title: The auto-generated fragment of the Usp1 deubiquitylase is a physiological substrate of the N-end rule pathway.
abstract: 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.
authors.affiliation: Division of Biology, California Institute of Technology, Pasadena, CA 91125, USA.
authors.forename: Konstantin I
authors.initials: KI
authors.lastname: Piatkov
authors.forename: Luca
authors.initials: L
authors.lastname: Colnaghi
authors.forename: Miklos
authors.initials: M
authors.lastname: Békés
authors.forename: Alexander
authors.initials: A
authors.lastname: Varshavsky
authors.forename: Tony T
authors.initials: TT
authors.lastname: Huang
mesh_terms: D000581:Amidohydrolases / Q000378:metabolism; D020816:Amino Acid Motifs; D019943:Amino Acid Substitution; D019881:Aminoacyltransferases / Q000378:metabolism; D000818:Animals; D029681:Arabidopsis Proteins; D002460:Cell Line; D010450:Endopeptidases / Q000235:genetics / Q000378:metabolism*; D004795:Enzyme Stability; D005260:Female; D006801:Humans; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D016297:Mutagenesis, Site-Directed; D010446:Peptide Fragments / Q000235:genetics / Q000378:metabolism*; D018809:Proliferating Cell Nuclear Antigen / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D059748:Proteolysis; D064570:Ubiquitin-Specific Proteases; D054875:Ubiquitination
chemical_list: D029681:Arabidopsis Proteins; D010446:Peptide Fragments; D018809:Proliferating Cell Nuclear Antigen; D019881:Aminoacyltransferases; C019727:arginyltransferase; D010450:Endopeptidases; C579228:USP1 protein, human; D064570:Ubiquitin-Specific Proteases; C579227:Usp1 protein, mouse; D000581:Amidohydrolases; C542242:Ntaq1 protein, mouse