Project description:Numerous proteins are targeted to two or multiple subcellular destinations where they exert distinct functional consequences. The balance between such differential targeting is thought to be determined post-translationally, relying on protein sorting mechanisms. Here, we show that protein targeting can additionally be determined by mRNA location and translation rate. Our model, the NET1 protein, distributes between the nucleus and cytosol and functions in cell motility. N-terminal NLSs and an internal PH domain competitively determine NET1 distribution. Peripheral localization of the NET1 mRNA and fast translation lead to higher cytosolic retention through the PH domain. By contrast, perinuclear mRNA location and/or slower translation rate favor nuclear targeting through importin β1. NET1 mRNA location is modulated by physiological stimuli and profoundly impacts NET1 function in cell motility. Indeed, perinuclear NET1 mRNA localization causes reduced RhoA activity, impedes focal adhesion maturation and results in slower cell migration to an extent similar as that observed upon knockdown of NET1 expression. Overall, these results reveal that the location of protein synthesis and the rate of translation elongation act in coordination to influence the ability of competing domains within a polypeptide to determine protein distribution and function.
Project description:METTL16 is a member of methyltransferase like (METTL) family. Unlike well-studied METTL3 and METTL14, we found a much higher percentage of METTL16 is localized in the cytosol. The subcellular distribution holds the ability to potentiate translation efficiency. Via Far-western blotting and Co-Immunoprecipitation (Co-IP) assays, we have identified the direct interactions between METTL16 and eukaryotic initiation factor 3 (eIF3) a and b. Via cross-linking immunoprecipitation and qPCR (CLIP-qPCR), we have discovered the direct associations between METTL16 and rRNAs. The METTL16-eIF3a/b and METTL16-rRNAs interactions induce the binding between eIF3 and 18S rRNA, promote the formation of 43S preinitiation complex, and eventually expedite translation initiation, the rate-limiting step of translation. To determine the exact effects of METTL16 on translation efficiency, we performed ribosome profiling (Ribo-seq) with HEK293T upon CRISPR-Cas9-induced METTL16 knockout. To guarantee the repeatability and avoid any potential off-target effects, we included 3 distint sgRNAs against METTL16.
Project description:There has been a surge of interest towards targeting protein synthesis to treat diseases and extend lifespan. Despite the progress, few options are available to assess translation in live animals, as their complexity limits the repertoire of experimental tools to monitor and manipulate processes within organs and individual cells. It this study, we developed a labeling-free method for measuring organ- and cell-type-specific translation elongation rates in vivo. It is based on time-resolved delivery of translation initiation and elongation inhibitors in live animals followed by ribosome profiling. It also reports translation initiation sites in an organ-specific manner. Using this method, we found that the elongation rates differ more than 50% among mouse organs and determined them to be 6.8, 5.0, and 4.3 amino acids per second for liver, kidney, and skeletal muscle, respectively. We further found that the elongation rate is reduced by 20% between young adulthood and mid-life. Thus, translation, a major metabolic process in cells, is tightly regulated at the level of elongation of nascent polypeptide chains.