p53

p53 activators and inhibitors act on the tumor suppressor p53, a transcription factor activated by cellular stress. In unstressed cells the ubiquitin ligase mouse double minute 2 (MDM2) keeps p53 levels low by promoting its degradation. RG7112 blocks the p53-MDM2 interaction, and SJ 172550 targets the related protein mouse double minute 4 (MDM4, also called MDMX). RITA binds p53 itself, while tenovin-1 and tenovin-6 raise cellular p53 levels. Tenovin-6 also inhibits the deacetylases sirtuin 1 and sirtuin 2 (SIRT1, SIRT2). Pifithrin-α hydrobromide works the other way, inhibiting p53-dependent transcription in cells exposed to genotoxic stress. Further compounds directed at MDM2 are listed in the neighboring MDM2 category.