Encapsidation of the herpes simplex virus type 1 genome

Lead Research Organisation: MRC Virology Unit

Abstract

We are carrying out research on herpes simplex virus type 1 (HSV-1). HSV-1 is one of eight members of the herpesviruses family able to infect humans and, together, these viruses are responsible for a wide range of both mild and severe diseases. The genetic information of HSV-1 is carried by a double-stranded DNA molecule. In infected cells thousands of copies of this DNA are synthesized and incorporated into new virus particles that are released from the cell. We are performing fundamental research in an attempt to understand the mechanisms by which these DNA molecules become packaged into the HSV-1 particle. The work involves developing and utilising assays to identify and characterize the various DNA and protein components that have roles in DNA packaging, and determining how these molecules function to package the DNA. Since DNA packaging is a vital step during the virus life cycle the acquired knowledge should hopefully suggest novel approaches to identifying compounds that can specifically inhibit virus growth. Moreover, since the mechanisms of DNA packaging are very similar for all members of the herpesvirus family, our studies will have additional relevance to other herpesviruses of clinical and veterinary importance.

Technical Summary

The major aim of this programme is to increase our understanding of the mechanisms by which the herpes simplex virus type 1 (HSV-1) genome is packaged into the viral capsid. The eight human herpesviruses are important pathogens responsible for a wide range of diseases, and vary greatly in their biological properties and clinical manifestations. The essential processes by which the viral DNA is replicated and the virus particle assembled are nevertheless very similar throughout the herpesvirus family and utilise a significant fraction of the 40 core genes conserved in all mammalian and avian herpesviruses. Our fundamental research into the HSV-1 packaging mechanism is therefore also relevant to other human and animal herpesviruses, and may suggest potential targets for antiviral chemotherapy and novel approaches to intervention. In addition studies on viral DNA packaging will contribute to our understanding of the action of molecular pumps and the process of DNA condensation. Encapsidation of the HSV-1 genome involves the site-specific cleavage of the concatemeric products of DNA replication into unit length genomes, a process that is tightly coupled to the injection of the DNA into a preformed structure, the procapsid. Seven HSV-1 genes have been identified which have direct and essential roles in the DNA packaging process. A pivotal role is likely to be performed by the virus-coded terminase which, by analogy with double-stranded DNA bacteriophage, is likely to interact with both the DNA substrate and portal vertex of the capsid, function as an ATP-driven pump to translocate the DNA into the capsid shell, and perform cleavage reactions to initiate and terminate packaging. Our major current areas of research interest are: (i) the functions of the cis-acting DNA packaging signals, and the mechanism of assembly of a packaging complex (ii) analysis of the proteins which comprising the terminase, and characterisation of its transient interaction with the capsid; (iii) structural and functional investigations of two DNA packaging proteins which remain stably associated with the capsid. These studies have more recently been extended to include examining the mechanism by which the linear viral genome is circularized upon infection. Our experiments employ a variety of molecular genetical techniques including gene cloning and expression, site-directed mutagenesis, transient transfection assays, RNA interference and biochemical assays of enzyme function. We have also recently collaborated with Dr Brian Bowman in the US in determining the crystallographic structure of one of the HSV-1 DNA packaging proteins.

Publications

10 25 50
 
Description Presentations to school children 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? Yes
Geographic Reach Regional
Primary Audience Schools
Results and Impact Formal presentation by PhD students to sixth form school children about their research projects at Glasgow Science Centre (2006 and 2008). Also regular contributions made by team members to workshops and demonstrations at Glasgow Science Centre and the Edinburgh Science Fair. Team members have also participated regularly in workshops at Schools Open Days hosted by our establishment (MRC Virology Unit)

These activities have encouraged gifted school children about science. The formal talks in particular were very positively received by both pupils and teachers.
Year(s) Of Engagement Activity 2006,2007,2008,2009