Site-specific repair of cyclobutane pyrimidine dimers in a positioned nucleosome by photolyase and T4 endonuclease V in vitro

EMBO J. 1998 Jan 2;17(1):306-16. doi: 10.1093/emboj/17.1.306.

Abstract

Since genomic DNA is folded into nucleosomes, and DNA damage is generated all over the genome, a central question is how DNA repair enzymes access DNA lesions and how they cope with nucleosomes. To investigate this topic, we used a reconstituted nucleosome (HISAT nucleosome) as a substrate to generate DNA lesions by UV light (cyclobutane pyrimidine dimers, CPDs), and DNA photolyase and T4 endonuclease V (T4-endoV) as repair enzymes. The HISAT nucleosome is positioned precisely and contains a long polypyrimidine region which allows one to monitor formation and repair of CPDs over three helical turns. Repair by photolyase and T4-endoV was inefficient in nucleosomes compared with repair in naked DNA. However, both enzymes showed a pronounced site-specific modulation of repair on the nucleosome surface. Removal of the histone tails did not substantially enhance repair efficiency nor alter the site specificity of repair. Although photolyase and T4-endoV are different enzymes with different mechanisms, they exhibited a similar site specificity in nucleosomes. This implies that the nucleosome structure has a decisive role in DNA repair by exerting a strong constraint on damage accessibility. These findings may serve as a model for damage recognition and repair by more complex repair mechanisms in chromatin.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • DNA / radiation effects
  • DNA Repair*
  • Deoxyribodipyrimidine Photo-Lyase / metabolism*
  • Deoxyribonuclease (Pyrimidine Dimer)
  • Endodeoxyribonucleases / antagonists & inhibitors
  • Endodeoxyribonucleases / metabolism*
  • Histones / metabolism
  • Nucleosomes / metabolism*
  • Pyrimidine Dimers / genetics*
  • Ultraviolet Rays
  • Viral Proteins*

Substances

  • Histones
  • Nucleosomes
  • Pyrimidine Dimers
  • Viral Proteins
  • DNA
  • Endodeoxyribonucleases
  • endonuclease V, phage T4
  • Deoxyribonuclease (Pyrimidine Dimer)
  • Deoxyribodipyrimidine Photo-Lyase