(A) In vitro ubiquitination of recombinant p53 with HDM2 and/or HDMX. (B) In vitro ubiquitination of recombinant p53 with HDM2(S395D) and/or HDMX(S403D). (C) In vitro ubiquitination of recombinant p53 with HDM2 or HDMXp60 and the phosphomimetic mutant, and HDMX (1-255). (D) In vitro ubiquitination of recombinant p53 with HDMX (322-490) wt and the phosphomimetic mutant. (E) Levels of expression of p53 in H1299 ∆HDM2 cell line transfected with the HDM2, HDMX, HDMXp60 and HDMX (1-255). (F) In vivo ubiquitination in H1299 ∆HDM2 cell line of p53 with HDM2, HDMX or HDMXp60 using MG 132 to inhibits proteasome activity.