Rad18-dependent SUMOylation of human specialized DNA polymerase eta is required to prevent under-replicated DNA

Nat Commun. 2016 Nov 4;7:13326. doi: 10.1038/ncomms13326.


Translesion polymerase eta (polη) was characterized for its ability to replicate ultraviolet-induced DNA lesions that stall replicative polymerases, a process promoted by Rad18-dependent PCNA mono-ubiquitination. Recent findings have shown that polη also acts at intrinsically difficult to replicate sequences. However, the molecular mechanisms that regulate its access to these loci remain elusive. Here, we uncover that polη travels with replication forks during unchallenged S phase and this requires its SUMOylation on K163. Abrogation of polη SUMOylation results in replication defects in response to mild replication stress, leading to chromosome fragments in mitosis and damage transmission to daughter cells. Rad18 plays a pivotal role, independently of its ubiquitin ligase activity, acting as a molecular bridge between polη and the PIAS1 SUMO ligase to promote polη SUMOylation. Our results provide the first evidence that SUMOylation represents a new way to target polη to replication forks, independent of the Rad18-mediated PCNA ubiquitination, thereby preventing under-replicated DNA.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Line
  • DNA Replication*
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism*
  • DNA-Directed DNA Polymerase / genetics
  • DNA-Directed DNA Polymerase / metabolism*
  • Humans
  • Proliferating Cell Nuclear Antigen / genetics
  • Proliferating Cell Nuclear Antigen / metabolism*
  • Protein Inhibitors of Activated STAT / genetics
  • Protein Inhibitors of Activated STAT / metabolism*
  • S Phase / genetics
  • Small Ubiquitin-Related Modifier Proteins / genetics
  • Small Ubiquitin-Related Modifier Proteins / metabolism*
  • Sumoylation / genetics
  • Ubiquitin-Protein Ligases / genetics
  • Ubiquitin-Protein Ligases / metabolism*


  • DNA-Binding Proteins
  • PIAS1 protein, human
  • Proliferating Cell Nuclear Antigen
  • Protein Inhibitors of Activated STAT
  • RAD18 protein, human
  • Small Ubiquitin-Related Modifier Proteins
  • Ubiquitin-Protein Ligases
  • DNA-Directed DNA Polymerase
  • Rad30 protein