Inhibition of Siah ubiquitin ligase function

Abstract

Tumor hypoxia induces the upregulation of hypoxia-inducible factor 1α (Hif-1α), which in turn induces the expression of genes including VEGF to recruit new blood vessel outgrowth, enabling tumor growth and metastasis. Interference with the Hif-1 pathway and neoangiogenesis is an attractive antitumor target. The hydroxylation of Hif-1α by prolyl-hydroxylase (PHD) proteins during normoxia serves as a recognition motif for its proteasomal degradation. However, under hypoxic conditions, hydroxylation is inhibited and furthermore, PHD proteins are themselves polyubiquitylated and degraded by Siah ubiquitin ligases. Our data demonstrate for the first time that inhibition of the interaction between..