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Nucleic Acids Res. 2006 Mar 20;34(5):1653-65. Print 2006.

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.

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1
Department of Cancer Immunology and AIDS, Dana-Farber Cancer Institute, Boston, MA 02115, USA.

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.

PMID:
16549878
PMCID:
PMC1405818
DOI:
10.1093/nar/gkl052
[Indexed for MEDLINE]
Free PMC Article
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