Tethering of viral genomes to host chromosomes has been recognised in several DNA and RNA viruses. Tethering is typically accomplished by dedicated viral proteins that simultaneously associate with both the viral genome and cellular chromatin via nucleic acid, histone and/or non-histone protein interactions. Some of the most prominent tethering proteins have been identified in DNA viruses establishing sustained latent infections, including members of the herpesviruses. Herpesvirus genomes circularise in infected cell nuclei and usually persist as extrachromosomal episomes. In several γ-herpesviruses, tethering facilitates the nuclear retention and faithful segregation of viral episomes during cell division, thus contributing to the lifelong persistence of these viruses.
We were the first to demonstrate that the episomes of human cytomegalovirus (CMV), the prototypical β-herpesvirus, are tethered to mitotic chromosomes following the infection of human cells (1). This viral association with chromosomes occurs at a slightly lower frequency in the absence of CMV immediate-early 1 (IE1) proteins1, which bind to the acidic patch formed by histones H2A and H2B on the nucleosome surface (2). Our findings suggest that IE1 plays a supporting but non-essential role in this process, and that other viral proteins are required. Histone-based proteomics screening for candidate viral tethering proteins identified several hits, including the CMV pp65 protein. Like IE1, pp65 binds to mitotic chromatin and targets the acidic patch on the nucleosome surface.
The project will reveal new mechanisms underlying the lifelong persistence of CMV genomes by focusing on the following aims:
1. Use established BAC recombination techniques to construct mutant viruses deficient for expression of one or more candidate CMV tethering proteins, including pp65.
2. Use fluorescent in situ hybridisation and live cell imaging to compare the requirement of candidate viral proteins, including pp65, for CMV episome tethering.
3. Use protein purification and cryo-EM to obtain high-resolution structures of the CMV IE1- and pp65-nucleosome complexes.
The successful candidate will receive training in the latest cellular, molecular, biochemical and computational techniques. Based in newly refurbished laboratories at the University of St Andrews, the project will see the PhD student working in a highly collaborative environment alongside virologists from the Universities of Edinburgh and Dundee.
HOW TO APPLY
Application instructions can be found on the EASTBIO website- How to Apply | EastBio Doctoral Training Partnership | Biology
1) Download and complete the Equality, Diversity and Inclusion survey.
2) Download and complete the EASTBIO Application Form.
3) Please complete an application on our online portal: How to apply - Study at St Andrews - University of St Andrews
4) Select the course ‘PhD with internship’
5) Your online application must include the following documents:
- Completed EASTBIO application form
- Academic Qualifications
- English Language Qualification (if applicable)
- 2 References: this must be completed on the EASTBIO Reference Form, also found on the EASTBIO website.
Please download the EASTBIO reference form and send it to your referees. They can either upload it directly to the portal using the automated email they will receive, or they can email it to Rachel at pgrecbiology@st-andrews.ac.uk
CONTACT
Queries on the project can be directed to the project supervisor.
Queries on the application process can be directed to Rachel Horn at pgrecbiology@st-andrews.ac.uk
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