Role of Integrase Acetylation in HIV-1 Replication Cycle and Search for Acetylation Inhibitors

HIV-1 integrase catalyzes the integration of the viral DNA into the genome of the host cells. This irreversible event is crucial to the pathogenesis of the infection and complicates its eradication both by the immune systems and by pharmacological treatments. The mode of action of this viral enzyme is still not completely characterized, although full understanding of some key aspects, as the mechanism of integration site selection, are relevant both for the development of new anti-integrase drugs and for potential application of HIV-derived vectors for gene therapy. Our group has demonstrated that integrase is post-translationally acetylated by two cellular histone-acetyl transferases (HATs), chromatin-modifying enzymes whose major role is that of transcriptional co-activators. Integrase acetylation is important for the viral infectivity and interaction with HATs might be one of the determinants of HIV-1 preferential integration in actively transcribed genomic regions. Integrase is a poorly exploited target of anti-HIV drugs, while traditional therapies based on combinations of reverse transcriptase inhibitors and protease inhibitors are facing the rapid diffusion of multi-drugs resistant viral variants. This pushes research towards new drugs and new targets, including integrase and, even better, its interactions with cellular cofactors like, for instance, HATs. This thesis deals with the selection of novel inhibitors of integrase acetylation, to be used as lead compound for the development of new generation anti-integrase drugs. A selective inhibitor of integrase acetylation was identifyied through in vitro screening of a library of synthetic compounds, designed based on the structures of natural HAT inhibitors. Structure-Activity-Relationships (SAR) studies led to the rational design of a smaller set of compounds, whose activity was tested with in vitro and in vivo assays. Finally, one molecule was chosen for further studies with HIV-1 derived lentiviral vectors. This cinnamoil compound was able to inhibit integrase acetylation in the virus and reduced viral integration in infected cells. In a reciprocal experiment, viral vectors containing hyper-acetylated integrase were generated by trans-incorporation of fusion integrase-HAT proteins, or of isolated HAT domains. The enhanced infectivity of these virions confirmed the role of acetylation for integrase function.