PROJECT SUMMARY Aging is a complex process where perturbation of multiple molecular pathways contributes to organ deterioration and aging-related morbidity and mortality. One component of the aging process is severe dysregulation of gene expression that contributes to changes in the proteome of aged cells, which can compromise cell function. Understanding the mechanisms responsible for aging-induced perturbation of gene expression will be key to develop the necessary medical therapies. Although significant progress has been made in understanding the transcriptional changes occurring with aging, very little is known about how post- transcriptional events, such as RNA modifications, control protein synthesis during aging. In this proposal we will examine the role of METTL3-mediated m6A mRNA methylation in the context of aging using muscle aging as a model system. We hypothesize that METTL3-dependent mRNA methylation regulates the process of aging by controlling the translation of specific pro-hypertrophic mRNAs. For the first time, utilizing gain- and loss-of-function approaches we will characterize this novel regulatory program by establishing the molecular mechanisms by which m6A regulates the life of select mRNAs and assess the global aging- and METTL3- dependent translation dynamics (aim 1), examining the therapeutic benefit of enhancing m6A content to counteract sarcopenia in clinically relevant animal models (aim 2), and define the role of m6A binding proteins in muscle aging (aim 3). Completion of the proposed aims will allow the uncovering of a novel mechanism responsible for post-transcriptional regulation of aging with significant therapeutics ramifications.