Mechanisms of Telomerase RNA Processing and Formation of Ribonucleoprotein Particles in Saccharomyces cerevisiae

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Recently, several RNA-containing sub-compartments have been discovered in the cytoplasm of eukaryotic cells. It has been suggested that these compartments are liquid and behave like oil in an oil-in-water emulsion. To this day, it is not understood why RNA processing requires such compartmentalization. Evolutionarily, some components of RNA bodies are very old, and these structures have been proposed to be remnants of the early RNA world that may have represented separate reaction spaces before the rise of lipid-bilayer enclosed life. Interestingly, Sm or Sm-like proteins are found in most RNA bodies described so far. These proteins form ring-like structures; however, their molecular function remains unclear. TLC1, the telomerase RNA of S. cerevisiae, serves as a model for non-coding RNAs that associate with the Sm-ring. In many respects, TLC1 maturation resembles the generation of spliceosomal snRNPs. While snRNP assembly has been studied extensively in higher eukaryotes, the process is less well understood in yeast, and seems to differ from the metazoan pathway in several important aspects. In mammalian cells, assembly of the Sm-complex takes place in the cytoplasm, potentially in a specialized RNA compartment. Although assembly occurs spontaneously in vitro, the process is highly regulated and involves various additional factors, many of which are, however, not conserved in yeast.I will use yeast TLC1 to study Sm-ring assembly in S. cerevisiae. To identify the assembly compartment, I will combine biochemistry with high-resolution microscopy on Sm proteins and associated RNAs. In addition, purification of TLC1 will allow the identification of protein components and will help to infer processing mechanisms. Using the experimental tractability of S. cerevisiae, my research will clarify important aspects of Sm-RNA processing and will help to shed light on the role of RNA processing compartments, the ubiquity and importance of which is just beginning to emerge.