Abstract
Immunoaffinity purification allows for the purification of epitope-tagged proteins and their associated multisubunit complexes from mammalian cells. Subsequent identification of the proteins by proteomic analysis enables unbiased biochemical characterization of their associated partners, potentially revealing the physiological or functional context of any given protein. Here, we use immunoaffinity isolation of the Activating Signal Co-integrator Complex (ASCC) from human cells as an example, demonstrating the utility of the approach in revealing protein complexes involved in genotoxic stress responses.