Biology subjects

Jeon, J.-H.

Publications and source records attributed to Jeon, J.-H..

7 recordsLinked to original sources

bioRxiv2025

PAF15 stabilizes PCNA on DNA and slows down its sliding dynamics

The PCNA-associated factor 15 (PAF15) protein is essential for human genome stability by regulating DNA replication and repair through its interaction with proliferating cell nuclear antigen (PCNA). Despite its significance, the mechanistic details of the PAF15-PCNA interaction remain insufficiently understood. Here, we reveal how PAF15 influences the sliding dynamics and function of PCNA. Using single-molecule diffusion analysis on a DNA skybridge platform, we show that PAF15 binding stabilizes PCNA in its DNA-bound state, reduces its diffusion rate along the duplex, restricts accessibility to PCNA PIP-box binding sites, and regulates PCNA loading and unloading on DNA via replication factor C (RFC). Our results are consistent with its coordinating role in both high-fidelity replication and lesion bypass. These findings establish PAF15 as a key regulator of PCNA function, serving as a mobile platform for DNA-editing enzymes and thereby influencing genome maintenance.

biophysics↗

bioRxiv2025

Inferring Spatially Varying Bending Stiffness of Biopolymers with Deep-Learning Approach

The bendability of biopolymers, including DNA, actin filaments, and microtubules, is crucial to diverse biological processes, such as cell motility and cytoskeletal organization. While conventional polymer models like the worm-like chain model assume uniform bending stiffness along the contour, biopolymers in reality often attain spatially varying bending stiffness as a result of complex cellular interactions. For instance, the bending stiffness of actin filaments and microtubules varies in response to associated binding proteins or chemical modifications. Despite its biological implications, measuring the position-dependent persistence length along polymer contours remains challenging. Here, we present a deep-learning-based method that quantitatively predicts spatially varying bending stiffness of biopolymers. Our framework segments a polymer chain into short over-lapping fragments, predicts local persistence lengths using a deep-learning model, and reconstructs full profiles. Using simulated data, we demonstrate that our approach achieves high accuracy and robustness even under data-scarce conditions. Applied to various biological systems, our method reveals a spatially varying stiffness from tip to base in filopodia as well as spatially heterogeneous stiffness in microtubules. Additionally, we investigate the internal mechanism of our deep-learning model and show that the model utilizes multiple physics-related features for persistence length estimation while adaptively adjusting its attention based on polymer stiffness.

biophysics↗

bioRxiv2025

DNA topological regulation by topoisomerase IIbeta-DNA-PK interaction is important for controlled hypoxia-inducible gene expression

Hypoxic stress responses are essential for cellular and organismal survival and drive gene regulation across diverse biological pathways, including cell cycle progression and energy metabolism. Here, we show that topoisomerase II{beta} (TOP2B) regulates DNA topology and transcription of hypoxia-inducible genes (HIGs) in a DNA-dependent protein kinase (DNA-PK)-dependent manner. Integrated cellular, biochemical, and genomic analyses reveal an antagonistic yet correlated relationship between TOP2B and DNA-PK activities. Under normoxic conditions, TOP2B associates with HIGs and represses transcription by suppressing DNA negative supercoiling formation and accessibility. Under hypoxic exposure, TOP2B dissociates from HIGs, while DNA-PK and HIF1 are recruited to activate HIGs. Notably, DNA-PK is required for the repressive function of TOP2B, as DNA-PK knockout abrogates TOP2B release and activity, resulting in elevated expression of a number of HIGs. Mechanistically, DNA-PK phosphorylates TOP2B at T1403, stimulating its catalytic activity to restrain DNA unwinding and accessibility, thereby suppressing HIG transcription. Collectively, these findings identify a novel role for TOP2B and DNA-PK-mediated regulation of TOP2B as key transcriptional regulators of HIG expression. We propose that phosphorylation-dependent modulation of TOP2B activity is coordinated with transcriptional states and determines DNA topology to regulate Pol II transcription.

molecular biology↗

bioRxiv2024

Innovative Strategies for Enhancing Signal-to-Noise Ratio in Single-molecule Imaging: The Influence of Molecular Motion

Single-molecule fluorescence imaging has extensively revealed the dynamic and structural characteristics of biomolecules. However, its application is limited by the upper concentration of fluorophore-tagged biomolecules, which is in the sub-ten nanomolar range. We found that the signal-to-noise ratio (SNR) in single-molecule fluorescence imaging is strongly influenced by the size of fluorophore-labeled molecules in solution. Our computational simulations suggest that the faster diffusion of background fluorophores can enhance the SNR of target molecules. Moreover, we identified that the molecular motion through fluid flow can improve SNR. This study provides a novel perspective by emphasizing the importance of molecular motion in SNR and propose a rapid barrier-free method to increase the upper concentration limit in single-molecule imaging.

biophysics↗

bioRxiv2024

Genomic insights into the evolution and adaptation of the memorial roses (Rosa lucieae; Rosaceae) in saline environments

Rosa lucieae (syn. Rosa wichurana or R. wichuraiana; Rosaceae) is one of the major wild progenitors of modern rose cultivars. In breeding roses, R. lucieae has contributed not only to white blooms and shiny leaves, but most of all, to succeed in various harsh conditions and high resistance to diseases and pests. The wild R. lucieae inhabits littoral sand banks or rocks, where drought stress and high salinity inhibit plant growth. In this study, we assembled the chromosome-level genome sequence of a wild accession of R. lucieae and identified potential genes that may responsible for the evolution of salt tolerance. Within the 544.7 Mb-long genome of R. lucieae, recent duplications and divergence of the genes responsible to stress tolerance were identified, including stress response, signaling, homeostasis, and detoxification. Additionally, the gene family evolution analyses elucidated rapid evolution of stress tolerant functions in R. lucieae. The first high-quality genome assembly of wild R. lucieae contributes significantly to our understanding of the genomic evolution and adaptive mechanism of R. lucieae, which promises the enhancement of our efforts in rose breeding programs.

plant biology↗

bioRxiv2022

Machine learning analysis reveals the dynamics of mode transition in dendritic cell migration

Dendritic cells (DCs) patrol the body as immunological sentinels and search for pathogens. Upon stimulation, immature DCs (imDCs) become mature DCs (mDCs), which migrate to the lymph nodes and present antigens to T cells. The migratory behavior is crucial for initiating and controlling immune responses; however, the properties of the highly heterogeneous and dynamic motility phenotype are not fully understood. Here, we established an unsupervised machine learning (ML) strategy to investigate spatiotemporal motility patterns in long-term, two-dimensional cell migration trajectories, and determined the number of motility patterns and how these are related to the maturation status. We identified three distinct migratory modes independent of the cell state: slow-diffusive (SD), slow-persistent (SP), and fast-persistent (FP). We found that maturation-dependent motility changes are emergent properties of the distribution and dynamic transitions of these three modes. Remarkably, imDCs changed their migration modes more frequently, and predominantly followed the SD[->]FP[->]SP[->]SD unicyclic transition, indicating that imDCs rapidly increase their speed during the shift from diffusive to persistent motility; however, persistence progressively declines when switching back to diffusive motility. In contrast, mDCs show no transition directionality. Our ML-promoted motility pattern analysis and history-dependent mode transition investigation may provide new insights into the complex process of biological motility.

biophysics↗

bioRxiv2021

Draft Genome of the Korean smelt (Hypomesus nipponensis) and its transcriptomic responses to heat stress in the liver and muscle

Pond smelt (Hypomesus nipponensis) is a cold-freshwater fish species as a winter economic resource of aquaculture in South Korea. Due to its high susceptibility to abnormal water temperature from global warming, a large number of smelt die in hot summer. Here, we present the first draft genome of H. nipponensis and transcriptomic changes in molecular mechanisms or intracellular responses under heat stress. We combined Illumina and PacBio sequencing technologies to generate the draft genome of H. nipponensis. Based on the reference genome, we conducted transcriptome analysis of liver and muscle tissues under normal (NT, 5{degrees}C) versus warm (HT, 23{degrees}C) conditions, to identify heat stress-induced genes and gene categories. We observed a total of 1,987 contigs, with N50 of 0.46 Mbp with a largest contig (3.03 Mbp) in the assembled genome. A total number of 20,644 protein coding genes were predicted, and 19,224 genes were functionally annotated: 15,955 genes for Gene Ontology (GO) terms; and 11,560 genes for KEGG Orthology (KO). We conducted the lost and gained genes analysis compared with three species that human, zebrafish and salmon. In the lost genes analysis, we detected smelt lost 4,461 (22.16%), 2,825 (10.62%), and 1,499 (3.09%) genes compare with above three species, respectively. In the gained genes analysis, we observed smelt gain 1,133 (5.49%), 1,670 (8.09%), and 229 (1.11%) genes compare with above species, respectively. From transcriptome analysis, a total of 297 and 331 differentially expressed genes (DEGs) with False discovery rate (FDR) < 0.05 were identified in the liver and muscle tissues, respectively. Gene enrichment analysis of DEGs indicates that up-regulated genes were significantly enriched for lipid biosynthetic process (GO:0008610, P < 0.001) and regulation of apoptotic process (GO:0042981, P < 0.01), and down-regulated genes by immune responses such as myeloid cell differentiation (GO:0030099, P < 0.001) in the liver under heat stress. In muscle tissue, up-regulated genes were enriched for hypoxia (GO:0001666, P < 0.05), transcription regulator activity (GO:0140110, P < 0.001) and calcium-release channel activity (GO:0015278, P < 0.01), and down-regulated genes for nicotinamide nucleotide biosynthetic process (GO:0019359, P < 0.01). The results of KEGG pathway analysis were similar to that of gene enrichment analysis. The draft genome and transcriptomic of H. nipponensis will be used as a useful genetic resource for functional and evolutionary studies. Our findings will improve understanding of the molecular mechanisms and heat responses and will be useful for predicting survival of the smelt and its closely related species under global warming.

genetics↗