The influence of DNA and nucleosome structure on integration events directed by HIV integrase

DNA copies of the human immunodeficiency virus (HIV) genome integrate nonrandomly into the chromosomal DNA of the host cell. In this report, we investigate the molecular basis of this selectivity using the virus-encoded HIV integrase to direct integration of a synthetic HIV long terminal repeat substrate into either DNA molecules of known structure or previously defined nucleosomal complexes. We find that the structure of the target greatly influences the site of integration, and, moreover, DNA curvature, flexibility, and rigidity in solution all influence the frequency of integration. Importantly, for DNA with all of these properties, the distortion of the double helix directed by association with the histone proteins promotes the integration reaction and alters the distribution of sites that are selected for integration. We suggest that both intrinsic DNA structure and the folding of DNA into chromosomal structures will exert a major influence on target site selection for integration of the viral genome.