Understanding The Role Of Phosphorylation Of The Upf Proteins In The Activity Of The Nonsense-Mediated Mrna Decay (Nmd) Pathway

Nonsense‐mediated mRNA decay (NMD) is an mRNA surveillance mechanism that degrades transcripts harboring premature termination codons (PTCs), preventing the synthesis of potentially deleterious proteins. Upf1p, Upf2p, and Upf3p are central components of the NMD pathway in Saccharomyces cerevisiae. Upf1p and Upf2p have been shown to be phosphorylated both in yeast and humans. Specifically, phosphorylation of the N‐terminal region of Upf2p is crucial for its ability to elicit NMD and for its interaction with Hrp1p, another component of this mRNA surveillance pathway. Previous studies have demonstrated that Upf1p phosphorylation is necessary for activation of the NMD pathway in C. elegans and humans. We have recently identified eleven phosphorylation sites in yeast Upf1p using mass spectrometry. Some of the phosphorylated residues in yeast Upf1p are evolutionary conserved in humans, Drosophila, Arabidopsis and C. elegans. Notably, mutations in some of these conserved phosphorylated residues disrupt the activity of the NMD pathway. We are currently conducting similar mass spectrometry analysis in yeast Upf3p. All together, these studies will allow us to better understand the role of phosphorylation in the activity of the NMD mRNA surveillance pathway in eukaryotes. Supported by RISE 2R25GM61151, NIH U54 CA96297–03, NIH‐NIGMS SCoRE GM008102–305, NIH‐NCRR P20RR016174, HRD‐01843,FIPI‐UPR.