Hrd1p/Der3p is a membrane-anchored ubiquitin ligase required for ER-associated degradation.
In eukaryotes, endoplasmic reticulum-associated degradation (ERAD) functions in cellular quality control and regulation of normal ER-resident proteins. ERAD proceeds by the ubiquitin-proteasome pathway, in which the covalent attachment of ubiquitin to proteins targets them for proteasomal degradation. Ubiquitin-protein ligases (E3s) play a crucial role in this process by recognizing target proteins and initiating their ubiquitination. Here we show that Hrd1p, which is identical to Der3p, is an E3 for ERAD. Hrd1p is required for the degradation and ubiquitination of several ERAD substrates and physically associates with relevant ubiquitin-conjugating enzymes (E2s). A soluble Hrd1 fusion protein shows E3 activity in vitro - catalysing the ubiquitination of itself and test proteins. In this capacity, Hrd1p has an apparent preference for misfolded proteins. We also show that Hrd1p functions as an E3 in vivo, using only Ubc7p or Ubc1p to specifically program the ubiquitination of ERAD substrates.
Bays
N W
NW
Section of Cell and Developmental Biology, Division of Biology, University of California San Diego, 9500 Gilman Drive, La Jolla, California 92093-0347, USA.
Gardner
R G
RG
Seelig
L P
LP
Joazeiro
C A
CA
Hampton
R Y
RY
D002384:Catalysis; D003546:Cysteine Endopeptidases / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism* / Q000648:ultrastructure; D006609:High Mobility Group Proteins / Q000378:metabolism; D007425:Intracellular Membranes / Q000378:metabolism* / Q000648:ultrastructure; D008025:Ligases / Q000378:metabolism*; D009097:Multienzyme Complexes / Q000378:metabolism; D010641:Phenotype; D046988:Proteasome Endopeptidase Complex; D017434:Protein Structure, Tertiary / Q000502:physiology; D011506:Proteins / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins; D044763:Ubiquitin-Conjugating Enzymes; D044767:Ubiquitin-Protein Ligases; D014452:Ubiquitins / Q000378:metabolism*; D015003:Yeasts
D006609:High Mobility Group Proteins; D009097:Multienzyme Complexes; D011506:Proteins; D029701:Saccharomyces cerevisiae Proteins; D014452:Ubiquitins; C066752:UBC1 protein, S cerevisiae; C079437:UBE2L3 protein, human; D044763:Ubiquitin-Conjugating Enzymes; C104621:HRD1 protein, S cerevisiae; D044767:Ubiquitin-Protein Ligases; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; D008025:Ligases