Human Stromal Antigen 1 (STAG1) Cohesin Subunit SA-1; A Target Enabling Package

Loss of function mutations in the cohesin subunit gene STAG2 are common in a variety of cancers (1). These cells become dependent on the paralogous cohesin subunit STAG1 (2-4). Mutants of STAG1 that disrupt the binding to the cohesin subunit RAD21 cannot complement the loss of STAG2. This TEP examines the druggability of STAG1 as a synthetic lethal strategy to treat stag2^- cancers. The TEP includes crystal structures of two domains of STAG1, alone and in complex with Rad21-rderived peptides. We performed screens of a fragment library and identified small molecules bound to pockets in the two domains of STAG1. We also developed assays for binding of RAD21 peptides to STAG1, which can be used to screen for molecules that disrupt binding.