic iently in transient transfections. 334V retained some activity in both assa ys despite being oligomerization-defective. The ability of the mutants to i nduce apoptosis correlated with their performance in the DNA binding and tr ansactivation assays. However, mutants 330H and 337C were able to provoke c ell death when overexpressed, which in combination with their failure to tr ansactivate genes suggests competence for the induction of transactivation- independent apoptosis at high protein levels. Although 334V and 337C failed to homo-oligomerize, they were able to hetero-oligomerize with a p53 with wild-type OD, and 334V was able to interfere with transactivation by wt p53 . All mutants showed a reduced reactivity with antibody PAb421 and a distin ct calpain cleavage pattern indicative of conformational alterations. In co nclusion, tumor-associated OD mutants of p53 can be functionally competent to different degrees despite of being oligomerization defective, (C) 2000 W iley Liss, inc.