The Auto-Generated Fragment of the Usp1 Deubiquitylase Is a Physiological Substrate of the N-End Rule Pathway

• Published in: Molecular cell Vol. 48; no. 6; pp. 926 - 933
• Main Authors: Piatkov, Konstantin I., Colnaghi, Luca, Békés, Miklos, Varshavsky, Alexander, Huang, Tony T.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 28-12-2012
• Subjects: amidase; Amidohydrolases - metabolism; Amino Acid Motifs; Amino Acid Substitution; Aminoacyltransferases - metabolism; Animals; Arabidopsis Proteins; Cell Line; chromosome segregation; deamidation; degradation; DNA; DNA repair; DNA-directed DNA polymerase; Endopeptidases - genetics; Endopeptidases - metabolism; Enzyme Stability; Female; Humans; hypersensitivity; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Mutagenesis, Site-Directed; Peptide Fragments - genetics; Peptide Fragments - metabolism; proliferating cell nuclear antigen; Proliferating Cell Nuclear Antigen - metabolism; Protein Processing, Post-Translational; Proteolysis; rules; Ubiquitin-Specific Proteases; Ubiquitination; ultraviolet irradiation; ultraviolet radiation
• ISSN: 1097-2765; 1097-4164
• DOI: 10.1016/j.molcel.2012.10.012

Deamidation of N-terminal Gln by the Ntaq1 NtQ-amidase is a part of the Arg/N-end rule pathway, a ubiquitin-dependent proteolytic system. Here we identify Gln-Usp1Ct, 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-Usp1Ct fragment is selectively destroyed by the Arg/N-end rule pathway. We also show that metabolic stabilization of Gln-Usp1Ct 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.
[Display omitted]
► Autocleaved Usp1 is targeted for degradation by the Arg/N-end rule pathway ► Autocleaved Usp1 is a physiological substrate of the Ntaq1 amidase ► Metabolic stabilization of Gln-Usp1 in cells inhibits PCNA monoubiquitylation