Identification and characterization of the chromatin-binding domains of the HIV-1 integrase interactor LEDGF/p75.

Depletion of the transcriptional co-activator LEDGF/p75 by RNA interference alters the genome-wide pattern of HIV-1 integration, reducing integration into active genes, reducing integration into LEDGF/p75-regulated genes, and increasing integration into G+C-rich sequences. LEDGF/p75 is also able to act as a molecular tether linking HIV-1 integrase protein to chromatin, a phenomenon likely to underlie the integration site distribution effects. The LEDGF/p75 integrase-binding domain has been established but the domain or domains responsible for the chromatin-binding component of tethering are unknown.

Identification of the LEDGF/p75 HIV-1 integrase-interaction domain and NLS reveals NLS-independent chromatin tethering.

To investigate the basis for the LEDGF/p75 dependence of HIV-1 integrase (IN) nuclear localization and chromatin association, we used cell lines made stably deficient in endogenous LEDGF/p75 by RNAi to analyze determinants of its location in cells and its ability to interact with IN. Deletion of C-terminal LEDGF/p75 residues 340-417 preserved nuclear and chromatin localization but abolished the interaction with IN and the tethering of IN to chromatin. Transfer of this IN-binding domain (IBD) was sufficient to confer HIV-1 IN interaction to GFP.

CCR5 and CXCR4 usage by non-clade B human immunodeficiency virus type 1 primary isolates.

CCR5 and CXCR4 usage has been studied extensively with a variety of clade B human immunodeficiency virus type 1 (HIV-1) isolates. The determinants of CCR5 coreceptor function are remarkably consistent, with a region critical for fusion and entry located in the CCR5 amino-terminal domain (Nt). In particular, negatively charged amino acids and sulfated tyrosines in the Nt are essential for gp120 binding to CCR5.