Identification of the RNA polymerase II subunit hsRPB7 as a novel target of the von Hippel-Lindau protein.
Inactivation of the von Hippel-Lindau (VHL) tumor suppressor gene is linked to the hereditary VHL disease and sporadic clear cell renal cell carcinomas (CCRCC). VHL-associated tumors are highly vascularized, a characteristic associated with overproduction of vascular endothelial growth factor (VEGF). The VHL protein (pVHL) is a component of the ubiquitin ligase E3 complex, targeting substrate proteins for ubiquitylation and subsequent proteasomic degradation. Here, we report that the pVHL can directly bind to the human RNA polymerase II seventh subunit (hsRPB7) through its beta-domain, and naturally occurring beta-domain mutations can decrease the binding of pVHL to hsRPB7. Introducing wild-type pVHL into human kidney tumor cell lines carrying endogenous mutant non-functional pVHL facilitates ubiquitylation and proteasomal degradation of hsRPB7, and decreases its nuclear accumulation. pVHL can also suppress hsRPB7-induced VEGF promoter transactivation, mRNA expression and VEGF protein secretion. Together, our results suggest that hsRPB7 is a downstream target of the VHL ubiquitylating complex and pVHL may regulate angiogenesis by targeting hsRPB7 for degradation via the ubiquitylation pathway and preventing VEGF expression.
Pubmed ID: 12912922 RIS Download
Cell Nucleus | Cysteine Endopeptidases | Endothelial Growth Factors | Gene Expression Regulation, Neoplastic | HeLa Cells | Humans | Intercellular Signaling Peptides and Proteins | Kidney Neoplasms | Lymphokines | Multienzyme Complexes | Mutation | Promoter Regions, Genetic | Proteasome Endopeptidase Complex | Protein Isoforms | Protein Structure, Tertiary | Protein Subunits | Proteins | RNA Polymerase II | RNA, Messenger | Transcriptional Activation | Transfection | Tumor Cells, Cultured | Ubiquitins | Vascular Endothelial Growth Factor A | Vascular Endothelial Growth Factors | von Hippel-Lindau Disease