Search bioRxiv⌕ Search

Biology subjects

Niu, K.

Publications and source records attributed to Niu, K..

10 recordsLinked to original sources

METEOR: joint genome-scale reconstruction and enzyme prediction

MotivationCurrent machine learning methods for enzyme function prediction primarily treat proteins as independent entities, ignoring the metabolic context in which they operate. This reductionist approach often generates biologically implausible annotations that fail to satisfy stoichiometric or thermodynamic constraints. While genome-scale metabolic models (GEMs) enforce systemic coherence, traditional reconstruction workflows decouple functional annotation from network assembly, resulting in information loss during the discretization of enzymatic evidence. ResultsWe developed METEOR, a framework that integrates continuous confidence scores from deep learning models directly into a Mixed-Integer Linear Programming (MILP) formulation. By conditioning predictions on global metabolic requirements, METEOR resolves functional ambiguities where sequence signals are weak. Evaluation on the Price-149 dataset shows that our method yields physiologically viable networks capable of sustaining growth and improve protein-level predictions over baseline methods. Validation on 6,894 bacterial genomes reveals that system-aware refinement increases the recall of experimentally observed phenotypes substantially. Furthermore, we show that constraint-driven selection can still improve annotation performance in highly incomplete genomes. Our results suggest that functional annotation should be treated as a unified inference problem where global system constraints supervise local predictions. AvailabilityMETEOR is freely available at https://github.com/bio-ontology-research-group/Meteor Contactrobert.hoehndorf@kaust.edu.sa Supplementary informationSupplementary data are available at Bioinformatics online.

bioinformatics↗

Therapeutic Potential of a Tectorigenin Derivative (TED) in Herpetic Stromal Keratitis: Antiviral and lmmunomodulatory Mechanisms

ObjectivesIn this study, the anti-HSV-1 effects of TED were investigated in vitro and in vivo, its therapeutic efficacy against herpetic stromal keratitis (HSK) was evaluated, and its mechanism of action was examined. MethodsWe assessed the cytotoxicity and anti-HSV-1 activity of TED in Vero cells using CCK-8 and plaque assays. The HSK model mice received TED (2.5, 5, or 15 mg/kg), and symptom progression was monitored. The therapeutic effects were evaluated through HE staining, corneal immunofluorescence, and HSV-1 gB quantification. Mechanistic studies were performed to examine the expression of TLR pathway genes, CD4+/CD8+ T-cell infiltration in the cornea and draining lymph nodes, and dendritic cell activation. ResultsTED showed potent anti-HSV-1 activity in vitro and ameliorated HSK in mice, improving body weight and reducing corneal pathology and the incidence of encephalitis. It decreased HSV-1 loads in the cornea, trigeminal ganglion, and brain while modulating cytokines (downregulating IFN-/{gamma}, TNF-, and IL-1{beta} and upregulating IL-10). TED suppressed the TLR pathway (TLR2/3/9, TRAF6, IRF3, and NF-{kappa}B) in the corneal epithelium and reduced CD4+/CD8+ T-cell and dendritic cell infiltration while increasing the number of CD4+ T cells in the lymph nodes. ConclusionsTED has significant anti-HSV-1 activity and effectively treats HSK by reducing viral loads, improving symptoms, and modulating immune responses through TLR pathway inhibition and immune cell regulation, suggesting its potential as an HSK therapeutic.

pharmacology and toxicology↗

Discovery of a wide variety of α-1,6-cyclized β-1,2-glucan synthases: a new entrance for host-microbe interactions.

-1,6-Cyclized {beta}-1,2-glucans (C{beta}G) are established virulence factors in Xanthomonas, yet functional breadth and distribution of C{beta}Gs in nature have remained unclear. Here, we biochemically identified enzymes synthesizing C{beta}Gs with specific chain lengths, exhibiting potential natural occurrence of various C{beta}Gs. Structural analyses identify subtle variations in a loop, named Loop X, as a key determinant of product size, leading to understanding of the whole picture of the mechanism that controls the sizes. We further demonstrated that C{beta}G composed of 13 glucose units contributes to plant-virulence in Ralstonia pseudosolanacearum, expanding the functional scope of virulence-associated cyclic glucans. Overall, it provides the potential targets for regulating various plant-microbe interactions and also serves as a vital lead to discovering unknown host-microbe interactions with significant potential for agricultural applications.

biochemistry↗

Poxvirus A52 is a host range factor for modified vaccinia virus Ankara (MVA) and promotes viral replication by disturbing the formation of autolysosomes

Many members of the poxvirus family are important zoonotic pathogens that pose a significant threat to human and animal health worldwide. Autophagy is a multi-step degradation pathway within cells, and one of its primary biological functions includes the clearance of invading viruses. Nevertheless, the interplay between poxviruses and host cell autophagy has not been fully elucidated. Here, we demonstrate that vaccinia virus (VACV) and lumpy skin disease virus (LSDV) induce incomplete autophagy and inhibit the fusion of autophagosomes and lysosomes, while modified vaccinia virus Ankara (MVA), an attenuated strain of VACV unable to replicate in almost all human cells, does not. Additionally, we screened and identified the VACV protein A52 as a key factor that obstruct the formation of autolysosomes. Mechanistically, A52 interacts with SNAP29 and inhibits its interaction with STX17 and VAMP8, both of which are binding partners of SNAP29 and are essential for complete autophagy. Moreover, A52 promotes the proteasomal degradation of SNAP29, which facilitates viral replication. We further revealed that SNAP29 functions as a restriction factor for MVA, as the suppression of SNAP29 allowed the replication of MVA in human cells. In summary, our data present a molecular mechanism by which poxviruses manipulate the cellular autophagic machinery and provide additional explanation for the restriction of MVA in human cells.

microbiology↗

DeepGOMeta: Predicting functions for microbes}

Analyzing microbial samples remains computationally challenging due to their diversity and complexity. The lack of robust de novo protein function prediction methods exacerbates the difficulty in deriving functional insights from these samples. Traditional prediction methods, dependent on homology and sequence similarity, often fail to predict functions for novel proteins and proteins without known homologs. Moreover, most of these methods have been trained on largely eukaryotic data, and have not been evaluated or applied to microbial datasets. This research introduces DeepGOMeta, a deep learning model designed for protein function prediction, as Gene Ontology (GO) terms, trained on a dataset relevant to microbes. The model is validated using novel evaluation strategies and applied to diverse microbial datasets. Data and code are available at https://github.com/bio-ontology-research-group/deepgometa

bioinformatics↗

DNA 5-methylcytosine regulates genome-wide formation of G-quadruplex structures

G-quadruplex structures (G4s) have been identified in genomes of multiple organisms and proven to play important epigenetic regulatory roles in various cellular functions. However, the G4 formation mechanism remains largely unknown. Here, we found a negative correlation between DNA 5mC methylation and G4 abundance. The abundance of genomic G4s significantly increased when the whole-genome methylation level was reduced in DNMT1-knockout cells. This increase was then suppressed by DNMT1 over-expression. And more G4s were detected in the hypomethylated cancer cell line HepG2 and rectal cancer tissues. Besides, 5mC modification significantly inhibited G4 formation of the potential G-quadruplex sequences (PQSs). The transcription of genes with 5mC modification sites in their promoter PQSs was affected after treatment with G4 stabilizer pyridostatin or methylation inhibitor 5-aza-dC. The global reduction of genomic methylation elevates gene transcription levels through increased G4s. Taken together, DNA 5mC methylation prevents PQSs from folding into G4s in genomes.

molecular biology↗

Human FAM111A inhibits vaccinia virus replication by degrading viral uncoating factor I3 and is antagonized by poxvirus host range factor SPI-1

Poxviruses are large double-stranded DNA viruses that infect a wide range of animals including humans. Since the eradication of smallpox, other members of the poxvirus family, such as monkeypox virus (MPXV) are still posing a great threat to public health. Vaccinia virus (VACV) is a prototypic poxvirus used as the vaccine strain for smallpox eradication. VACV encodes a serine protease inhibitor 1 (SPI-1) conserved in all orthopoxviruses, which has been recognized as a host range factor for modified vaccinia virus Ankara (MVA), an approved smallpox vaccine and a promising vaccine vector. FAM111A, a nuclear protein that regulates host DNA replication, was shown to restrict the replication of VACV-{Delta}SPI-1 in human cells. Nevertheless, the detailed antiviral mechanisms of FAM111A were unresolved. Here, we show that FAM111A is a potent restriction factor for VACV-{Delta}SPI-1 and MVA. Deletion of FAM111A rescued the replication of MVA and VACV-{Delta}SPI-1 and overexpression of FAM111A significantly reduced viral DNA replication and virus titers but did not affect viral early gene expression. The antiviral effect of FAM111A necessitated its trypsin-like protease domain and DNA binding domain but not the PCNA-interacting motif. We further discovered that FAM111A translocated into the cytoplasm upon VACV infection and this process was mediated by the cGAS-STING signaling pathway. Infection-triggered FAM111A degraded the nuclear pore complex via its protease activity, translocated to the cytoplasm, and interacted with and promoted the degradation of virus DNA binding protein I3 in a DNA-dependent manner. Interestingly, the protease activity of FAM111A was only needed for nuclear export but not I3 degradation as further analysis showed I3 was degraded through autophagy. Moreover, VACV SPI-1 was found primarily in the nucleus of infected cells and antagonized FAM111A by prohibiting its nuclear export. MPXV and lumpy skin disease virus SPI-1s also inhibited human FAM111A. Our findings reveal the detailed mechanism by which FAM111A functions to restrict a cytoplasmic DNA virus and provide explanations for the immune evasive function of VACV SPI-1.

microbiology↗

A new species of Nanhsiungchelys (Testudines: Cryptodira: Nanhsiungchelyidae) from the Upper Cretaceous of Nanxiong Basin, China, and the role of anterolateral processes on the carapace in drag reduction

Nanhsiungchelyidae are a group of large turtles that lived in Asia and North America during the Cretaceous. Here we report a new species of nanhsiungchelyid, Nanhsiungchelys yangi sp. nov., from the Upper Cretaceous of Nanxiong Basin, China. This is the second valid species of Nanhsiungchelys, and the holotype consists of a well-preserved skull and lower jaw, as well as the anterior parts of the carapace and plastron. The diagnostic features of Nanhsiungchelys include a huge estimated body size (~55.5 cm), a special network of sculptures on the surface of the skull and shell, weak cheek emargination and temporal emargination, deep nuchal emargination, and a pair of anterolateral processes on the carapace. However, Nanhsiungchelys yangi differs from the other species of Nanhsiungchelys in having a triangular-shaped snout and wide anterolateral processes. A phylogenetic analysis of nanhsiungchelyids places Nanhsiungchelys yangi and Nanhsiungchelys wuchingensis as sister taxa. Some nanhsiungchelyids bear special anterolateral processes on the carapace, which are unknown in extant turtles. Here we test the function of these processes in Nanhsiungchelys yangi using computational fluid dynamics, and the results suggest these processes could enhance locomotory performance by remarkably reducing drag force when the animal was swimming through water.

paleontology↗

Precision engineering of the transcription factor Cre1 in Hypocrea jecorina (Trichoderma reesei) for efficient cellulase production in the presence of glucose

In Trichoderma reesei, carbon catabolite repression (CCR) significantly downregulates the transcription of cellulolytic enzymes, which is usually mediated by the zinc finger protein Cre1. It was found that there is a conserved region at the C-terminus of Cre1/CreA in several cellulase-producing fungi that contains up to three continuous S/T phosphorylation sites. Here, S387, S388, T389, and T390 at the C-terminus of Cre1 in T. reesei were mutated to valine for mimicking an unphosphorylated state, thereby generating the transformants Tr_Cre1S387V, Tr_Cre1S388V, Tr_Cre1T389V, and Tr_Cre1T390V, respectively. Transcription of cel7a in Tr_ Cre1S388V was markedly higher than that of the parent strain when grown in glucose-containing media. Under these conditions, both filter paperase (FPase) and p-nitrophenyl-{beta}-D-cellobioside (pNPCase) activities, as well as soluble proteins from Tr_Cre1S388V were significantly increased by up to 2- to 3-fold compared with that of other transformants and the parent strain. To our knowledge, this is the first report demonstrating an improvement of cellulase production in fungal species under CCR by mimicking dephosphorylation at the C-terminus of Cre1. Taken together, we developed a precision engineering strategy based on the modification of phosphorylation sites of Cre1 transcription factor to enhance the production of cellulase in fungal species under CCR.

bioengineering↗

Epigenetic Drift of H3K27me3 in Aging Links Glycolysis to Healthy Longevity

Epigenetic alteration has been implicated in aging. However, the mechanism by which epigenetic change impacts aging is unclear. H3K27me3, a highly conserved histone modification signifying transcriptional repression, is marked and maintained by Polycomb Repressive Complexes (PRCs). Here, we explore the mechanism by which age-modulated increase of H3K27me3 impacts adult lifespan. Using Drosophila, we reveal that aging leads to loss of fidelity in epigenetic marking and drift of H3K27me3 and consequential reduction in the expression of glycolytic genes with negative effects on energy production and redox state. Moreover, we show that a reduction of H3K27me3 by PRCs-deficiency promotes glycolysis and healthy lifespan. While perturbing glycolysis by gene mutation diminishes the pro-lifespan benefits mediated by PRCs-deficiency, transgenic increase of glycolytic genes in wild-type animals extends longevity. Together, we propose that epigenetic drift of H3K27me3 defines a new aging mechanism and that stimulation of glycolysis promotes metabolic health and longevity.

molecular biology↗