Investigating the effects of increased levels of the translation elongation factor eEF1A within eukaryotic cells

The highly conserved eukaryotic elongation factor 1A (eEF1A) plays a canonical role in translation elongation, where it is responsible for delivering the aminoacylated tRNA to the A-site of the 80S ribosome. Further to this essential role it is reported to be involved in a plethora of moonlighting functions that are not fully characterised or understood. One of the human isoforms, eEF1A2, is known to induce cancer when expressed in non-native tissues, although the mechanism by which it promotes tumour growth is not yet known. In this study we have characterised eEF1A overexpression in yeast and provided evidence to suggest that elevated levels of eEF1A result spindle defects which lead to chromosomal abnormalities that have the potential to induce uncontrolled cell growth in human cells. Moreover, we have confirmed conservation of this chromosomal abnormality in human cell lines suggesting that the mechanism that eEF1A utilises to induce these effects are highly conserved. We have also observed that in yeast, eEF1A overexpression results in increased metabolic activity, a hallmark of cancer cells. We hypothesise that eEF1A interacts with the dynactin complex, a regulator of spindle dynamics, resulting in aberrant spindle formation. This in turn leads to chromosomal abnormalities that appear toxic to the cell. Cells appear to overcome the toxicity induced by eEF1A by suppressing plasmid copy number to the lowest levels possible. This however, brings its own problems and appears to result in synthetic effects together with eEF1A overexpression

The control of translational accuracy is a determinant of healthy ageing in yeast

Life requires the maintenance of molecular function in the face of stochastic processes that tend to adversely affect macromolecular integrity. This is particularly relevant during ageing, as many cellular functions decline with age, including growth, mitochondrial function and energy metabolism. Protein synthesis must deliver functional proteins at all times, implying that the effects of protein synthesis errors like amino acid misincorporation and stop-codon read-through must be minimized during ageing. Here we show that loss of translational accuracy accelerates the loss of viability in stationary phase yeast. Since reduced translational accuracy also reduces the folding competence of at least some proteins, we hypothesize that negative interactions between translational errors and age-related protein damage together overwhelm the cellular chaperone network. We further show that multiple cellular signalling networks control basal error rates in yeast cells, including a ROS signal controlled by mitochondrial activity, and the Ras pathway. Together, our findings indicate that signalling pathways regulating growth, protein homeostasis and energy metabolism may jointly safeguard accurate protein synthesis during healthy ageing