USP7 Is a Suppressor of PCNA Ubiquitination and Oxidative-Stress-Induced Mutagenesis in Human Cells

Cell Rep. 2015 Dec 15;13(10):2072-80. doi: 10.1016/j.celrep.2015.11.014. Epub 2015 Dec 8.


Mono-ubiquitinated PCNA activates error-prone DNA polymerases; therefore, strict regulation of PCNA mono-ubiquitination is crucial in avoiding undesired mutagenesis. In this study, we used an in vitro assay system to identify USP7 as a deubiquitinating enzyme of mono-ubiquitinated PCNA. Suppression of USP1, a previously identified PCNA deubiquitinase, or USP7 increased UV- and H2O2-induced PCNA mono-ubiquitination in a distinct and additive manner, suggesting that USP1 and USP7 make different contributions to PCNA deubiquitination in human cells. Cell-cycle-synchronization analyses revealed that USP7 suppression increased H2O2-induced PCNA ubiquitination throughout interphase, whereas USP1 suppression specifically increased ubiquitination in S-phase cells. UV-induced mutagenesis was elevated in USP1-suppressed cells, whereas H2O2-induced mutagenesis was elevated in USP7-suppressed cells. These results suggest that USP1 suppresses UV-induced mutations produced in a manner involving DNA replication, whereas USP7 suppresses H2O2-induced mutagenesis involving cell-cycle-independent processes such as DNA repair.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Line
  • DNA Damage / physiology
  • Flow Cytometry
  • Humans
  • Hydrogen Peroxide / toxicity
  • Mutagenesis / physiology*
  • Mutagenesis, Site-Directed
  • Oxidative Stress / physiology*
  • Polymerase Chain Reaction
  • Proliferating Cell Nuclear Antigen / metabolism*
  • RNA, Small Interfering
  • Transfection
  • Ubiquitin Thiolesterase / metabolism*
  • Ubiquitin-Specific Peptidase 7
  • Ubiquitination


  • Proliferating Cell Nuclear Antigen
  • RNA, Small Interfering
  • Hydrogen Peroxide
  • USP7 protein, human
  • Ubiquitin Thiolesterase
  • Ubiquitin-Specific Peptidase 7