The auto-generated fragment of the Usp1 deubiquitylase is a physiological substrate of the N-end rule pathway

Mol Cell. 2012 Dec 28;48(6):926-33. doi: 10.1016/j.molcel.2012.10.012. Epub 2012 Nov 15.


Deamidation of N-terminal Gln by the Ntaq1 Nt(Q)-amidase is a part of the Arg/N-end rule pathway, a ubiquitin-dependent proteolytic system. Here we identify Gln-Usp1(Ct), the C-terminal fragment of the autocleaved Usp1 deubiquitylase, as the first physiological Arg/N-end rule substrate that is targeted for degradation through deamidation of N-terminal Gln. Usp1 regulates genomic stability, in part through the deubiquitylation of monoubiquitylated PCNA, a DNA polymerase processivity factor. The autocleaved Usp1 remains a deubiquitylase because its fragments remain associated with Uaf1, an enhancer of Usp1 activity, until the Gln-Usp1(Ct) fragment is selectively destroyed by the Arg/N-end rule pathway. We also show that metabolic stabilization of Gln-Usp1(Ct) results in a decreased monoubiquitylation of PCNA and in a hypersensitivity of cells to ultraviolet irradiation. Thus, in addition to its other functions in DNA repair and chromosome segregation, the Arg/N-end rule pathway regulates genomic stability through the degradation-mediated control of the autocleaved Usp1 deubiquitylase.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amidohydrolases / metabolism
  • Amino Acid Motifs
  • Amino Acid Substitution
  • Aminoacyltransferases / metabolism
  • Animals
  • Arabidopsis Proteins
  • Cell Line
  • Endopeptidases / genetics
  • Endopeptidases / metabolism*
  • Enzyme Stability
  • Female
  • Humans
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Mutagenesis, Site-Directed
  • Peptide Fragments / genetics
  • Peptide Fragments / metabolism*
  • Proliferating Cell Nuclear Antigen / metabolism
  • Protein Processing, Post-Translational*
  • Proteolysis
  • Ubiquitin-Specific Proteases
  • Ubiquitination


  • Arabidopsis Proteins
  • Peptide Fragments
  • Proliferating Cell Nuclear Antigen
  • Aminoacyltransferases
  • arginyltransferase
  • Endopeptidases
  • USP1 protein, human
  • Ubiquitin-Specific Proteases
  • Usp1 protein, mouse
  • Amidohydrolases
  • Ntaq1 protein, mouse