Background:  Lens epithelium-derived growth factor/transcriptional co-activator LEDGF/p75 was identified as a dominant binding partner for lentiviral integrases in mammalian cells. Association of HIV and FIV integrases with endogenous LEDGF/p75 protein determines nuclear and chromosomal localization of the viral integrases. In addition, LEDGF/p75 as well as it close homolog HRP2 greatly promote strand transfer activity of HIV integrase in vitro. These data suggest that LEDGF/p75 or its homologs pose as cellular host factors in retroviral replication likely acting at the levels of chromosomal targeting of the viral preintegration complex or strand-transfer.

Methods: We used heteronuclear NMR spectroscopy, and structure-based alanine-scanning mutagenesis and GST pull-down assays.

Results:  We determined the solution structure of the integrase-binding domain of LEDGF/p75, and identified residues of LEDGF/p75 essential for its interaction with integrase. In addition, several HIV-1 integrase mutants defective for binding to LEDGF/p75 were identified.

Conclusions:  The LEDGF/p75 integrase-binding domain is comprised of 5 α-helices folded into a compact right-handed bundle. Results of our mutagenesis scan and in vitro binding assays indicate residues 363-369 forming the loop between the first and the second α-helices of the integrase-binding domain are involved in the interaction with HIV-1 integrase. We confirmed that V165A integrase mutant is defective for binding to LEDGF/p75 and identified several other class II HIV-1 integrase mutants with greatly reduced affinity for this human protein.

Keywords: integration; virus-host interaction; structure biology