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A supramolecular assembly mediates lentiviral DNA integration

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Science  06 Jan 2017:
Vol. 355, Issue 6320, pp. 93-95
DOI: 10.1126/science.aah7002

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High-resolution insights into the intasome

An essential step in the life cycle of lentiviruses such as HIV-1 is when viral DNA integrates into the host genome, establishing a permanent infection of the host cell. The viral integrase enzyme catalyzes this process and is a major drug target. During viral integration, integrase binds the ends of viral DNA, forming a higher-order structure called the intasome. Passos et al. and Ballandras-Colas et al. used cryo—electron microscopy to solve the structures of the intasomes from HIV-1 and maedi-visna virus (ovine lentivirus), respectively. These structures reveal how integrase self-associates to form a functional intasome and help resolve previous conflicting models of intasome assembly.

Science, this issue p. 89, p. 93

Abstract

Retroviral integrase (IN) functions within the intasome nucleoprotein complex to catalyze insertion of viral DNA into cellular chromatin. Using cryo–electron microscopy, we now visualize the functional maedi-visna lentivirus intasome at 4.9 angstrom resolution. The intasome comprises a homo-hexadecamer of IN with a tetramer-of-tetramers architecture featuring eight structurally distinct types of IN protomers supporting two catalytically competent subunits. The conserved intasomal core, previously observed in simpler retroviral systems, is formed between two IN tetramers, with a pair of C-terminal domains from flanking tetramers completing the synaptic interface. Our results explain how HIV-1 IN, which self-associates into higher-order multimers, can form a functional intasome, reconcile the bulk of early HIV-1 IN biochemical and structural data, and provide a lentiviral platform for design of HIV-1 IN inhibitors.

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