Elaine Nguyen - Berman Lab
"Identifying the molecular determinants that drive the LARP1 DM15 interaction with 5’ TOP mRNAs"
Friday, April 9th, 2021
12:10 PM
Virtual Zoom seminar
Abstract:
Cells adapt to their dynamic environment through the precise control of gene expression. One way that eukaryotes alter gene expression occurs at the mRNA level through the 5’ and 3’ untranslated regions (UTRs). To mediate mRNA fate, RNA binding proteins (RBPs) coat the mRNA via the recognition of sequence, chemical, or structural elements within the UTRs. 5’ TOP (terminal oligopyrimidine) mRNAs are a class of transcripts that must be stringently regulated because they encode all the protein components of the ribosome and many translation factors. Whether the translation of 5’ TOP mRNAs is turned on or off is hierarchically dictated by mTORC1, a protein kinase complex that integrates environmental cues and transduces this information to a well-conserved target, La-related protein 1 (LARP1). How LARP1 impacts translation is controversial; many contradictory hypotheses have been proposed, in part due to the compounding effects of the different cellular environments in which the experiments were performed. Additionally, the targets and functions of the multiple RNA-binding domains of LARP1 are still under investigation. However, given that the C-terminal region of LARP1 containing the DM15 domain is both necessary and sufficient for mTORC1 control of 5’ TOP translation in mammalian cells, the goal of my dissertation is to dissect the structural, biochemical, and biophysical details that drive the LARP1 DM15 interaction with 5’ TOP mRNAs in vitro. To this end, I found that this interaction is 5’ TOP motif length-dependent and is likely dependent on the structural context of the 5’ UTR. I have also solved the crystal structure of a homologous DM15 domain from Drosophila melanogaster to interrogate structural contributions that may confer binding plasticity, since this homolog of LARP1 recognizes different RNA targets. This work will elucidate the binding mechanism that underlies the translational regulation of a class of transcripts fundamental for life.