Project description:How biomolecules condense to organize subcellular processes is of fundamental significance. Nitrogen-starved Escherichia coli form a single condensate, which we termed Bacterial Stress Body (BSB). Its formation is triggered by long polyphosphate chains, which scaffold the RNA chaperone Hfq into high molecular weight complexes with distinct sequence-specific RNA and DNA binding properties. We show that polyP is crucial for the stabilization of select RNAs, the sequestration of translation- and RNA metabolism-associated proteins that likely stall protein synthesis, and the specific nucleoid-associated localization of BSBs. Together, these functions ensure bacterial survival and recovery from N-starvation. Mammalian polyphosphate associates with P-bodies but not stress granules suggesting that polyphosphate’s interaction with select RNA binding proteins contributed to the evolution of functionally and compositionally distinct condensates in higher organisms.
Project description:How biomolecules condense to organize subcellular processes is of fundamental significance. Nitrogen-starved Escherichia coli form a single condensate, which we termed Bacterial Stress Body (BSB). Its formation is triggered by long polyphosphate chains, which scaffold the RNA chaperone Hfq into high molecular weight complexes with distinct sequence-specific RNA and DNA binding properties. We show that polyP is crucial for the stabilization of select RNAs, the sequestration of translation- and RNA metabolism-associated proteins that likely stall protein synthesis, and the specific nucleoid-associated localization of BSBs. Together, these functions ensure bacterial survival and recovery from N-starvation. Mammalian polyphosphate associates with P-bodies but not stress granules suggesting that polyphosphate’s interaction with select RNA binding proteins contributed to the evolution of functionally and compositionally distinct condensates in higher organisms.
Project description:How biomolecules condense to organize subcellular processes is of fundamental significance. Nitrogen-starved Escherichia coli form a single condensate, which we termed Bacterial Stress Body (BSB). Its formation is triggered by long polyphosphate chains, which scaffold the RNA chaperone Hfq into high molecular weight complexes with distinct sequence-specific RNA and DNA binding properties. We show that polyP is crucial for the stabilization of select RNAs, the sequestration of translation- and RNA metabolism-associated proteins that likely stall protein synthesis, and the specific nucleoid-associated localization of BSBs. Together, these functions ensure bacterial survival and recovery from N-starvation. Mammalian polyphosphate associates with P-bodies but not stress granules suggesting that polyphosphate’s interaction with select RNA binding proteins contributed to the evolution of functionally and compositionally distinct condensates in higher organisms.
Project description:Microbes exhibit remarkable adaptability to environmental fluctuations. Signaling mechanisms, such as two-component systems and secondary messengers, have long been recognized as critical for sensing and responding to environmental cues. However, recent research has illuminated the potential of a physical adaptation mechanism in signaling-phase separation, which may represent a ubiquitous mechanism for compartmentalizing biochemistry within the cytoplasm in the context of bacteria that frequently lack membrane-bound organelles. This review considers the broader prospect that phase separation may play critical roles as rapid stress sensing and response mechanisms within pathogens. It is well established that weak multivalent interactions between disordered regions, coiled-coils, and other structured domains can form condensates via phase separation and be regulated by specific environmental parameters in some cases. The process of phase separation itself acts as a responsive sensor, influenced by changes in protein concentration, posttranslational modifications, temperature, salts, pH, and oxidative stresses. This environmentally triggered phase separation can, in turn, regulate the functions of recruited biomolecules, providing a rapid response to stressful conditions. As examples, we describe biochemical pathways organized by condensates that are essential for cell physiology and exhibit signaling features. These include proteins that organize and modify the chromosome (Dps, Hu, SSB), regulate the decay, and modification of RNA (RNase E, Hfq, Rho, RNA polymerase), those involved in signal transduction (PopZ, PodJ, and SpmX) and stress response (aggresomes and polyphosphate granules). We also summarize the potential of proteins within pathogens to function as condensates and the potential and challenges in targeting biomolecular condensates for next-generation antimicrobial therapeutics. Together, this review illuminates the emerging significance of biomolecular condensates in microbial signaling, stress responses, and regulation of cell physiology and provides a framework for microbiologists to consider the function of biomolecular condensates in microbial adaptation and response to diverse environmental conditions.
Project description:Ribonucleoprotein (RNP) granules are membraneless compartments within cells, formed by phase separation, that function as regulatory hubs for diverse biological processes. However, the mechanisms by which RNAs and proteins interact to promote RNP granule structure and function in vivo remain unclear. In Xenopus laevis oocytes, maternal mRNAs are localized as large RNPs to the vegetal hemisphere of the developing oocyte, where local translation is critical for proper embryonic patterning. Here we demonstrate that RNPs containing vegetally localized RNAs represent a new class of cytoplasmic RNP granule, termed localization-bodies (L-bodies). We show that L-bodies contain a dynamic protein-containing phase surrounding a nondynamic RNA-containing phase. Our results support a role for RNA as a critical component within these RNP granules and suggest that cis-elements within localized mRNAs may drive subcellular RNA localization through control over phase behavior.
Project description:Bronchial epithelial cells play a pivotal role in airway inflammation, but little is known about posttranscriptional regulation of mediator gene expression during the inflammatory response in these cells. Here, we show that activation of human bronchial epithelial BEAS-2B cells by proinflammatory cytokines interleukin-4 (IL-4) and tumor necrosis factor alpha (TNF-alpha) leads to an increase in the mRNA stability of the key chemokines monocyte chemotactic protein 1 and IL-8, an elevation of the global translation rate, an increase in the levels of several proteins critical for translation, and a reduction of microRNA-mediated translational repression. Moreover, using the BEAS-2B cell system and a mouse model, we found that RNA processing bodies (P bodies), cytoplasmic domains linked to storage and/or degradation of translationally silenced mRNAs, are significantly reduced in activated bronchial epithelial cells, suggesting a physiological role for P bodies in airway inflammation. Our study reveals an orchestrated change among posttranscriptional mechanisms, which help sustain high levels of inflammatory mediator production in bronchial epithelium during the pathogenesis of inflammatory airway diseases.