Herpesvirus assembly group
This new group is led by Dr Gill Elliott.
Alphaherpesviruses are large multicomponent complexes containing a double-stranded DNA genome. A major characteristic of the life cycle of these viruses is that following a primary infection they establish a life-long latent infection in the host from which they can be reactivated at any time. In the case of the human alphaherpesviruses herpes simplex virus type 1 and type 2 (HSV-1 & HSV-2), and varicella zoster virus (VZV) these latent infections occur within sensory neurons.
During a single lytic replication cycle in the infected cell these viruses manufacture thousands of copies of themselves in a highly regulated, stepwise fashion. To do so, they exploit cellular processes to ensure that their individual components are produced in the cell at the correct time, are targeted to the right location, and are modified appropriately to enable efficient particle assembly and release from the cell. Hence a major challenge for herpesvirologists is to determine the mechanisms and interactions involved in the herpesvirus assembly pathway, so that our understanding of and ability to interfere with primary infection and reactivation events is enhanced.
In the Herpesvirus Assembly Group we use a combination of detailed cell biology studies, biochemical analyses and virus mutagenesis technology to investigate virus assembly. In particular we exploit the powerful tool of fluorescent virus technology, whereby viruses are engineered to express fluorescent structural proteins, to investigate protein localisation and trafficking in the infected cell in real time. Time-lapse microscopy and photobleaching technology can then be used to look at the dynamic association of various virus proteins with cellular structures and compartments. The ongoing research projects within our laboratory focus mainly on the tegument structure of the virus particle, the region located between the capsid and envelope. At least fifteen components are recruited into the tegument, but the role that many of these play in virus infection and the molecular interactions involved in virus formation have not yet been defined.
Our studies to date have concentrated particularly on two major tegument proteins known as VP22 (UL49) and VP13/14 (UL47), and have revealed novel properties of these proteins that provide valuable information on virus-host cell interactions. For example, we have shown that VP22 is a microtubule-binding protein that exhibits an interesting relationship with the secretory pathway in the infected cell. We have also shown that VP13/14 is a nuclear-cytoplasmic shuttling protein that has RNA-binding properties and appears to enter and exit the nucleus via unusual receptors. Furthermore, through biochemical studies and production of viruses expressing mutated forms of these proteins, we are beginning to build up a picture of how these tegument proteins interact with each other and therefore how they may come together within the cell to form the structure of the tegument.
Donnelly, M., J. Verhagen and G. Elliott. (2007). RNA binding by the herpes simplex virus type 1 nucleocytoplasmic shuttling protein UL47 is mediated by an N-terminal arginine-rich domain that also functions as its nuclear localisation signal. J.Virol. 81: 2283-2296
Verhagen, J, M. Donnelly and G. Elliott. (2006). Characterisation of a novel transferable CRM-1 independent nuclear export signal in a herpesvirus structural protein that shuttles between the nucleus and the cytoplasm. J. Virol. 80: 10021-10035.
Verhagen, J, I. Hutchinson, and G. Elliott. (2006). Nucleocytoplasmic shuttling of the bovine herpes virus type 1 UL47 protein in infected cells. J. Virol. 80: 1059-1063.
Potel, C. and G. Elliott. (2005). Phosphorylation of the herpes simplex virus tegument protein VP22 has no effect on the incorporation of VP22 into the virus but is involved in optimal expression and virion packaging of ICP0. J. Virol. 79: 14088-14094.
Hafezi, W., E. Bernard, R. Cook and G. Elliott. (2005). Herpes simplex virus tegument protein VP22 contains an internal VP16 interaction domain and a C-terminal domain that are both required for VP22 assembly into the virus particle. J. Virol. 79: 13082-13093.
Elliott, G., W. Hafezi, A. Whiteley and E. Bernard. (2005). Deletion of the herpes simplex virus VP22-encoding gene (UL49) alters the expression, localisation, and virion incorporation of ICP0. J. Virol. 79: 9735-9745.
Figure 1: Vero cells infected with HSV-1 expressing a phosphorylation mutant of the structural protein VP22 (green) that results in the nuclear retention of the virus immediate-early protein ICP0 (red).
Figure 2: Vero cells infected with HSV-1, showing localisation of the structural protein VP22 (green) in relation to early endosomes (red). Nuclear DNA is stained blue.
Figure 3: Vero cells infected with HSV-1 expressing CFP-tagged ICP4 (green) and YFP-tagged UL47 (red), showing co-localisation of these proteins in nuclear sites of replication.