Brd4 and HEXIM1: Multiple Roles in P-TEFb Regulation and Cancer

Figure 4

HEXIM1 stabilizes p53 by blocking the HDM2-mediated ubiquitination of p53. Human p53 protein can be divided into five domains: transactivation (TA), proline rich (PR), DNA binding (DB), oligomerization (OLI), and negative (NEG) domains. The HDM2 ubiquitination sites are located with the NEG domain. HEXIM1 interacts with the NEG domain of p53 and prevents the binding between p53 and HDM2.