S100 proteins interact with the N-terminal domain of MDM2.

S100 proteins interact with the transactivation domain and the C-terminus of p53. Further, S100B has been shown to interact with MDM2, a central negative regulator of p53. Here, we show that S100B bound directly to the folded N-terminal domain of MDM2 (residues 2-125) by size exclusion chromatography and surface plasmon resonance experiments. This interaction with MDM2 (2-125) is a general feature of S100 proteins; S100A1, S100A2, S100A4 and S100A6 also interact with MDM2 (2-125). These interactions with S100 proteins do not result in a ternary complex with MDM2 (2-125) and p53. Instead, we observe the ability of a subset of S100 proteins to disrupt the extent of MDM2-mediated p53 ubiquitylation in vitro.