9-1-1: PCNA's specialized cousin

Trends Biochem Sci. 2011 Nov;36(11):563-8. doi: 10.1016/j.tibs.2011.08.002. Epub 2011 Oct 4.


All living organisms are vulnerable to DNA damage. Cells respond to this hazard by activating a complex network of checkpoint and repair proteins to preserve genomic integrity. The DNA-encircling, ring-shaped heterotrimeric 9-1-1 complex, a relative of the replication protein PCNA, is a central coordinator of these events. 9-1-1 is loaded to damaged sites where it serves as a platform for the selective recruitment of checkpoint and repair proteins. In this Opinion article, 9-1-1 and proliferating cell nuclear antigen (PCNA) are compared and discussed in light of their respective structures and functions. We propose that the interaction partners of 9-1-1 possess specific 9-1-1-interaction boxes, which discriminate between 9-1-1 and PCNA thereby enabling specific interactions with individual 9-1-1 subunits.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Cycle Proteins / chemistry
  • Cell Cycle Proteins / metabolism*
  • Exonucleases / chemistry
  • Exonucleases / metabolism*
  • Humans
  • Proliferating Cell Nuclear Antigen / chemistry
  • Proliferating Cell Nuclear Antigen / metabolism*


  • Cell Cycle Proteins
  • HUS1 protein, human
  • Proliferating Cell Nuclear Antigen
  • rad9 protein
  • Exonucleases
  • Rad1 protein, human