Biology subjects

Jiang, V.

Publications and source records attributed to Jiang, V..

9 recordsLinked to original sources

bioRxiv2026

Enhanced GPP synthesis by Erg20p-peptide fusions and biomolecular condensates boosts monoterpene production in yeast

Monoterpenes are a diverse class of natural products with broad industrial and pharmaceutical applications. While there is great interest in transitioning their production from chemical synthesis and natural source extraction to yeast bioprocesses, this approach remains limited by the dual functionality of the endogenous farnesyl diphosphate synthase Erg20p, which produces the monoterpene precursor geranyl diphosphate (GPP) but favors its subsequent conversion to farnesyl diphosphate (FPP). To address this limitation, we recruited Erg20p and monoterpene synthases into synthetic membraneless organelles, improving production. In doing so, we found that short C-terminal peptide fusions used for recruitment also significantly enhance GPP synthase activity relative to FPP synthase activity. The combined effects of metabolic spatial organization and GPP synthase activity enhancement significantly boost production of different monoterpenes, including geraniol titers exceeding 4 g/L. The strategies presented here can be readily integrated with other traditional metabolic engineering approaches to build yeast strains with high levels of monoterpene production.

bioengineering↗

bioRxiv2026

Spatial organization of enzymes and cofactors in synthetic membrane-associated condensates (sMACs)

Cells spatially organize metabolic enzymes to optimize flux through complex biochemical networks. Here, we engineered synthetic Membrane-Associated Condensates (sMACs), artificial assemblies that form on intracellular membranes through liquid-liquid phase separation, to couple metabolic compartmentalization with cofactor partitioning. Using intrinsically disordered regions (IDRs) characterized by simulations and validated by experiments, we identified an IDR sequence, Dbp1n, that selectively enrich NADH and NADPH, establishing distinct local redox microenvironments. At the endoplasmic reticulum (ER) membrane, NADPH-enriched sMACs enhanced cytochrome P450 activity by improving electron transfer and supporting in situ regeneration. At the plasma membrane, NADH-enriched sMACs provided scaffolds for a xylose uptake and assimilation pathway that exploits localized NADH/NAD recycling to improve flux. These results collectively demonstrated that condensate composition and membrane context can be engineered to enhance metabolic functions. sMACs thus provide a modular framework for creating programmable, membrane-associated microreactors, enabling new strategies for metabolic engineering and offering insights into how phase separation can be exploited in living cells.

synthetic biology↗

bioRxiv2025

Structural insights into xyloglucan recognition by an ABC transporter from a Gram-positive, thermophilic bacterium

Xyloglucan (an -1,6-xylosyl-substituted {beta}-1,4-glucan) is a major hemicellulose of the primary cell wall of many plants and an important growth substrate for biomass-degrading bacteria in diverse ecological niches, including the gut microbiome and hot springs. In Gram-positive bacteria, xyloglucan is deconstructed into soluble oligosaccharides in the extracytoplasmic space before import by ATP-Binding Cassette (ABC) transporters, but the structural basis for this process remains poorly understood. Here, we identified an ABC transporter for xyloglucan uptake (Athe_2052-2054) in the Gram-positive, plant biomass-degrading thermophile Anaerocellum bescii, which is conserved across the Anaerocellum genus. We solved the apo crystal structure of its extracellular substrate-binding protein (SBP), Athe_2052, revealing a unique tertiary fold found only in a small subset of SBPs that bind complex oligosaccharides. This structure represents the first ABC SBP known to bind xyloglucan oligosaccharides. Biophysical analysis showed that while Athe_2052 binds unsubstituted {beta}-glucan chains, recognition of xyloglucan side chains in the binding pocket markedly increases affinity (Kd = 14 nM) for xyloglucan heptasaccharide (XXXG), the principal oligosaccharide released during xyloglucan deconstruction. Molecular modeling revealed that xyloglucan heptasaccharide, owing to its branched substitutions, is bound in a distinct conformation compared to unsubstituted {beta}-glucans. This represents a unique mode of xyloglucan recognition driven by -linked side-chain interactions rather than {beta}-glucan backbone recognition alone. Together, these findings provide the first structural basis for xyloglucan oligosaccharide recognition by an ABC transporter in Gram-positive bacteria.

molecular biology↗

bioRxiv2025

STcompare: comparative spatial transcriptomics data analysis of structurally matched tissues to characterize differentially spatially patterned genes

MotivationComparative analysis of spatial transcriptomics (ST) data is needed to identify genes that spatially change in their expression patterns between conditions, such as in diseased versus healthy tissues. Existing methods generally fail to distinguish changes in spatial patterning by focusing only on changes in gene expression magnitude for methods adapted from non-spatial data or on changes in significance of spatial variability for methods focusing on spatially-resolved data. ResultsTo address these limitations, we develop STcompare, a statistical framework for comparative analysis of ST data by testing for differences in spatial correlation and spatial fold-change across structurally matched locations. Using simulated data, we demonstrate how STcompare provides distinct insights from bulk differential gene expression analysis and spatially variable gene expression analysis as well as other spatial comparison methods. STcompare further robustly controls for false positives even in the presence of spatial autocorrelation common in ST data. We apply STcompare to real ST data of biological replicates of mouse brains to confirm high spatial correspondence of gene expression patterns across samples. We apply STcompare to identify genes that spatially change in mouse kidneys with acute kidney injury compared to a healthy control, revealing tissue compartment-specific molecular dysregulation. Overall, the application of this spatially-aware comparative analysis will enable the discovery of differential spatially patterned genes across various physiological and technological axes of interest. Availability and ImplementationSTcompare is implemented as an open-source R package at https://github.com/JEFworks-Lab/STcompare with additional documentation and tutorials available at https://jef.works/STcompare/.

bioinformatics↗

bioRxiv2025

An RNA-mediated DNA melting mechanism for CRISPR-Cas9

CRISPR-Cas9 systems, adaptive defense mechanisms in bacteria and archaea, have been widely adopted as powerful gene editing tools, revolutionizing biological and medical research. In the first steps of CRISPR-Cas9 gene editing, the Cas9 protein, in complex with RNA, facilitates DNA melting and subsequent RNA-DNA hybrid formation, but the atomic-level mechanism of this fundamental process is not fully understood. Here, we present the results of long-timescale molecular dynamics simulations in which Cas9-RNA complexes bound to double-helical DNA and promoted the formation of RNA-DNA base pairs in a unidirectional, stepwise manner. Unexpectedly, we observed a direct role for the RNA in facilitating DNA melting events through a mechanism in which RNA bases intercalated within the DNA and promoted strand separation. In addition, breathing motions within the Cas9 DNA-binding cleft contributed to the sequential formation of RNA-DNA base pairs. These simulation results, obtained for two structurally distinct Cas9 proteins, together with supporting experimental work, suggest a novel RNA-dependent mechanism for DNA melting that may be conserved in other Cas proteins.

biophysics↗

bioRxiv2025

A Highly Conserved ABC Transporter Mediates Cello-Oligosaccharide Uptake in the Extremely Thermophilic, Lignocellulolytic Bacterium Anaerocellum (f. Caldicellulosiruptor) bescii

Cellulose deconstruction and utilization are key to unlocking renewable fuel and chemical production. Anaerocellum bescii (formerly Caldicellulosiruptor bescii) is an extremely thermophilic cellulolytic bacterium, among the most effective at degrading lignocellulosic biomass due to its arsenal of multi-domain cellulases and hemicellulases. However, little is known about how it transports the assorted sugars released from lignocellulose degradation into the cell for catabolism. Among its twenty-three ATP-Binding Cassette (ABC) sugar transporters, the mechanism for uptake of cello-oligosaccharides released from cellulose degradation remains unclear. Here, we identify an ABC transporter locus (Athe_0595 -- 0598), highly conserved in the genus with two extracellular binding proteins, Athe_0597 and Athe_0598. Biophysical analyses, including Differential Scanning Calorimetry (DSC) and Isothermal Titration Calorimetry (ITC), reveal that Athe_0597, binds cello-oligosaccharides of varying lengths (G2-5), while Athe_0598 is specific to cellobiose (G2). Computational modeling of ligand docking supports these findings and sheds light on the subsite configuration of the substrate binding proteins. To assess its physiological importance, we genetically deleted this transporter locus in A. bescii strain HTAB187, which does not grow on cellulose and grows poorly on cellobiose. Comparison of growth with a msmK deletion strain that cannot consume oligosaccharides shows that HTAB187 can grow on non-cello-oligosaccharides (e.g. maltose) or monosaccharides. Taken together, this study integrates biophysical characterization, structural modeling, and genetic perturbation to elucidate how A. bescii transports cello-oligosaccharides release from cellulose, opening doors for its future use in applied bioprocessing contexts. ImportanceAnaerocellum bescii is the most thermophilic cellulolytic bacterium known, and holds potential for bioprocessing lignocellulosic biomass into renewable fuels. Its diverse ATP-Binding Cassette (ABC) sugar transporters make it a valuable model for studying thermophilic sugar uptake. Here, we identify a single ABC transporter with two substrate binding proteins (Athe_0597 and Athe_0598) responsible for cello-oligosaccharide uptake. Genetic deletion of this transporter impaired growth on cellobiose and eliminated growth on cellulose. This is the first genetic manipulation in A. bescii to modulate transport of a specific sugar. We also characterize the substrate specificity of the substrate binding proteins associated with the locus; one binds various cellodextrins (G2-5), while the other specifically binds cellobiose (G2). Computational modeling reveals how each sugar docks within the binding pocket of these proteins. Understanding the mechanism of cello-oligosaccharide uptake by A. bescii expands opportunities for its metabolic engineering and furthers our understanding of thermophilic sugar transport.

microbiology↗

bioRxiv2025

YX0798 Is a Highly Potent, Selective, and Orally Effective CDK9 Inhibitor for Treating Aggressive Lymphoma

Non-genetic transcription evolution has been increasingly explored and recognized to drive tumor cell progression and therapeutic resistance. As the regulation hub of transcription machinery, cyclin-dependent kinase 9 (CDK9) is the gatekeeper of RNA polymerase II (Pol II) transcription, and CDK9 dysfunction results in transcriptomic reprogramming and tumor cell progression. We recently reported that the HSP90-MYC-CDK9 network drives therapeutic resistance in mantle cell lymphoma (MCL) through transcriptomic reprogramming. We also showed that targeting CDK9 by AZD4573 and enitociclib is a safe and effective treatment in preclinical MCL models, supporting CDK9 as a valid therapeutic target for MCL. However, current CDK9 inhibitors (CDK9i) under therapeutic development have room for improvement due to limited target selectivity and oral bioavailability. To this end, YX0798 was discovered to be a novel CDK9i through structural optimization. YX0798 demonstrated remarkable target selectivity and high affinity in binding to CDK9. Furthermore, YX0798 showed good oral bioavailability. YX0798, when administrated orally (5 mg/kg, daily), led to an efficacious anti-tumor activity in vivo and showed the potency in overcoming therapeutic resistance. Mechanistically, YX0798 downregulated the short-lived oncoprotein c-MYC and pro-survival protein MCL-1 as a common mechanism of CDK9 inhibition. Moreover, YX0798 disrupted the cell cycle and resulted in transcriptomic reprogramming, eventually leading to cell death. Together, these data demonstrate that YX0798 has oral bioavailability, exquisite selectivity, and anti-tumor potency that results from driving transcription reprogramming towards tumor cell killing. KEY POINTSO_LIYX0798 showed high selectivity, target binding affinity, and anti-tumor efficacy in overcoming resistance to various therapies. C_LIO_LIYX0798 had good oral pharmacokinetics and anti-tumor effects that resulted from transcription reprogramming towards tumor cell killing. C_LI

cancer biology↗

bioRxiv2024

Maltodextrin Transport in the Extremely Thermophilic, Lignocellulose Degrading Bacterium Anaerocellum bescii (f. Caldicellulosiruptor bescii)

Sugar transport into microbial cells is a critical, yet understudied step in the conversion of lignocellulosic biomass to metabolic products. Anaerocellum bescii (formerly Caldicellulosiruptor bescii) is an extremely thermophilic, anaerobic bacterium that readily degrades the cellulose and hemicellulose components of lignocellulosic biomass into a diversity of oligosaccharide substrates. Despite significant understanding of how this microorganism degrades lignocellulose, the mechanisms underlying its highly efficient transport of the resulting oligosaccharides into the cell are comparatively underexplored. Here, we identify and characterize the ATP-Binding Cassette (ABC) transporters in A. bescii governing maltodextrin transport. Utilizing past transcriptomic studies on Anaerocellum and Caldicellulosiruptor species, we identify two maltodextrin transporters in A. bescii and express and purify their substrate-binding proteins (Athe_2310 and Athe_2574) for characterization. Using differential scanning calorimetry and isothermal titration calorimetry, we show that Athe_2310 strongly interacts with shorter maltodextrins such as maltose and trehalose with dissociation constants in the micromolar range, while Athe_2574 binds longer maltodextrins, with dissociation constants in the sub-micro molar range. Using a sequence-structure-function comparison approach combined with molecular modeling we provide context for the specificity of each of these substrate-binding proteins. We propose that A. bescii utilizes orthogonal ABC transporters to uptake malto-oligosaccharides of different lengths to maximize transport efficiency. ImportanceHere, we reveal the biophysical and structural basis for oligosaccharide transport by two maltodextrin ABC transporters in A. bescii. This is the first biophysical characterization of carbohydrate uptake in this organism and establishes a workflow for characterizing other oligosaccharide transporters in A. bescii and similar lignocellulosic thermophiles of interest for lignocellulosic bioprocessing. By deciphering the mechanisms underlying high affinity sugar uptake in A. bescii, we shed light on an underexplored step between extracellular lignocellulose degradation and intracellular conversion of sugars to metabolic products. This understanding will expand opportunities for harnessing sugar transport in thermophiles to reshape lignocellulose bioprocessing as part of a renewable bioeconomy.

biophysics↗

bioRxiv2021

Computational Structure Prediction Provides a Plausible Mechanism for Electron Transfer by the Outer Membrane Protein Cyc2 from Acidithiobacillus ferrooxidans

Cyc2 is the key protein in the outer membrane of Acidithiobacillus ferrooxidans that mediates electron transfer between extracellular inorganic iron and the intracellular central metabolism. This cytochrome c is specific for iron and interacts with periplasmic proteins to complete a reversible electron transport chain. A structure of Cyc2 has not yet been characterized experimentally. Here we describe a structural model of Cyc2, and associated proteins, to highlight a plausible mechanism for the ferrous iron electron transfer chain. A comparative modeling protocol specific for trans membrane beta barrel (TMBB) proteins in acidophilic conditions (pH ~2) was applied to the primary sequence of Cyc2. The proposed structure has three main regimes: extracellular loops exposed to low-pH conditions, a TMBB, and a N-terminal cytochrome-like region within the periplasmic space. The Cyc2 model was further refined by identifying likely iron and heme docking sites. This represents the first computational model of Cyc2 that accounts for the membrane microenvironment and the acidity in the extracellular matrix. This approach can be used to model other TMBBs which can be critical for chemolithotrophic microbial growth. Importance of workAcidithiobacillus ferrooxidans can oxidize both iron and reduced sulfur compounds and plays a key role in metal sulfide ore bioleaching used for the industrial recovery of metals. A. ferrooxidans has also been explored as a potential organism for emerging technologies such as e-waste recycling and biofuel production. Synthetic biology efforts are hampered by lack of knowledge about the mechanisms of iron oxidation and reduction, which is mediated by the Cyc2 transmembrane beta barrel (TMBB) protein.

bioinformatics↗