Format

Send to

Choose Destination
J Biol Chem. 2016 Jun 3;291(23):12105-18. doi: 10.1074/jbc.M116.726877. Epub 2016 Apr 11.

A Conserved C-terminal Element in the Yeast Doa10 and Human MARCH6 Ubiquitin Ligases Required for Selective Substrate Degradation.

Author information

1
From the Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06520 and.
2
From the Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06520 and the Department of Biology, University of Konstanz, Universitaetsstrasse 10, 78457 Konstanz, Germany.
3
From the Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06520 and mark.hochstrasser@yale.edu.

Abstract

Specific proteins are modified by ubiquitin at the endoplasmic reticulum (ER) and are degraded by the proteasome, a process referred to as ER-associated protein degradation. In Saccharomyces cerevisiae, two principal ER-associated protein degradation ubiquitin ligases (E3s) reside in the ER membrane, Doa10 and Hrd1. The membrane-embedded Doa10 functions in the degradation of substrates in the ER membrane, nuclear envelope, cytoplasm, and nucleoplasm. How most E3 ligases, including Doa10, recognize their protein substrates remains poorly understood. Here we describe a previously unappreciated but highly conserved C-terminal element (CTE) in Doa10; this cytosolically disposed 16-residue motif follows the final transmembrane helix. A conserved CTE asparagine residue is required for ubiquitylation and degradation of a subset of Doa10 substrates. Such selectivity suggests that the Doa10 CTE is involved in substrate discrimination and not general ligase function. Functional conservation of the CTE was investigated in the human ortholog of Doa10, MARCH6 (TEB4), by analyzing MARCH6 autoregulation of its own degradation. Mutation of the conserved Asn residue (N890A) in the MARCH6 CTE stabilized the normally short lived enzyme to the same degree as a catalytically inactivating mutation (C9A). We also report the localization of endogenous MARCH6 to the ER using epitope tagging of the genomic MARCH6 locus by clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9-mediated genome editing. These localization and CTE analyses support the inference that MARCH6 and Doa10 are functionally similar. Moreover, our results with the yeast enzyme suggest that the CTE is involved in the recognition and/or ubiquitylation of specific protein substrates.

KEYWORDS:

Doa10; E3 ubiquitin ligase; MARCH6; TEB4; endoplasmic-reticulum-associated protein degradation (ERAD); proteasome; proteolysis; ubiquitin

PMID:
27068744
PMCID:
PMC4933261
DOI:
10.1074/jbc.M116.726877
[Indexed for MEDLINE]
Free PMC Article

Supplemental Content

Full text links

Icon for HighWire Icon for PubMed Central
Loading ...
Support Center