mRNA-specific translational control: A novel mechanism.

The proteins that make up our cells are encoded by genes that serve as a genetic blueprint. The information stored in genes is decoded to produce proteins by a two-step process, the second of which is known as translation. Since it is crucial that proteins are made at the right time and in the right amount for the cell to function properly, it is important that translation is carefully regulated. Indeed, a failure to do so has been shown to underlie a growing number of diseases. The ability to regulate translation is also crucial for cells to respond to viral infection. In turn, viruses rely entirely on the cells they infect to produce the viral proteins necessary for infection to proceed and have therefore developed ways in which to subvert normal cellular protein production to suit their own needs. Thus the study of host-virus interactions has provided much of our current understanding of the basic translational machinery and its regulation. By studying the mechanism of a herpes simplex virus protein, as an example of a novel regulator of translation, we aim to increase our knowledge of how cells normally control this process. Understanding normal cellular function is critical to elucidating the pathways that lead to disease. Moreover, as even distantly related members of this large viral family have similar proteins that are essential to their ability to infect cells, knowledge of the action of this protein may also be beneficial in developing new ways to combat a broad range of herpesviruses that cause a wide variety of diseases both in humans and animals.

Many genes are regulated at the level of translation in an mRNA-specific manner. However, despite their importance, few mRNA-specific activators have been studied in detail but all appear to act via the initial cap-binding event. In contrast, our work on the herpesvirus ICP27 protein suggests that it acts to promote initiation independently of the cap. It acts through a direct interaction with the basal translation initiation factor PABP, via a mechanism that is dependent on one of PABP's interacting factors, eIF4G. Intriguingly, while ICP27 appears to act at/or prior to 43S joining, this is not achieved through the characterised effects of the PABP-eIF4G interaction on cap binding, indicating additional early functions of this complex. This suggests that a deeper understanding of ICP27 action will not only increase our knowledge of mRNA-specific activation but will also elucidate novel roles of the PABP-eIF4G interaction during the early steps of initiation. Thus this proposal aims to further define the mechanism of ICP27 action utilising cutting-edge cell-free approaches that allow a direct assessment of the interaction (and activity) of ribosomal subunits and initiation factors with ICP27-bound mRNAs. This will enable us to determine whether ICP27 directly stimulates the recruitment of small ribosomal subunits (or upstream events i.e. RNA unwinding) and uncover how this is mediated at an initiation factor level (focusing on eIF4G, eIF3 and eIF4A function). Similarly, we will determine whether ICP27 has additional roles downstream of small subunit joining, as PABP and eIF4G also have poorly defined late effects on initiation. Recent findings that improper translational control underlies disparate diseases has further highlighted its central importance to cell biology and a fundamental understanding of its mechanisms forms the first step towards intervention in this central process for either clinical or commercial purposes.

1. Academic community. The research co-investigator in this proposal will benefit from training in methodologies that can be applied to other scientific questions in academic, clinical or industrial settings. Training in novel methodologies imported from our non-UK collaborators can be extended to other UK scientists further improving UK competitiveness (see Pathways to Impact). The results of the proposal will be of particular interest to those in the fields of translation and other forms of post-transcriptional control (see Academic Beneficiaries). However the fundamental nature of translational control in both normal physiology and patho-physiology gives our findings potential relevance to a wide range of researchers. Our results may provide a better understanding of current questions and enable the formulation of new ideas and approaches to biological problems. The outcomes of this research will be disseminated through publication, presentations and, if appropriate, via press releases coordinated through the University of Edinburgh press office (as detailed in Pathways to Impact). Materials generated during the research will be made available to other researchers upon request (see Academic Beneficiaries). 2. Clinical and pharmacological impact. Herpesviruses cause a variety of diseases, including cancer, in humans and in animals resulting in significant economic impact. ICP27 is one of few regulatory proteins conserved throughout this large and diverse viral family and its counterparts are essential for the lytic viral life cycle in nearly all viruses studied. As a consequence, ICP27 and its homologues form potential targets for broad range herpes antiviral therapy. Although we do not anticipate that the work outlined in this proposal will be directly applicable in this respect, it will clearly add to the understanding of mechanisms of ICP27-mediated virus host interaction which may in the long term benefit the pharmaceutical industry and human and veterinary health. Moreover, by providing a paradigm for translational activators our work may indirectly impact other clinical areas. For instance, the DAZ family of cellular mRNA-specific translational activators implicated in male infertility and premature ovarian failure in women interact with PABP similarly to ICP27. Thus our findings may be of interest to clinicians treating the 12-15% couples worldwide that suffer fertility problems which impact quality of life and cause a significant economic burden. PABP also has roles in nonsense-mediated decay and miRNA-mediated regulation that are intimately linked to its roles in translation, with both of these processes being associated with a wide variety of human diseases. Understanding fundamental molecular mechanisms is key to the future development of interventions. Our position in the College of Medicine and Veterinary Medicine and the work of the University technology transfer company, ERI, places us an ideal position to exploit clinical/commercial opportunities as they arise (see Pathways to Impact for details). 3. Industry: Translational control (both mRNA-specific and global) is central to regulating protein synthesis rates and is linked to bulk cell growth in eukaryotes from yeast to humans. Thus understanding regulatory mechanisms can impact a variety of industrial applications including the production of recombinant proteins, and as a result people working within industry keep abreast of developments in the field of translational control through the scientific literature and attendance at international conferences to which the PI and members of her research group regularly contribute. 4. Wider community and public engagement. The University has a press office which can disseminate information in a manner suitable to a wide audience. Moreover, the PI has a strong track record in public engagement (see Pathways to Impact and CV).