Substrate channeling in mammalian base excision repair pathways: passing the baton

J Biol Chem. 2010 Dec 24;285(52):40479-88. doi: 10.1074/jbc.M110.155267. Epub 2010 Oct 14.

Abstract

The current model for base excision repair (BER) involves two general sub-pathways termed single-nucleotide BER and long patch BER that are distinguished by their repair patch sizes and the enzymes/co-factors involved. Both sub-pathways involve a series of sequential steps from initiation to completion of repair. The BER sub-pathways are designed to sequester the various intermediates, passing them along from one step to the next without allowing these toxic molecules to trigger cell cycle arrest, necrotic cell death, or apoptosis. Although a variety of DNA-protein and protein-protein interactions are known for the BER intermediates and enzymes/co-factors, the molecular mechanisms accounting for step-to-step coordination are not well understood. In the present study we designed an in vitro assay to explore the question of whether there is a channeling or "hand-off" of the repair intermediates during BER in vitro. The results show that when BER enzymes are pre-bound to the initial single-nucleotide BER intermediate, the DNA is channeled from apurinic/apyrimidinic endonuclease 1 to DNA polymerase β and then to DNA ligase. In the long patch BER subpathway, where the 5'-end of the incised strand is blocked, the intermediate after DNA polymerase β gap filling is not channeled to the subsequent enzyme, flap endonuclease 1. Instead, flap endonuclease 1 must recognize and bind to the intermediate in competition with other molecules.

Publication types

  • Research Support, N.I.H., Intramural

MeSH terms

  • Animals
  • Apoptosis / physiology
  • DNA / genetics
  • DNA / metabolism*
  • DNA Polymerase beta / genetics
  • DNA Polymerase beta / metabolism*
  • DNA Repair / physiology*
  • DNA-(Apurinic or Apyrimidinic Site) Lyase / genetics
  • DNA-(Apurinic or Apyrimidinic Site) Lyase / metabolism*
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism
  • Flap Endonucleases / genetics
  • Flap Endonucleases / metabolism*
  • Humans
  • Models, Biological*
  • Necrosis

Substances

  • DNA-Binding Proteins
  • DNA
  • DNA Polymerase beta
  • Flap Endonucleases
  • FEN1 protein, human
  • DNA-(Apurinic or Apyrimidinic Site) Lyase