New technique resolves HIV capsid structure alone and in complex with host factors


A novel technique using electron tomography and averaging subtomograms at the Diamond Electron Bioimaging Center (eBIC), has resolved the structure of the HIV capsid alone and in complex with host factors. This work also led to the construction of an atomistic model of the entire HIV capsid using information obtained from electron tomography, which the team believes could serve as a model for the development of antivirals targeting the virus. capsid.

The research paper detailing this major breakthrough is published today (November 19) in Science Advances. Referred to as “High resolution cryoET structures of native HIV-1 capsid in complex with IP6 and CypA;” The work was a collaboration between scientists from the University of Oxford, eBIC – the UK’s national cryomicroscopy facility within Diamond Light Source and the University of Delaware.

The team was led by Professor Peijun Zhang, director of the eBIC at Diamond and professor of structural biology at the University of Oxford. Lead author Dr Tao Ni, University of Oxford, explained the background to this important work: “Despite global efforts to combat HIV / AIDS and the achievement of antiviral treatments, there are still approximately 38 million people with HIV / AIDS without a full recovery to date. “

He explains that the human immunodeficiency virus (HIV) is a retrovirus whose RNA genome is encapsulated in a conical-shaped capsid. During infection, HIV assembles and buds as immature virions with the polyprotein Gag, which undergoes a maturation process, a stage involving proteolysis and a conformational change, which changes from an immature spherical shape. to a mature conical capsid. The capsid plays multiple essential roles during the early stage of HIV-1 replication, including protecting the genome against innate cellular immune responses and stimulating reverse transcription, as well as regulating intracellular transport and entry into the kernel. Many of these functions are affected by its interactions with host cell factors and small molecules.

However, due to the metastable property of the HIV-1 capsid, isolation of the fully intact native capsid in quantities and concentrations suitable for high-resolution structural analyzes has been a challenge: the capsid undergoes artefactual dissociation afterwards. dissolving the membrane with detergent, a traditional method for capsid purification.

To solve this problem, Peijun Zhang’s team devised a new approach. Instead of detergent extraction, we punctuate the membrane of HIV virus-like particles with a porogenic toxin, which avoids the trauma of virion lysis and nuclei isolation, but also makes the capsid accessible to patients. external cellular factors and small molecules. “

Dr Tao Ni, senior author, University of Oxford

After establishing the experimental approach, the authors studied the interactions between the authentic capsid of HIV and a cellular factor cyclophilin A (CypA), and a small molecule cofactor IP6 (inositol hexakisphosphate). The team then applied electron tomography and averaging sub-tomograms to these samples.

Using this new technique, the team resolved the structures of the HIV-only capsid and its complex with CypA and IP6 at a resolution of approximately 5.4 Ã…. These structures confirm the IP6 double binding site in the capsid of mature HIV and provide insight into the role of IP6 and CypA in regulating the stability of the HIV capsid.

Professor Zhang concludes; “In collaboration with the group of Professor Juan Perilla at the University of Delaware, using information derived from electron tomography, we also constructed an atomistic model of the entire HIV capsid that could serve as a model for the development of antivirals targeting the capsid. Perforation of the enveloped viral membrane also provides a novel approach to study host-virus interaction for other viral systems. “

Professor Peijun Zhang is an internationally renowned scientist who undertakes groundbreaking research on HIV and other infectious diseases. Over the past year, she and her team have also made significant contributions to SARS-CoV-2 Covid-19 research for vaccines and antivirals.

Earlier this year, she and her team received one of 209 CER Advanced scholarships awarded to outstanding researchers across Europe. The awards are selected by the European Research Council (ERC) on the basis that research has the potential to make a difference in people’s daily lives and provide solutions to some of the world’s most pressing challenges by triggering breakthroughs and major scientific advances. Professor Zhang’s prize, over five years, is to continue his work on chemotaxis – specifically molecular choreography and the biological behavior of bacterial chemotaxis that allow movement of a cell or organism to or from products. chemical. Modification of these microorganisms by pharmaceutical agents can decrease or inhibit infections or the spread of infectious diseases.

She has received numerous awards, including the Carnegie Science Emerging Female Scientist Award, the Senior Vice Chancellor’s Award, the On-the-Spot Award from the US Department of Health and Human Services. His research focuses on structural and functional studies of large molecular complexes and assemblies, viruses and cellular machinery using integrated structural, biochemical and computational approaches to understand biological complexity.

As Director of the eBIC, Professor Zhang is establishing and leading the eBIC to become a center for cryo-EM research, expertise and training and a user-friendly facility. cutting-edge cryo-EM technologies. eBIC focuses on the use of advanced electron microscopy techniques to determine the 3D structures of molecules, cells and tissues at high resolution, as well as the development of new methods and technologies to advance 3D EM imaging.


Journal reference:

Ni, T., et al. (2021) A new technique resolves the structure of the HIV capsid and could be the model for antivirals targeting the capsid. Scientists progress.


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