CHARACTERIZATION OF THE E3 UBIQUITIN LIGASE SIAH2 AS AN ANTI-CANCER TARGET

Abstract

Siah ubiquitin ligases play an important role in a number of signaling pathways in cancer progression and metastasis. One such critical pathway regulated by Siah2 in cancer is the hypoxia inducible factor 1a (Hif-1a) dependent pathway, which gets activated in response to hypoxia. The substrate binding domain (SBD) of Siah2 is of importance in the induction of the Hif-1a dependent pathway by regulating prolyl hydroxylase 3 (PHD3), a well-studied substrate of Siah2 under hypoxia. Since this pathway is critical in human cancers, various studies have suggested that Siah2 may be a suitable target for developing inhibitors. We applied in silico structure-based high-throughput virtual screening (HTVS) and identified 5 ligands which interact with the SBD of Siah2. We further experimentally validated these identified compounds using in vitro and in vivo binding assays targeting protein-protein interactions. The obtained results show partial inhibitory effect of these compounds in Siah2 binding with its substrate. We have further identified the critical Siah2 residues that are involved in substrate specificity. Our study offers a promise for overcoming the challenges in identifying Siah specific inhibitors.