The effect of cadmium on growth and PCA1 expression in Saccharomyces cerevisiae strains with a functional and non-functional nonsense-mediated mRNA decay pathway




Pratt, Maria

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Regulation of gene expression at the messenger RNA (mRNA) level is vital for initiating a rapid and precise response to environmental stimuli. The Nonsense-Mediated mRNA Decay (NMD) pathway is a conserved physiological process in all eukaryotes that is involved in regulating gene expression. This pathway has been shown to target and degrade mRNAs that prematurely terminate translation and natural mRNAs that encode fully functional proteins. Regulation of mRNAs by NMD is specific to certain cellular contexts and environmental conditions. Importantly, the NMD pathway in Saccharomyces cerevisiae has an essential role in bio metal homeostasis, including a protein called PCA1. PCA1 is an integral protein that transports metals and ions across membranes, specifically functioning as a cadmium efflux pump. Cadmium is a non-essential and toxic metal ion for eukaryotes, causing an imbalance of cellular redox, inhibiting DNA repair, etc. Therefore, it must be pumped out of the cell in order for it to function and grow. Here, I examined the growth of two yeast strains RM11-1 (with a functional PCA1) and W303a (with a non-functional PCA1) in cadmium to confirm the role of PCA1 in the cell. I found that the strain with a functional PCA1 was able to grow in cadmium, whereas the strain with a non-functional PCA1 was not, confirming its role in the cell. I also sought to examine the accumulation of PCA1 mRNA over time of one yeast strain with a functional and non-functional NMD pathway in the presence of cadmium. I found that PCA1 mRNA accumulates to a higher degree in the yeast strain with a non-functional NMD pathway, hinting that NMD may play a role in its accumulation.



Saccharomyces cerevisiae. Cadmium. PCA1 expression. Nonsense-mediated decay pathway.