Monoubiquitinated histone H2A destabilizes photolesion-containing nucleosomes with concomitant release of UV-damaged DNA-binding protein E3 ligase

J Biol Chem. 2012 Apr 6;287(15):12036-49. doi: 10.1074/jbc.M111.307058. Epub 2012 Feb 10.


How the nucleotide excision repair (NER) machinery gains access to damaged chromatinized DNA templates and how the chromatin structure is modified to promote efficient repair of the non-transcribed genome remain poorly understood. The UV-damaged DNA-binding protein complex (UV-DDB, consisting of DDB1 and DDB2, the latter of which is mutated in xeroderma pigmentosum group E patients, is a substrate-recruiting module of the cullin 4B-based E3 ligase complex, DDB1-CUL4B(DDB2). We previously reported that the deficiency of UV-DDB E3 ligases in ubiquitinating histone H2A at UV-damaged DNA sites in the xeroderma pigmentosum group E cells contributes to the faulty NER in these skin cancer-prone patients. Here, we reveal the mechanism by which monoubiquitination of specific H2A lysine residues alters nucleosomal dynamics and subsequently initiates NER. We show that DDB1-CUL4B(DDB2) E3 ligase specifically binds to mononucleosomes assembled with human recombinant histone octamers and nucleosome-positioning DNA containing cyclobutane pyrimidine dimers or 6-4 photoproducts photolesions. We demonstrate functionally that ubiquitination of H2A Lys-119/Lys-120 is necessary for destabilization of nucleosomes and concomitant release of DDB1-CUL4B(DDB2) from photolesion-containing DNA. Nucleosomes in which these lysines are replaced with arginines are resistant to such structural changes, and arginine mutants prevent the eviction of H2A and dissociation of polyubiquitinated DDB2 from UV-damaged nucleosomes. The partial eviction of H3 from the nucleosomes is dependent on ubiquitinated H2A Lys-119/Lys-120. Our results provide mechanistic insight into how post-translational modification of H2A at the site of a photolesion initiates the repair process and directly affects the stability of the human genome.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Substitution
  • Cell Line
  • Cullin Proteins / chemistry
  • DNA / chemistry
  • DNA / radiation effects
  • DNA Damage
  • DNA Repair
  • DNA-Binding Proteins / chemistry
  • Histones / chemistry*
  • Histones / genetics
  • Humans
  • Nucleosomes / chemistry*
  • Polyubiquitin / chemistry
  • Protein Binding
  • Protein Processing, Post-Translational
  • Pyrimidine Dimers / chemistry
  • Ubiquitin-Protein Ligases / chemistry*
  • Ubiquitinated Proteins / chemistry*
  • Ubiquitination
  • Ultraviolet Rays*


  • CUL4B protein, human
  • Cullin Proteins
  • DDB1 protein, human
  • DDB2 protein, human
  • DNA-Binding Proteins
  • Histones
  • Nucleosomes
  • Pyrimidine Dimers
  • Ubiquitinated Proteins
  • pyrimidine-pyrimidone dimer
  • Polyubiquitin
  • DNA
  • Ubiquitin-Protein Ligases