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:Uncovering what drives select biomolecules to form phase-separated condensates in vivo and identifying their physiological significance are topics of fundamental importance. Here we show that nitrogen-starved Escherichia coli produce long-chain polyphosphates, which scaffold the RNA chaperone Hfq into phase-separating high molecular weight complexes together with components of the RNA translation and processing machinery. The presence of polyphosphate within these condensates, which we termed HP-bodies, controls Hfq function by selectively stabilizing polyadenylated RNAs involved in transcription and protein translation, and promoting interactions with translation- and RNA-metabolism-associated proteins involved in de novo protein synthesis. Lack of polyphosphate prevents HP-body formation, which increases cell death and significantly hinders recovery from N-starvation. In functional analogy, we demonstrate that polyP contributes specifically to the formation of Processing (P)-bodies in human cell lines, revealing that a single, highly conserved and ancestral polyanion serves as the universal scaffold for functional phase-separated condensate formation across the tree of life.
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.