Biology subjects

Kim, H.

Publications and source records attributed to Kim, H..

At least 37 records · Page 2Linked to original sources

bioRxiv2026

Conditions and properties of non-Mendelian transmission of recombinants in female meiosis

In female meiosis, each of the four chromatids in a tetrad has a 25% chance to be selected for transmission through the pronucleus, realizing Mendel's second law. Here, we characterize a cheating but unselfish behaviour that has documented cases across diverse animal taxa including humans and flies, whereby chromatids with crossovers (COs) have a transmission advantage, resulting in increased production of recombinant offspring. Taking advantage of Drosophila ovarian physiology, we show that this form of meiotic cheating which we call recombinant drive occurs on the autosomes when females are under nutrient stress, potentially as a mechanism for recombination plasticity, while curiously, the effect is suppressed on the X by the distributive system. We explored recombinant drive using simulations and identified unique quantitative signatures that are at odds with several intrinsic properties of linkage. One violation is the production of more offspring with recombinant versus parental allele combinations, which we empirically demonstrated to be possible. Further, we show that recombinant drive can appear to modify CO patterning effectively acting as assurance and interference mechanisms, even when it has no influence on and acts downstream of CO spacing. We discuss the potential benefits and consequences of having a conserved method that can rapidly increase recombination in response to stress, and speculate on a mechanism for the preferential transmission of COs at meiosis II. Overall, our study revealed distinct properties and behaviours of a poorly understood, but potentially widespread, conserved phenomenon and offers avenues for broad detection and mechanistic dissection.

genetics↗

bioRxiv2026

Cross-domain confidence reliability and remappability of frozen single-cell representations

Single-cell foundation models are increasingly adopted for downstream applications such as cell-type prediction. However, these predictions are often utilized without assessing their reliability, or by relying on a simple cutoff applied to the maximum softmax probability (MSP) derived from the classifier. This raises a critical question: can raw MSP be trusted as a reliable measure of confidence on unseen data (target) exhibiting diverse technical and biological variations? To address this, we introduce an audit framework to systematically evaluate the confidence estimates derived from the training set (source) against the realities of the target test set. We demonstrate that raw MSP fundamentally fails to represent true confidence when applied to target datasets. By decomposing the confidence gap between source and target data, we reveal that these discrepancies stem from a combination of rank-ordering errors and systemic probability drift. We further show that the drift can be successfully recalibrated by leveraging a small subset of labeled target data. While this recalibration improves the reliability of automated acceptance, it inherently introduces a trade-off by increasing the volume of cells requiring manual review. Ultimately, our framework establishes that the safe deployment of these models necessitates target-specific confidence adjustment using representative local labels.

bioinformatics↗

bioRxiv2026

Cellular integration of surface and nutrient signals during the early stage of filamentous growth in Saccharomyces cerevisiae

Budding yeast cells can transition from vegetative to filamentous growth under specific environmental stimuli. Saccharomyces cerevisiae has served as a model to understand this process, which is linked to the virulence of many fungal pathogens. One manifestation of filamentation in S. cerevisiae is the formation of pseudohyphal cells, which are elongated and divide in a polarized manner. Here, we established a live-cell imaging assay to monitor this morphogenetic transition and developed a set of fluorescent expression reporters to probe the activity of various signaling pathways during the first 10 hours of this transition. This approach allowed us to identify the stimulus that activates the filamentous growth Mitogen-Activated Protein Kinase (fgMAPK) pathway, which has long evaded identification. Our results indicate that the fgMAPK cascade senses mechanical cues and becomes activated when cells grow on a solid surface. In addition, we have observed that the stimulation of the transcription factor Gln3 regulated by the TOR pathway in low ammonium condition correlates with the elongation of the cells.

cell biology↗

bioRxiv2026

Ancient Somatosensory Circuit Architectures Employ Flexible Molecular Strategies

The extent to which conserved neural circuit architectures depend on shared molecular specification programs remains unclear. Here, we address this question by examining the somatosensory system of the little skate, Leucoraja erinacea, an early-diverging vertebrate that retains ancestral features of both finned and limb-based body plans. We show that core features of somatosensory circuit organization, including laminar organization of the spinal cord and dorsally restricted targeting of sensory afferents, are deeply conserved. Unexpectedly, the molecular programs specifying dorsal root ganglion (DRG) sensory subtypes diverge extensively from those of mammals. Although DRG neuron subtype specification and spinal connectivity rely on target-derived cues, skates employ distinct neurotrophin receptor and transcription factor identity codes. These findings support a model in which conserved spinal circuit architectures provide a stable scaffold that leverages flexible sensory neuron specification programs, enabling the evolutionary diversification of vertebrate somatosensory systems.

neuroscience↗

bioRxiv2026

Phenotype-associated spatial biomarker discovery in spatial transcriptomics with spHOT

Spatial transcriptomics now profiles patient cohorts at single-cell resolution, enabling analysis of disease-associated cell organization in situ. However, discovering such spatial biomarkers remains challenging because relevant structures occur at unknown scales and cell-or niche-level annotations are rarely available. We present spHOT, a deep learning framework that localizes phenotype-associated spatial biomarkers from sample-level labels. spHOT combines spatial foundation model embeddings, a hierarchical domain tree for multi-resolution tissue representation, and a teacher-student multiple instance learning architecture that converts sample labels into cell-level biomarker scores. In controlled simulations and real-tissue benchmarks, spHOT outperformed existing spatial and single-cell methods in localizing ground-truth biomarkers. Across fibrotic, metabolic, and autoimmune disease datasets, spHOT recovered disease-relevant niches and tissue states reported by supervised analyses in the original studies. Cross-disease application of spHOT transferred biomarkers across chronic lung diseases without retraining. spHOT enables scalable, annotation-efficient spatial biomarker discovery in cohort-scale spatial transcriptomics.

bioinformatics↗

bioRxiv2026

Structural proteomics reveals a coagulation-complement accessibility signature of macrovascular invasion in hepatocellular carcinoma

Macrovascular invasion (MVI) and extrahepatic spread (EHS) define the most aggressive, treatment-refractory hepatocellular carcinoma (HCC), yet blood-based markers that report the underlying protein-network biology are lacking. Conventional proteomics measures protein abundance but not the conformational and protein-protein-interaction (PPI) states that govern function. We applied covalent proteome painting (CPP)--a dimethylation-based accessibility assay that reads out binding-site openness--to matched tumor and serum, reasoning that intravascular tumor dissemination remodels plasma protein complexes in a manner detectable as changes in accessibility. Eight treatment-native HCC patients were profiled by CPP using matched FFPE tumor and top-14- depleted serum on a Q Exactive Orbitrap HF. The 85 tumor-serum common proteins defined an 81-protein targeted panel, validated by multiple-reaction-monitoring (MRM) mass spectrometry with heavy stable-isotope-standard peptides (296 peptides; 3,717 light/heavy transition pairs) in 22 FFPE tumors and 22 matched sera. Accessibility was the light/heavy ratio (high, open; low, closed). We assessed differential accessibility, serum-tissue translatability, pathway enrichment, and biomarker/survival performance. Aggressive disease showed broadly decreased protein accessibility. MVI-associated changes were directionally concordant between tumor and serum (Spearman {rho}=0.21; 59% concordant), driven by coagulation and complement proteins (FGG, CTSD, LBP, C4BPA); the EHS axis did not translate. Decreased-accessibility proteins were enriched for complement-coagulation cascades and IGF/IGFBP transport. A six-protein serum accessibility signature discriminated MVI (leave-one-out cross-validated AUC 0.80; best single markers ceruloplasmin 0.83 and haemoglobin- 0.77), and MVI status trended with shorter overall survival (log-rank p=0.06). Accessibility-based serum proteomics captures MVI-associated protein-complex remodeling that abundance assays miss, nominating a coagulation/complement-anchored serum signature for vascular-invasive HCC that warrants prospective validation.

systems biology↗

bioRxiv2026

In vivo reconstruction of the cell lineage history of a developing mouse with DNA Typewriter, from zygote to late organogenesis

The complete cell lineage of C. elegans, mapped over four decades ago, was tractable because the animal is small, transparent, and lineage invariant1. Most animals are none of these, having orders of magnitude more cells, being opaque, and developing with substantial stochasticity2. Since 2016, genome editing-based lineage tracing has opened the door to dense cell lineage reconstruction in such organisms3-8, but delivering on that promise has proven technically challenging. Here we apply DNA Typewriter9-11, a prime editing-based recorder that writes stochastic symbolic insertions to an engineered genomic TAPE in strictly sequential order, to trace mouse development from zygote (E0) to late organogenesis (E13.5). We introduce constructs encoding a prime editor, engineered prime editing guide RNAs (epegRNAs), and Pol-III-driven circularized TAPE RNA (circTAPE) into wildtype zygotes by pronuclear injection (PNI), then assay embryos by single-nucleus transcriptional profiling (sci-RNA-seq3)12 with paired circTAPE recovery. From one E13.5 embryo bearing [~]7 integrations of a constitutively expressed prime editor and 11 integrations of 6-unit circTAPE, we recover [~]1.75M single-nucleus transcriptomes and reconstruct a time-calibrated phylogeny of 1,340,794 annotated cells with parsimony-based node support. The first cell division is marked unequivocally, and although the resulting blastomeres contribute asymmetrically to the embryo proper, they are fate-neutral and serve as internal replicates that reproduce every finding. A modest cohort of pre-gastrulation founders dominates the embryo, with inequality exceeding neutral expectation within one to two cell cycles of founder allocation, yet these founders remain broadly multipotent; a second phase of clonal dominance arises in specific lineages during organogenesis. At the finest scale, sibling cells share cell type 9-fold in excess of chance, reaching 68- to 107-fold for cell types arising from spatially restricted founder pools, while the recent differentiations of organogenesis are legible in the heterotypic structure of terminal clades. From clade co-occurrence alone, we recover germ-layer organization and a dated hierarchy of cell-type couplings with branch points from E8.5 onwards. Finally, by integrating these data with our single-cell time-series of mouse development13, we impute transcriptional states and annotations for the majority of internal nodes and recover established state histories for diverse cell types. All data are made freely available, together with NextCell, an interactive browser for this annotated cellular phylogeny of mouse development from zygote to late organogenesis.

developmental biology↗

bioRxiv2026

A targeted plasma-proteomic axis separates autoimmune thyroid disease from growth-hormone deficiency

Targeted mass spectrometry (multiple-reaction monitoring, MRM) enables reproducible, multiplexed quantification of plasma proteins, but whether a fixed targeted panel can resolve endocrine disorders with overlapping systemic features is unknown. We analyzed a 256-protein targeted panel (1,894 peptides; 3,790 transitions) quantified in 57 participants spanning autoimmune thyroid disease (Hashimotos thyroiditis, n=7; Graves disease, n=5) and growth-hormone deficiency (GHD; partial, n=26; complete, n=19). Protein abundances were obtained by transition summation, log2 transformation, and per-sample median normalization. We applied unsupervised analysis (PCA, PERMANOVA), differential expression (limma), an ordered severity-trend test, and leave-one-out cross-validated classification with feature selection performed strictly inside each fold. All 256 proteins were quantified in every sample (median inter-sample r=0.875). PC1 (36% variance) separated autoimmune thyroid disease from GHD (p=0.016), whereas the global four-group structure was not significant (PERMANOVA p=0.17). No protein reached FDR<0.05, but the autoimmune-versus-GHD contrast was strongly enriched for low p-values (26 proteins at p<0.05; binomial p=5.4x10-4). The signal was biologically coherent: immunoglobulin/B-cell-receptor proteins, including CD79A, were lower, whereas proteasome subunits (PSMC5, PSMC3) and the NF-{kappa}B subunit RELA were higher in autoimmune disease. A cross-validated classifier separated the two classes (AUC 0.72; permutation p=0.05; eight proteins selected in all folds), whereas GHD severity was not predictable (AUC 0.31). A fixed 256-protein targeted panel reproducibly captures an immunoglobulin/B-cell-receptor and proteasome/NF-{kappa}B axis that distinguishes autoimmune thyroid disease from GHD but cannot resolve within-class severity.

systems biology↗

bioRxiv2026

Multiomics profiling of APECED peripheral blood highlights compositional increases in alternatively activated B cell subsets

APECED (Autoimmune PolyEndocrinopathy Candidiasis Ectodermal Dystrophy) is a rare syndrome of multi-organ autoimmunity driven by the presence of self-reactive T cells and autoantibodies caused by mutations in the gene Autoimmune regulator (AIRE). Compared to the well-defined role of AIRE in establishing and maintaining T cell central tolerance, less is known about how AIRE deficiency impacts B cell phenotypes that may contribute to a breakdown in peripheral B cell tolerance. Here we analyzed serum and peripheral blood cells from APECED patients and healthy donors using autoantibody profiling, proteomics, flow cytometry, scRNAseq based subset analysis, BCRseq, and autoantigen binding assays finding significant changes to the APECED B cell compartment. We show that while Naive and Transitional B cells are reduced, alternatively activated B cell subsets are expanded in APECED patients including IgM CD27+ and class switched Atypical B cells which exhibit BCR chain features prone to autoreactivity. Antibodies derived from either APECED or Healthy class switched atypical B cells bind autoantigens at significantly higher rates than control IgG B cells. Serum autoantibodies and proteomics highlight APECED common and patient variable changes. These results together show that APECED causes a compositional shift towards subsets that may promote broken B cell tolerance and autoimmunity.

immunology↗

bioRxiv2026

Locus-Scale Massively Parallel Reporter Assays

Interactions among cis-regulatory elements (CREs) are central to mammalian gene regulation. Long @$$ massively parallel reporter assays (LAMPRAs) integrate combinatorial cloning, molecular barcoding and long- and short-read sequencing, to scalably measure how CRE identities, numbers, spacings, orders, orientations, and interactions shape regulatory output at multi-kilobase length scales. As a proof-of-concept, we assay 36,000 x 5-kb synthetic cis-regulatory loci (sCRLs), each a 5 x 1-kb random combination of enhancers, insulators and spacers, to model how locus composition drives gene expression.

genomics↗

bioRxiv2026

Sex and race shape serum protein biomarkers and bias diagnostic reference intervals

Clinical protein biomarkers--whether measured by FDA-cleared in-vitro diagnostic (IVD) assays or deployed as laboratory-developed tests (LDTs)--are routinely interpreted against fixed, population-agnostic reference intervals. Whether the baseline serum concentrations of these proteins differ systematically by sex and by self-reported race in healthy individuals has not been tested across a broad clinical panel on a single standardized platform. Using scheduled multiple reaction monitoring - mass spectrometry (MRM-MS) with stable-isotope-labelled internal standards, we quantified 87 proteins (39 FDA-cleared analytes; 48 LDT/research markers) in 60 healthy, age-matched donors balanced across three races (White, Hispanic, Black) and both sexes. Sex was a pervasive axis of variation: donors separated by sex in unsupervised multivariate space (PERMANOVA p = 0.020) but not by race (p = 0.14). Three FDA-target proteins differed by sex at FDR q < 0.05--sex hormone-binding globulin, haemoglobin- and albumin--with directions preserved within every race. Race differences were real but protein-specific, exemplified by ancestry-associated CD14. Critically, applying a single pooled 95% reference interval mis-flagged as many as [~]25% of a demographic subgroup as abnormal, versus the 5% expected. Demographic context should therefore be incorporated into reference intervals and decision thresholds for protein-based diagnostics.

molecular biology↗

bioRxiv2026

Unmasking Early Renal Fibrosis in Polycystic Kidney Disease Using Noninvasive Precision Molecular MRI of Collagen

Fibrotic remodeling of extracellular matrix is a central driver of autosomal dominant polycystic kidney disease (ADPKD) progression since early stages of the disease. Unfortunately, it cannot be assessed with currently available methodologies before irreversible structural and functional decline, creating a diagnostic blind spot that hinders accurate early risk stratification and management. Here, we report the development of Gd-hProCA32.Collagen, a collagen -targeted protein MRI contrast agent that enables precision molecular MRI (pMRI) of early fibrosis by directly imaging collagen type I deposition in vivo before conventional laboratory and imaging methods detect changes in kidneys and liver of Pkhd1PCK/PCK (PCK) rats and Pkd2 mutant mice. Gd-hProCA32.Collagen, used at 10-fold lower dose, outperformed the widely clinically used agent gadobutrol (Gadovist), detecting approximately 2.8-fold greater total renal cyst volume ([~]8,500 vs [~]3,000 mm3, p<0.0001) and 1.5-fold higher total cyst count ([~]245 vs [~]160, p<0.0001), with superior T1W and T2W kidney AUC (p<0.01 and p<0.001) and preferential sensitivity to small and medium cysts. Signal enhancement in kidneys and liver correlated strongly with histological collagen burden quantified by Sirius red staining, whereas Gadovist showed no meaningful correlation. Gd-hProCA32.Collagen also enabled in vivo visualization of previously undetectable changes resembling radial striations at sites of microcyst cluster-adjacent microfibrosis and sustained delayed MRI enhancement due to specific collagen binding. These results reveal a previously inaccessible subclinical fibrotic phase of cystic kidney and liver disease and establish collagen-targeted pMRI as a strategy for early noninvasive detection and spatial mapping of multi-organ extracellular matrix remodeling when conventional biomarkers remain non-discriminating. One-sentence summaryWe report a first-in-class collagen-targeted MRI contrast agent with Precision molecular MRI that noninvasively reveals a previously inaccessible subclinical fibrotic phase of polycystic kidney disease across kidney and liver, overcoming limitations of current diagnostic methodology.

molecular biology↗

bioRxiv2026

A targeted mass-spectrometry plasma proteome for simultaneous multi-disease screening

Population health screening is fragmented across dozens of single-condition assays. We asked whether one targeted mass-spectrometry measurement of the plasma proteome could screen simultaneously for many common diseases. Using multiple-reaction-monitoring LC-MS/MS, we quantified 126 proteins (509 peptides) directly in crude plasma from 490 individuals spanning 16 diseases (eight cancers, three inflammatory or renal conditions, and five metabolic and lifestyle disorders) plus age- and sex-matched controls, each protein referenced to a stable-isotope-labelled internal standard. Proteome variation was organised primarily by disease rather than demographics. Cross-validated classifiers detected each disease against matched controls with a mean AUROC of 0.979, a 17-way model identified the specific disease at roughly ten times chance, and a 20-protein subset reproduced full-panel performance. We show that these within-cohort estimates are optimistic upper bounds because each disease was acquired as a separate case-control batch without independent validation. We quantify this, establishing analytical feasibility and defining the validation required for translation.

molecular biology↗

bioRxiv2026

Age-dependent Structural Reorganization of the Human Plasma Proteome

Aging is characterized by progressive physiological decline, yet the molecular mechanisms underlying these changes remain incompletely understood. Although extensive work has examined age-related alterations in protein abundance, the age-dependent structural reorganization of proteins and their interaction networks remains largely unexplored. Here, we quantitatively characterize the structural dynamics of plasma proteins across healthy adult aging and identify age-dependent accessibility patterns that may serve as candidate structural biomarkers. We employed Covalent Protein Painting (CPP) coupled with multiple reaction monitoring (MRM)-based LC-MS/MS to analyze plasma from 24 healthy individuals spanning four age groups (20s to 50s, n = 6 per group). Lysine surface accessibility changes were analyzed using cosine similarity trajectory matching and limma-based linear modeling. The intersection of the two approaches defined five reproducible age-dependent trajectories encompassing 27 proteins and 57 peptides. Integrating STRING/Cytoscape network analysis with AlphaFold3 multimer complex prediction localized several CPP-detected peptides to within [~]5 [A] of predicted protein-protein interaction interfaces (KNG1, C3; REN, ALB; and ALB, FGB), suggesting that age-associated accessibility changes are organized at interaction interfaces rather than occurring as isolated local events. Our findings indicate that the human plasma proteome undergoes coordinated, network-level changes in structural accessibility during adult aging, providing a framework for structure-based biomarker discovery. Because CPP signal reflects both conformational accessibility and protein abundance, and because the cohort is modest and cross-sectional, the trajectories reported here are framed as hypothesis-generating and are interpreted with these constraints made explicit throughout.

molecular biology↗

bioRxiv2026

Microbial mechanistic requirements for eliciting a topical and intranasal immune response

The skin colonist Staphylococcus epidermidis elicits a potent antibody response that can be redirected against an antigen of interest, but this process relies on genetic engineering.1 Here, by adapting bioorthogonal chemistry methods to conjugate antigens to the cell surface, we make the process of generating a commensal vaccine rapid and efficient. A wide variety of bacteria displaying tetanus toxin fragment C (TTFC) elicit an antibody response when applied to mice topically, indicating that the inductive process is not limited to colonists. Colonization occurs at two different sites, the skin and nostril; by colonizing each with S. epidermidis-TTFC, we show that skin colonization yields a moderate IgG response, while nostril colonization elicits a highly potent systemic IgG response and an exuberant IgA response in the nostrils, lungs, and intestine. Two lines of evidence are consistent with the nasal-associated lymphoid tissue (NALT) as the inductive site for nostril colonization: imaging suggesting robust bacterial translocation, and the induction of commensal-specific B cells following colonization. On the skin, TTFC must be conjugated to live S. epidermidis to elicit an antibody response; in the nostrils, live S. epidermidis-TTFC and S. epidermidis mixed with TTFC are equally potent. Commensal vaccination yields a robust response in pet shop mice, and chemical conjugation facilitates antibody responses to a broad array of antigens, including a whole viral capsid and a rotavirus immunogen. Collectively, these findings provide compelling evidence of a translational path for commensal vaccines.

microbiology↗

bioRxiv2026

A pectin-based formulation protects milk fat globule membranes in stored human milk

During household storage, expressed human milk can develop odor and flavor changes that trigger infant refusal and lead caregivers to discard their saved milk supply. We show that typical refrigeration and freezing conditions disrupt the milk fat globule membrane (MFGM), exposing milk lipids to lipases that catalyze hydrolysis and oxidation. A pectin-based formulation (PBF) maintains MFGM integrity during storage and following lipase challenge, suppressing production of glycerol, free fatty acid, and oxylipin byproducts without broadly affecting milk macronutrients, the proteome, and culturable microbial burden. Across an independent cohort of lactating individuals, lipase activity varied but tracked with maternal milk lipase gene expression, implicating endogenous lipolysis in stored-milk deterioration. In a blinded olfactory panel, PBF-treated, lipase-challenged milk smelled more like fresh milk than untreated controls. Together, these findings show that stabilizing the MFGM can protect stored human milk from lipase-driven deterioration, preserve sensory quality, and support use for infant feeding.

biochemistry↗

bioRxiv2026

AI-Informed neoantigen prioritization enables a multi-epitope mRNA/LNP vaccine with antigen-specific immunogenicity and antitumor activity

Personalized neoantigen vaccines are an emerging strategy for cancer immunotherapy, but their effectiveness depends on selecting tumor-specific antigens capable of inducing functional T-cell responses. The VACINUS AI-informed neoantigen prioritization framework previously identified and peptide-validated three immunogenic Tier 1 neoantigens in the B16F10 melanoma model. In this study, we extended that framework by translating these validated neoantigens into a multi-epitope messenger RNA vaccine formulated with lipid nanoparticles and evaluating its preclinical immunogenicity and antitumor activity. The three VACINUS-prioritized B16F10 neoantigens were encoded within a single multi-epitope construct, BF-V1_27-Ser, and formulated to generate BF-RNA-P. In B16F10 tumor-bearing mice, BF-RNA-P induced neoantigen-specific CD8+T-cell responses, with the strongest response directed against the B16F10-1-4 epitope. Combination with anti-PD-1 further enhanced vaccine-induced CD44+IFN-{gamma}+ CD8+ T-cell activation, whereas anti-PD-1 alone did not induce detectable peptide-specific responses. BF-RNA-P also suppressed tumor growth in vivo, and combination treatment produced the strongest antitumor effect, reflected by reduced tumor volume and lower endpoint tumor burden. Together, these findings demonstrate that VACINUS-prioritized and peptide-validated neoantigens can be reformatted into a multi-epitope messenger RNA/lipid nanoparticle vaccine while retaining antigen-specific immunogenicity and antitumor activity. This study provides preclinical proof-of-concept for integrating AI-informed, TCR-aware neoantigen prioritization with messenger RNA/lipid nanoparticle delivery as a translational strategy for personalized cancer vaccine development.

immunology↗

bioRxiv2026

A dual-function regulatory element couples ParB expression and DNA substrate specificity

Chromosome segregation is essential for cell survival. Most bacteria encode the chromosome partitioning ParABS system. Although even small changes in ParA or ParB levels disrupt genome maintenance, the mechanisms that control their abundance have remained unresolved. Using Caulobacter crescentus, we provide the first mechanistic evidence that ParB levels are regulated post-transcriptionally. Through single-nucleotide substitutions and compensatory mutation analyses, we identify an mRNA secondary structure at the 5' end of the parB transcript that enhances ParB cellular abundance. Loss of this regulatory mechanism sensitizes cells to modest increases in ParA levels, causing cell death. Additionally, we demonstrate that ParB substrate specificity is not determined solely by the central helix-turn-helix domain that interacts with parS but is unexpectedly modulated by the N-terminal domain. Together, our findings reveal an uncharacterized layer of chromosome segregation control and highlight post-transcriptional regulation of ParB abundance as a potential mechanism for maintaining the precise ParA-ParB balance required for bacterial viability.

microbiology↗