Biology subjects

Ding, B.

Publications and source records attributed to Ding, B..

At least 19 recordsLinked to original sources

bioRxiv2026

An integrated genome-wide resource reveals distinct replication environments of DNA breakage in human cancer cell lines

Replication stress is a major source of genome instability in cancer, yet the genomic features that determine where DNA double-strand breaks (DSBs) arise remain incompletely defined. Here, we establish an integrated genome-wide resource of DSBs, DNA replication, replication timing, transcription, and R-loops in two widely used cancer cell lines, U2-OS and HeLa, under steady-state conditions and following prolonged low-dose DNA polymerase inhibition. We combine these datasets with systematic statistical testing and comparative analytical approaches to define the replication environments associated with genome fragility. Endogenous DSBs preferentially accumulated at origin-rich initiation zones, where R-loops were enriched, whereas prolonged DNA polymerase inhibition redirected DSB formation toward origin-poor, late-replicating regions. Among the replication features examined, replication initiation zones and late-replicating areas were most sensitive to prolonged replication stress. R-loops were specifically enriched at initiation zones but depleted from late-replicating regions and recurrent DNA break clusters (RDCs), demonstrating that their association with genome fragility is context dependent. Replication stress further induced RDCs within long, actively transcribed genes, while their locations only partially overlapped with common fragile sites. Functional analyses identified MUS81 as a major regulator of RDC formation. MUS81 loss increased RDCs, whereas restoration of its catalytic activity suppressed them, indicating that MUS81 resolves replication intermediates before they persist into late-replicating fragile regions. Together, this resource and analytical framework provide a systematic basis for dissecting how replication architecture, transcription, and DNA processing shape genome fragility in cancer cells.

genomics↗

bioRxiv2026

Dystonia-associated TorsinA-ΔE mutation induces a gain-of-function interaction with XPO1 via its N-terminal hydrophobic segment

Childhood-onset DYT1 dystonia is a neurodevelopmental movement disorder caused by a three-base-pair deletion ({Delta}GAG; {Delta}E) in the TOR1A gene, which encodes TorsinA, a membrane-associated AAA+ (ATPase associated with diverse cellular activities) ATPase. However, the mechanisms by which the {Delta}E mutation causes neuronal dysfunction remain poorly understood. Using patient-derived neurons, we previously demonstrated that TorsinA-{Delta}E disrupts the nucleocytoplasmic transport (NCT) of both RNA and protein cargos. In the present study, proteomic analysis of induced human motor neurons revealed a markedly enhanced association between {Delta}E and exportin 1 (XPO1), a major nuclear export receptor. This aberrant association was enriched at the nuclear envelope and accompanied by impaired XPO1-mediated nuclear export. By integrating AlphaFold-based structural modeling with molecular, biochemical, and cellular analyses, we identified the N-terminal hydrophobic segment (HS) of TorsinA as a critical contributor to its interaction with XPO1. Deletion of the HS from {Delta}E reduced its association with XPO1, altered its nuclear envelope enrichment, and restored nuclear export. Moreover, expression of HS-derived peptides in patient-derived DYT1 neurons improved nuclear export, neurite outgrowth and branching, maturation-associated gene expression, and neuronal survival. Together, these findings identify an aberrant gain-of-function association between TorsinA-{Delta}E and XPO1 as a mechanism contributing to NCT dysfunction in DYT1 dystonia and establish the HS-dependent {Delta}E-XPO1 interaction as a potential therapeutic target.

neuroscience↗

bioRxiv2025

Recurrent DNA Break Clusters Regulated by Polymerase Theta Are Essential for Replication Stress Induced Copy Number Variation

Copy number variations (CNVs) are a form of genetic alteration strongly implicated in numerous neurological and psychiatric disorders, as well as brain cancer. Replication stress is a common cause of CNVs. Despite the prevailing model that CNVs arise from DNA double strand breaks (DSBs), there has been no assay that directly perturbs presumed DSB sources and measures CNV output. Here, we identified a subset of recurrent DNA break clusters (RDCs) as a causal factor for CNV formation. In murine neural progenitor cells under replication stress, mapping the formation of CNVs revealed their location in RDC regions that contain actively transcribed genes. CRISPR/Cas9-mediated transcriptional suppression abrogated both RDC and CNV formation, but does not alter their replication timing. We found that DNA polymerase theta (Pol {theta}), a protector against CNV formation, plays a critical but context dependent role upstream of RDC formation. Chemically inhibiting the activity of Pol {theta} reduced end filling and micro-homology-mediated end joining in XRCC4/P53-deficient cells. Conversely, Pol {theta} inhibition led to elevated DSB density detection at RDC-containing loci in wild-type neural stem and progenitor cells, suggesting its role in preventing transcription-replication conflicts. Our data identify RDCs as contributors to genomic heterogeneity with plausible downstream effects on brain disorders and malignancy.

molecular biology↗

bioRxiv2025

Dysregulated nuclear Lamin B1 in DYT1 dystonia thickens the nuclear lamina and disrupts 14-3-3 proteins

Childhood-onset DYT1 dystonia is caused by a heterozygous {Delta}E mutation in the TOR1A gene, which encodes a membrane-embedded AAA+ (ATPase Associated with diverse cellular Activities) ATPase. However, the mechanism by which {Delta}E induces dystonia remains poorly understood. Previously, using patient-derived neurons, we identified dysregulation of nuclear Lamin B1, at both expression levels and subcellular distribution, as a key contributor to DYT1 pathology. In the present study, we utilized DYT1 patient fibroblast cells and induced human neurons to investigate the molecular basis and consequences of Lamin B1 dysregulation. We found that elevated nuclear Lamin B1 thickens the nuclear lamina and deforms the nucleus, impairing nucleocytoplasmic transport. Proteomic analysis of human iPSC-derived neurons revealed that mislocalized Lamin B1 disrupts essential signaling pathways involved in neuronal function. Notably, 14-3-3 proteins, abundant brain molecular chaperones critical for neuronal development and homeostasis, were the most strongly associated with mislocalized Lamin B1. Functional studies showed that downregulation of 14-3-3 proteins impairs neurodevelopment in healthy neurons, while their upregulation rescues DYT1 neuronal defects by reducing Lamin B1 mislocalization. These findings elucidate a mechanistic link between nuclear deformation and cellular dysfunction in DYT1 dystonia and highlight Lamin B1 and 14-3-3 proteins as potential therapeutic targets.

neuroscience↗

bioRxiv2024

Oncogenic Mutant p53 Sensitizes Non-Small Cell Lung Cancer Cells to Proteasome Inhibition via Oxidative Stress-Dependent Induction of Mitochondrial Apoptosis

Non-small cell lung cancer (NSCLC) cells with oncogenic mutant p53 alleles (Onc-p53) exhibit significantly higher levels of proteasome activity, indicating that Onc-p53 induces proteotoxic stress which may be leveraged as a therapeutic vulnerability. Proteasome inhibitors (PIs), such as bortezomib (BTZ), can induce toxic levels of oxidative stress in cancer cells and thus we investigated whether PIs exhibit preferential cytotoxicity in Onc-p53 NSCLC cells. Indeed, BTZ and other PIs exhibited the IC50 6-7-fold lower in Onc-p53 cells vs. wild-type (WT) p53 cells. BTZ cytotoxic effects in Onc-p53 cells were nearly completely rescued by antioxidants such as N-acetyl cysteine, indicating that oxidative stress is the critical driver of BTZ-dependent cytotoxic effects in Onc-p53 cells. Importantly, we observed oxidative stress-dependent transcriptional induction of the pro-apoptotic NOXA with downstream cleaved caspase-3, consistent with apoptotic cell death in Onc-p53 but not in WT p53 cells treated with BTZ, and BTZ-generated oxidative stress was linked to nuclear translocation of NRF2 and transcriptional activation of ATF3, which in turn was required for NOXA induction. Validating BTZs translational potential in Onc-p53 NSCLC, BTZ and carboplatin or the BH3-mimetic navitoclax were synergistically cytotoxic in Onc-p53 but not WT p53 cells in vitro, and BTZ effectively limited growth of Onc-p53 NSCLC xenografts when combined with either carboplatin or navitoclax in vivo. Our data therefore support further investigation of the therapeutic utility of PIs combined with carboplatin or BH3-mimetics in Onc-p53 human NSCLC as novel therapeutic strategies. SignificanceNon-small cell lung cancer (NSCLC) is the leading cause of cancer death due, in part, to a lack of active therapies in advanced disease. We demonstrate that proteasome inhibitor/BH3-mimetic combination therapy is an active precision therapy in NSCLC cells and tumors expressing oncogenic mutant p53 alleles (Onc-p53).

cancer biology↗

bioRxiv2024

BLADE-ON-PETIOLE interacts with CYCLOIDEA to fine-tune CYCLOIDEA-mediated flower symmetry in Monkeyflowers (Mimulus)

AbstractMorphological novelties, or key innovations, are instrumental to the diversification of the organisms. In plants, one such innovation is the evolution of zygomorphic flowers, which is thought to promote outcrossing and increases flower morphological diversity. We isolated three allelic mutants from two Mimulus species displaying altered floral symmetry and identified the causal gene as the orthologue of Arabidopsis BLADE-ON-PETIOLE. We found that MlBOP and MlCYC2a physically interact and this BOP-CYC interaction module is highly conserved across the angiosperms. Furthermore, MlBOP self-ubiquitinates and suppresses MlCYC2a self- activation. MlCYC2a, in turn, impedes MlBOP ubiquitination. Thus, this molecular tug-of-war between MlBOP and MlCYC2a fine-tunes the expression of MlCYC2a, contributing to the formation of bilateral symmetry flowers, a key trait in angiosperm evolution. One Sentence SummaryMolecular tug-of-war between MlBOP and MlCYC2a fine-tunes the expression of MlCYC2a, contributing to the bilateral flower symmetry formation.

developmental biology↗

bioRxiv2024

Dynamic parallel transmit diffusion MRI at 7T

Diffusion MRI (dMRI) is inherently limited by SNR. Scanning at 7T increases intrinsic SNR but 7T MRI scans suffer from regions of signal dropout, especially in the temporal lobes and cerebellum. We applied dynamic parallel transmit (pTx) to allow whole-brain 7T dMRI and compared with circularly polarized (CP) pulses in 6 subjects. Subject-specific 2-spoke dynamic pTx pulses were designed offline for 8 slabs covering the brain. We used vendor-provided B0 and B1+ mapping. Spokes positions were set using the Fourier difference approach, and RF coefficients optimized with a Jacobi-matrix high-flip-angle optimizer. Diffusion data were analyzed with FSL. Comparing whole-brain averages for pTx against CP scans: mean flip angle error improved by 15% for excitation (2-spoke-VERSE 15.7{degrees} vs CP 18.4{degrees}, P=0.012) and improved by 14% for refocusing (2-spoke-VERSE 39.7{degrees} vs CP 46.2{degrees}, P=0.008). Computed spin-echo signal standard deviation improved by 14% (2-spoke-VERSE 0.185 vs 0.214 CP, P=0.025). Temporal SNR increased by 5.4% (2-spoke-VERSE 8.47 vs CP 8.04, P=0.004) especially in the inferior temporal lobes. Diffusion fitting uncertainty decreased by 6.2% for first fibres (2-spoke VERSE 0.0655 vs CP 0.0703, P<0.001) and 1.3% for second fibers (2-spoke VERSE 0.139 vs CP 0.141, P=0.01). In conclusion, dynamic parallel transmit improves the uniformity of 7T diffusion-weighted imaging. In future, less restrictive SAR limits for parallel transmit scans are expected to allow further improvements.

neuroscience↗

bioRxiv2023

Pan-genome of pear provides insights into the differentiation of fruit quality traits between Asian and European pears

The pear (Pyrus spp.) is a remarkable fruit, well known for its diverse flavors, textures, culinary versatility, and global horticultural importance. However, the genetic diversity responsible for its extensive phenotypic variations remains largely unexplored. Here, we de novo assembled and annotated the genomes of the maternal (PsbM) and paternal (PsbF) lines of the hybrid Yuluxiang pear and constructed the first pear pangenome of 1.15Gb by combining these two genomes with five previously published pear genomes. Using the constructed pangenome, we identified 21,224 gene PAVs and 1,158,812 SNPs in the non-reference genome that were absent in the PsbM reference genome. Compared with SNP markers, we found that PAV-based analysis provides additional insights into the pear population structure. In addition, we also revealed that some genes associated with pear fruit quality traits have differential occurrence frequencies and differential gene expression between Asian and European populations. Moreover, our analysis of the pear pangenome revealed a mutated SNP and an insertion in the promoter region of the gene PsbMGH3.1 potentially enhances sepal shedding in Xuehuali which is vital for pear quality. This research helps further capture the genetic diversity of pear populations and provides valuable genomic resources for accelerating pear breeding.

genomics↗

bioRxiv2023

Transcription-Replication Conflict Shapes DNA Break Dynamics

Recurrent DNA break clusters (RDCs) are replication-transcription collision hotspots; many are unique to neural progenitor cells. Through high-resolution replication sequencing and a capture-ligation assay in mouse neural progenitor cells experiencing replication stress, we unraveled the replication features dictating RDC location and orientation. Most RDCs occur at the replication forks traversing timing transition regions (TTRs), where sparse replication origins connect unidirectional forks. Leftward-moving forks generate telomere-connected DNA double-strand breaks (DSBs), while rightward-moving forks lead to centromere-connected DSBs. Strand-specific mapping for DNA-bound RNA revealed co-transcriptional dual-strand DNA:RNA hybrids present at a higher density in RDC than in other actively transcribed long genes. In addition, mapping RNA polymerase activity revealed that head-to-head interactions between replication and transcription machinery resulted in 60% DSB contribution to the head-on compared to 40% for co-directional. Our findings revealed TTR as a novel fragile class and highlighted how the linear interaction between transcription and replication impacts genome stability.

genomics↗

bioRxiv2022

Arf GTPase activates the WAVE Regulatory Complex through a novel binding site

Crosstalk between Rho- and Arf-family GTPases plays an important role in linking actin cytoskeletal remodeling to membrane protrusion, organelle structure, and vesicle trafficking. The central actin regulator, WAVE Regulatory Complex (WRC), is a converging point of Rac1 (a Rho-family GTPase) and Arf signaling in many processes, but how Arf promotes WRC activation is unknown. Here we reconstituted a direct interaction between Arf and WRC. This interaction can be greatly enhanced by Rac1 binding to the D site of the WRC. Arf1 binds to a newly identified conserved surface on Sra1 located between the D site and the WH2 helix of WAVE1, which can drive WRC activation using a mechanism distinct from that of Rac1. Mutating Arf binding site abolishes Arf1-WRC interaction, disrupts Arf1-mediated WRC activation, and impairs lamellipodia morphology. This work uncovers a new mechanism underlying WRC activation and provides a mechanistic foundation for studying how WRC-mediated actin polymerization links Arf and Rac signaling in the cell.

biochemistry↗

bioRxiv2022

Structures reveal a key mechanism of WAVE Regulatory Complex activation by Rac1 GTPase

Rho-family GTPase Rac1 activates the WAVE regulatory complex (WRC) to drive Arp2/3-mediated actin polymerization in many essential processes. Rac1 binds to WRC at two distinct sites--the A and D sites. Precisely how Rac1 binds and how the binding triggers WRC activation remain unknown. Here we report WRC structures by itself, and when bound to single or double Rac1 molecules, at [~]3 [A] resolutions by cryogenic-electron microscopy. The structures reveal that Rac1 binds to the two sites by distinct mechanisms, and binding to the A site, but not the D site, drives WRC activation. Activation involves a series of unique conformational changes leading to the release of sequestered WCA (WH2- central-acidic) polypeptide, which stimulates the Arp2/3 complex to polymerize actin. Together with biochemical and cellular analyses, the structures provide a novel mechanistic understanding of how the Rac1-WRC-Arp2/3-actin signaling axis is regulated in diverse biological processes and diseases.

biochemistry↗

bioRxiv2021

The E3 Ubiquitin Ligase RNF5 Facilitates SARS-CoV-2 Membrane Protein-Mediated Virion Release

As enveloped virus, SARS-CoV-2 membrane protein (M) mediates viral release from cellular membranes, but the molecular mechanisms of SARS-CoV-2 virions release remain poorly understood. Here, we performed RNAi screening and identified the E3 ligase RNF5 which mediates ubiquitination of SARS-CoV-2 M at residue K15 to enhance the interaction of viral envelope (E) with M. M-E complex ensures the uniform size of viral particles for viral maturation and mediates viral release. Moreover, overexpression of M induces complete autophagy which is dependent on RNF5-mediated ubiquitin modification. M inhibits the activity of lysosome protease, and uses autolysosomes for virion release. Consequently, all these results demonstrate that RNF5 mediates ubiquitin modification of SARS-CoV-2 M to stabilize the M-E complex and induce autophagy for virion release.

microbiology↗

bioRxiv2020

Non-coding loci without epigenomic signals can be essential for maintaining global chromatin organization and cell viability

The majority of the non-coding regions in the human genome do not harbor any annotated element and are even not marked with any epigenomic signal or protein binding. An understudied aspect of these regions is their possible roles in stabilizing the 3D chromatin organization. To illuminate their "structural importance", we chose to start with the non-coding regions forming many 3D contacts (referred to as hubs) and identified dozens of hubs essential for cell viability. Hi-C and single cell transcriptomic analyses showed that their deletion could significantly alter chromatin organization and impact gene expression located distal in the genome. This study revealed the 3D structural importance of non-coding loci that are not associated with any functional element, providing a new mechanistic understanding of the disease-associated genetic variations (GVs). Furthermore, our analyses also suggested a powerful approach to develop "one-drug-multiple-targets" therapeutics targeting the disease-specific non-coding regions.

genetics↗

bioRxiv2020

Regulatory elements can be essential for maintaining broad chromatin organization and cell viability

Increasing evidence shows that promoters and enhancers could be related to 3D chromatin structure, thus affecting cellular functions. Except for functioning through the canonical chromatin loops formed by promoters and enhancers, their roles in maintaining broad chromatin organization have not been well studied. Here, we focused on the active promoters/enhancers (referred to as hotspots) predicted to form many 3D contacts with other active promoters/enhancers, and identified dozens of loci critical for cell survival. While the essentiality of hotspots is not resulted from their association with essential genes, deletion of an essential hotspot could lead to change of broad chromatin organization and expressions of distal genes. We demonstrated that multiple affected genes that are individually non-essential could have synergistic effects to cause cell death.

bioinformatics↗

bioRxiv2020

Power analysis of transcriptome-wide association study

The transcriptome-wide association study (TWAS) has emerged as one of several promising techniques for integrating multi-scale omics data into traditional genome-wide association studies (GWAS). Unlike GWAS, which associates phenotypic variance directly with genetic variants, TWAS uses a reference dataset to train a predictive model for gene expressions, which allows it to associate phenotype with variants through the mediating effect of expressions. Although effective, this core innovation of TWAS is poorly understood, since the predictive accuracy of the genotype-expression model is generally low and further bounded by expression heritability. This raises the question: to what degree does the accuracy of the expression model affect the power of TWAS? Furthermore, would replacing predictions with actual, experimentally determined expressions improve power? To answer these questions, we compared the power of GWAS, TWAS, and a hypothetical protocol utilizing real expression data. We derived non-centrality parameters (NCPs) for linear mixed models (LMMs) to enable closed-form calculations of statistical power that do not rely on specific protocol implementations. We examined two representative scenarios: causality (genotype contributes to phenotype through expression) and pleiotropy (genotype contributes directly to both phenotype and expression), and also tested the effects of various properties including expression heritability. Our analysis reveals two main outcomes: (1) Under pleiotropy, the use of predicted expressions in TWAS is superior to actual expressions. This explains why TWAS can function with weak expression models, and shows that TWAS remains relevant even when real expressions are available. (2) GWAS outperforms TWAS when expression heritability is below a threshold of 0.04 under causality, or 0.06 under pleiotropy. Analysis of existing publications suggests that TWAS has been misapplied in place of GWAS, in situations where expression heritability is low. Author SummaryWe compared the effectiveness of three methods for finding genetic effects on disease in order to quantify their strengths and help researchers choose the best protocol for their data. The genome-wide association study (GWAS) is the standard method for identifying how the genetic differences between individuals relate to disease. Recently, the transcriptome-wide association study (TWAS) has improved GWAS by also estimating the effect of each genetic variant on the activity level (or expression) of genes related to disease. The effectiveness of TWAS is surprising because its estimates of gene expressions are very inaccurate, so we ask if a method using real expression data instead of estimates would perform better. Unlike past studies, which only use simulation to compare these methods, we incorporate novel statistical calculations to make our comparisons more accurate and universally applicable. We discover that depending on the type of relationship between genetics, gene expression, and disease, the estimates used by TWAS could be actually more relevant than real gene expressions. We also find that TWAS is not always better than GWAS when the relationship between genetics and expression is weak and identify specific turning points where past studies have incorrectly used TWAS instead of GWAS.

bioinformatics↗

bioRxiv2020

kTWAS: integrating kernel-machine with transcriptome-wide association studies improves statistical power and reveals novel genes

The power of genotype-phenotype association mapping studies increases greatly when contributions from multiple variants in a focal region are meaningfully aggregated. Currently, there are two popular categories of variant aggregation methods. Transcriptome-wide association studies (TWAS) represent a category of emerging methods that select variants based on their effect on gene expressions, providing pretrained linear combinations of variants for downstream association mapping. In contrast, kernel methods such as SKAT model genotypic and phenotypic variance using various kernel functions that capture genetic similarity between subjects, allowing non-linear effects to be included. From the perspective of machine learning, these two methods cover two complementary aspects of feature engineering: feature selection/pruning, and feature modeling. Thus far, no thorough comparison has been made between these categories, and no methods exist which incorporate the advantages of TWAS and kernel-based methods. In this work we developed a novel method called kTWAS that applies TWAS-like feature selection to a SKAT-like kernel association test, combining the strengths of both approaches. Through extensive simulations, we demonstrate that kTWAS has higher power than TWAS and multiple SKAT-based protocols, and we identify novel disease-associated genes in WTCCC genotyping array data and MSSNG (Autism) sequence data. The source code for kTWAS and our simulations are available in our GitHub repository (https://github.com/theLongLab/kTWAS).

bioinformatics↗

bioRxiv2019

Unique structural features of the mitochondrial AAA+ protease AFG3L2 reveal the molecular basis for activity in health and disease

Mitochondrial AAA+ quality control proteases regulate diverse aspects of mitochondrial biology through specialized protein degradation, but the underlying molecular mechanisms that define the diverse activities of these enzymes remain poorly defined. The mitochondrial AAA+ protease AFG3L2 is of particular interest, as genetic mutations localized throughout AFG3L2 are linked to diverse neurodegenerative disorders. However, a lack of structural data has limited our understanding of how mutations impact enzymatic activity. Here, we used cryo-EM to determine a substrate-bound structure of the catalytic core of human AFG3L2. This structure identifies multiple specialized structural features within AFG3L2 that integrate with conserved structural motifs required for hand-over-hand ATP-dependent substrate translocation to engage, unfold and degrade targeted proteins. Mapping disease-relevant AFG3L2 mutations onto our structure demonstrates that many of these mutations localize to these unique structural features of AFG3L2 and distinctly influence its activity and stability. Our results provide a molecular basis for neurological phenotypes associated with different AFG3L2 mutations, and establish a structural framework to understand how different members of the AAA+ superfamily achieve specialized, diverse biological functions.

molecular biology↗

bioRxiv2018

Formation of periodic pigment spots by the reaction-diffusion mechanism

Many organisms exhibit visually striking spotted or striped pigmentation patterns. Turings reaction-diffusion model postulates that such periodic pigmentation patterns form when a local autocatalytic feedback loop and a long-range inhibitory feedback loop interact. At its simplest, this network only requires one self-activating activator that also activates a repressor, which inhibits the activator and diffuses to neighboring cells. However, the molecular activators and repressors fully fitting this versatile model remain elusive. Here, we characterize an R2R3-MYB activator and an R3-MYB repressor in monkeyflowers that correspond to Turings model and explain how periodic anthocyanin spots form. Notably, disrupting this pattern impacts pollinator visitation. Thus, subtle changes in simple reaction-diffusion networks are likely essential contributors to the evolution of the remarkable diversity of periodic pigmentation patterns in flowers.

plant biology↗