Nicolas Locker

My previous research has focused on the molecular mechanisms by which viral RNAs elements regulate protein synthesis, focusing on Hepatitis C and Human Immunodeficiency Viruses. To decipher the mechanism by which internal ribosome entry site (IRES) interact with the translation machinery, I set up new biochemical tools to study translation in vitro and unravelled the pathway of 80S ribosome formation mediated by the HCV IRES and shed light on a new, original, translation initiation mechanism used by lentiviruses to produce several isoforms of the Gag polyprotein.

Translational control during calicivirus infection
Based on previous experience about translational control mediated by viral RNAs, our goal is to dissect host—pathogen interactions and understand translational control during norovirus infection. Human norovirus (HuNV) is a member of the calicivirus family and is a major cause of viral gastroenteritis. Norovirus lacks a suitable cell culture system, so its replication mechanisms are poorly understood, but two animal caliciviruses, the feline calicivirus (FCV) and mouse norovirus (MNV) provide models to increase our understanding of norovirus translation and replication. Unlike cellular mRNAs, the calicivirus RNA genome does not possess a 5' cap structure but instead has a 13–15 kDa viral protein, genome linked (VPg) directing translation and hijacking the host protein synthesis machinery.

Previous work from the Roberts (Surrey) and Goodfellow (University of Cambridge) demonstrated that VPg acts as a novel proteinaceous ‘cap substitute’ and interacts with eIF4E (the cap-binding protein), eIF4G and eIF4A (Goodfellow et al. 2005, Chaudhry et al. 2006), while it is known that the eIF4E phosphorylation and availability is subject to fine regulation during viral infection (Mohr et al. 2011), either to control the host antiviral response or to promote viral translation. Therefore, supported by the BBSRC, we investigate how caliciviruses modulate the host protein synthesis machinery, especially eIF4E and 4E-BP1, the cell signalling pathways involved in this process, and the effect on host and viral mRNA translation. To deepen our knowledge of modulation of mRNA metabolism by viruses we are also studying how Stress Granules and P-bodies, which are sites of mRNA storage and degradation respectively, are affected during caliciviruses infection.

Role of Internal ribosome entry sites (IRES) during viral translation
To better understand the role of specific viral RNA domains during translation and the regulation of their activities we are dissecting the structure-function relationship of several viral IRESes. In collaboration between Dr Locker, Prof Roberts (Surrey) and Prof Belsham (DTU National Veterinary Institute, Denmark) we investigate the role of HCV-like IRES elements of Seneca Valley Virus (SVV) and classical swine fever virus (CSFV) infection. In collaboration with Prof Shih (Chang Gung University Taiwan) we study how cellular proteins can assist viral IRES RNAs in the takeover of the virus-infected cell translation machinery during enterovirus 71 (EV71) infection. We are also characterizing a new IRES element directing the synthesis of vFLIP, a key tumorigenesis factor during Kaposi’s sarcoma-associated herpesvirus (KSHV) infection.