A tripartite DNA-binding element, comprised of the nuclear localization signal and two AT-hook motifs, mediates the association of LEDGF/p75 with chromatin in vivo

Nucleic Acids Res. 2006 Mar 20;34(5):1653-65. doi: 10.1093/nar/gkl052. Print 2006.

Abstract

Lens epithelium-derived growth factor p75 (LEDGF/p75) is a DNA-binding, transcriptional co-activator that participates in HIV-1 integration site targeting. Using complementary approaches, we determined the mechanisms of LEDGF/p75 DNA-binding in vitro and chromatin-association in living cells. The binding of highly-purified, recombinant protein was assayed by surface plasmon resonance (SPR) and electrophoretic mobility gel shift. Neither assay revealed evidence for sequence-specific DNA-binding. Residues 146-197 spanning the nuclear localization signal (NLS) and two AT-hook motifs mediated non-specific DNA-binding, and DNA-binding deficient mutants retained the ability to efficiently stimulate HIV-1 integrase activity in vitro. Chromatin-association was assessed by visualizing the localization of EGFP fusion proteins in interphase and mitotic cells. Although a conserved N-terminal PWWP domain was not required for binding to condensed mitotic chromosomes, its deletion subtly affected the nucleoplasmic distribution of the protein during interphase. A dual AT-hook mutant associated normally with chromatin, yet when the mutations were combined with NLS changes or deletion of the PWWP domain, chromatin-binding function was lost. As the PWWP domain did not readily bind free DNA in vitro, our results indicate that chromatin-association is primarily affected through DNA-binding, with the PWWP domain likely contributing a protein interaction to the overall affinity of LEDGF/p75 for human chromatin.

Publication types

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

MeSH terms

  • AT-Hook Motifs
  • Adaptor Proteins, Signal Transducing / chemistry*
  • Adaptor Proteins, Signal Transducing / metabolism*
  • Amino Acid Sequence
  • Binding Sites
  • Chromatin / metabolism*
  • Consensus Sequence
  • DNA / chemistry
  • DNA / metabolism
  • DNA-Binding Proteins / chemistry*
  • DNA-Binding Proteins / metabolism*
  • HIV Integrase / metabolism
  • HeLa Cells
  • Humans
  • Molecular Sequence Data
  • Nuclear Localization Signals
  • Protein Structure, Tertiary
  • Transcription Factors / chemistry*
  • Transcription Factors / metabolism*

Substances

  • Adaptor Proteins, Signal Transducing
  • Chromatin
  • DNA-Binding Proteins
  • Nuclear Localization Signals
  • PSIP1 protein, human
  • Transcription Factors
  • DNA
  • HIV Integrase