Biology subjects

CHEN, H.

Publications and source records attributed to CHEN, H..

6 recordsLinked to original sources

bioRxiv2026

A brain-tumour axis links chronic stress to gastric cancer progression through NPY signalling

Chronic stress promotes gastric tumour growth, but the central neural pathways remain largely enigmatic. Here, we identify a brain-tumour axis, implicating the central amygdala (CeA) activity in promoting gastric cancer growth through sympathetic neuropeptide Y (NPY) signalling occurring within the tumour. Using clinical datasets, patient samples, pathway tracing, electrophysiology and chemogenetic manipulation, we demonstrate that stress selectively increases NPY Y1 receptor (NPY1R) synthesis in the patients gastric cancer tissue; moreover, the NPY1R density correlates with advanced cancer stage and poor prognosis. In mice, daily constraint chronic stress enhances CeA excitability and promotes sympathetic neurotransmitter norepinephrine release within the tumour microenvironment. Norepinephrine, in turn, increases tumour endogenous NPY/NPY1R production and the activation of downstream MAPK/Erk1/2 signalling pathway, which drives cancer cell proliferation and invasion. Manipulating CeA neuronal activity alone can regulate tumour growth, whereas selectively blocking tumour NPY1R prevents stress-induced tumour progression in vivo and cancer cell migration in vitro. This study identifies a central-to-peripheral circuit linking chronic stress to gastric cancer growth, and highlights NPY1R as a potential therapeutic target.

Cancer Biology↗

bioRxiv2025

Architecture and mechanism of a dual-enzyme retron system in prokaryotic immunity

Retrons are bacterial genetic retroelements encoding a reverse transcriptase (RT) and a non-coding RNA (ncRNA)-multi-copy single-stranded DNA (msDNA) hybrid. Diverse effector proteins or domains are found to associate with retrons, typically forming tripartite toxin-antitoxin systems involved in anti-phage defense. Although retrons have attracted growing interest in genome editing technologies, the mechanisms underlying most retron-mediated immune systems remain poorly understood. Here, we characterized a distinct quaternary retron system, Ec78, harboring a dual-enzymatic effector complex, in which the PtuA ATPase and PtuB nuclease act in concert to mediate phage clearance. The cryo-EM structure of the Ec78 complex adopts a flower-basket-like architecture, with two Ec78 retrons engaging the PtuAB effector complexes through a unique msDNA-insertion assembly mechanism. Interestingly, a sensing loop on the RT protein tightly monitors the length of the msDNA, which is likely responsible for phage detection and the subsequent release of the toxic effector complex. We further determined the cryo-EM structure of the retron-unbound effector complex, revealing an arginine-lysine finger loop on the PtuB nuclease that undergoes an ordered-to-disordered transition for enzymatic activation. Together, our work not only delineates the molecular basis underlying the Ec78 system in antiviral defense but also highlights the mechanistic diversity of retron systems in prokaryotic immunity.

biochemistry↗

bioRxiv2025

RIPK3-dependent sequential recruitment of MLKL and RIPK1 drives PANoptotic cell death and chemokine production

PANoptosis, an immunogenic programmed cell death (PCD) modality, integrates features of pyroptosis, apoptosis, and necroptosis through assembly of the PANoptosome complex. Despite its conceptualization as a distinct PCD form, PANoptosis remains controversial due to insufficient characterization of its morphological hallmarks and molecular regulation. This study aimed to investigate the molecular mechanisms underlying the assembly of PANoptosomes in the PANoptotic pathway. We identified a novel receptor-interacting protein kinase 3 (RIPK3)-initiated PANoptotic pathway that functions without pattern recognition receptors (PRRs) and the ASC (apoptosis-associated speck-like protein containing a CARD) inflammasome. Using multimodal imaging and biochemical approaches, we identify unique morphological signatures distinguishing PANoptotic cells from canonical pyroptotic, apoptotic, or necroptotic counterparts. Mechanistically, RIPK3 forms round homopolymeric scaffolds--distinct from necroptotic amyloid-like fibers--to sequentially recruit MLKL and RIPK1, forming a dynamic RIPK3-MLKL-RIPK1-FADD-caspase-8 complex (RIPK3-PANoptosome). This platform coordinates concurrent activation of pyroptotic, apoptotic, and necroptotic effectors. Cross-regulatory interactions between these pathways establish a homeostatic system where perturbations bias death modality into a certain cell death type, altering the death process and outcomes. Functionally, PANoptotic cells orchestrate chemokine secretion through parallel kinase-dependent (RIPK3-MLKL) and kinase-independent (RIPK1-IKK-NF-{kappa}B) mechanisms, driving macrophage recruitment. Our findings resolve the molecular logic of PANoptosome assembly, redefine PANoptosis as a tunable PCD paradigm, and establish its role in immunomodulation, providing a framework for targeting inflammatory cell death in disease.

cell biology↗

bioRxiv2023

The exotic thymidine modification 5-hydroxymethyluridine in dinoflagellate Amphidinium carterae

Dinoflagellate chromosomes are extraordinary, as their organization is independent of architectural nucleosomes unlike typical eukaryotes and shows a cholesteric liquid crystal state. 5-hydroxymethyluridine (5hmU) is present at unusually high levels and its function remains an enigma in dinoflagellates chromosomal DNA. Here, we demonstrate that 5hmU exhibits content variations in different dinoflagellates and is generated at the poly-nucleotide level through hydroxylation of thymidine. Importantly, we identified the enzyme, which is a putative dinoflagellate TET/JBP homologue, catalyzing 5hmU production using either in vivo or in vitro biochemical assay. Based on the near-chromosomal level genome assembly of dinoflagellate Amphidinium carterae, we depicted a comprehensive 5hmU landscape and found that most 5hmU peaks share a conserved TG-rich motif, and are significantly enriched in repeat elements, which mark partially overlapping regions with 5-methylcytosine (5mC) sites. Moreover, inhibition of 5hmU via dioxygenase inhibitor leads to transcriptional activation of 5hmU-marked transposable elements (TEs), implying that 5hmU appears to serve as epigenetic marks for silencing retrotransposon. Together, our results revealed the biogenesis, genome-wide landscape and molecular function of dinoflagellate 5hmU, providing mechanic insight into the function of this enigmatic DNA mark.

molecular biology↗

bioRxiv2021

Two interacting transcriptional coactivators cooperatively control plant immune responses

The phytohormone salicylic acid (SA) plays a pivotal role in plant defense against biotrophic and hemibiotrophic pathogens. Genetic studies have identified NPR1 and EDS1 as two central hubs in plant local and systemic immunity. However, it is unclear how NPR1 orchestrates gene regulation and whether EDS1 directly participates in transcriptional reprogramming. Here we show that NPR1 and EDS1 synergistically activate Pathogenesis-Related (PR) genes and plant defenses by forming a protein complex and co-opting with Mediator. In particular, we discover that EDS1 functions as an autonomous transcriptional coactivator with intrinsic transactivation domains and physically interacts with the CDK8 subunit of Mediator. Upon SA induction, EDS1 is directly recruited by NPR1 onto the PR1 promoter via physical NPR1-EDS1 interactions, thereby potentiating PR1 activation. We further demonstrate that EDS1 stabilizes NPR1 protein and NPR1 transcriptionally upregulates EDS1 in plant-pathogen interactions. Our results reveal an elegant interplay of key coactivators with Mediator and elucidate novel molecular mechanisms for activating transcription during immune responses.

plant biology↗

bioRxiv2020

METTL5, an 18S rRNA-specific m6A methyltransferase, modulates expression of stress response genes

RNA N6-methyladenosine (m6A) modification is present in different RNA molecules, including protein-coding mRNAs and non-coding RNAs such as ribosomal RNAs (rRNAs). Previous studies identified m6A in both the 18S and 28S rRNAs, but the roles of these methylation events are poorly understood due to the lack of knowledge of the responsible methyltransferases. Here, we report that mammalian METTL5, a member of a highly conserved methyltransferase family, specifically methylates adenosine 1832 (A1832) in the 18S rRNA in vivo and in vitro. We identify TRMT112 as a near stoichiometric partner of METTL5 important for the enzymatic activity of METTL5. By mapping the positions of translating ribosomes (Ribo-seq), we found translation of multiple stress response-related mRNAs, including Atf4 mRNA, is selectively reduced in the Mettl5 knockout (KO) mouse B16 melanoma cells. Atf4 is a key transcription factor that mediates the Integrated Stress Response (ISR), as exemplified by the Endoplasmic Reticulum (ER) stress. Consistently, transcription of ISR effector genes is reduced in Mettl5 KO cells during ER stress, suggesting a compromised ISR. Our findings reveal a new mechanism that regulates expression of stress response genes and suggest that chemical modifications of ribosomal RNAs may play a key role in selectively impacting translation and possibly ISR.

biochemistry↗