Quantitative proteomics identifies the Myb-binding protein p160 as a novel target of the von Hippel-Lindau tumor suppressor.

Yanlai Lai,Yuzuru Shiio,Susan T Weintraub,Meihua Song,Mei Qiao

doi:10.1371/journal.pone.0016975

Abstract

BackgroundThe von Hippel-Lindau (VHL) tumor suppressor gene encodes a component of a ubiquitin ligase complex, which is best understood as a negative regulator of hypoxia inducible factor (HIF). VHL ubiquitinates and degrades the α subunits of HIF, and this is proposed to suppress tumorigenesis and tumor angiogenesis. However, several lines of evidence suggest that there are unidentified substrates or targets for VHL that play important roles in tumor suppression.Methodology/Principal FindingsEmploying quantitative proteomics, we developed an approach to systematically identify the substrates of ubiquitin ligases and using this method, we identified the Myb-binding protein p160 as a novel substrate of VHL.Conclusions/SignificanceA major barrier to understanding the functions of ubiquitin ligases has been the difficulty in pinpointing their ubiquitination substrates. The quantitative proteomics approach we devised for the identification of VHL substrates will be widely applicable to other ubiquitin ligases.

Highlights

Mutation of the von Hippel-Lindau (VHL) tumor suppressor gene is associated with a hereditary cancer syndrome called von HippelLindau (VHL) disease, which is characterized by an increased risk of clear cell renal carcinoma, hemangioblastoma of the nervous system, and adrenal pheochromocytoma
Since the VHL ubiquitin ligase catalyzes the formation of lysine48-linked poly-ubiquitin chains which target proteins for proteasomal degradation, we reasoned that the VHL substrates would accumulate in cells that do not have functional VHL, which can be detected by comparing the global protein expression in cells with and without functional VHL (Figure 1)
Our ICAT proteomic analysis identified the Myb-binding protein p160 as a protein whose expression is induced upon iron chelation, and further analyses demonstrated that p160 is a ubiquitination substrate of VHL

Summary

Introduction

Mutation of the von Hippel-Lindau (VHL) tumor suppressor gene is associated with a hereditary cancer syndrome called von HippelLindau (VHL) disease, which is characterized by an increased risk of clear cell renal carcinoma, hemangioblastoma of the nervous system, and adrenal pheochromocytoma (for reviews see [1,2,3,4]). Biallelic VHL inactivation is common in sporadic (non-hereditary) clear cell renal carcinomas and hemangioblastomas. VHL is best understood as a negative regulator of hypoxia inducible factor (HIF), a family of transcription factors regulating genes involved in the cellular response to hypoxia. The von Hippel-Lindau (VHL) tumor suppressor gene encodes a component of a ubiquitin ligase complex, which is best understood as a negative regulator of hypoxia inducible factor (HIF). Several lines of evidence suggest that there are unidentified substrates or targets for VHL that play important roles in tumor suppression

Methods

Results

Conclusion