Poster abstracts
Poster number 153 submitted by Hadi Yassine
BR-bodies switch from mRNA decay to mRNA storage in stationary phase
Hadi Yassine (Biological Sciences, Wayne State University), Luis Ortiz-Rodriguez (Chemistry, University of Michigan Ann Arbor), Nadra Al-Husini (Biological Sciences, Wayne State University), Vidhyadhar Nandana (Biological Sciences, Wayne State University), Julie Biteen (Chemistry, University of Michigan Ann Arbor), Jared Schrader (Biological Sciences, Wayne State University)
Abstract:
Bacterial Ribonucleoprotein bodies (BR-bodies) are phase-separated condensates found in Caulobacter crescentus (Ccr) that help organize mRNA decay machinery during exponential growth phase. During exponential growth, BR-bodies quickly assemble to promote mRNA decay on the 1-4 minute timescale, and upon mRNA decay, BR bodies rapidly disassemble. Interestingly, mRNA decay rates drop in stationary phase of many bacteria, yet it has remained unclear what role BR-bodies play in the deceleration of mRNA decay in stationary phase. Time-lapse microscopy and FRAP revealed that BR-bodies become dynamically arrested upon entry into stationary phase, resembling a solid-like state. We observe that as BR-body dynamics become gradually arrested, there is a corresponding reduction in mRNA decay rates. However, upon nutrient replenishment, solid-like BR-bodies melt back into a dynamic liquid-like state, which occurs prior to when the cells resume growth. Translation rates assayed by amino acid incorporation (BONCAT) demonstrated that upon the addition of fresh media to stationary phase cells, we find an anti-correlation of translation activity and BR-body assembly, suggesting that solid-like BR-bodies may be sequestering poorly translated mRNAs. RNase E together with RNA drive BR-bodies phase separation, where its intrinsically disordered C-terminal domain (CTD) is necessary and sufficient to drive phase separation. To investigate the physiological roles of BR-bodies in stationary phase, we generated an RNEΔCTD strain that cannot form BR-bodies. When comparing its growth rate to the wild-type, RNEΔCTD has only subtle growth defects in log phase. However, when stationary phase cells are provided with fresh media, RNEΔCTD tends to have an extended lag-phase phenotype compared to wild-type. This suggested that BR-bodies promote faster entry into log-growth upon nutrient replenishment. Overall, we propose that BR-bodies shift their function from mRNA decay to mRNA storage when cells enter the stationary phase, and upon nutrient availability, BR-bodies dissolve and release the stored mRNA to promote fast regrowth.
References:
1- Al-Husini N, Tomares DT, Pfaffenberger ZJ, Muthunayake NS, Samad MA, Zuo T, Bitar O, Aretakis JR, Bharmal MM, Gega A, Biteen JS, Childers WS, Schrader JM. BR-Bodies Provide Selectively Permeable Condensates that Stimulate mRNA Decay and Prevent Release of Decay Intermediates. Mol Cell. 2020 May 21;78(4):670-682.e8. doi: 10.1016/j.molcel.2020.04.001.
2- Al-Husini N, Tomares DT, Bitar O, Childers WS, Schrader JM. α-Proteobacterial RNA Degradosomes Assemble Liquid-Liquid Phase-Separated RNP Bodies. Mol Cell. 2018 Sep 20;71(6):1027-1039.e14. doi: 10.1016/j.molcel.2018.08.003.
Keywords: BR-bodies, Material properties, mRNA storage