Structural and RNA-Binding Characteristics of Three Yeast LA Motif Domains

Abstract

La-related proteins (LARP) are a conserved class of RNA-binding proteins that function in RNA metabolism, including mRNA stabilization, translation regulation, and non-coding RNA processing. In humans, La-related protein 1 (LARP1) regulates translation and stability of 5′ terminal oligopyrimidine (TOP) tract-containing mRNAs linked to cell growth and proliferation. Although its role as a downstream effector of the mTORC1 pathway is established, the molecular interactions of LARP1 and yeast homologs remain poorly defined. This thesis examines the structure–function relationship of the La motif domain (LaM) in yeast proteins Slr1p, Slf1p, and Sro9p using isothermal titration calorimetry (ITC), circular dichroism (CD), nuclear magnetic resonance (NMR), and differential scanning calorimetry (DSC). Findings show these proteins share conserved features and bind RNA and ligands with high affinity (low micromolar Kd). NMR line broadening observed for Slf1p–RNA interactions suggests conformational sampling. Collectively, these results advance understanding of conserved mechanisms underlying LARP1-mediated translational regulation.