... understanding life in molecular detail

Dr Juan Fontana

Virus structure, electron microscopy, Herpes Simplex Virus, Influenza


My laboratory is interested in the structural characterization of viruses that are a current public health risk, like HIV, Influenza and herpesviruses. To this end, we take advantage of electron microscopy techniques combined with other structural approaches.

Current major projects include:
  • Intermediate conformations of Influenza Virus fusion protein
  • Pre-fusion conformation of Herpes Simplex Virus fusion protein
  • Influenza vRNP transport from the nucleus to the assembly site

Our laboratory has a broad interest in virus structure.

Current efforts of the laboratory are focused on Enveloped Virus Fusion, a process that involves merging of viral and cellular membranes, allowing the viral genome to access the interior of the cell. Enveloped virus fusion is mediated by viral transmembrane proteins, and mounting evidence suggests that these proteins have converged on the same overall strategy among different viruses and classes of fusion protein. The generally accepted models for how fusion occurs are based on X-ray crystallographic studies of the initial (pre-fusion) and final (post-fusion) conformations. However, many details of the process remain unclear, especially those regarding the intermediate steps. Using cryo-EM as a main approach, I plan to capture fusion intermediates of Influenza and Herpes Simplex Virus (HSV) that will help us unravel the mechanisms of fusion for these viruses.

We have previously analysed the structural intermediates of Influenza Virus fusion protein (hemagglutinin, HA) and M1 matrix protein prior to viral fusion. Specifically, we found two intermediate and reversible conformations of HA that reflect an outwards movement of the fusion peptide and a rearrangement of the receptor-binding subunits; and we described a conformation of the M1 matrix protein that precedes its dissociation from the envelope, in which the M1 matrix layer appeared thinner and/or closer to the membrane. We are now following up on these results and studying how Influenza fuses with artificial membranes (liposomes) and endosomes.

With respect to HSV, we are collaborating with Drs. Gary Cohen and Roselyn Eisenberg, world-recognised leaders in HSV entry, to produce and image vesicles expressing full-length gB. Combined with the use of Fabs, this approach will allow us to localise the different domains of gB in the pre-fusion conformation.

Examples of previous projects include:

- The characterisation of the replication complexes formed by Bunyamwera and Rubella viruses, both of which replicate their genome in cytoplasmic viral factories. This study allowed the proposal of novel working models for each replication complex, which helped to elucidate the mechanism by which viral macromolecular complexes interact with cellular components to create the unique architecture of virus factories.

- The effects of several drugs and mutations that affect HIV maturation, a process essential for viral infectivity that involves proteolysis of precursor proteins by the viral protease and assembly of a conical core.

- The structural characterization of the shell protein of a bacterial protein-bound nanocompartment, which led to an atomic model in which the HK97 fold (from the HK97 bacteriophage capsid protein) is present. This result, together with physiological data, allowed us to conclude that this protein assembles as a virus-like icosahedral shell to protect bacteria from oxidative stress through iron sequestration.

- The morphogenesis of Herpes Simplex Virus, including capsid maturation and exit from the nucleus.

 

Detailed research programme                  Close ▲
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Lecturer and University Academic Fellow
BSc, PhD (Universidad Autonoma de Madrid, Spain)


Group Leader and University Academic Fellow (Leeds) 2016-present
Post-doctoral Fellow (NIH, USA) 2009-2016

Astbury 8.109
School of Molecular and Cellular Biology
0113 343 4170
J.Fontana@leeds.ac.uk

Selected Publications

  1. Fontana J.*#, Atanasiu D.*, Saw W.T., Gallagher J.R., Cox R.G., Whitbeck J.C., Brown L.M., Eisenberg R.J., Cohen G.H. (2017). The Fusion Loops of the Initial Prefusion Conformation of Herpes Simplex Virus 1 Fusion Protein Point Toward the Membrane mBio, 8(4). pii: e01268-17.*Equal contribution. #Corresponding Author.

  2. Newcomb W.W.*, Fontana J.*, Winkler D.C.*, Cheng N., Heymann J.B., Steven A.C. (2017). The Primary Enveloped Virion of Herpes Simplex Virus 1: Its Role in Nuclear Egress. MBio, 8(3). pii: e00825-17. *Equal contribution.

  3. Fontana J.*, Jurado K.A.*, Cheng N., Engelman A. and Steven A.C. (2015). Distribution and redistribution of HIV-1 nucleocapsid protein in immature, mature, and integrase-inhibited virions: a role for integrase in maturation. Journal of Virology, 89(19):9765-9780. *Equal contribution.

  4. McHugh C.A.*, Fontana J.*, Nemecek D., Cheng N., Aksyuk A.A., Heymann J.B., Winkler D.C., Lam A.S., Wall J.S., Steven A.C. and Hoiczyk E. (2014). A virus capsid-like nanocompartment that stores iron and protects bacteria from oxidative stress. EMBO Journal, 33(17):1896-1911. *Equal contribution.