Alternative ubiquitin activation/conjugation cascades interact with N-end rule ubiquitin ligases to control degradation of RGS proteins

Mol Cell. 2011 Aug 5;43(3):392-405. doi: 10.1016/j.molcel.2011.05.034.


Vertebrates express two enzymes for activation of ubiquitin-UBA1, which is responsible for activation of the vast majority of E2 conjugating enzymes, and UBA6, which uses the dedicated E2, USE1. However, targets and E3s for UBA6-USE1 are unknown. Here, we demonstrate that UBA6-USE1 functions with the UBR1-3 subfamily of N-recognin E3s to degrade the N-end rule substrates RGS4, RGS5, and Arg (R)-GFP. This pathway functions in the cytoplasm in parallel with the UBA1-UBE2A/B-UBR2 cascade, which promotes turnover of nuclear RGS4/5 proteins and an apparently phenotypically distinct pool of cytoplasmic RGS4/5. UBR2 promotes Lys48 (K48)-specific ubiquitin discharge from, and RGS4 ubiquitylation by, both USE1 and UBE2A in vitro. This work provides insight into the machinery employed by the UBA6-USE1 cascade to promote protein turnover and suggests that the UBA6 and UBA1 pathways can function in parallel with the same E3 to degrade the same targets in a spatially distinct manner.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Consensus Sequence
  • HEK293 Cells
  • Humans
  • Mice
  • Molecular Sequence Data
  • NIH 3T3 Cells
  • Protein Structure, Tertiary
  • RGS Proteins / metabolism*
  • SNARE Proteins
  • Sequence Alignment
  • Ubiquitin-Activating Enzymes / metabolism*
  • Ubiquitin-Activating Enzymes / physiology
  • Ubiquitin-Conjugating Enzymes / metabolism
  • Ubiquitin-Protein Ligases / chemistry
  • Ubiquitin-Protein Ligases / metabolism
  • Ubiquitin-Protein Ligases / physiology
  • Ubiquitins / metabolism*
  • Ubiquitins / physiology
  • Vesicular Transport Proteins


  • RGS Proteins
  • SNARE Proteins
  • UBA6 protein, human
  • Ubiquitins
  • Use1 protein, human
  • Vesicular Transport Proteins
  • UBE2A protein, human
  • Ubiquitin-Conjugating Enzymes
  • UBR1 protein, human
  • UBR2 protein, human
  • Ubiquitin-Protein Ligases
  • Ubiquitin-Activating Enzymes