Geraldine Seydoux, Huntington Sheldon Professor in Medical Discovery, Dept of Molecular Biology and Genetics, Johns Hopkins School of Medicine; Investigator, Howard Hughes Medical Institute, will give a talk on "Assembly and Function of RNA granules in C. elegans."

ABSTRACT

RNA granules are assemblies of RNA and proteins not limited by membranes. RNA granules contain factors for RNA biogenesis and turnover and are often assumed to represent specialized compartments for RNA biochemistry. We use the C. elegans model to study RNA granules in a native, whole animal context.  Our studies support the view that RNA granules are assembled by phase separation, a thermodynamic process that causes interacting proteins and RNAs to de-mix from the cytoplasm to form condensed droplets.  I will discuss active mechanisms used by cells to control the assembly and distribution of P granules in embryos, including protein clusters that form a type of “primitive membrane” on the surface of P granules to reduce surface tension and regulate granule dynamics. I will also discuss recent experiments that challenge the view that RNA granules represent specialized compartments for RNA biochemistry and present evidence that some are “incidental condensates”, non-functional minor condensation by-products that form when sub-soluble RNA-protein complexes saturate the cytoplasm.