Aaron A. Hoskins
New Approaches for Studying Ribonuclioprotein Biogenesis and Recycling
University of Wisconsin, Madison
Cells are filled with tiny machines that carry out the biology necessary for life including gene expression, transport of biomolecules, and cell division. Like the machines we use everyday to prepare our meals or carry us about town, cellular machines can be composed of dozens and often hundreds of parts that are precisely put together for the machine to work. These parts often include both proteins and nucleic acids such as RNA. Understanding how these machines are built and function in live cells is an important challenge in modern biochemistry. Our laboratory studies the spliceosome: a eukaryotic machine that processes precursor mRNA transcripts into mRNAs that can be translated into proteins. The spliceosome is made up of both RNA and proteins and contains different subunits called small nuclear ribonucleoproteins (snRNPs). Little is known about how snRNPs are built inside cells, but defects in snRNP assembly can lead to devestating diseases such as spinal muscular atrophy or retinitis pigmentosa, a genetic form of blindness. In order to study snRNPs, we are developing new tools for attaching small and very bright fluorophores to snRNP RNAs in order to watch the snRNP being built and later function in the spliceosome. Using chemical biology, we are developing RNA sequences that can tightly bind fluorophores that allow us to watch single molecules in a live cell. In another approach we are creating fluorescent RNAs in a test tube and using a very small needle to inject these RNAs into live human cells. We can then watch these RNAs one-at-a-time move about the cell using a cutting-edge microscope technique called Hi-Lo Microscopy. These experiments are providing never-before-seen pictures of how spliceosomal RNAs are transported in the cell and how the cell does or does not deal with defective RNAs.