Identification of an evolutionarily conserved domain in human lens epithelium-derived growth factor/transcriptional co-activator p75 (LEDGF/p75) that binds HIV-1 integrase

Abstract

Human lens epithelium-derived growth factor/transcriptional co-activator p75 (LEDGF/p75) protein was recently identified as a binding partner for HIV-1 integrase (IN) in human cells. In this work, we used biochemical and bioinformatic approaches to define the domain organization of LEDGF/p75. Using limited proteolysis and deletion mutagenesis we show that the protein contains a pair of evolutionarily conserved domains, assuming about 35% of its sequence. Whereas the N-terminal PWWP domain had been recognized previously, the second domain is novel. It is comprised of ∼80 amino acid residues and is both necessary and sufficient for binding to HIV-1 IN. Strikingly, the integrase binding domain (IBD) is not unique to LEDGF/p75, as a second human protein, hepatoma-derived growth factor-related protein 2 (HRP2), contains a homologous sequence. LEDGF/p75 and HRP2 IBDs avidly bound HIV-1 IN in an in vitro GST pull-down assay and each full-length protein potently stimulated HIV-1 IN activity in vitro. LEBGF/p75 and HRP2 are predicted to share a similar domain organization and have an evident evolutionary and likely functional relationship.