Biology subjects

Tomares, D. T.

Publications and source records attributed to Tomares, D. T..

6 recordsLinked to original sources

bioRxiv2025

Mast cell extracellular granules are bioactive condensates driven by heparin and polyamine

Biomolecular condensates are membraneless bodies that organize biochemical reactions typically within cells. However, the roles of condensates in extracellular space--where conditions differ substantially from intracellular space--remain poorly understood. Here, we report mast cell extracellular granules (MCEGs), a stable membraneless entity, are condensates assembled via electrostatic interactions between glycosaminoglycans and polyamines. Disrupting polyamine synthesis or trafficking blocks MCEG formation and compromises the storage of proteases and cytokines. Granules reconstituted with heparin and spermine are sufficient to enrich mediators such as CPA3 and TNF, maintaining an elevated pH and higher concentrations of calcium and zinc compared to the extracellular milieu. This unique environment enhances CPA3 enzymatic activity. Furthermore, the granules increase TNF binding and its bioactivity toward endothelial cells. Together, we reveal MCEGs as functionally active biomolecular condensates with distinct biochemical and immunological properties; MCEGs are formed through sugar-metabolite interactions, expanding the mechanisms of condensate assembly beyond classical protein-protein and protein-RNA interactions.

cell biology↗

bioRxiv2025

BR-Bodies Facilitate Adaptive Responses and Survival During Copper Stress in Caulobacter crescentus

Microbes must rapidly adapt to environmental stresses, including toxic heavy metals like copper, by sensing and mitigating their harmful effects. Here, we demonstrate that the phase separation properties of bacterial ribonucleoprotein bodies (BR-bodies) enhance Caulobacter crescentus fitness under copper stress. To uncover the underlying mechanism, we identified two key interactions between copper and the central scaffold of BR-bodies, RNase E. First, biochemical assays and fluorescence microscopy experiments show that reductive chelation of Cu{superscript 2} leads to cysteine oxidation, driving the transition of BR-bodies into more solid-like condensates. Second, tryptophan fluorescence and EPR assays reveal that RNase E binds Cu{superscript 2} at histidine sites, creating a protective microenvironment that prevents mismetallation and preserves PNPase activity. More broadly, this example highlights how metal-condensate interactions can regulate condensate material properties and establish specialized chemical environments that safeguard enzyme function.

microbiology↗

bioRxiv2025

Nuclear speckle proteins form intrinsic and MALAT1-dependent microphases

Nuclear speckles are enriched in serine / arginine rich splicing factors (SRSFs), such as SRSF1. Splicing factors and proteins such as TDP-43 concentrate into distinct speckle territories to enable pre-mRNA processing. We have discovered that SRSFs and TDP-43 are block copolymers and the protein-specific interplay of inter-block repulsions and attractions drives spontaneous microphase separation. This gives rise to size-limited, ordered assemblies, that are 30 - 45 nm in diameter. Depending on the protein, each microphase comprises several tens to hundreds of molecules. The sub-micron scale territories observed in cells are shown to be clusters of microphases. The regulatory lncRNA MALAT1 binds preferentially to SRSF1 microphases to enhance microphase separation and alter microphase structures. Microphase separation enables the concentration of finite numbers of splicing factors into assemblies with distinct nanoscale structures that can be modulated by MALAT1. Our findings provide a structural framework for the functional organization of splicing factors.

biophysics↗

bioRxiv2019

BR-bodies provide selectively permeable condensates that stimulate mRNA decay and prevent release of decay intermediates

Biomolecular condensates play a key role in organizing RNAs and proteins into membraneless organelles. Bacterial RNP-bodies (BR-bodies) are a biomolecular condensate containing the RNA degradosome mRNA decay machinery, but the biochemical function of such organization remains poorly defined. Here we define the RNA substrates of BR-bodies through enrichment of the bodies followed by RNA-seq. We find that long, poorly translated mRNAs, small RNAs, and antisense RNAs are the main substrates, while rRNA, tRNA, and other conserved ncRNAs are excluded from these bodies. BR-bodies stimulate the mRNA decay rate of enriched mRNAs, helping to reshape the cellular mRNA pool. We also observe that BR-body formation promotes complete mRNA decay, avoiding the build-up of toxic endo-cleaved mRNA decay intermediates. The combined selective permeability of BR-bodies for both, enzymes and substrates together with the stimulation of the sub-steps of mRNA decay provide an effective organization strategy for bacterial mRNA decay.

biochemistry↗

bioRxiv2018

A circuit of protein-protein regulatory interactions enables polarity establishment in a bacterium

Asymmetric cell division generates specialized daughter cells that play a variety of roles including tissue morphogenesis in eukaryotes and pathogenesis in bacteria. In the gram-negative bacterium Caulobacter crescentus, asymmetric localization of two biochemically distinct signaling hubs at opposite cell poles provides the foundation for asymmetric cell division. Through a set of genetic, synthetic biology and biochemical approaches we have characterized the regulatory interactions between three scaffolding proteins. These studies have revealed that the scaffold protein PodJ functions as a central mediator for organizing the new cell signaling hub, including promoting bipolarization of the central developmental scaffold protein PopZ. In addition, we identified that the old pole scaffold SpmX serves as a negative regulator of PodJ subcellular accumulation. These two scaffold-scaffold regulatory interactions serve as the core of an integrated cell polarization circuit that is layered on top of the cell-cycle circuitry to coordinate cell differentiation and asymmetric cell division.

microbiology↗

bioRxiv2018

α-proteobacterial RNA degradosomes assemble liquid-liquid phase separated RNP bodies

Ribonucleoprotein (RNP) granules play an important role in organizing eukaryotic mRNA metabolism via liquid-liquid phase separation (LLPS) of mRNA decay factors into membrane-less \"droplet\" organelles in the cytoplasm. Here we show that the bacterium Caulobacter crescentus Ribonuclease (RNase) E assembles RNP LLPS droplets that we term bacterial RNP-bodies (BR-bodies) similar to eukaryotic P-bodies and stress granules. RNase E requires RNA to assemble a BR-body, and disassembly requires RNA cleavage, suggesting BR-bodies provide localized sites of RNA degradation. The unstructured C-terminal domain of RNase E is both necessary and sufficient to assemble the core of the BR-body, is functionally conserved in related -proteobacteria, and influences mRNA degradation. BR-bodies are rapidly induced under cellular stresses and provide enhanced cell growth under stress. To our knowledge, Caulobacter RNase E is the first bacterial protein identified that forms LLPS droplets, providing an effective strategy for subcellular organization in cells lacking membrane bound compartments.

molecular biology↗