Spatially regulated ubiquitin ligation by an ER/nuclear membrane ligase

Nature. 2006 Oct 19;443(7113):827-31. doi: 10.1038/nature05170.


The ubiquitin system targets many cellular proteins. Doa10 (also known as Ssm4), a yeast transmembrane ubiquitin ligase (E3), resides in the endoplasmic reticulum (ER), but it attaches ubiquitin to soluble proteins that concentrate in the nucleus. A central question is how nuclear substrates gain access to an enzyme in the ER. Here we show that Doa10 reaches the inner nuclear membrane. A subcomplex of nuclear pore subunits is important for this transport. Notably, another ER transmembrane E3, Hrd1 (also known as Der3), cannot localize efficiently to the inner nuclear membrane. Tethering Doa10 at the cell periphery inhibits degradation of soluble nuclear substrates but not cytoplasmic ones. If Doa10 is released from these peripheral sites, localization of Doa10 to the nuclear envelope and degradation of its nuclear substrates are restored in parallel. Thus, localization of Doa10 to the inner nuclear membrane is necessary for nuclear substrate degradation. These data indicate that different membrane ubiquitin ligases are spatially sorted within the ER-nuclear envelope membrane system and that this differential localization contributes to their specificity.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Endoplasmic Reticulum / enzymology*
  • Endoplasmic Reticulum / metabolism
  • Gene Silencing
  • Nuclear Envelope / enzymology*
  • Nuclear Envelope / metabolism
  • Nuclear Pore / enzymology
  • Nuclear Pore / metabolism
  • Protein Transport
  • Saccharomyces cerevisiae / cytology*
  • Saccharomyces cerevisiae / enzymology*
  • Saccharomyces cerevisiae / genetics
  • Saccharomyces cerevisiae / metabolism
  • Saccharomyces cerevisiae Proteins / genetics
  • Saccharomyces cerevisiae Proteins / metabolism*
  • Ubiquitin / metabolism*
  • Ubiquitin-Protein Ligases / genetics
  • Ubiquitin-Protein Ligases / metabolism*


  • Saccharomyces cerevisiae Proteins
  • Ubiquitin
  • HRD1 protein, S cerevisiae
  • SSM4 protein, S cerevisiae
  • Ubiquitin-Protein Ligases