UBE2O is a quality control factor for orphans of multiprotein complexes

Science. 2017 Aug 4;357(6350):472-475. doi: 10.1126/science.aan0178.

Abstract

Many nascent proteins are assembled into multiprotein complexes of defined stoichiometry. Imbalances in the synthesis of individual subunits result in orphans. How orphans are selectively eliminated to maintain protein homeostasis is poorly understood. Here, we found that the conserved ubiquitin-conjugating enzyme UBE2O directly recognized juxtaposed basic and hydrophobic patches on unassembled proteins to mediate ubiquitination without a separate ubiquitin ligase. In reticulocytes, where UBE2O is highly up-regulated, unassembled α-globin molecules that failed to assemble with β-globin were selectively ubiquitinated by UBE2O. In nonreticulocytes, ribosomal proteins that did not engage nuclear import factors were targets for UBE2O. Thus, UBE2O is a self-contained quality control factor that comprises substrate recognition and ubiquitin transfer activities within a single protein to efficiently target orphans of multiprotein complexes for degradation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Active Transport, Cell Nucleus
  • Cytosol / enzymology
  • HEK293 Cells
  • Humans
  • Hydrophobic and Hydrophilic Interactions
  • Multiprotein Complexes / metabolism*
  • Proteolysis*
  • Reticulocytes / enzymology
  • Ribosomal Proteins / metabolism*
  • SEC Translocation Channels / metabolism
  • Ubiquitin / metabolism
  • Ubiquitin-Conjugating Enzymes / metabolism*
  • Ubiquitination*
  • alpha-Globins / metabolism
  • beta-Globins / metabolism

Substances

  • Multiprotein Complexes
  • Ribosomal Proteins
  • SEC Translocation Channels
  • SEC61A1 protein, human
  • Ubiquitin
  • alpha-Globins
  • beta-Globins
  • Ubiquitin-Conjugating Enzymes
  • UBE2O protein, human