Mechanisms of eIF3-mediated translation regulation

Project Summary Exquisite spatial and temporal control of the proteins that are expressed in a cell is essential for correct differentiation and cell growth decisions. Despite being a central step in gene expression, how mRNA translation is regulated remains poorly understood. There is a gap in our understanding of the molecular basis of specialized translation of specific transcripts, and of the overall functional significance of this regulation on cellular responses to signaling cues. Here we propose to investigate the contribution of mRNA translation regulation to the dynamic gene expression programs that underlie cell physiology. The system we will focus on is the 13-subunit eIF3 translation initiation factor complex, which acts as a scaffold during general translation to organize interactions between the small ribosomal proteins and other initiation factors. We recently discovered that eIF3 can also control the translation of select cellular transcripts through novel RNA-binding and cap-binding activities. These findings demonstrate that canonical translation initiation factors moonlight in roles outside of general translation to drive expression of distinct gene programs. Despite these intriguing findings, and eIF3 being the largest component of the translation machinery besides the ribosome, ascribing functions to the majority of subunits has been challenging. Standard genetic techniques cannot be applied to eIF3; eIF3 subunits are essential for viability, and the assembly of the multi-subunit eIF3 complex is hindered by alterations to subunit levels. These methods also cannot segregate activities in general versus specialized translation. We will develop an innovative set of high-throughput methodologies to address these difficulties and comprehensively discover how eIF3 controls the dynamic gene programs during cell differentiation and cellular response to extrinsic signals. By combining these broad approaches with detailed biochemical and cell-based approaches, we will provide molecular understanding of the translation regulation networks that coordinate the precise control required for correct cellular function and signaling. This research will create new insights into fundamental principles of gene regulation. As eIF3 and other initiation factors are genetically associated with cancer, aging, congenital disorders, this work will also guide unconventional approaches to target translation regulation in disease.