title: Alternative ubiquitin activation/conjugation cascades interact with N-end rule ubiquitin ligases to control degradation of RGS proteins.
abstract: 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.
authors.affiliation: Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA.
authors.forename: Peter C W
authors.initials: PC
authors.lastname: Lee
authors.forename: Mathew E
authors.initials: ME
authors.lastname: Sowa
authors.forename: Steven P
authors.initials: SP
authors.lastname: Gygi
authors.forename: J Wade
authors.initials: JW
authors.lastname: Harper
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D016384:Consensus Sequence; D057809:HEK293 Cells; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D041681:NIH 3T3 Cells; D017434:Protein Structure, Tertiary; D020710:RGS Proteins / Q000378:metabolism*; D050600:SNARE Proteins; D016415:Sequence Alignment; D044764:Ubiquitin-Activating Enzymes / Q000378:metabolism* / Q000502:physiology; D044763:Ubiquitin-Conjugating Enzymes / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000737:chemistry / Q000378:metabolism / Q000502:physiology; D014452:Ubiquitins / Q000378:metabolism* / Q000502:physiology; D033921:Vesicular Transport Proteins
chemical_list: D020710:RGS Proteins; D050600:SNARE Proteins; C521757:UBA6 protein, human; D014452:Ubiquitins; C521756:Use1 protein, human; D033921:Vesicular Transport Proteins; C471545:UBE2A protein, human; D044763:Ubiquitin-Conjugating Enzymes; C113474:UBR1 protein, human; C499858:UBR2 protein, human; D044767:Ubiquitin-Protein Ligases; D044764:Ubiquitin-Activating Enzymes