Comprehensive Identification of FXR1 Targets Using pSILAC-BONCAT Proteomics

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The purpose of this project is to determine the post-transcriptional regulation that changes the progression of oral cancer via the RNA-binding protein FXR1 and its mRNA translational control that govern cellular senescence. FXR1 was considered as a critical regulator of gene expression in most of the eukaryotic cells by controlling mRNA stability and translation. Thus, the main goal of this project is to understand the molecular mechanisms of FXR1-mediated mRNA translation and their implications in oral squamous cell carcinoma (OSCC) cellular senescence. Cellular senescence is an important mechanism for preventing the proliferation of potential cancer cells. Hence, underpinning the mechanistic aspects of cellular machinery by dissection the protein expression profiles provides novel biomarkers and/or therapeutic targets. Our laboratory has extensive experience in studying RNA-binding proteins and high throughput analysis of protein expression by pulsed-stable isotope labeling with amino acids in cell culture (pSILAC). We have developed a genome- wide shRNA screen of RBPs to test the cellular senescence in oral cancer cells. By studying oral cancer cells for cellular senescence, we have discovered FXR1 is overexpressed and depletion of FXR1 induces cellular senescence. Interestingly, FXR1 is a major player to control the expression of protein at the translational level that could mediate cellular senescence. Hence, we plan to systematically study the phenotypic changes of cellular senescence in oral cancer cells by understanding the expression of proteins that are controlled by FXR1. Thus, our central hypothesis is to understand how overexpression of FXR1 in oral cancer cells alter the protein expression by modulating RNA processing machinery to control cellular senescence. We propose the following specific aims to test this hypothesis: 1) to determine the critical role of FXR1 in bypassing OSCC senescence. We will test if the gain- and loss-of-function of FXR1 affects senescence in OSCC cells through various cell biological senescence assays, 2) to determine the consequence of FXR1 dysregulation on the cellular proteome. The protein targets of FXR1 will be identified using pulsed-Stable Isotope Labeling of Cells in cultured OSCC cells with click-chemistry Bioorthogonal Noncanonical Amino Acid Tagging (pSILAC- BONCAT) and Mass Spectrometry.