In response to DNA damage, the activity of the p53 tumor suppressor is modulated by protein stabilization and post-translational modifications including acetylation. Interestingly, both acetylation and ubiquitination can modify the same lysine residues at the C terminus of p53, implicating a role of acetylation in the regulation of p53 stability. However, the direct effect of acetylation on Mdm2-mediated ubiquitination of p53 is still lacking because of technical difficulties. Here, we have developed a method to obtain pure acetylated p53 proteins from cells, and by using an in vitro purified system, we provide the direct evidence that acetylation of the C-terminal domain is sufficient to abrogate its ubiquitination by Mdm2. Importantly, even in the absence of DNA damage, acetylation of the p53 protein is capable of reducing the ubiquitination levels and extending its half-life in vivo. Moreover, we also show that acetylation of p53 can affect its ubiquitination through other mechanisms in addition to the site competition. This study has significant implications regarding a general mechanism by which protein acetylation modulates ubiquitination-dependent proteasome proteolysis.

Hausp is a deubiquitinase that has been shown to regulate the p53-Mdm2 pathway. Cotransfection of p53 and Hausp stabilizes p53 through the removal of ubiquitin moieties from polyubiquitinated p53. Interestingly, knockout or RNA interference-mediated knockdown of Hausp in human cells also resulted in the stabilization of p53 due to the destabilization of Mdm2, suggesting a dynamic role of Hausp in p53 activation. To understand the physiological functions of Hausp, we generated hausp knockout mice. Hausp knockout mice die during early embryonic development between embryonic days E6.5 and E7.5. The hausp knockout embryos showed p53 activation, but no apparent increase in apoptosis. Embryonic lethality was caused by a dramatic reduction in proliferation and termination in development, in part due to p53 activation and/or abrogation of p53-independent functions. Although deletion of p53 did not completely rescue the embryonic lethality of the hausp knockout, embryonic development was extended in both hausp and p53 double knockout embryos. These data show that Hausp has a critical role in regulating the p53-Mdm2 pathway.

Introduction: Consensus definitions for clinical remission and super-response were recently established for severe asthma. Benralizumab is an interleukin-5 (IL-5) receptor a-directed monoclonal antibody for severe, uncontrolled asthma; efficacy and safety were demonstrated in previous pivotal phase 3 trials (SIROCCO, CALIMA, ZONDA). This analysis applied a composite remission definition to characterize individual responses to benralizumab after 6 and 12 months. Methods: In previous phase 3 studies, eligible patients were those with severe, uncontrolled asthma receiving medium-or high-dosage inhaled corticosteroids plus long-acting b 2 -agonists. This post hoc analysis included patients randomized to the approved benralizumab dose and not receiving oral corticosteroids (OCS) at baseline (SIROCCO/CALIMA) or OCS B 12.5 mg per day (ZONDA). Individual remission components were zero exacerbations; zero OCS use; Asthma Control Questionnaire-6