The role of translational control in regulating chronological lifespan

Trying to understand why do we age has been a long standing question. It is a complicated question because it is not only our genes, but the environment and diet that affects the way we age. In order to identify mechanisms underlying the ageing processes, simple model organisms have been studied. The budding yeast, Saccharomyces cerevisiae, provides one of the simplest and widely adopted model organisms to study ageing. It provides a relatively simple, genetically tractable system, and has provided a number of significant advances in our understanding of the ageing process in human cells. For example, it has been used to identify major pro-ageing pathways which are highly conserved in organisms ranging from yeast to humans. We are using this model and have found that a that a key protein synthesis factor is important for ensuring longevity. Protein synthesis factors are required to synthesize all new proteins in each cell, a process referred to as "translation". These 'protein synthesis factors' translate RNA, a messenger molecule that encodes gene sequences, into protein molecules. There are many thousands of RNA molecules in each cell, each one carrying instructions (or coding) for a different protein. The protein synthesis factors must interact with each RNA in the right way so that each new protein is made correctly and in the correct proportions. By improving our fundamental understanding of how such processes work in normal cells it can help scientists understand diseases in which this process is altered. Our preliminary data indicate that one such translation factor (eIF4G) is essential for longevity in our yeast model of ageing. This project will address how eIF4G regulates translation during ageing and whether there are specific eIF4G target RNAs that ensure a normal healthy ageing process.

Our preliminary data provide evidence for isoform-specific roles of translation initiation factor 4G (eIF4G) in ageing, since yeast mutants lacking eIF4G2 show a longer chronological lifespan (CLS) than wild-type and mutants lacking eIF4G1. We will test the hypothesis that eIF4G isoforms promote mRNA-specific translation, hence controlling which isoform associates with the closed loop complex may allow mRNA-specific translational regulation during particular growth and stress conditions. We have used an RNA-immunoprecipitation sequencing approach to Identify the mRNAs associated with eIF4G and show that eIF4G1-bound mRNAs are enriched for mRNAs encoding products involved in DNA recombination and repair. This is interesting since DNA repair has been proposed to play an important role in the ageing process in diverse eukaryotic organisms. We will construct homogenic yeast mutants lacking eIF4G1 or eIF4G2 and use these mutants to monitor the age-dependent accumulation of different types of DNA mutations during CLS. The roles of eIF4G1 and eIF4G2 in translation will be studied to determine whether they are differentially required to maintain translational activity during ageing and whether they promote mRNA-specific translation. A key focus will be on the translation of mRNAs encoding DNA repair genes. We will also examine the role of eIF4G during oxidative stress conditions. Our preliminary data indicate that eIF4G1 is specifically required for oxidant tolerance and there are many established links between reactive oxygen species and longevity. Finally, we will examine whether eIF4G influences the TORC1-Sch9 nutrient signalling pathway, which is a highly conserved lifespan regulatory pathway. This pathway is known to regulate longevity via effects on translation and we will examine whether it involves eIF4G-isoform specific effects. This study will ultimately increase our understanding of the role of translational activity and mRNAs-specific translation during ageing.

Who will benefit from this research?
Academic researchers with wide-ranging interests in the cell biology and biochemistry of ageing will benefit from the methodology and data generated from this research project. The research will be of interest to researchers in medical biosciences since alterations in gene expression are implicated in numerous disease processes. Additionally, data generated from this research will be of benefit to industrial researchers who are interested in how cells respond to stress conditions and the use of yeasts in biotechnological applications.

How will they benefit from this research?
This research will increase our understanding of how cells alter gene expression patterns during ageing and in response to oxidative stress conditions. All organisms must respond to changes in their external environment and the translation of mRNA into protein is a fundamental component of the gene expression pathway. Our yeast studies will provide a framework for researchers in medical and disease-related fields to understand these changes. This will potentially benefit researchers in the study of diverse diseases and pathologies which involve reactive oxygen species. The yeast system offers significant advantages in terms of its tractability to genetic and biochemical manipulation. An added benefit is that studies using the yeast model system provide an alternative to animal-based studies. Living with environmental change is a priority area for the BBSRC and our research will uncover mechanisms used by cells to cope with changes in oxidative stress. This research will provide information and tools to increase the knowledge needed to enable organisms to build resilience and adapt to environmental change. The project may have significant industrial implications since yeast fermentations are extensively used in baking and brewing as well as for the production of biofuels and biophamaceuticals. Industrial yeast strains are subjected to various stress conditions during the course of manufacturing processes. Our findings will increase understanding of the yeast oxidative stress response which may be extended to industrial usage of yeast in commercial settings. Commercial yeasts need to be active in a variety of environments (e.g. doughs of different sugar contents) and following a range of treatments that expose them to stress (e.g. drying). Our studies will examine the changes in gene expression in which yeast cells are exposed to during changing growth and stress conditions. Researchers in these industries will benefit from conceptual advances generated during this work.

What will be done to ensure that they benefit from this research?
Results will be disseminated through research seminars, presentations at conferences and publications in scientific journals. Funding is requested to attend national and international research conferences to allow the researchers to publicize this research. Resources generated from this project are likely to include yeast strains, plasmids and RNA-Seq data and will be made available to the scientific community upon request. Detailed protocols and primary data will be made freely available to academic collaborators. Manchester University has a good track record of encouraging public engagement. This includes regular open days to inform school children and the public about University research and tours of the research facilities at Manchester. This will allow the researchers to share their research findings with the wider public and to raise awareness of the importance of basic research. Manchester University maintains excellent links with the business sector which will allow us to exploit any potential for collaboration with industry. This is managed by the faculty Business Development Team which provides support and information for staff wishing to develop relationships with business.