Protein & Cell

PUF60 is a splicing factor related to the polypyrimidine-tract binding protein U2AF2. PUF60 is deleted in developmental disorders such as Verheij syndrome and amplified in approximately 8% of cancers. Thus, both increases and decreases in PUF60 expression can have profound physiological effects. However, little is known about how changes in PUF60 expression impact global splicing patterns. Here, we created a model system of CRISPRa/i in mouse stem cells (mESCs) to transcriptionally upregulate or downregulate Puf60. Our results uncovered extensive transcriptional, post-transcriptional, and post-translational regulation of Puf60 protein expression. We observed that Puf60 protein levels in normal mESCs drop dramatically at a critical cell density, leading to cell death. Puf60 is very essential in stem cells, and its repression causes cell death and impacts specific splicing events, including its own splicing autoregulation, providing valuable insights into the functional consequences of PUF60 dysregulation. Analysis of phosphoprotein data revealed phosphorylation of threonine at the N-terminus of PUF60. Our results showed that mutating threonine to glutamate downregulates the protein and alters its localization. Thus, our study reveals a novel regulatory mechanism of Puf60 phosphorylation that mediates its function and may be related to its frequent overexpression in cancer cells.

Oncolytic virotherapy is an innovative approach to cancer treatment that uses replication-competent viruses to selectively target and destroy cancer cells while leaving healthy tissues largely unaffected. Zika virus (ZIKV), a neurotropic orthoflavivirus, has recently gained attention as a potential oncolytic agent due to its ability to infect neural-derived cells and suppress tumor growth in preclinical models. Although existing studies have examined ZIKVs oncolytic effects, the mechanisms underlying these effects remain largely unexplored. Additionally, the roles of individual ZIKV proteins and their interactions with host factors remain incompletely understood. Here, we used RNA sequencing, affinity purification-mass spectrometry, and functional assays to uncover previously unidentified mechanisms underlying ZIKVs oncolytic activity in pediatric neural tumors. We found that the ZIKV non-structural proteins NS4A and NS5 exert oncolytic effects, reducing tumorsphere size. ZIKV-host protein-protein interaction networks were characterized and showed that integrin 3 (gene: ITGA3), a mediator of cell-matrix adhesion, interacts with ZIKV NS2B and NS4A. Integrin 3 was further shown to be involved in ZIKV- and NS4A-induced tumorsphere size reduction, while ITGA3 knockdown and ZIKV infection additively inhibited 3D invasion. These findings provide critical mechanistic insights that could inform the rational design of ZIKV-based virotherapies and highlight opportunities for combination treatment strategies.

Translation efficiency remains a major limitation for RNA therapeutics. Conventional optimization targets the 5 untranslated region (5 UTR), while the 3 UTR is viewed mainly as a stabilizing element. Here, we demonstrate that the 3 UTR can be rationally engineered to actively enhance translation. Using an intracellular directed-evolution platform based on the SINEB2 element, we identified RNA modules P51 and its compact variant P51t3,which markedly increased protein output without affecting mRNA levels. P51t3 consistently boosted expression two- to six-fold across plasmid, in vitro transcribed mRNA, and recombinant AAV systems. Mechanistic studies revealed that P51t3 binds ribosomal protein RPL39, recruiting 60S subunits to the initiation site through the natural closed-loop translation model. By integrating evolutionary selection with 3 UTR design, this work redefines the 3 UTR as an active translational enhancer and provides a broadly applicable regulatory element for next-generation mRNA and gene-delivery therapeutics.

H3K27ac and H3K4me3 are enriched at transcriptional start sites and have been implicated in transcription. However, how these marks concertedly regulate transcription is not fully understood. Here, we developed a dual chemically inducible CRISPR/dCas9-based epigenome editing system that enables independent, temporal and transcription stage-specific modulation of H3K27ac and H3K4me3 at a specific gene locus. Stage-specific removal of H3K4me3 impaired RNA polymerase II recruitment, increased promoter-proximal pausing, reduced productive elongation, and accelerates mRNA decay via increased m6A deposition. Losing both H3K27ac and H3K4me3 rapidly abolished transcriptional activity, while preserving H3K4me3 without H3K27ac can partially sustain transcription. These findings revealed a functional hierarchy and interdependence between H3K27ac and H3K4me3 in different transcription stages and the established versatile tool will contribute to the functional dissection of the temporal dynamics of chromatin modifications in gene regulation.

The Rcs phosphorelay regulates gene expression in response to cell envelope stress and is critical for the virulence of pathogenic bacteria, including Klebsiella pneumoniae, due to its regulation of genes related to extracellular capsule, cell division, and motility. The RcsC histidine kinase, RcsD phosphotransfer protein and RcsB response regulator, which form the core of the Rcs phosphorelay, are negatively regulated by the unique inner membrane protein IgaA via interaction with RcsD. An outer membrane lipoprotein, RcsF, activates signaling by interaction with IgaA, but the precise activation mechanisms remain unclear. In this study, we determined the structures of IgaA and the IgaA/RcsF complex using Cryo-electron microscopy (Cryo-EM). We also determined the structures of RcsC and RcsD, which both form homodimers stabilized by hydrophobic interactions, creating ladder-like structures. Combining the Cryo-EM structures, AlphaFold3 structure predictions of IgaA/RcsD and RcsF/IgaA/RcsD, and genetic studies, we describe a model for how RcsF modifies the IgaA/RcsD interaction, lifting negative regulation and activating the Rcs phosphorelay. Our findings provide a high-resolution depiction of the Rcs stress response system and suggest potential targets for small molecule inhibitors.

TAR DNA-binding protein 43 (TDP-43) is a multifunctional DNA/RNA-binding protein implicated in transcriptional and post-transcriptional regulation. Dysregulation of TDP-43 is closely correlated with human diseases such as cancer and neurodegenerative diseases. Although its roles in RNA metabolism are well characterized, its function in transcriptional regulation remains largely underexplored. DNA G-quadruplexes (dG4s) are non-canonical nucleic acid structures enriched at gene promoters and regulatory elements, where they facilitate chromatin looping and gene transcription. Here, we investigated the transcriptional regulatory role of TDP-43 by integrating multi-omics datasets, including Hi-C, dG4 ChIP-seq, TDP-43 ChIP-seq, RNA-seq and ATAC-seq from K562 and HepG2 cells. Our analyses demonstrate TDP-43 binding and dG4s formation are highly colocalized at chromatin loop anchors, particularly at promoter and enhancer regions. TDP-43 occupancy at these anchors correlates with increased dG4 stability, chromatin loop interaction frequency, elevated chromatin accessibility, and upregulated gene expression. Morover, TDP-43 knockdown in HepG2 cells revealed a significant reduction in dG4 formation and loop interaction strength, accompanied by widespread transcriptional dysregulation. Collectively, our findings highlight a novel regulatory role of TDP-43 in facilitating long-range chromatin interactions and transcriptional activation through binding to and stabilizing dG4 structures, providing a mechanistic basis for gene dysregulation driven by TDP-43 dysfunction in diseases.

Mitochondria and lipid droplets (LDs) are functionally coupled to coordinate fatty acid utilization and storage. However, a comprehensive understanding of mitochondria-LD alliances remains elusive. We have identified a previously unrecognized role for optical atrophy 1 (OPA1), a mitochondrial fusion factor, in the regulation of fatty acid release from LDs. We demonstrated that OPA1s exon 4 adapts an amphipathic helix to target OPA1 to LDs. OPA1 localized to LDs promote fatty acid release by facilitating the recruitment of lipases to LDs. In addition, OPA1s residence on LDs competes with its mitochondrial entry, influencing mitochondria fusion and connectivity. Furthermore, the S158N polymorphism within OPA1s exon 4 exhibiting attenuated fatty acid release from LDs is associated with changes in metabolic traits in pediatric cancer survivors. Altogether, our findings reveal that OPA1 actively mediates fatty acid release from LDs and provide a mechanistic link between OPA1 and human metabolism.

Heterogeneous nuclear ribonucleoprotein U (HNRNPU) deficiency is a rare genetic cause of neurodevelopmental disorders (NDDs) lacking targeted therapies. Here, we developed a transcriptomic-guided compound prioritization pipeline using Connectivity Map (CMap) analysis on multi-model transcriptomic signatures from HNRNPU-deficient human cells and mouse models. Ten compounds were selected through manual curation and functionally screened in patient-derived HNRNPU-deficient neuroepithelial stem (NES) cells with earlier observed cellular phenotypes. Two of the compounds, AS601245 and Lenalidomide, significantly reduced the elevated neural progenitor population during differentiation, and their combination further decreased primary cilia incidence, indicating partial rescue of the patient-specific cellular phenotypes. To understand the mechanisms underlying the partial rescue, we employed proteome integral solubility alteration (PISA) and expression proteomics. PISA assay identified TMEM150C and GSK3A as proximal targets of combined treatment. Additionally, we observed reversal of multiple biological pathways including downregulation of Wnt signalling and upregulation of mitochondrial pathways and transmembrane proteins. Altogether, we established a computational-experimental pipeline for transcriptomic-guided drug repurposing for a monogenic NDD, and demonstrated that the network-level modulation partially rescues the delayed neural differentiation in HNRNPU-deficient neural cells.

Acetylation of histone H3 regulates chromatin dynamics and transcription, but how specific acetylation sites affect RNA polymerase II (RNAPII) transcription through nucleosomes remains unclear. Here, we found that H3 acetylation at Lys56 and Lys122 markedly enhances RNAPII transcription through nucleosomes, whereas acetylation at Lys64 has little effect. To elucidate the structural basis for these functional differences, we determined cryo-electron microscopy (cryo-EM) structures of nucleosomes bearing site-specific acetylation at H3K56, H3K64, or H3K122. The cryo-EM structures revealed that H3K56ac and H3K122ac locally weaken histone-DNA interactions at the DNA entry/exit region and near the dyad, respectively, while H3K64ac induces no detectable structural changes. These structural differences correlate with the observed transcriptional outcomes, indicating that acetylation at H3K56 and H3K122, but not H3K64, alleviates the nucleosomal barrier to RNAPII progression. Our findings provide direct structural evidence that specific acetylations within the histone fold domain of H3 finetune nucleosome dynamics to facilitate RNAPII transcription.

Head and neck squamous cell carcinoma (HNSCC) ranks as the seventh most common cancer, with increasing incidence and mortality rates and limited therapeutic progress. The heterohexameric prefoldin complex, a highly conserved co-chaperone assembly composed of six PFDN subunits, exhibits expression levels strongly correlated with cancer progression. Among these subunits, the PFDN5 gene presents a paradoxical role in cancer biology, demonstrating both tumor-promoting and tumor-suppressive activities. Notably, the PFDN5 gene generates two distinct protein isoforms through alternative splicing, yet their individual contributions to cancer remain unexplored. In this study, we reveal that an elevated short-to-long PFDN5 alternative splice variants ratio is significantly associated with improved overall survival in HNSCC patients. Using proximity-dependent biotin identification (BioID), we mapped shared and isoform-specific protein-protein interaction networks for PFDN5. Our analysis uncovered novel proximal interactors, implicating PFDN5 isoforms in unexpected functions, including spindle organization, transcriptional complexes, and NF-{kappa}B signaling. These results provide a foundation for exploring PFDN5 isoforms as potential therapeutic targets in HNSCC.

Mixed-lineage leukemia translocated to 3 (MLLT3) is vital for maintaining the stemness of hematopoietic stem cells. Loss of MLLT3 in megakaryocyte (MK)-erythrocyte progenitor (MEP) cells leads to its differentiation into MKs. Despite its significance in stemness, the regulatory mechanism of MLLT3 during differentiation remains elusive. In this study, we investigate the regulatory role of histone deacetylase 6 (HDAC6) in modulating MLLT3 levels via heat shock protein 90 (Hsp90) activation during myeloid lineage differentiation into MKs, monocytes, and macrophages. We found that HDAC6 activates Hsp90 through deacetylation, enabling Hsp90 to retain MLLT3 in the cytoplasm where protein kinase C (PKC) phosphorylates MLLT3 at serine residues; leading to loss of MLLT3 during MK and macrophage differentiation but not during monocyte differentiation. This research provides valuable insights into the regulatory mechanisms underlying myeloid lineage commitment and opens new avenues for future investigations into stem cell biology and therapeutic applications.

Bacteria have evolved multiple immune systems to resist phage invasion, however, only a small part of the defensive mechanisms have been clearly uncovered. In this study, we report a type III Druantia two-component defense system, DruH-DruE, identified from Mycobacterium smegmatis. The DruH-DruE prevents phage DNA cyclization and replication.DruE can be replaced from the defense system by either homolog in M. tuberculosis or M. smegmatis. The physical interaction between this two components is essential for fighting against phage infection. Mutations in the interaction sites led to the loss of phage-defending function of the system. The broad-spectrum antiphage ability of the defense system could be activated by the small tail protein Gp25 of phage A10ZJ24. This study fills a major gap in current knowledge of antiphage mechanism of type III Druantia defense system, expanding our understanding of the immune mechanisms in prokaryotic cells.

Pluripotent stem cells (PSCs) have remarkable capacity for unlimited self-renewal and differentiation into all somatic lineages. Although translational regulation has been implicated in the maintenance of PSC identity, the specific mechanisms involved remain poorly understood. Here, we identified EIF3H, a conserved subunit of the eIF3 translation initiation complex, as an essential regulator of human primed PSC proliferation and differentiation. CRISPR interference-mediated knockdown of EIF3H markedly reduced colony size, impaired proliferation, and diminished differentiation potential in all three germ layers. Integrated transcriptomic and translatomic profiling revealed that EIF3H loss decreased the translation of metal ion-related genes. Notably, the targeted suppression of metallothionein genes encoding metal-binding proteins recapitulated the proliferative defects observed in EIF3H-deficient PSCs, demonstrating a functional requirement for EIF3H-mediated translation of this gene family. Taken together, these findings establish EIF3H as a critical translational regulator that sustains PSC self-renewal and differentiation by maintaining the expression of key metabolic and stress-response genes, providing new insights into the molecular basis of pluripotency.

Personalized T cell therapy empowered by chimeric antigen receptor (CAR) that recognizes specific tumor antigen has cured numerous blood cancer patients since its initial approval in 2017. However, its access to a broader population has been limited by the unavailability of an off-the-shelf product derived from an allogeneic donor that can evade immune rejection, which is mediated by polymorphic class I and class II human leukocyte antigens (HLAs). Since class II HLAs are only expressed in specialized antigen-presenting cells but not T cells, it might suffice to evade T cells by deleting the common class I HLA light chain Beta-2 Microglobulin (B2M) (1). However, B2M-deficient cells can trigger a "missing-self" response to activate natural killer (NK) cells (2), a second function that was evolved to compensate loss of T cell response. Inserting a less polymorphic class I HLA gene encoding a known NK inhibitory ligand, namely HLA-E or HLA-G (3), into the B2M locus so that the endogenous B2M expression is disrupted could theoretically allow evasion of both T and NK cells. Despite being a seemingly better candidate in that HLA-G is uniquely expressed in immune-privileged sites such as the placenta with a believed function in protecting the fetus from immune rejection by the pregnant mother, whereas ubiquitously-expressing HLA-E is known to bind both inhibitory and activating NK receptors (4, 5), only HLA-E engineering has been attempted yet without convincing success in vivo (6, 7). Here, we generate an off-the-shelf CAR-T product with B2M replaced by a gene fusion encoding an HLA-G single-chain trimer under minimally impacted B2M epigenetic landscape, and observe its immune evasion property and a tumor-inhibitory function that is equivalent to its autologous control using a humanized mouse model for the first time with T and NK cells reconstituted from a donor with a distant HLA haplotype. HLA-G engineering may thus reprogram T cells into an immune-privileged state that can be utilized for all cell-based therapies.

Adeno-associated virus (AAV) is the preferred viral vector platform in gene therapy. Yet its packaging capacity, about 4.7 kb (kilobases), limits its therapeutic potential and represents a major bottleneck in the field. The packaging capacity of AAV is constrained by its small capsid, which forms a 26-nm-diameter shell assembled from 60 capsid proteins in a T=1 icosahedral architecture. Here, we propose increasing the cargo capacity of AAV vectors by engineering the next possible icosahedral architecture, T=3 (180 capsid proteins), which is predicted to provide a fivefold increase in volume capacity. Oligomers of VP3, the main capsid protein of AAV, were folded using AI-based methods. This identified triangular trimers as the optimal multimer compatible with the tiles of icosahedral lattices in the geometrical theory of capsids. The VP3 trimers were assembled into a T=3 architecture and coarse-grained at 5[A] resolution. It was necessary to introduce 15 deletions (VP3{Delta}15) to accommodate the T=3 curvature. Molecular simulations under physiological conditions demonstrated the stability of the 45 nm-diameter T=3 capsid. Structural analysis measured a five- to sixfold increase in internal volume and estimated a potential upper cargo limit of 35 kb. The engineered VP3{Delta}15 could enable delivery of multicistronic constructs, larger regulatory elements, and CRISPR systems beyond the reach of current AAV vectors. Additionally, the introduced generalized protein design framework could be used to engineer capsids with larger T-numbers and to modify the capacity of other icosahedral delivery systems.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) packages its single-stranded genomic RNA (gRNA) having about 30,000 nucleotides into virions by forming 35-40 granular ribonucleoprotein (RNP) units. Each RNP unit has a diameter of [~]15 nm. While it is generally assumed that the assembly of these RNPs is driven by the binding of the nucleocapsid (N) protein to the gRNA in the cytoplasm, the precise molecular mechanism remains to be fully elucidated. In this study, we develop an experimental strategy based on single-molecule fluorescence and fluorescence correlation spectroscopies to examine the formation of long-range base pairing within a candidate structural domain corresponding to nt 12230-12686 of the gRNA (gRNA12k). Our results demonstrate that the 5 and 3 regions of gRNA12k autonomously form long-range base pairing in near-physiological buffers containing mono- and divalent cations, independently of the N protein. This domain possesses an extensive secondary structure, is compact, and can unfold and refold reversibly upon heat treatment and cooling. Notably, the addition of the N protein melts the long-range base pairs, and causes the aggregation of multiple molecules of gRNA12k. Based on these observations, we propose a refined mechanism for the genome assembly in SARS-CoV-2: gRNA initially forms autonomous granular structures, which are subsequently reorganized and condensed by the N protein to chaperone the assembly of the entire gRNA. SignificanceSARS-CoV-2 organizes its exceptionally long genomic RNA (gRNA) having about 30,000 nt into 35-40 granular ribonucleoprotein (RNP) units for viral packaging. It has been assumed that the nucleocapsid (N) protein drives the formation of the RNP granules. In this study, we challenge this prevailing view by demonstrating that a specific region of the gRNA sequence inherently encodes the information to fold into a compact, granular architecture independently of any proteins. Unexpectedly, we found that the N protein partially melts the autonomous structures, suggesting that it acts as an RNA chaperone to facilitate flexible genome assembly. Our findings redefine the interplay between viral proteins and gRNA, offering a new perspective on the mechanism of coronavirus replication.

Spatiotemporal regulation of mRNA translation is central to gene expression. Over the past decade, translation has become directly observable in live cells at single-mRNA resolution by tagging nascent chains with tandem arrays of short epitope tags recognized by genetically encodable fluorescent intracellular antibodies (intrabodies). While this technology has revolutionized our understanding of translation regulation, the current toolbox of tagging systems remains limited. Here, we developed a novel and tight-binding intrabody against a short (11-amino acid) HIV protease epitope (named UTag). To ensure robust intracellular folding of the anti-UTag intrabody, we further engineered a cysteine-free variant that folds and functions independently of disulfide-bond formation, as validated by X-ray crystallography. The cysteine-free anti-UTag intrabody retains high binding affinity comparable to the parental intrabody while exhibiting significantly improved thermostability ([~]80 {degrees}C). Importantly, the cysteine-free UTag system enables real-time tracking of single-mRNA translation in live cells with performance on par with the parental UTag system as well as the established SunTag and ALFA-tag. Collectively, these results demonstrate that the newly developed UTag system expands the toolbox for live-cell translation tracking and provides complementary tools for multiplexed applications.

Programmed ribosomal frameshifting (PRF) is an essential strategy used by many RNA viruses to expand their coding capacity within compact genomes. This process is governed by frameshifting elements (FSEs), specialized RNA structures that regulate translation through dynamic secondary and tertiary conformations. While the structural adaptability of the SARS-CoV-2 FSE has been extensively characterized, the conformational landscapes of FSEs across other pathogenic viruses remain poorly understood. Here, we present a comparative structural analysis of FSEs from Japanese Encephalitis Virus (JEV), West Nile Virus (WNV), Hepatitis C Virus (HCV), and Human Immunodeficiency Virus (HIV) using integrative computational modeling and molecular simulations. Our analysis reveals previously uncharacterized, virus-specific conformational ensembles, alongside a conserved core architecture that exhibits pronounced length-dependent structural plasticity. Extension of flanking sequences induces substantial conformational rearrangements, highlighting the role of sequence context in shaping FSE topology and potentially modulating PRF efficiency. Importantly, we demonstrate that antisense oligonucleotide (ASO) binding can reprogram FSE architectures, disrupting native structural motifs and stabilizing alternative conformations with altered thermodynamic stability. Collectively, these findings establish viral FSEs as dynamic RNA ensembles governed by sequence context and external interactions, and position ASO-mediated structural perturbation as a promising strategy for modulating frameshifting and viral gene expression.

Deep-sea corals are vital in maintaining coral ecosystem biodiversity, yet their genetic characteristics remain largely unexplored. Here, we present 11 deep-sea coral genome assemblies, including four Hexacorallia and seven Octocorallia species, significantly contributing new genomic information across two orders. Our analysis reveals the historical dynamics of coral speciation and the influence of environmental factors on the evolution of coral reef ecosystems.Total of 126 horizontal gene transfer (HGT) events were detected, among which genes from the ancestor of symbiodiniaceae indicate that the ancestors of deep-sea corals may have inhabited shallow-sea environments. Notably, several of these HGTs are involved in phosphorus (PhnX/PhnW) and cholesterol (DHCR7) metabolisms within corals, indicating that HGTs may serve as an adaptive survival strategy for the coral holobionts. Deep-sea corals also rely on symbiotic bacteria to synthesize 10 essential amino acids (such as valine and tyrosine), retaining only partial amino acid synthesis capacity. In addition, we investigated the evolution of key biological rhythm genes and temperature adaptation in corals. The loss of key rhythm genes (e.g., clock and cry) in deep-sea corals and copy number difference of genes related to heat stress (e.g., Cbl-b and Rchy) revealed genetic difference between deep-sea and shallow-sea corals. Our new genome assemblies enhance the understanding of deep-sea coral evolution, biodiversity, and adaptation, providing a genetic foundation for coral conservation.

Aberrant activation of type I interferon (IFN-I) is closely related to the development of autoimmune diseases. The metabolic regulation of cytokine signaling is essential for immune homeostasis. In this study, we characterized Urolithin A(UA), a natural gut-derived metabolite, as an inhibitor of Janus kinase (JAK) signaling. UA was found to broadly dampen JAK phosphorylation and the downstream signaling induced by cytokines such as type I interferons (IFN-I), type II interferons (IFN-II), and interleukin-6 (IL-6). UA can directly bind to JAK1 JH1 domain and treatment with UA attenuated autoimmune pathogenesis in Trex1-KO mice, IMQ-induced SLE and psoriasis models. Our findings unveil that UA is an anti-inflammatory metabolite that promotes immune homeostasis and could be used to treat inflammatory and autoimmune diseases.