Sczaniecka, M., Gladstone, K., Pettersson, S., McLaren, L., Huart, A.S. and Wallace, M.
Notes: The E3 ubiquitin ligase murine double minute 2 (MDM2) regulates transcriptional activity and expression levels of the p53 tumor suppressor protein. In this article, the authors show that the cell fate determinant NUMB interacts with MDM2, disrupting the interaction of MDM2 and p53 and preventing the ubiquitination of p53. To study protein-protein interactions between NUMB and MDM2, the authors used the pFN2A (GST) Flexi® Vector to express full-length and partial NUMB sequences as GST fusion proteins for protein pull-down experiments. To examine their hypothesis that the interaction between NUMB and MDM2 increases p53 levels and thus apoptosis in cells, they treated ZR75 human breast carcinoma cells and A375 human melanoma cells with NUMB-derived peptides and small molecule ligands that block the interaction between NUMB and MDM2. These treatments resulted in increased levels of p53 protein, Annexin V staining as well as caspase-3/7 activity, as determined using the Caspase-Glo® 3/7 Assay System. (4351)