N-terminal acetylation of the yeast Derlin Der1 is essential for Hrd1 ubiquitin-ligase activity toward luminal ER substrates.
Two conserved ubiquitin ligases, Hrd1 and Doa10, mediate most endoplasmic reticulum-associated protein degradation (ERAD) in yeast. Degradation signals (degrons) recognized by these ubiquitin ligases remain poorly characterized. Doa10 recognizes the Deg1 degron from the MATα2 transcription factor. We previously found that deletion of the gene (NAT3) encoding the catalytic subunit of the NatB N-terminal acetyltransferase weakly stabilized a Deg1-fusion protein. By contrast, a recent analysis of several MATα2 derivatives suggested that N-terminal acetylation of these proteins by NatB was crucial for recognition by Doa10. We now analyze endogenous MATα2 degradation in cells lacking NatB and observe minimal perturbation relative to wild-type cells. However, NatB mutation strongly impairs degradation of ER-luminal Hrd1 substrates. This unexpected defect derives from a failure of Der1, a Hrd1 complex subunit, to be N-terminally acetylated in NatB mutant yeast. We retargeted Der1 to another acetyltransferase to show that it is the only ERAD factor requiring N-terminal acetylation. Preventing Der1 acetylation stimulates its proteolysis via the Hrd1 pathway, at least partially accounting for the ERAD defect observed in the absence of NatB. These results reveal an important role for N-terminal acetylation in controlling Hrd1 ligase activity toward a specific class of ERAD substrates.
Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, USA.
Dimitrios
D
Zattas
David J
DJ
Adle
Eric M
EM
Rubenstein
Mark
M
Hochstrasser
D000107:Acetylation; D000123:Acetyltransferases / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D004721:Endoplasmic Reticulum / Q000378:metabolism; D060746:Endoplasmic Reticulum-Associated Degradation; D015151:Immunoblotting; D019751:Intramolecular Transferases / Q000235:genetics / Q000378:metabolism; D013058:Mass Spectrometry; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation; D063210:N-Terminal Acetyltransferase B / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000235:genetics; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism*; D056811:Unfolded Protein Response / Q000235:genetics
C098515:DER1 protein, S cerevisiae; C062928:MATA2 protein, S cerevisiae; D008565:Membrane Proteins; C570986:Nat3 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D000123:Acetyltransferases; C556312:NatB protein, S cerevisiae; D063210:N-Terminal Acetyltransferase B; C104621:HRD1 protein, S cerevisiae; C091362:SSM4 protein, S cerevisiae; D044767:Ubiquitin-Protein Ligases; D019751:Intramolecular Transferases; C068903:DEG1 protein, S cerevisiae