Talk abstracts
Talk on Saturday 10:00-10:15am submitted by Amber LaPeruta
RNA Folding as a Trigger for the Release of Pre-Ribosomes from the Nucleolus
Amber J. LaPeruta (Carnegie Mellon University Department of Biological Sciences), Jelena Micic (Carnegie Mellon University Department of Biological Sciences), Melissa Tosiano (Carnegie Mellon University Department of Biological Sciences), David Kim (Carnegie Mellon University Department of Biological Sciences), John L. Woolford Jr. (Carnegie Mellon University Department of Biological Sciences)
Abstract:
Ribosome biogenesis is an extremely dynamic process requiring the assembly of ~80 ribosomal proteins and 4 rRNAs into the large and small ribosomal subunits in eukaryotes. This process is enabled by ~200 assembly factors, including RNA chaperones, RNA modifiers, scaffolds, molecular mimics, switches and timers, as well as structural and functional proofreaders. Ribosome assembly begins in the nucleolus, continues in the nucleoplasm, and is completed in the cytoplasm. We want to determine what triggers the exit of nascent large ribosomal precursors from the nucleolus to the nucleoplasm at a very specific point in subunit maturation. This transition coincides with a particularly complicated, energetically expensive, and dramatic alteration in preribosome protein composition and rRNA structure, which irreversibly alters the biophysical properties of the particles.
Knocking out the gene encoding the non-essential assembly factor Puf6, a known RNA folding chaperone in the PUF family of proteins, slows down this stage of ribosome assembly at cold temperatures. Thus, this puf6Δ mutant is a powerful tool to accumulate assembly intermediates within this stage, and to discern the role of rRNAs, assembly factors and ribosomal proteins in facilitating this uncharacterized transition. To identify interactions among factors participating at this stage, we carried out a multicopy suppressor screen and a selection for genomic suppressors of the puf6Δ cold sensitive phenotype. By coupling these results to biochemical and structural assays, we discerned distinct stages of assembly that occur during this essential transition and discovered additional functions for a number of ribosomal proteins and rRNA structures during this step. Because most molecules work in concert with other molecules in multimolecular complexes, this study will be important for defining principles of RNA and protein cooperation in molecular machines, and how multimolecular complexes are assembled.
Keywords: RNA chaperones, Ribosome Biogenesis, RNA folding