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Role of translation elongation factor 1B (eEF1B) in regulating protein synthesis in response to oxidative stress in yeast

Reference	BB/F011016/1
Principal Investigator / Supervisor	Professor Christopher Grant
Co-Investigators / Co-Supervisors
Institution	The University of Manchester
Department	Life Sciences
Funding type	Research
Value (£)	386,684
Status	Completed
Type	Research Grant
Start date	01/10/2008
End date	30/09/2011
Duration	36 months

Abstract

Inhibition of protein synthesis is a common response to cellular stress. We have found that a complex pattern of translational regulation occurs in response to oxidative stress, with many mRNAs differentially regulated. This regulation involves the well-known Gcn2-mediated inhibition of translation initiation. Additionally, our data indicate that translation is regulated at the post-initiation phase by elongation factor 1B (eEF1B). Elongation begins with the insertion of an aminoacyl-tRNA into the empty A-site of an elongating ribosome catalysed by elongation factor 1 (eEF1). eEF1 comprises a G protein (eEF1A) and a guanine nucleotide exchange factor (eEF1B). eEF1B contains two subunits (alpha and gamma). TEF5 encodes the catalytic subunit (eEF1B alpha), which is essential for viability. Two non-essential genes, TEF3 and TEF4, encode gamma isoforms. Our preliminary data indicate that a tef3 mutant shows less inhibition of protein synthesis and mutants lacking TEF3 are resistant to H2O2 implicating eEF1B in the response to oxidants. This project will identify the role of eEF1B in the oxidative stress response. We will determine how eEF1B activity is modulated in response to oxidants by examining the composition and activity of the eEF1B complex during different growth and stress conditions. The role eEF1B in the response to oxidants will be determined by examining the rate and fidelity of translation elongation. We will investigate the overlapping roles of translation initiation and elongation in the response to oxidative stress by comparing the roles of eEF1B and Gcn2 in mRNA-specific translational regulation. Post-initiation regulation of translation has not been widely considered as a regulated step in protein synthesis and this work programme will provide a better understanding of how gene expression is modulated by ROS to control protein production.

Summary

All organisms must respond to changes in their external environment. With the availability of genome sequences much attention has focused on analyzing the changes in gene expression/transcription profiles during these adaptive responses. The translation of mRNA into protein is a fundamental component of the gene expression pathway. However, relatively little is known regarding the role of translational control mechanisms in the response to stress conditions, which is the focus of this proposed study. This application is based on our preliminary findings showing that oxidative stress causes a rapid inhibition of protein synthesis. Such a global inhibition of protein synthesis is widely recognised as a response of biological systems to stress conditions. Preventing protein synthesis during stress conditions may allow time for organisms to direct gene expression towards the production of new molecules required to protect against or detoxify the stress. Our data show that oxidative stress inhibits protein synthesis at multiple levels. The goal of this comprehensive research programme is to understand the molecular details of these regulatory mechanisms. This study will focus on oxidative stress which is a major problem for most biological systems. Reactive oxygen species and free radicals are produced as toxic by-products of normal metabolism and through exposure to environmental factors including sunlight. All organisms, including humans, contain effective antioxidants such as vitamins A and C and enzymes, such as catalase and superoxide dismutase, that can detoxify these harmful molecules. However, under extreme conditions reactive oxygen species can overwhelm the antioxidant defences resulting in a so-called 'oxidative stress'. It is important to understand how cells respond to an oxidative stress because it is implicated in many diseases including cancer, neurodegenerative and cardiovascular diseases. In addition, oxidative damage to cells and tissues can contribute to the decline in physiological function that occurs in ageing cells. This research will make use of the yeast Saccharomyces cerevisiae as a model organism. Yeast offers an ideal model system to study these types of processes since it is genetically tractable and has served as the organism of choice for most post-genomic studies. There is also a high degree of conservation between the stress-protective systems in yeast and human cells making it an ideal organism for this study.

Committee	Closed Committee - Biochemistry & Cell Biology (BCB)
Research Topics	Microbiology
Research Priority	X – Research Priority information not available
Research Initiative	X - not in an Initiative
Funding Scheme	X – not Funded via a specific Funding Scheme

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