Biology subjects

Nayak, A.

Publications and source records attributed to Nayak, A..

At least 19 recordsLinked to original sources

bioRxiv2026

Reverse engineering Lewy bodies suggests alpha-synuclein pathology as condensatopathy

Understanding how soluble monomeric alpha-synuclein transitions into pathological alpha-synuclein (Lewy bodies) has remained a central challenge in neurodegeneration. Existing models, largely based on treating cells and animals with pre-formed alpha-synuclein fibrils cannot account for the emergence of the first inclusion without pre-existing seeds. Here, we combine in vitro reconstitutions, computational modeling and a minimal cellular system to show that phase separation of alpha-synuclein with an interacting scaffold can recapitulate Lewy body-like structures. An unbiased proteomics screen, live-cell imaging, correlative light-electron microscopy, and soft X-ray tomography show that Lewy body-like structures are associated with redistribution of actin and membrane-bound organelles, with mitochondria accumulating at their periphery in an actin-dependent manner. Structural analyses further indicate that alpha-synuclein condensates provide local environments in which the insoluble beta-sheets can form. Together, these findings support a seed-independent trajectory from soluble alpha-synuclein through condensation and progressive immobilization to Lewy body-like assemblies and, subsequently, insoluble beta-sheet fibrils. This framework offers a new mechanistic route for understanding the disease progression and promises to guide the design of innovative therapeutic interventions.

neuroscience↗

bioRxiv2026

Myotropes unveil two myosin cycles with distinct kinetics and stroke size

Cardiac contraction relies on cyclic interactions between myosin II motors and actin filaments, powered by the free energy of ATP turnover. Targeting of this fundamental process has emerged as a promising therapeutic strategy; Mavacamten, a cardiac myosin inhibitor was recently approved for treating obstructive hypertrophic cardiomyopathy whereas omecamtiv mecarbil was developed as a myosin activator for heart failure. Both myotropes bind to the same myosin pocket but their mechanisms of action remain incompletely understood. Here, we investigate these using optical tweezers mechanoenzymology and single-molecule fluorescence-based actomyosin kinetics applied to {beta}-myosin from donor hearts and recombinant human {beta}-myosin subfragment 1. Our findings reveal unexpected layers of complexity. Both mavacamten and omecamtiv mecarbil partially slow the ATP turnover, giving one fast (similar to physiological) and one drug-induced slow ATP turnover cycle at saturating drug concentrations with different rate-limiting steps for the two compounds. In one of the parallel cycles, mavacamten increases stroke size and appreciably delays the power-stroke, allowing direct visualization of a strongly bound pre-power-stroke state. No power-stroke delay is seen in the other cycle, but a reduced stroke size is observed. Our findings uncover a new paradigm in cardiac regulation at the single-molecule level, demonstrating partial inhibition of myosin as a powerful therapeutic strategy.

biophysics↗

bioRxiv2026

Conformation of the Catalytic Lysine is a Key Determinant of 2-Deoxyribose-5-phosphate Aldolase (DERA) Stereoselectivity

2-Deoxyribose-5-Phosphate Aldolase (DERA) is a key enzyme in the pentose phosphate pathway. Due to its C-C bond formation and stereoselective capabilities, DERA has been widely used for biocatalytic applications including the synthesis of chiral intermediates for antiviral and anticancer drugs. While protein engineering has expanded its substrate pool, improved yield, and enhanced stereoselectivity, the molecular basis of stereoselectivity remains unclear. Here, we determined the crystal structures of wildtype DERA from Geobacillus sp. and two of its variants with opposite stereoselectivity. Using a combination of structural biology, biochemistry, organic synthesis and molecular dynamic simulations, we show that the catalytic Lysine adopts two conformations and the Lysine conformation is a key determinant of DERA stereoselectivity. We also identified a mechanism of regulating stereoselectivity via a key amino acid. Using DERA from E. coli, we show that these findings are most likely conserved among bacteria.

biochemistry↗

bioRxiv2026

Insulin-degrading enzyme activity is modulated by interaction with pyrroline-5-carboxylate reductase 1

Insulin-degrading enzyme (IDE, insulysin, insulinase) is a peptidase that hydrolyzes a number of bioactive peptides including insulin and the amyloid beta peptide, making it a promising therapeutic target for diabetes and Alzheimers disease. Aspects of its physiological role are still controversial, however. In an attempt to further define IDEs role in cells, we used co-immunoprecipitation experiments to identify potential IDE interacting proteins. The enzyme pyrroline-5-carboxylate reductase 1 (PYCR1) was found associated with IDE in three different cell lines, and the two proteins colocalize in HeLa cells. Purified PYCR1 activates IDE toward small peptide substrates, suggesting a modulatory role for the interaction in vivo. Modeling suggests that the unstructured N-terminal region of PYCR1 inserts into allosteric sites of IDE, contributing to the observed activation. Deleting this sequence alters, but does eliminate, the interaction between PYCR1 and IDE. Since pyrroline-5-carboxylate reductase 1 is a mitochondrial protein, we posit that their interaction could regulate a previously described mitochondrial pool of IDE, which may serve to degrade mitochondrial targeting sequences or amyloid beta peptide that localizes to that organelle.

biochemistry↗

bioRxiv2026

The Viability Gambit: An Optimized Sterilisation Protocol for Industrial Hemp ( Cannabis sativa L.) Seeds

Hemp (Cannabis sativa L.) is an increasingly important crop with applications spanning fibre, seed oil and bioactive cannabinoid production, yet the development of reliable tissue culture systems for this species remains a significant challenge. The establishment of axenic seedling cultures is a prerequisite for hypocotyl-based regeneration and future genetic transformation pipelines, but hemp seeds harbour diverse endophytic microbial communities that frequently overwhelm standard surface sterilisation protocols. Here, we present a systematic comparative evaluation of seed sterilisation strategies across seven industrial hemp accessions, examining the effects of sterilisation chemistry, seed provenance and accession identity on both contamination outcome and the subsequent morphogenic competence of hypocotyl explants. Across all treatments and accessions, in-house glasshouse-harvested seeds achieved higher sterility rates than commercially sourced material regardless of protocol applied. This provenance effect, combined with considerable batch-to-batch variation within seed sources, indicates that contamination load is a primary determinant of successful hemp seed sterilisation. Among the sterilisation treatments evaluated, a baseline of 75% ethanol combined with sequential 1% hydrogen peroxide incubation performed consistently well for low-load seed batches, while supplementation with Plant Preservative Mixture (PPMTM) might be necessary to achieve acceptable rates of non-contaminated seedlings from high contamination load batches. Beyond their effect on contamination, sterilisation treatments influenced the morphogenic fate of hypocotyl explants independently of sterility outcomes. Notably, seedling treatment with the Prochloraz-based fungicide Octave promoted shoot and root co-regeneration in the absence of exogenous plant growth regulators in some cases. Hormone-free organogenesis from hypocotyl explants was achievable across multiple hemp accessions, demonstrating that this developmental capacity is broadly distributed within hemp, though its frequency and consistency varied with accession identity and protocol conditions. Together, these findings provide a practical framework for axenic hemp seed culture that can be used as starting point requiring local adaptation based on seed source, batch history and the intended downstream application.

Plant Biology↗

bioRxiv2026

Collective behavior drives diversification across the tree of ray-finned fishes

Trait evolution and lineage diversification are thought to be driven by selection on the phenotypes of individuals. However, many important phenotypes are only manifested when individuals interact. Collective behavior is one such phenotype. During collective behavior, interactions among individuals lead to emergent group-level phenotypes that can govern individual fitness. Yet, whether collective behaviors exhibit similar patterns of trait evolution to individual traits and whether these group phenotypes have influenced macroevolutionary diversification is unknown. In ray-finned fishes, the most species-rich of all vertebrate classes, many species exhibit striking displays of collective behavior in the form of collective movement. Here, we use state-of-the-art machine learning methods for text and image analysis to quantify collective movement phenotypes for 2,839 Actinopterygian fishes, comprising nearly 10% of all extant species. We find that collective movement is highly evolutionarily stable in some clades and extremely labile in others, exhibiting over 300 evolutionary transitions. Consistent with theoretical predictions, collective movement is associated with more patchy diets and higher predation pressure. Finally, we find that the evolution of collective movement coincides with an increase in net macroevolutionary diversification rate. Our analyses reveal that collective behavior is deeply intertwined with ecological and evolutionary dynamics across a vast phylogenetic scale, unlocking new questions about the role of collective phenotypes in shaping the diversity of life on Earth. SignificanceCollective behavior is thought to contribute to the fitness of individuals that live in groups, but we still do not understand why some species exhibit collective behavior and others do not. We developed machine learning methods to quantify collective phenotypes for thousands of species spanning the phylogeny of ray-finned fishes and found collective behavior to be widespread and consistently correlated with experiencing higher predation pressure and foraging for grouping prey. Lineages that evolve collective movement show a higher net diversification rate. Our results illustrate that collective behavior is foundational to the broad-scale patterns of evolution and diversification in the largest vertebrate class.

evolutionary biology↗

bioRxiv2026

Single-molecule analysis sheds light on cardiac myosin dysfunction due to hypertrophic cardiomyopathy mutation A57D in ventricular myosin light chain-1 (MLC1v)

Ventricular myosin light chain-1 (MLC1v) is a key structural and function-modulating component of the {beta}-cardiac myosin ({beta}M-II) motor complex. Single-point mutations in MLC1v are linked to severe forms of hypertrophic cardiomyopathy (HCM) and sudden cardiac death (SCD) at a young age. However, the molecular mechanisms underlying the motor dysfunction responsible for HCM phenotype development are not fully understood. Here, we investigated native {beta}M-II motors isolated from septal myectomy sample of an HCM patient, harboring a rare homozygous mutation in MLC1v (A57D). Using a pure population of mutant motors (MUT), and sensitive single-molecule functional analysis approach, we directly assessed the primary functional alterations in {beta}M-II bearing A57D MLC1v mutation. In optical trap single-molecules measurements, the mutant motors displayed increased actomyosin (AM) interaction duration in strongly bound state (ton), corresponding to 3-fold reduced AM detachment rate than wild type myosin (WT). The MUT myosin also generated a shorter powerstroke size ({delta}). Ensemble average analysis of AM interaction events demonstrated that both the first powerstroke ({delta}1) associated with Pi release and the second powerstroke ({delta}2) linked to ADP release were reduced in MUT myosin. Moreover, the increased actomyosin cross-bridge stiffness in the AM.ADP state was observed for MUT compared to WT motors. Consistent with slower AM detachment rate and shorter stroke size, reconstituted human mutant {beta}M-II displayed slower actin filament gliding speed. Alterations in sarcomere-level mechanics included increased Ca2+ sensitivity of force generation and prolonged relaxation time, as predicted by FiberSim modelling. Molecular dynamics simulations indicated that the substitution of alanine by aspartate altered MLC1v interactions with myosin heavy chain (MyHC) and light chain 2 (MLC2v), affecting the curvature and flexibility of the lever arm. Overall, these studies establish the molecular mechanism underlying the primary myosin dysfunction due to A57D MLC1v mutation and further highlight the crucial role of MLC1v-mediated regulation of myosin function. Understanding the precise changes in the mutant myosins biomechanical properties is directly relevant to comprehending the initial triggers for pathological cardiac remodeling in HCM patients and designing tailored therapeutic interventions.

biophysics↗

bioRxiv2026

Accelerating Inference in Genomic Foundation Models via Speculative Decoding

Genomic and protein foundation models (GFMs and PFMs) have demonstrated strong performance in learning the language of DNA and proteins, but their use in large-scale sequence generation is limited by the latency of autoregressive decoding. Because every token triggers a forward pass of a large Transformer, whose inference is relatively slow, long-sequence generation quickly becomes costly. In this work we adapt speculative decoding to a representative GFM: the DNA model DNAGPT and two representative PFMs: ProGen2 and ProtGPT2. We implement a probabilistic variant of speculative decoding, in which a lightweight draft model proposes short token spans and a larger target model verifies or corrects them in parallel, while preserving the target models sampling distribution. Across all three models we systematically study the effect of speculation window length, temperature, draft architecture and prompt length, and we benchmark tokens per second over multiple runs per configuration. Speculative decoding yields consistent speedups over standard key-value cached decoding, with maximum observed speedup reaching 100% increase, while average gains across models ranging between 20% and 40% (e.g. 1.2x-1.4x), without changing the underlying target model predictions. Our results show that speculative decoding is a practical and model-agnostic strategy for accelerating genomic and proteomic sequence generation without sacrificing prediction quality.

genomics↗

bioRxiv2025

Identification and characterization of host-modulating effectors encoded by the Cluster F1 mycobacteriophage NormanBulbieJr

NormanBulbieJr (NBJ) is a temperate siphovirus isolated on the host Mycobacterium smegmatis mc2155 that encodes 102 gene products, 60 of which have no known function (NKF). Based on gene content, NBJ is classified as a Cluster F, Subcluster F1 phage and shares 70% of its encoded gene phamilies with Girr, another F1 mycobacteriophage that was recently analyzed in a genome-wide overexpression screen and found to encode 29 diverse gene products capable of inhibiting growth of M. smegmatis. Similar functional screens in other mycobacteriophages have uncovered a growing repertoire of diverse, phage-encoded bacterial growth inhibitors, providing prime candidates for dissecting novel bacterial-phage interactions. An arrayed overexpression library encoding all 102 genes was constructed and systematically screened using a plate-based cytotoxicity assay, identifying 29 genes that inhibit mycobacterial growth. Because mycobacteriophage genomes are also known to encode systems involved in phage-phage competition, we conducted additional phage defense assays for a subset of NBJ genes in our library. This analysis confirmed homotypic immunity by the predicted immunity repressor and identified gp45 as a second defense factor that protects against Cluster F phages and promotes NBJ lysogen stability. Additional mechanistic analyses indicate that gp45 functions in a secretion-dependent manner, acting after phage adsorption to reduce productive infection and early phage transcript accumulation. Escape mutant and bacterial two-hybrid analyses implicate Cluster F tape measure proteins as the likely target of gp45, consistent with disruption of an early step in phage genome delivery. Finally, we extended our analysis to explore the essentiality of all identified host-modulating genes in the NBJ life cycle, using CRISPR-enhanced recombineering to generate phage deletion mutants, revealing two host modulators that are critical for lytic growth. Conducted as part of the SEA-GENES undergraduate research consortium, this study adds to a growing functional genomics resource and provides new insights into the complex interactions between phage gene products and the mycobacterial host cell.

microbiology↗

bioRxiv2025

The cumulative impact of passenger mutations on cancer development

The traditional binary classification of somatic mutations in cancer as either drivers or passengers overlooks the potential cumulative impact of smaller-effect mutations. Here, we analyze 2,263 whole-genome-sequenced primary tumors across 31 cancer types to assess the functional contribution of passenger mutations in cancer development. We find that in the absence of canonical driver mutations, passenger mutations in cancer genes are significantly enriched, exhibit higher predicted pathogenicity, and are associated with aberrant expression, splicing disruption, altered transcription factor binding, and clinical outcomes that resemble those in the presence of driver mutations. The accumulation of passenger mutations in tumor suppressor genes correlates with significantly reduced expression and poorer prognosis, mirroring the functional outcomes of driver mutations. Notably, this is a previously uncharacterized mechanism of tumor suppressor inactivation, in which the accumulation of somatic mutations results in its progressive inactivation. Our results support a continuum model of mutational impact, where the collective influence of passenger mutations contributes to oncogenesis and clinical outcomes. This work advocates for integrative cancer models that incorporate all somatic mutations to more accurately reflect the complexity of tumor evolution.

cancer biology↗

bioRxiv2025

Designing smart spatial omics experiments with S2Omics

Spatial omics technologies have transformed biomedical research by enabling high-resolution molecular profiling while preserving the native tissue architecture. These advances provide unprecedented insights into tissue structure and function. However, the high cost and time-intensive nature of spatial omics experiments necessitate careful experimental design, particularly in selecting regions of interest (ROIs) from large tissue sections. Currently, ROI selection is performed manually, which introduces subjectivity, inconsistency, and a lack of reproducibility. Previous studies have shown strong correlations between spatial molecular patterns and histological features, suggesting that readily available and cost-effective histology images can be leveraged to guide spatial omics experiments. Here, we present S2Omics, an end-to-end workflow that automatically selects ROIs from histology images with the goal of maximizing molecular information content in the ROIs. Through comprehensive evaluations across multiple spatial omics platforms and tissue types, we demonstrate that S2Omics enables systematic and reproducible ROI selection and enhances the robustness and impact of downstream biological discovery.

genomics↗

bioRxiv2025

Single-Assay Characterization of Ternary Complex Assembly and Activity in Targeted Protein Degradation

Targeted protein degradation (TPD) is a rapidly advancing therapeutic strategy that selectively eliminates disease-associated proteins by co-opting the cells protein degradation machinery. Covalent modification of proteins with ubiquitin is a critical event in TPD, yet the analytical tools for quantifying the ubiquitination kinetics have been limited. Here, we present a real-time, high-throughput fluorescent assay utilizing purified, FRET-active E2-Ub conjugates to monitor ubiquitin transfer. This assay is highly versatile, requiring no engineering of the target protein or ligase, thereby accelerating assay development and minimizing the risk of artifacts. The single-step, single-turnover nature of the monitored reaction enables rigorous and quantitative analysis of ubiquitination kinetics. We show that this assay can be used to measure key degrader characteristics such as degrader affinity for the target protein, degrader affinity for the ligase, affinity of ternary complex assembly, and catalytic efficiency of the ternary complex. The high sensitivity and accuracy of this comprehensive, single-assay approach to ternary complex characterization will empower the discovery and optimization of heterobifunctional degraders and molecular glues.

biochemistry↗

bioRxiv2025

Interactions of Natural Compounds and Biomolecules with Hepatitis C Virus RNA Untranslated Regions: Exploring Structural Modifications to Advance Pathogenesis Understanding and Antiviral Strategy Design

Hepatitis C virus (HCV), a 10 kb positive-strand RNA virus, primarily infects liver cells and is a major cause of liver cirrhosis, which can progress to hepatocellular carcinoma. The HCV RNA untranslated regions (UTRs) adopt topologies that serve as binding sites for host proteins and miRNAs, crucial for viral replication and pathogenesis. However, the precise interactors and mechanisms of these interactions remain unclear. This study investigates the architectural landscape of HCV UTRs alone and in the presence of various interactors. Structural analysis reveals stable HCV UTR topologies, but significant alterations occur upon interaction with miRNAs and phytochemicals, potentially critical for viral pathogenicity. Additionally, proteins SRSF7 and AKAP8L are identified as novel interactors, which could have implication in host immune evasion and enhanced virulence. These findings highlight new miRNAs, proteins, and small molecules as interactors of HCV UTRs, offering insights into HCV infectivity and therapeutic targets for antiviral interventions.

molecular biology↗

bioRxiv2025

Improved synapsis dynamics accompany meiotic stability in Arabidopsis arenosa autotetraploids

During meiosis, the correct pairing, synapsis, and recombination of homologous chromosome pairs is critical for fertility of sexual eukaryotes. These processes are challenged in polyploids, which possess additional copies of each chromosome. Polyploidy thus provides a unique context to study how evolution can modify meiotic programs in response to challenges. We previously observed that in Arabidopsis arenosa newly formed (neo-)polyploids, synapsis defects precede chromosomes associating in aberrant multivalent and univalent configurations. Here we study synapsis dynamics in genotypes with varying levels of meiotic stability to ask whether efficient synaptic progression is a key component of evolving stable tetraploid meiosis. We develop a method to quantify synapsis dynamics using the progression of foci of the pro-crossover factor HEI10 as a reference. HEI10 initially appears at many small loci before accumulating only at crossover sites. In diploids, this transition begins while there is still significant asynapsis, which quickly declines as HEI10 accumulation to fewer foci progresses. In neo-tetraploids, suboptimal elongation of synaptic initiation sites, and perhaps defective pairing, precedes synapsis stalling before the onset of HEI10 accumulation. In established tetraploids, HEI10 accumulation begins only when asynapsis is minimal, suggesting an enhanced HEI10/synapsis co-dynamic (even compared to diploids). Hybrids generated by crossing neo- and established tetraploids exhibit intermediate phenotypes. We find the extent of asynapsis correlates positively with crossover numbers, as well as a higher frequency of multivalents and univalent, which can disturb chromosome segregation. Our work supports the hypothesis that improving the efficiency of synapsis is important for evolving polyploid meiotic stability. Significance StatementDuring meiosis, homologous chromosomes pair and subsequently form the synaptonemal complex, which provides a context for maturation of DNA recombination events. How synapsis and crossover formation are coordinated in polyploids, where multiple chromosome sets complicate pair-wise interactions, remains unclear. Leveraging the dynamics of the pro-crossover factor HEI10 as a developmental clock, we quantified synapsis progression in new and established tetraploids of Arabidopsis arenosa. Synapsis is severely compromised in neo-tetraploids, while in established ones it is more efficient even than diploids. Notably, the extent of synaptic defects correlated with excess crossovers, which compromises meiotic stability in tetraploids by connecting connect multiple homologs in multivalents. These findings highlight that improving synapsis dynamics are important for the evolution of meiotic stability in polyploids.

genetics↗

bioRxiv2024

invertiaDB: A Database of Inverted Repeats Across Organismal Genomes

Inverted repeats are repetitive elements that can form hairpin and cruciform structures. They are linked to genomic instability, however they also have various biological functions. Their distribution differs markedly across taxonomic groups in the tree of life, and they exhibit high polymorphism due to their inherent genomic instability. Advances in sequencing technologies and declined costs have enabled the generation of an ever-growing number of complete genomes for organisms across taxonomic groups in the tree of life. However, a comprehensive database encompassing inverted repeats across diverse organismal genomes has been lacking. We present InvertiaDB, the first comprehensive database of inverted repeats spanning multiple taxa, featuring repeats identified in the genomes of 118,070 organisms across all major taxonomic groups. The database currently hosts 30,067,666 inverted repeat sequences, serving as a centralized, user-friendly repository to perform searches, interactive visualization, and download existing inverted repeat data for independent analysis. invertiaDB is implemented as a web portal for browsing, analyzing and downloading inverted repeat data. invertiaDB is publicly available at https://invertiadb.netlify.app/homepage.html.

genomics↗

bioRxiv2024

Characterization of hairpin loops and cruciforms across 118,065 genomes spanning the tree of life

Inverted repeats (IRs) can form alternative DNA secondary structures called hairpins and cruciforms, which have a multitude of functional roles and have been associated with genomic instability. However, their prevalence across diverse organismal genomes remains only partially understood. Here, we examine the prevalence of IRs across 118,065 complete organismal genomes. Our comprehensive analysis across taxonomic subdivisions reveals significant differences in the distribution, frequency, and biophysical properties of perfect IRs among these genomes. We identify a total of 29,589,132 perfect IRs and show a highly variable density across different organisms, with strikingly distinct patterns observed in Viruses, Bacteria, Archaea, and Eukaryota. We report IRs with perfect arms of extreme lengths, which can extend to hundreds of thousands of base pairs. Our findings demonstrate a strong correlation between IR density and genome size, revealing that Viruses and Bacteria possess the highest density, whereas Eukaryota and Archaea exhibit the lowest relative to their genome size. Additionally, the study reveals the enrichment of IRs at transcription start and termination end sites in prokaryotes and Viruses and underscores their potential roles in gene regulation and genome organization. Through a comprehensive overview of the distribution and characteristics of IRs in a wide array of organisms, this largest-scale analysis to date sheds light on the functional significance of inverted repeats, their contribution to genomic instability, and their evolutionary impact across the tree of life.

genomics↗

bioRxiv2024

Ribosomal DNA arrays are the most H-DNA rich element in the human genome

Repetitive DNA sequences can form non-canonical structures such as H-DNA which is an intramolecular triplex DNA structure. The new Telomere-to-Telomere (T2T) genome assembly for the human genome has eliminated gaps, enabling the examination of highly repetitive regions including centromeric and pericentromeric repeats and ribosomal DNA arrays. This gapless assembly allows for the examination of the distribution of H-DNA sequences in parts of the human genome that were not previously annotated. We find that H-DNA appears once every 30,000 bps in the human genome. Its distribution is highly inhomogeneous with H-DNA motif hotspots being detectable in acrocentric chromosomes. Ribosomal DNA arrays in acrocentric chromosomes are the genomic element with the highest H-DNA enrichment, with 13.22% of total H-DNA motifs being found in ribosomal DNA arrays, representing a 42.65-fold enrichment over what would be expected by chance. Across the acrocentric chromosomes we report that 55.87% of all H-DNA motifs found in these chromosomes are in rDNA array loci. The H-DNA motifs are primarily found in the intergenic spacer regions of the ribosomal DNA arrays, generating repeated clusters. We also discover that binding sites for PRDM9, a protein that regulates the formation of double-strand breaks and determines the meiotic recombination hotspots in humans and most mammals, are over 5-fold enriched for H-DNA motifs. Finally, we provide evidence that our findings are consistent in other non-human great ape genomes. We conclude that ribosomal DNA arrays are the most enriched genomic loci for H-DNA sequences in human and other great ape genomes.

genomics↗

bioRxiv2024

Quadrupia: Derivation of G-quadruplexes for organismal genomes across the tree of life

G-quadruplex DNA structures exhibit a profound influence on essential biological processes, including transcription, replication, telomere maintenance, and genomic stability. These structures have demonstrably shaped organismal evolution. However, a comprehensive, organism-wide G-quadruplex map encompassing the diversity of life has remained elusive. Here, we introduce Quadrupia, the most extensive and well-characterized G-quadruplex database to date, facilitating the exploration of G-quadruplex structures across the evolutionary spectrum. Quadrupia has identified G-quadruplex sequences in 108,449 reference genomes, with a total of 140,181,277 G-quadruplexes. The database also hosts a collection of 319,784 G-quadruplex clusters of 20 or more members, annotated by taxonomic distributions, multiple sequence alignments, profile Hidden Markov Models and cross-references to G-quadruplex 3D structures. Examination of G-quadruplexes across functional genomic elements in different taxa indicates preferential orientation and positioning, with significant differences between individual taxonomic groups. For example, we find that G-quadruplexes in bacteria with a single replication origin display profound preference for the leading orientation. Finally, we experimentally validate the most frequently observed G-quadruplexes using CD-spectroscopy, UV melting, and fluorescent-based approaches. Quadrupia is publicly available through https://www.pavlopoulos-lab.org/quadrupia.

genomics↗