Virus Evolution Reveals an Exclusive Role for LEDGF/p75 in Chromosomal Tethering of HIV

Abstract

Retroviruses by definition insert their viral genome into the host cell chromosome. Although the key player of retroviral integration is viral integrase, a role for cellular cofactors has been proposed. Lentiviral integrases use the cellular protein LEDGF/p75 to tether the preintegration complex to the chromosome, although the existence of alternative host proteins substituting for the function of LEDGF/p75 in integration has been proposed. Truncation mutants of LEDGF/p75 lacking the chromosome attachment site strongly inhibit HIV replication by competition for the interaction with integrase. In an attempt to select HIV strains that can overcome the inhibition, we now have used T-cell lines that stably express a C-terminal fragment of LEDGF/p75. Despite resistance development, the affinity of integrase for LEDGF/p75 is reduced and replication kinetics in human primary T cells is impaired. Detection of the integrase mutations A128T and E170G at key positions in the LEDGF/p75–integrase interface provides in vivo evidence for previously reported crystallographic data. Moreover, the complementary inhibition by LEDGF/p75 knockdown and mutagenesis at the integrase–LEDGF/p75 interface points to the incapability of HIV to circumvent LEDGF/p75 function during proviral integration. Altogether, the data provide a striking example of the power of viral molecular evolution. The results underline the importance of the LEDGF/p75 HIV-1 interplay as target for innovative antiviral therapy. Moreover, the role of LEDGF/p75 in targeting integration will stimulate research on strategies to direct gene therapy vectors into safe landing sites.

Author Summary

Viruses have a limited genome and therefore exploit the cellular machinery of infected host cells to complete the replication cycle. Today there is a growing interest to unravel these virus–host interactions. Lentiviral integrases use the cellular protein LEDGF/p75 to tether the preintegration complex to the chromosome, although the existence of alternative host proteins substituting for the function of LEDGF/p75 has been proposed. Here, we used virus evolution to investigate the role and importance of LEDGF/p75 in HIV integration and replication. We selected a virus that is resistant against overexpression of the integrase binding domain of LEDGF/p75. This virus displays a reduced affinity for its own cofactor but still depends on the cofactor for replication. We demonstrate the unique and essential role of LEDGF/p75 in HIV replication and support the LEDGF/p75 HIV-1 interplay as target for innovative antiviral therapy. Moreover, elucidation of the role of LEDGF/p75 in targeting integration will stimulate research on strategies to direct gene therapy vectors into safe landing sites.