Specialized post-transcriptional mechanisms of gene expression in quiescence

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Abstract Specialized post-transcriptional mechanisms of gene expression in quiescence Vision Quiescence (G0) is an assortment of reversible, cell-cycle arrested phases, that permits cells to avoid death due to harsh conditions or stress. Our studies uncovered powerful RNA regulators, and modifications in G0 cells, revealing inhibition of conventional translation and its replacement by non-canonical mechanisms to enable specific gene expression for G0 roles and survival. Based on our data, G0 cells are perpetuated by specialized post-transcriptional mechanisms that elicit distinct gene expression. G0 cells switch to a gene expression profile that maintains the transient arrested state, enables survival, and retains the ability of the cell to re-enter proliferation. This permits important G0 functions: survival of G0 drug resistant cancer stem cells, immune cell extravasation, tissue regeneration and development by dormant stem cells. G0 is important in cancer and immunity, producing critical cytokines to promote inflammation and tumor persistence. G0 is poorly understood despite its medical significance. The objective of my research is to investigate post-transcriptional mechanisms and regulated gene expression in G0 in vitro and in vivo to understand G0 roles and survival. Premise based on our research findings The key finding of our studies is that conventional translation is inhibited by G0 signals and replaced by non-canonical factors that enable specific expression of genes that are critical for survival. Significantly, such non-canonical factors alter translation start site selection, expanding the proteome by creating new frames (PNAS 2014). We identified noncoding microRNAs, associated RNA-protein complexes (RNPs), and non-canonical translation factors that mediate select expression of few immune and cell state regulators in G0 (Molecular Cell 2016). Our data revealed signaling changes that modify RNPs in G0 to enable specific gene expression, which allowed targeting of drug resistant G0 in disease (Biorxiv/ 418715). Our studies indicate important layers of undiscovered regulation: modification of ribosomes, mRNAs and RNPs and associated non-canonical translation. Characterization of G0 post-transcriptional mechanisms, will provide insights into the specialized gene expression and mechanisms that underlie G0 survival in disease. Directions in the next 5 years First, profiling, purifications, depletions, mutations, and biochemical analyses of snoRNAs and ribosomes, will map snoRNPs and ribosome modifications, providing insights on changes to the translation machinery underlying gene expression in G0. Second, required modifications on mRNAs, associated regulatory RNPs, non-canonical translation factors, translated targets and unique start sites in G0 will be identified. These data will be verified in vivo to uncover the G0 translatome, expanded at the translation frame, and will reveal post-transcriptional mechanisms of gene expression that impacts G0 roles and viability. Impact These studies uncover new insights into post-transcriptional mechanisms, provide a map of ribosome and mRNA modifications, and translation frames in G0, and their impact on G0 roles and survival in disease.