PROJECT SUMMARY/ABSTRACT Translation is a dynamic process with a high degree of specificity conferred by multiple factors including mRNA transcript sequence, composition of the translation machinery, and cellular milieu. A striking demonstration of this specificity is the tissue-specific (e.g. craniofacial anomalies, bone marrow failure) rather than global nature of the developmental defects seen in human ribosomopathies caused by congenital mutations in ribosomal factors. Moreover, ribosomopathy-driven bone marrow failure is characterized by selective, rather than global, defects in mRNA translation. Thus, even the composition of the ribosome can affect mRNA translational efficiency in a tissue-specific manner. These observations point to a particularly nuanced regulation of translation in the hematopoietic system; elucidating the mechanisms of this regulation is therefore essential for understanding hematopoietic cell development, function, and dysfunction in disease states. As such, my long-term research goal is to elucidate mechanisms of translational control in hematolymphoid cells during normal immune function and in disease states, focusing on ribosome-associated proteins (RAPs)—a poorly studied class of proteins which physically interact with the core ribosomal proteins to tune the translational efficiency of specific mRNAs. My central hypothesis is that, in immune cells poised for rapid responses to infection, inflammatory stimuli may induce dynamic interactions of RAPs with ribosomes, where they may effect rapid changes in the translational efficiency of specific mRNAs with important immunoregulatory consequences. In previous work, I have defined the repertoire of ribosome-bound RAPs in in vitro bone marrow-derived macrophages. In Aim 1 of this proposal, I will use global, unbiased proteomics to temporally profile RAP-ribosome interactions in activated macrophages following TLR stimulation. In Aim 2, I will use CRISPR gene editing, ribosome profiling, and cytokine secretion assays to 1) identify mRNA targets that are specifically regulated by two RAPs I have already identified, Rnf213 and Helz2, as well as other RAPs identified in Aim 1, and 2) determine the function of these RAPs in the macrophage inflammatory response. Having completed MD-PhD training and clinical training as a clinical pathologist and hematopathologist, I am applying for the K38 Award to support my goal of becoming an independent physician investigator. UCSF’s exceptional training environment, especially in the areas of immunology and proteostasis, make it an ideal place for me to pursue my efforts. Critical elements of my career development plan include leveraging the expertise of my primary mentor Dr. Davide Ruggero, a pioneer in the field of ribosome biology, and my co-mentors Dr. Jason Cyster, an expert immunologist, and Dr. Karthik Ganapathi, an expert diagnostic hematopathologist; guidance by physician-scientist advisors; coursework in data science and resear...