Biology subjects

Sharma, S.

Publications and source records attributed to Sharma, S..

At least 19 recordsLinked to original sources

bioRxiv2026

Discrete-time quantum walks reveal critical residues involved in long-range interactions in proteins

Abstract: Long-range interactions between residues in proteins underlie diverse biological processes such as signal transmission, conformational regulation, and catalysis. Identifying residues that mediate such communication remains a major challenge. Herein, we introduce a framework based on quantum walks and entropy, and employ it on protein structures to predict important residues participating in long-range interactions. The selected proteins have been well-studied experimentally in literature. Our approach models information flow through protein contact networks using discrete-time quantum walk dynamics, where quantum superposition and interference govern transition amplitudes at the residue level. Normalized time-averaged transition probabilities quantify interaction strength between residues, while Shannon entropy calculations identify residues exhibiting delocalized interaction behavior. We find that the residues identified by us are known to be structurally and functionally important in literature. We experimentally validate our formalism on AsLOV2 (PDB: 2V0U) using site-directed mutagenesis, protein purification, and dark-recovery kinetics. The predicted residues are important for understanding the mechanism of photosensing in AsLOV2. Significance: This study bridges quantum transport theory and structural biology by introducing discrete-time quantum walks as a mechanism to model communication between residues. We provide a scalable and interpretable method to predict key residues, without requiring molecular dynamics or prior functional annotation. The present method, inspired by quantum physics and quantum information, and validated by experiments, offers a broad and robust framework to study communication in biomolecular systems. It further demonstrates how quantum principles such as coherence and interference can enhance our understanding of information flow in biological macromolecules.

systems biology↗

bioRxiv2026

Human prion proteins and mutants through the lens of systems biology

Autocatalytic conformational changes of cellular prion proteins (PrPC) to the {beta}-sheet-enriched scrapie isoform (PrPSC) drive prion diseases, yet the precise molecular mechanisms remain unclear. To address this, we employ a multi-pronged framework integrating network-theoretic analyses, molecular dynamics (MD) simulations, and experimental validation to characterize critical residues governing human PrP (huPrP) structural integrity. Residue Interaction Networks (RINs) of: (A) wild-type (WT) huPrP, and, (B) five disease-associated point mutants (Met166Val, Glu220Lys, Glu200Lys, Asp178Asn, and Ser170Asn) were evaluated using three rigorous network methods: centrality measures, Shortest Path Alteration Fraction (SPAF), and Differential Networks (DN). Across all the diverse point mutations, five residues (Met206, Val209, Val210, Met213, and Cys214) consistently exhibit high centrality scores. SPAF and DN analyses demonstrate that alterations at these positions disrupt connectivity and increase the propensity for misfolding and protease resistance. To validate these topological findings, key residues within the C-terminal domain (121-230) were substituted via site-directed mutagenesis. Thermal denaturation monitored by circular dichroism (CD) spectroscopy reveals that the Met213Ala substitution significantly lowers the melting temperature, Tm, relative to the WT, whereas the Val210Ala variant unfolds with a Tm comparable to the WT. Furthermore, MD simulations of de novo AlphaFold-predicted mutant structures corroborate these findings. Mutants exhibit greater structural flexibility and deviation, with average root Mean Square Deviations rising from 0.18 nm (WT) to 0.32 nm (Cys214Ala), 0.29 nm (Met206Ala), and 0.25 nm (Val210Lys). This integration of theoretical and experimental techniques provides a robust framework for identifying critical determinants of protein stability.

systems biology↗

bioRxiv2026

Nanotherapy-mediated biased antigen-presenting cell reprogramming supports T cell anergy to prevent type 1 diabetes

Engineering immune tolerance using endogenously expressed autoantigens could enable early intervention in autoimmune disease. Present therapies suppress T cells to slow disease progression. Here, we develop rapamycin-loaded poly(ethylene glycol)-b-poly(propylene sulfide) polymersomes (rPS) to modulate antigen-presenting cells (APCs) during disease-associated antigen presentation. The rPS morphology enables lymphatic drainage following subcutaneous administration to access APCs in draining lymph nodes. Treatment reduced APC costimulatory marker coexpression and shifted CD4+ T cells toward an FR4hi CD73hi anergic phenotype. In a type 1 diabetes (T1D) nonobese diabetic (NOD) mouse model, rPS significantly delayed disease onset relative to the standard of care and selectively prevented hyperglycemia. Mediation via APCs, rPS avoids adverse effects including transient lymphopenia. These findings demonstrate how biomaterial-directed drug delivery can reshape APC--T cell interactions, supporting an antigen-agnostic strategy for delaying autoimmune diabetes without systemic lymphocyte depletion.

bioengineering↗

bioRxiv2026

Reliable and Efficient Agentic Protein Design with Toolset Harnessing

Computational protein design workflows require the orchestration of multiple tools, data formats, and analysis steps that are often fragmented. Here, we introduce Chaperone, a lightweight and customizable framework that enables seamless integration of RFdiffusion3 (RFD3) with downstream sequence design, structure prediction, and evaluation tools, including ProteinMPNN, AlphaFold3 (AF3), and more than 50 other protein design tools. By combining a programmable agent-friendly interface with parallelized execution on high-performance computing systems, Chaperone as a harness enables rapid iteration and scalable exploration of complex protein design workflows. Across an evaluation of nine biomolecular design tasks, we find using Chaperone reduces total token usage relative to baseline agents by 86% and GPU costs by 64%, while increasing the overall computational design pass rate. We demonstrate Chaperones utility for large-scale design-space exploration through a two-week end-to-end small-molecule binder design campaign, yielding low nanomolar binders to cortisol zero shot. We further demonstrate its versatility across distinct design challenges, including the design of a symmetric 12-subunit self-assembly nanoparticle and a linker that mediates interactions between C2- and D3-symmetric protein complexes to form crystalline assemblies. Together, these results demonstrate how agent harnesses built around standardized tool interfaces can substantially improve the efficiency and success of complex, long-horizon agentic design workflows in biology. We make Chaperone freely available to the community on GitHub: https://github.com/RosettaCommons/chaperone.

biochemistry↗

bioRxiv2026

Interdependent mode of RNA recognition by the interacting KH-domain proteins KhpA and KhpB

RNA-binding proteins (RBPs) are central regulators of gene expression. In bacteria, two KH domain-containing proteins, KhpA and KhpB, are increasingly recognized as globally-acting RBPs, including in pathogens that lack well-studied RBPs, such as Hfq and ProQ. While KhpA and KhpB interact with various RNAs in diverse bacteria, their crosstalk and molecular basis of RNA recognition remain poorly understood. Here, we explored the mutual dependence between KhpA and KhpB in the food-borne pathogen Campylobacter jejuni. We demonstrate KhpA and KhpB interact in vivo, and their individual global RNA recognition is largely dependent on the presence of the partner protein. Using RNA co-immunoprecipitation, we reveal that KhpA requires a conserved KH domain motif for RNA binding, whereas KhpB relies on an atypical R3H domain. Moreover, mutating the RNA-binding domain of one protein compromises the RNA interactome of the other. Overall, we demonstrate an interdependent RNA-binding mode of KhpA and KhpB and anticipate that such KH-proteins have co-evolved to elicit joint RNA regulation in bacteria.

microbiology↗

bioRxiv2026

BoNTax: a curated genome-based framework for taxonomic classification and characterization of Clostridium botulinum Group I and Clostridium sporogenes

Clostridium botulinum Group I and Clostridium sporogenes are closely related genomic lineages for which historical toxin-based nomenclature can obscure species-level relationships. We developed BoNTax, a curated taxonomy-first framework that separates average nucleotide identity (ANI)-based species assignment from botulinum neurotoxin (BoNT) characterization while integrating assembly quality assessment, multilocus sequence typing (MLST), AMRFinderPlus-based detection of bont genes, other virulence-associated genes, and antimicrobial resistance genes into standardized outputs. Analysis of 966 genomes informed genome-size criteria and the selection of 46 representative references comprising 22 C. botulinum Group I and 24 C. sporogenes genomes. Pairwise ANI resolved these references into two distinct species clusters: within-species ANI values were >95%, whereas between-species values were <95%, supporting a 95% species-level assignment threshold. BoNTax was implemented in GalaxyTrakr as complementary FASTQ- and FASTA-input workflows that converge on a common downstream analysis. The workflow completed analysis of all 42 validation genomes. Among the 32 genomes with a reported taxonomic identity, 29 assignments were concordant and three prompted taxonomic re-evaluations. For the ten genomes reported as taxonomically unknown, BoNTax provided ANI-based assignments. Of the three discordances, BT-22100019 was assigned to C. sporogenes rather than the reported C. botulinum Group I, whereas R1125/03 and R1135/03 showed 99.96% ANI to C. caseinilyticum DSM 46279, supporting their identification as C. caseinilyticum. MLST assignments were concordant for genomes with established profiles except PNUSAB000061, for which ST183 was not assigned by the MLST database version used in this analysis. BoNT type and subtype detection was fully concordant across toxigenic genomes, including bivalent strains. Thirty-one genomes met the predefined assembly-size QC criterion, whereas 11 received QC warnings, including all eight datasets representing four known mixed cultures. BoNTax therefore provides a reproducible genomic framework for resolving closely related clostridial lineages, identifying taxonomic annotations requiring re-evaluation, and reporting clinically relevant toxin information without conflating toxin genotype with species identity.

genomics↗

bioRxiv2026

Genetic Mapping Reveals a Major Locus for Boron Exclusion in Wild Vitis

Boron toxicity constrains grapevine (Vitis) production in irrigated arid and semi-arid regions, yet most available rootstocks are sensitive to excessive boron. Although underutilized Vitis species may harbor sources of adaptation, the genetic basis of natural variation in boron exclusion remains poorly understood, limiting the development of boron-tolerant rootstocks. We screened 267 wild Vitis accessions representing 16 species for their ability to limit leaf boron accumulation under excess boron conditions. Leaf boron concentration varied 190-fold among accessions and was highly heritable (entry-mean H^2 = 0.71). Its correlation with stomatal conductance was modest (r = 0.34), indicating that transpiration rate explained only a small proportion of the variation in leaf boron accumulation. Leaf boron was correlated with leaf chloride (r = 0.36), but their largely non-overlapping association profiles supported distinct genetic control. Genome-wide association analysis identified a suggestive association on chromosome 11. Independent quantitative trait locus mapping in a full-sib F1 population (n = 158) derived from Longii-9018 (V. acerifolia) x GRN3 (commercial rootstock) identified qBEx11.1 in the same syntenic region on chromosome 11, which explained 19.5% of the phenotypic variance. Positional candidate genes near the association peak included a pectinesterase and a MATE efflux transporter, suggesting roles for cell wall modification and membrane transport. Leaf spectral reflectance was associated with leaf boron concentration in both populations, particularly at visible and red-edge wavelengths, indicating potential for high-throughput phenotyping. Together, these findings identify qBEx11.1 as a priority locus for boron exclusion and support integrated genetic and spectral approaches for breeding boron-tolerant grapevine rootstocks.

plant biology↗

bioRxiv2026

Resource-access breadth marks protective strains against toxigenic Clostridioides difficile

Antibiotic disruption of gut microbiota creates opportunities for toxigenic Clostridioides difficile. One strategy is to occupy this niche with a non-toxigenic or weakly virulent strain, but even strains that cause little disease may fail to compete during pathogen challenge. We screened 21 sequence type 1 (ST1) isolates for their ability to protect mice co-colonized with toxigenic VPI10463, separating disease potential from protection. Some strains, such as ST1-75, caused little disease and protected, whereas others, such as ST1-68, caused little disease but failed to protect. Metabolomics showed that ST1-75 depleted more proline than ST1-68, whereas another protective strain, ST1-6, had a different metabolic profile; both protective strains nevertheless responded to many substrates. Substrate-utilization profiling revealed that protection across the 21 isolates correlated with amino-acid overlap with VPI10463, but not overall nutrient overlap or shared genome-encoded protein families. Relative amino-acid access explained variation beyond mono-colonization disease potential, and a consumer-resource model showed how nutrient overlap together with additional resource access can support persistence during competition. Additional experiments support that ST1-mediated protection occurs even in the absence of mature B and T cells. These findings distinguish low disease potential from protection, link protection to strain competition, and identify relative resource access as an informative phenotype for prioritizing strains for biotherapeutic testing.

microbiology↗

bioRxiv2026

CDX2 Drives Divergent Regional Programs During Intestinal Development and Redeploys Them During Regeneration

Region-specific transcription factors (TFs) establish small intestinal and colonic identity, yet what activates their region-specific expression during development is unresolved. Moreover, discrete fetal gene sets reactivate during post-injury regeneration, but their full scope, and what reactivates the programs required to restore regional identity and tissue structure, remain unclear. By determining CDX2 and partner TF binding, enhancer activity, and gene expression dynamics across intestinal regions, in stem and differentiating cells, and through development and adult regeneration, here we show that CDX2, despite uniform expression across the fetal and adult intestinal epithelium, organizes a hierarchical enhancer network. This network cooperates with partner factors such as CTCF to establish a shared, plastic fetal enhancer landscape, which resolves into region-specific programs upstream of regional TFs. During regeneration, rather than reactivating a general fetal state, CDX2 selectively rebinds many region-specific and common enhancers for genes associated with fetal cell-motility and tissue-morphogenesis signatures along with a more recently active adult stem-cell program, each deployed across distinct crypt tiers. CDX2 thus functions as a central, context-responsive regulator, deploying fetal, adult stem-cell differentiation, and regenerative programs as tissue context requires.

developmental biology↗

bioRxiv2026

Patient-Derived Melanoma Organoids Preserve Tumor-Immune Heterogeneity and Reveal Context-Dependent Responses to Immune Checkpoint Blockade

Abstract Background: Experimental models that retain endogenous tumor immune complexity are needed to investigate heterogeneous responses to immune checkpoint inhibitors (ICIs) in melanoma. We established patient-derived melanoma organoids (PDMOs) to examine retention of parental tumor cellular components and investigate patient-specific and context-dependent responses to checkpoint blockade. Methods: Fresh melanoma specimens (n=50), including primary tumors, neoadjuvant-treated tumors and tumor-infiltrating lymphocyte (TIL) associated samples were processed for Matrigel-embedded culture of patient-derived melanoma organoids (PDMOs). Characterization and functional studies were performed in subsets of established cultures. Immunofluorescence assessed tumor, stromal, immune, and checkpoint-marker expression in PDMOs and matched parental tissues. NGFR expression was evaluated in relation to organoid establishment and growth. Responses to anti PD1 alone or combined with anti-LAG3 or anti-CTLA4 therapies were evaluated using viability and morphological analyses, with selected models undergoing immune phenotyping and multiplex cytokine profiling. Available clinical outcomes were used for exploratory comparison. PDMOs and matched two-dimensional cultures were evaluated under 21% and 5% oxygen conditions. Results: PDMOs were established from 30 of 50 specimens (60%) and retained melanoma, stromal, lymphoid, and myeloid components identified in matched parental tissues during early culture, together with immune checkpoint expression. Higher NGFR (CD271) expression was associated with greater organoid-forming capacity in an exploratory subset. Responses to checkpoint blockade varied across patient-derived models and regimens, with combination blockade not uniformly producing lower viability than PD1 monotherapy. Ex vivo responses showed parallels with available clinical outcomes, with discordant cases also observed. In three selected PDMOs, divergent PD-1 responses were accompanied by differences in T-cell and myeloid representation, MHCII and AXL expression, and inflammatory versus immunoregulatory cytokine profiles. Under normoxic conditions, PDMOs and matched two-dimensional cultures exhibited divergent treatment sensitivities, including clinically responding cases in which sensitivity was retained in PDMOs but attenuated in monolayers. Changing oxygen tension further altered checkpoint sensitivity within individual PDMOs, with the direction and magnitude of the observed shifts varying by model and regimen. Conclusions: Early passage PDMOs retain key endogenous tumor, immune, and stromal components and support functional investigation of patient-derived melanoma biology. Their heterogenous responses across checkpoint regimens and oxygen conditions provide a platform for investigating how tumor-immune composition and environmental context influence treatment sensitivity.

immunology↗

bioRxiv2026

YAP/TAZ-controlled ERK dynamics coordinate progenitor expansion and differentiation commitment

Progenitor cells must proliferate to expand the cell population, yet terminal differentiation requires this proliferative state to end. How signaling controls the duration of this proliferative window remains poorly understood. Using adipogenesis and live single-cell imaging of differentiation, cell-cycle, and ERK-activity reporters, we show that YAP and TAZ coordinate progenitor expansion with differentiation commitment by regulating ERK dynamics. YAP/TAZ maintain cells in a fluctuating high-ERK state that promotes proliferation while actively keeping the differentiation driver PPARG below the threshold for irreversible commitment. Crucially, this differentiation block is not explained by proliferation alone: inhibiting CDK4/6 or AKT suppressed proliferation without restoring differentiation, whereas MEK-ERK inhibition restored differentiation even when YAP/TAZ activity remained high. As YAP/TAZ activity decreases, dampened ERK fluctuations trigger PPARG activation. These findings support a self-limiting model in which YAP/TAZ-driven progenitor expansion progressively increases cell density and contact-dependent Hippo signaling, reducing YAP/TAZ activity and terminating the proliferative phase. Consequently, transient YAP/TAZ activation expands the progenitor pool while preserving subsequent differentiation, whereas sustained activation suppresses commitment. Together, these findings identify YAP/TAZ-controlled ERK dynamics as the nexus coordinating progenitor expansion with terminal differentiation and suggest that slower density-dependent Hippo feedback may set the duration of this proliferative window to regulate differentiated cell-number output.

cell biology↗

bioRxiv2026

Angiogenin activity regulates RNA remodeling during the maternal-to-zygotic transition in early mouse embryogenesis

Angiogenin (ANG), a member of the RNase A superfamily, regulates multiple aspects of RNA metabolism, including rRNA processing and the generation of tRNA-derived small RNAs. However, its function during early mammalian embryogenesis remains unknown. Here, we identify a previously unrecognized requirement for ANG activity during early mouse embryonic development. Pharmacological inhibition of ANG during the first embryonic cell cycle did not prevent progression to the 2-cell stage but markedly impaired subsequent development to the 4-cell stage, indicating a critical requirement for ANG activity during the maternal-to-zygotic transition. Transcriptome-wide analysis revealed that ANG inhibition disrupted the normal remodeling of the embryonic transcriptome, characterized by persistent accumulation of a subset of transcripts that are normally reduced during the 2-cell transition, including many maternally deposited RNAs, together with altered expression of transcripts associated with zygotic genome activation. Small-RNA profiling further revealed widespread alterations in miRNA and tRNA-derived small-RNA populations. Notably, a large proportion of transcripts retained following ANG inhibition contained predicted target sites for miRNAs that were concomitantly reduced, suggesting a potential link between ANG-dependent small-RNA regulation and maternal transcript clearance. ANG inhibition was also associated with altered abundance and organization of components of RNA regulatory granules, including Tudor, TIAR, Dcp1a and Ago2, and increased association of selected retained transcripts Reep4 and Esrrb with Tudor-positive structures. Together, these findings identify ANG activity as an important regulator of RNA remodeling during the maternal-to-zygotic transition and suggest that ANG coordinates maternal transcript clearance, small-RNA dynamics and mRNP organization to support early mouse embryonic development.

developmental biology↗

bioRxiv2026

Multi-omics Reveals Divergent Endothelial Molecular Responses to New and Old World Hantaviruses

Hantaviruses cause vascular leakage syndromes that vary in clinical manifestation and severity. Although tissue tropism contributes to these differences, both Old and New World hantaviruses infect endothelial cells, where species-specific disease phenotypes remain poorly understood. Here we integrated time-resolved global RNA sequencing, mass spectrometry proteomics, and phosphoproteomics of human endothelial cells infected with New World Andes virus (ANDV) or Old World Hantaan virus (HTNV). Despite equivalent early viral RNA and protein levels, ANDV elicited a stronger innate immune protein response, preceding its restriction while HTNV replication continued. At later stages of infection, HTNV induced downregulation of cytoskeletal and junctional protein phosphorylation, accompanied by visual disruption of cellular actin architecture. Additionally, ANDV induced heightened activity of ERBB-family kinases, whose chemical inhibition by neratinib and afatinib reduced viral replication. Together, these data define species-specific responses in endothelial cells, identify druggable host targets, and reveal mechanisms with relevance to divergent vascular leakage symptomology.

systems biology↗

bioRxiv2026

Low-cost rhizotron imaging and zero-shot deep-learning resolve temporal, spatial, and genetic variation in grapevine rootstock root systems

Root system architecture shapes how grapevine rootstocks take up water and nutrients, yet roots remain the least phenotyped grapevine organ because they are hidden and hard to image. We present a low-cost phenotyping pipeline that pairs custom acrylic rhizotrons (about US$30 each) with a consumer flatbed scanner and BiRefNet, a general-purpose deep-learning model used without training on root images, followed by automated mask cleaning, skeleton-based trait extraction, and soil moisture mapping. We tested it on nine commercial rootstocks scanned 16 times over 42 days after transplanting (DAT), with half under a ten-day water deficit. From 1,108 images we extracted 21 whole-root, depth-resolved, and topological traits. Genotypes differed in nearly every trait and in how they changed over time. Heritability of size and branching traits peaked at 0.92-0.93 between 21 and 31 DAT and fell for width, depth, and convex hull once roots reached the rhizotron walls, defining the best measurement window. The image-derived soil moisture map accurately tracked the deficit and its recovery. Deficit plants shifted new root growth to deeper soil without growing less overall, and the substrate dried fastest around older and denser roots. Root brightness decreased with root age and local moisture, and transport segments (axes serving several tips) were brighter than terminal laterals in every genotype. Root system size was associated with stomatal conductance in well-watered plants, and stomatal recovery after re-watering correlated with new root growth. The pipeline turns simple hardware into a quantitative, time-resolved root phenotyping platform suitable for breeding.

plant biology↗

bioRxiv2026

Aryl Hydrocarbon Receptor (Ahr) Pathway Drives TBBPA Induced Cartilage Development Defects.

Tetrabromobisphenol A (TBBPA), is one the most widely produced brominated flame retardant, detected in human matrices including cord plasma, raising concern over its impact on embryonic development. Our previous work demonstrated that TBBPA disrupts craniofacial cartilage development in zebrafish; however, inhibition of bone morphogenetic protein (BMP) signaling did not rescue these defects, suggesting the involvement of alternative molecular mechanisms. Transcriptomic profiling revealed significant upregulation of aryl hydrocarbon receptor (Ahr) signaling genes, including cyp1a and cyp1c, as well as reactive oxygen species (ROS) responsive genes, such as nfe and gstp. Consistent with these findings, KEGG pathway enrichment analysis identified significant enrichment of pathways involved in xenobiotic metabolism, cytochrome P450-mediated metabolism, and molecular docking predicted stronger binding of TBBPA to Ahr2 than the Ahr2 agonist TCDD. Then we investigated the role of Ahr signaling and ROS in TBBPA-induced craniofacial cartilage defects using microinjection of Ahr2 translation-blocking morpholino and the antioxidant N-acetylcysteine (NAC), respectively. Immunohistochemistry confirmed concentration-dependent induction of Cyp1a and ROS at environmentally relevant concentrations (0.05;0.005 uM). Ahr2 knockdown using a translation-blocking morpholino rescued TBBPA-induced alterations in Cyp1a expression, ROS levels, DNA damage, the expression of chondrogenesis-related markers (Sox10 and Sox2), and epithelial to mesenchymal transition (EMT) markers (E-cadherin, N-cadherin, and Snail2). Furthermore, Ahr2 knockdown rescued several TBBPA-induced alterations in craniofacial cartilage parameters. Co-exposure of TBBPA with the antioxidant NAC rescued the ROS and DNA damage and rescued only ceratohyal cartilage length, whereas other cartilage parameters remained disrupted. These findings establish a causal role for the Ahr-Cyp1a axis in TBBPA-induced craniofacial cartilage developmental toxicity and identify ROS as an important downstream contributor, indicating that both ROS-dependent and ROS-independent Ahr mechanisms underlined the observed TBBPA induced craniofacial defects.

pharmacology and toxicology↗

bioRxiv2026

Structure of the human mitochondrial RNA degradosomereveals a distinct mode of helicase-nuclease coupling

RNA degradation shapes cellular and organellar gene expression. In human mitochondria, this process is mediated by a dedicated degradosome comprising the helicase SUV3 and the exoribonuclease PNPase, but how these enzymes assemble and cooperate to degrade structured RNA has remained unknown. Here, we report the cryo-EM structure of the complete human mitochondrial RNA degradosome bound to RNA. The structure reveals an asymmetric heteropentamer composed of a SUV3 dimer and the trimeric PNPase. Degradosome assembly is accompanied by conformational rearrangements in PNPase that reshape the RNA-entry channel and generate an asymmetric S1-domain platform for SUV3 binding. This creates a continuous electropositive path from SUV3 to PNPase, suggesting how RNA may be guided during degradation. Together, these findings reveal a mode of helicase-nuclease coupling distinct from other RNA degradation machineries and provide a structural framework for understanding human mitochondrial RNA degradation, its regulation, and association with disease.

biochemistry↗

bioRxiv2026

Benchmarking long-read RNA sequencing for de novo transcriptome assembly in non-model plant species: insights from Moricandia arvensis

De novo transcriptome assembly is the standard approach for constructing a reference transcriptome in non-model plants that lack a high-quality genome, yet short-read assemblies struggle to resolve full-length isoforms. Long-read Iso-Seq (PacBio) captures full-length transcripts directly, but its use as a primary reference and the choice of downstream assembly pipeline remains poorly benchmarked. Here, we construct genome-free Iso-Seq reference transcriptomes for two organs, flower and leaf, of the non-model species Moricandia arvensis (L.) DC. (Brassicaceae), and systematically compare pipeline strategies combining Iso-Seq clustering, CD-HIT redundancy reduction, and Cogent graph-based reconstruction, benchmarked by BUSCO completeness, RSEM short-read mapping, and TransDecoder ORF completeness. We find that the optimal pipeline is organ specific. For flower, CD-HIT pre-filtering followed by Cogent reconstruction produced a high-quality reference (95.3% BUSCO complete). For the leaf, the same Cogent step was detrimental, reducing BUSCO completeness from 90.1% to 78.0% by incorrectly merging distinct genes; therefore, CD-HIT at 95% identity without reconstruction was retained. We trace this divergence to organ-specific input-data characteristics: leaf transcripts show extreme full-length-read expression skew and predominantly single-isoform gene support, depriving Cogent's graph algorithm of the multi-isoform evidence it requires. We find that the concentration of full-length reads among the most highly expressed transcripts predicts pipeline suitability before reconstruction, with per-transcript read depth acting as a necessary but non-discriminating floor. Because the leaf reference lacked gene-level structure, we further recovered gene-isoform grouping using expression-aware read-clustering (Corset), which preserved completeness while restoring the paralog structure expected of a paleopolyploid genome and outperformed sequence-only clustering. Our results provide a robust, genome-free framework for constructing full-length reference transcriptomes in non-model plant species and demonstrate that pipeline choice must be evaluated per organ rather than assuming one size fits all.

bioinformatics↗

bioRxiv2026

A Compendium of 49 Experimental SBS Signatures for Decoding Human Cancer Mutational Processes

Human cancer genomes harbor distinct mutational patterns that reflect past processes of DNA damage and repair. However, the precise attribution of these signatures to specific chemical carcinogens lacks a standardized experimental reference framework. To address this gap, we curated 4,282 genome-wide sequencing datasets from 42 model systems across five species exposed to 146 cancer-risk agents. This platform yielded 49 robust experimental single-base substitution signatures (eSS), with 28 matching 19 established COSMIC signatures and 21 defining novel mutational processes. We reconstructed 24 COSMIC signatures, assigning candidate etiologies to five signatures of unknown origin and revising two contested assignments. Pan-cancer decomposition detected four eSS-like mutational processes enriched in smokers across 4,951 tumors. Lastly, independent single-molecule sequencing of primary human organoids reproduced these profiles with high fidelity, confirming true platform-independent biological reproducibility across complex human models. This eSS repertoire provides a reference that links human mutational processes to mechanistic classes of DNA damage.

genomics↗