Talk abstracts
Talk on Saturday 08:30-08:45am submitted by Vidhyadhar Nandana
Bacterial Ribonucleoprotein bodies (BR-bodies) organize mRNA decay and coordinate other steps of RNA metabolism in bacteria
Vidhyadhar Nandana (Departments of Chemistry and Biological Sciences, Wayne State University), Luis A. Ortiz Rodrguez, Julie S Biteen (Department of Chemistry, Wayne State University), Ali Hatami, Kaveendya S Mallikaarachchi, Yingxi Elaine Zhu (Department of Chemical Engineering, Departments of Chemistry and Biological Sciences, Wayne State University), Katherine Lopez (Phillips Exeter Academy), Seth W Childers (Department of Chemistry, University of Pittsburgh), Jared M Schrader (Departments of Chemistry and Biological Sciences, Wayne State University)
Abstract:
Biomolecular condensates are membraneless assemblies of proteins and RNAs that compartmentalize various biochemical processes in all forms of life. Biomolecular condensates can accelerate enzymatic reactions, impart specificity to the reactions, or serve as storage sites for proteins and RNAs1. Bacterial ribonucleoprotein bodies (BR-bodies) are a type of biomolecular condensates found in bacteria, containing the RNA degradosome and mRNAs. Disrupting BR-bodies in the α-proteobacterium Caulobacter crescentus resulted in a 3-4 fold slowdown in global mRNA decay2. Based on this, we hypothesized that the phase separation of mRNA with components of the RNA degradosome, RNase E, PNPase, and the DEAD Box RNA helicase RhlB may enhance the degradation rate of bacterial mRNAs. Using in-vitro reconstituted minimal BR-bodies and in vivo reconstitutions, we demonstrate that BR-bodies significantly enhance the endonucleolytic activity of RNase E, the exonucleolytic activity of PNPase, and the ATPase activity of DEAD box RNA helicase RhlB, suggesting an acceleration of enzyme kinetics within the condensed state. In line with the role of accelerated decay, in vivo mRNA tracking experiments showed that mRNAs are rapidly degraded when colocalized with BR-bodies. While BR-bodies appear to accelerate enzymatic RNA decay activities during exponential growth, when cells enter stationary phase growth arrests and the cytoplasm becomes more compact and less dynamic3. Single-molecule microscopy revealed that BR-bodies transition from a dynamic, liquid-like state during exponential growth to a more static, arrested state with diminished internal dynamics in stationary phase. mRNA tracking experiments revealed that the reduced dynamics correlated with a switch of internal decay, to mRNA storage, where mRNAs remain colocalized with BR-bodies for extended durations. Finally, by aging in vitro reconstituted BR-bodies, we find that aging reduces internal recovery by FRAP which leads to a strong reduction in RNase E cleavage. Taken together, this suggests that BR-bodies switch from mRNA decay BR-bodies in actively growing cells to mRNA storage bodies in stationary phase.
References:
1. Banani, S.F., Lee, H.O., Hyman, A.A., and Rosen, M.K. (2017). Biomolecular condensates: organizers of cellular biochemistry. Nature Reviews Molecular Cell Biology 18, 285–298. https://doi.org/10.1038/nrm.2017.7.
2. Al-Husini, N., Tomares, D.T., Pfaffenberger, Z.J., Muthunayake, N.S., Samad, M.A., Zuo, T., Bitar, O., Aretakis, J.R., Bharmal, M.-H.M., Gega, A., et al. (2020). BR-Bodies Provide Selectively Permeable Condensates that Stimulate mRNA Decay and Prevent Release of Decay Intermediates. Molecular Cell 78, 670-682.e8. https://doi.org/10.1016/j.molcel.2020.04.001.
3. Parry, B.R., Surovtsev, I.V., Cabeen, M.T., O’Hern, C.S., Dufresne, E.R., and Jacobs-Wagner, C. (2014). The Bacterial Cytoplasm Has Glass-like Properties and Is Fluidized by Metabolic Activity. Cell 156, 183–194. https://doi.org/10.1016/j.cell.2013.11.028.
Keywords: Ribonucleoprotein complexes, biomolecular condensates, RNA decay