Profiling B cell immunodominance after SARS-CoV-2 infection reveals antibody evolution to non-neutralizing viral targets.

Dissecting the evolution of memory B cells (MBCs) against SARS-CoV-2 is critical for understanding antibody recall upon secondary exposure. Here, we used single-cell sequencing to profile SARS-CoV-2-reactive B cells in 38 COVID-19 patients. Using oligo-tagged antigen baits, we isolated B cells specific to the SARS-CoV-2 spike, nucleoprotein (NP), open reading frame 8 (ORF8), and endemic human coronavirus (HCoV) spike proteins. SARS-CoV-2 spike-specific cells were enriched in the memory compartment of acutely infected and convalescent patients several months post symptom onset. With severe acute infection, substantial populations of endemic HCoV-reactive antibody-secreting cells were identified and possessed highly mutated variable genes, signifying preexisting immunity. Finally, MBCs exhibited pronounced maturation to NP and ORF8 over time, especially in older patients. Monoclonal antibodies against these targets were non-neutralizing and non-protective in vivo. These findings reveal antibody adaptation to non-neutralizing intracellular antigens during infection, emphasizing the importance of vaccination for inducing neutralizing spike-specific MBCs.

Photocatalytic doping of organic semiconductors.

Chemical doping is an important approach to manipulating charge-carrier concentration and transport in organic semiconductors (OSCs)1-3 and ultimately enhances device performance4-7. However, conventional doping strategies often rely on the use of highly reactive (strong) dopants8-10, which are consumed during the doping process. Achieving efficient doping with weak and/or widely accessible dopants under mild conditions remains a considerable challenge. Here, we report a previously undescribed concept for the photocatalytic doping of OSCs that uses air as a weak oxidant (p-dopant) and operates at room temperature. This is a general approach that can be applied to various OSCs and photocatalysts, yielding electrical conductivities that exceed 3,000 S cm-1. We also demonstrate the successful photocatalytic reduction (n-doping) and simultaneous p-doping and n-doping of OSCs in which the organic salt used to maintain charge neutrality is the only chemical consumed. Our photocatalytic doping method offers great potential for advancing OSC doping and developing next-generation organic electronic devices.

AMPK directly phosphorylates TBK1 to integrate glucose sensing into innate immunity.

Nutrient sensing and damage sensing are two fundamental processes in living organisms. While hyperglycemia is frequently linked to diabetes-related vulnerability to microbial infection, how body glucose levels affect innate immune responses to microbial invasion is not fully understood. Here, we surprisingly found that viral infection led to a rapid and dramatic decrease in blood glucose levels in rodents, leading to robust AMPK activation. AMPK, once activated, directly phosphorylates TBK1 at S511, which triggers IRF3 recruitment and the assembly of MAVS or STING signalosomes. Consistently, ablation or inhibition of AMPK, knockin of TBK1-S511A, or increased glucose levels compromised nucleic acid sensing, while boosting AMPK-TBK1 cascade by AICAR or TBK1-S511E knockin improves antiviral immunity substantially in various animal models. Thus, we identify TBK1 as an AMPK substrate, reveal the molecular mechanism coupling a dual sensing of glucose and nuclei acids, and report its physiological necessity in antiviral defense.

Bright and stable perovskite light-emitting diodes in the near-infrared range.

Perovskite light-emitting diodes (LEDs) have attracted broad attention due to their rapidly increasing external quantum efficiencies (EQEs)1-15. However, most high EQEs of perovskite LEDs are reported at low current densities (<1 mA cm-2) and low brightness. Decrease in efficiency and rapid degradation at high brightness inhibit their practical applications. Here, we demonstrate perovskite LEDs with exceptional performance at high brightness, achieved by the introduction of a multifunctional molecule that simultaneously removes non-radiative regions in the perovskite films and suppresses luminescence quenching of perovskites at the interface with charge-transport layers. The resulting LEDs emit near-infrared light at 800 nm, show a peak EQE of 23.8% at 33 mA cm-2 and retain EQEs more than 10% at high current densities of up to 1,000 mA cm-2. In pulsed operation, they retain EQE of 16% at an ultrahigh current density of 4,000 mA cm-2, along with a high radiance of more than 3,200 W s-1 m-2. Notably, an operational half-lifetime of 32 h at an initial radiance of 107 W s-1 m-2 has been achieved, representing the best stability for perovskite LEDs having EQEs exceeding 20% at high brightness levels. The demonstration of efficient and stable perovskite LEDs at high brightness is an important step towards commercialization and opens up new opportunities beyond conventional LED technologies, such as perovskite electrically pumped lasers.

Structural insight into BRCA1-BARD1 complex recruitment to damaged chromatin.

The BRCA1-BARD1 complex directs the DNA double-strand break (DSB) repair pathway choice to error-free homologous recombination (HR) during the S-G2 stages. Targeting BRCA1-BARD1 to DSB-proximal sites requires BARD1-mediated nucleosome interaction and histone mark recognition. Here, we report the cryo-EM structure of BARD1 bound to a ubiquitinated nucleosome core particle (NCPUb) at 3.1 Å resolution and illustrate how BARD1 simultaneously recognizes the DNA damage-induced mark H2AK15ub and DNA replication-associated mark H4K20me0 on the nucleosome. In vitro and in vivo analyses reveal that the BARD1-NCPUb complex is stabilized by BARD1-nucleosome interaction, BARD1-ubiquitin interaction, and BARD1 ARD domain-BARD1 BRCT domain interaction, and abrogating these interactions is detrimental to HR activity. We further identify multiple disease-causing BARD1 mutations that disrupt BARD1-NCPUb interactions and hence impair HR. Together, this study elucidates the mechanism of BRCA1-BARD1 complex recruitment and retention by DSB-flanking nucleosomes and sheds important light on cancer therapeutic avenues.

The ZATT-TOP2A-PICH Axis Drives Extensive Replication Fork Reversal to Promote Genome Stability.

Replication fork reversal is a global response to replication stress in mammalian cells, but precisely how it occurs remains poorly understood. Here, we show that, upon replication stress, DNA topoisomerase IIalpha (TOP2A) is recruited to stalled forks in a manner dependent on the SNF2-family DNA translocases HLTF, ZRANB3, and SMARCAL1. This is accompanied by an increase in TOP2A SUMOylation mediated by the SUMO E3 ligase ZATT and followed by recruitment of a SUMO-targeted DNA translocase, PICH. Disruption of the ZATT-TOP2A-PICH axis results in accumulation of partially reversed forks and enhanced genome instability. These results suggest that fork reversal occurs via a sequential two-step process. First, HLTF, ZRANB3, and SMARCAL1 initiate limited fork reversal, creating superhelical strain in the newly replicated sister chromatids. Second, TOP2A drives extensive fork reversal by resolving the resulting topological barriers and via its role in recruiting PICH to stalled forks.

Induced phase separation of mutant NF2 imprisons the cGAS-STING machinery to abrogate antitumor immunity.

Missense mutations of the tumor suppressor Neurofibromin 2 (NF2/Merlin/schwannomin) result in sporadic to frequent occurrences of tumorigenesis in multiple organs. However, the underlying pathogenicity of NF2-related tumorigenesis remains mostly unknown. Here we found that NF2 facilitated innate immunity by regulating YAP/TAZ-mediated TBK1 inhibition. Unexpectedly, patient-derived individual mutations in the FERM domain of NF2 (NF2m) converted NF2 into a potent suppressor of cGAS-STING signaling. Mechanistically, NF2m gained extreme associations with IRF3 and TBK1 and, upon innate nucleic acid sensing, was directly induced by the activated IRF3 to form cellular condensates, which contained the PP2A complex, to eliminate TBK1 activation. Accordingly, NF2m robustly suppressed STING-initiated antitumor immunity in cancer cell-autonomous and -nonautonomous murine models, and NF2m-IRF3 condensates were evident in human vestibular schwannomas. Our study reports phase separation-mediated quiescence of cGAS-STING signaling by a mutant tumor suppressor and reveals gain-of-function pathogenesis for NF2-related tumors by regulating antitumor immunity.

ATR limits Rad18-mediated PCNA monoubiquitination to preserve replication fork and telomerase-independent telomere stability.

Upon replication fork stalling, the RPA-coated single-stranded DNA (ssDNA) formed behind the fork activates the ataxia telangiectasia-mutated and Rad3-related (ATR) kinase, concomitantly initiating Rad18-dependent monoubiquitination of PCNA. However, whether crosstalk exists between these two events and the underlying physiological implications of this interplay remain elusive. In this study, we demonstrate that during replication stress, ATR phosphorylates human Rad18 at Ser403, an adjacent residue to a previously unidentified PIP motif (PCNA-interacting peptide) within Rad18. This phosphorylation event disrupts the interaction between Rad18 and PCNA, thereby restricting the extent of Rad18-mediated PCNA monoubiquitination. Consequently, excessive accumulation of the tumor suppressor protein SLX4, now characterized as a novel reader of ubiquitinated PCNA, at stalled forks is prevented, contributing to the prevention of stalled fork collapse. We further establish that ATR preserves telomere stability in alternative lengthening of telomere (ALT) cells by restricting Rad18-mediated PCNA monoubiquitination and excessive SLX4 accumulation at telomeres. These findings shed light on the complex interplay between ATR activation, Rad18-dependent PCNA monoubiquitination, and SLX4-associated stalled fork processing, emphasizing the critical role of ATR in preserving replication fork stability and facilitating telomerase-independent telomere maintenance.

A non-canonical role of the inner kinetochore in regulating sister-chromatid cohesion at centromeres.

The 16-subunit Constitutive Centromere-associated Network (CCAN)-based inner kinetochore is well-known for connecting centromeric chromatin to the spindle-binding outer kinetochore. Here, we report a non-canonical role for the inner kinetochore in directly regulating sister-chromatid cohesion at centromeres. We provide biochemical, X-ray crystal structure, and intracellular ectopic localization evidence that the inner kinetochore directly binds cohesin, a ring-shaped multi-subunit complex that holds sister chromatids together from S-phase until anaphase onset. This interaction is mediated by binding of the 5-subunit CENP-OPQUR sub-complex of CCAN to the Scc1-SA2 sub-complex of cohesin. Mutation in the CENP-U subunit of the CENP-OPQUR complex that abolishes its binding to the composite interface between Scc1 and SA2 weakens centromeric cohesion, leading to premature separation of sister chromatids during delayed metaphase. We further show that CENP-U competes with the cohesin release factor Wapl for binding the interface of Scc1-SA2, and that the cohesion-protecting role for CENP-U can be bypassed by depleting Wapl. Taken together, this study reveals an inner kinetochore-bound pool of cohesin, which strengthens centromeric sister-chromatid cohesion to resist metaphase spindle pulling forces.

Multimodal probing of T-cell recognition with hexapod heterostructures.

Studies using antigen-presenting systems at the single-cell and ensemble levels can provide complementary insights into T-cell signaling and activation. Although crucial for advancing basic immunology and immunotherapy, there is a notable absence of synthetic material toolkits that examine T cells at both levels, and especially those capable of single-molecule-level manipulation. Here we devise a biomimetic antigen-presenting system (bAPS) for single-cell stimulation and ensemble modulation of T-cell recognition. Our bAPS uses hexapod heterostructures composed of a submicrometer cubic hematite core (α-Fe2O3) and nanostructured silica branches with diverse surface modifications. At single-molecule resolution, we show T-cell activation by a single agonist peptide-loaded major histocompatibility complex; distinct T-cell receptor (TCR) responses to structurally similar peptides that differ by only one amino acid; and the superior antigen recognition sensitivity of TCRs compared with that of chimeric antigen receptors (CARs). We also demonstrate how the magnetic field-induced rotation of hexapods amplifies the immune responses in suspended T and CAR-T cells. In addition, we establish our bAPS as a precise and scalable method for identifying stimulatory antigen-specific TCRs at the single-cell level. Thus, our multimodal bAPS represents a unique biointerface tool for investigating T-cell recognition, signaling and function.

Small RNA SmsR1 modulates acidogenicity and cariogenic virulence by affecting protein acetylation in Streptococcus mutans.

Post-transcriptional regulation by small RNAs and post-translational modifications (PTM) such as lysine acetylation play fundamental roles in physiological circuits, offering rapid responses to environmental signals with low energy consumption. Yet, the interplay between these regulatory systems remains underexplored. Here, we unveil the cross-talk between sRNAs and lysine acetylation in Streptococcus mutans, a primary cariogenic pathogen known for its potent acidogenic virulence. Through systematic overexpression of sRNAs in S. mutans, we identified sRNA SmsR1 as a critical player in modulating acidogenicity, a key cariogenic virulence feature in S. mutans. Furthermore, combined with the analysis of predicted target mRNA and transcriptome results, potential target genes were identified and experimentally verified. A direct interaction between SmsR1 and 5'-UTR region of pdhC gene was determined by in vitro binding assays. Importantly, we found that overexpression of SmsR1 reduced the expression of pdhC mRNA and increased the intracellular concentration of acetyl-CoA, resulting in global changes in protein acetylation levels. This was verified by acetyl-proteomics in S. mutans, along with an increase in acetylation level and decreased activity of LDH. Our study unravels a novel regulatory paradigm where sRNA bridges post-transcriptional regulation with post-translational modification, underscoring bacterial adeptness in fine-tuning responses to environmental stress.

UFL1 triggers replication fork degradation by MRE11 in BRCA1/2-deficient cells.

The stabilization of stalled forks has emerged as a crucial mechanism driving resistance to poly(ADP-ribose) polymerase (PARP) inhibitors in BRCA1/2-deficient tumors. Here, we identify UFL1, a UFM1-specific E3 ligase, as a pivotal regulator of fork stability and the response to PARP inhibitors in BRCA1/2-deficient cells. On replication stress, UFL1 localizes to stalled forks and catalyzes the UFMylation of PTIP, a component of the MLL3/4 methyltransferase complex, specifically at lysine 148. This modification facilitates the assembly of the PTIP-MLL3/4 complex, resulting in the enrichment of H3K4me1 and H3K4me3 at stalled forks and subsequent recruitment of the MRE11 nuclease. Consequently, loss of UFL1, disruption of PTIP UFMylation or overexpression of the UFM1 protease UFSP2 protects nascent DNA strands from extensive degradation and confers resistance to PARP inhibitors in BRCA1/2-deficient cells. These findings provide mechanistic insights into the processes underlying fork instability in BRCA1/2-deficient cells and offer potential therapeutic avenues for the treatment of BRCA1/2-deficient tumors.

FUS reads histone H3K36me3 to regulate alternative polyadenylation.

Complex organisms generate differential gene expression through the same set of DNA sequences in distinct cells. The communication between chromatin and RNA regulates cellular behavior in tissues. However, little is known about how chromatin, especially histone modifications, regulates RNA polyadenylation. In this study, we found that FUS was recruited to chromatin by H3K36me3 at gene bodies. The H3K36me3 recognition of FUS was mediated by the proline residues in the ZNF domain. After these proline residues were mutated or H3K36me3 was abolished, FUS dissociated from chromatin and bound more to RNA, resulting in an increase in polyadenylation sites far from stop codons genome-wide. A proline mutation corresponding to a mutation in amyotrophic lateral sclerosis contributed to the hyperactivation of mitochondria and hyperdifferentiation in mouse embryonic stem cells. These findings reveal that FUS is an H3K36me3 reader protein that links chromatin-mediated alternative polyadenylation to human disease.

Nuclear F-actin assembly on damaged chromatin is regulated by DYRK1A and Spir1 phosphorylation.

Nuclear actin-based movements support DNA double-strand break (DSB) repair. However, molecular determinants that promote filamentous actin (F-actin) formation on the damaged chromatin remain undefined. Here we describe the DYRK1A kinase as a nuclear activity that promotes local F-actin assembly to support DSB mobility and repair, accomplished in part by its targeting of actin nucleator spire homolog 1 (Spir1). Indeed, perturbing DYRK1A-dependent phosphorylation of S482 mis-regulated Spir1 accumulation at damaged-modified chromatin, and led to compromised DSB-associated actin polymerization and attenuated DNA repair. Our findings uncover a role of the DYRK1A-Spir1 axis in nuclear actin dynamics during early DSB responses, and highlight the intricate details of nuclear cytoskeletal network in DSB repair and genome stability maintenance.

Correlated surface-charging behaviors of two electrodes in an electrochemical cell.

It is revealed herein that surface-charging behaviors of the two electrodes constituting an electrochemical cell cannot be described independently by their respective electric double-layer (EDL) properties. Instead, they are correlated in such a way that the surface-charging behavior of each electrode is determined by the EDL and the reaction kinetics at both electrodes. Two fundamental equations describing the correlated surface-charging behaviors are derived, and approximate analytical solutions are obtained at low and high current densities, respectively, to facilitate transparent understanding. Important implications of the presented conceptual analysis for theoretical and computational electrochemistry are discussed. A strategy of modulating the activity of one electrode by tuning EDL parameters of the other in a two-electrode electrochemical cell is demonstrated.

Efficient Bayesian inference under the multispecies coalescent with migration.

Analyses of genome sequence data have revealed pervasive interspecific gene flow and enriched our understanding of the role of gene flow in speciation and adaptation. Inference of gene flow using genomic data requires powerful statistical methods. Yet current likelihood-based methods involve heavy computation and are feasible for small datasets only. Here, we implement the multispecies-coalescent-with-migration model in the Bayesian program bpp, which can be used to test for gene flow and estimate migration rates, as well as species divergence times and population sizes. We develop Markov chain Monte Carlo algorithms for efficient sampling from the posterior, enabling the analysis of genome-scale datasets with thousands of loci. Implementation of both introgression and migration models in the same program allows us to test whether gene flow occurred continuously over time or in pulses. Analyses of genomic data from Anopheles mosquitoes demonstrate rich information in typical genomic datasets about the mode and rate of gene flow.

The RPA-RNF20-SNF2H cascade promotes proper chromosome segregation and homologous recombination repair.

The human tumor suppressor Ring finger protein 20 (RNF20)-mediated histone H2B monoubiquitination (H2Bub) is essential for proper chromosome segregation and DNA repair. However, what is the precise function and mechanism of RNF20-H2Bub in chromosome segregation and how this pathway is activated to preserve genome stability remain unknown. Here, we show that the single-strand DNA-binding factor Replication protein A (RPA) interacts with RNF20 mainly in the S and G2/M phases and recruits RNF20 to mitotic centromeres in a centromeric R-loop-dependent manner. In parallel, RPA recruits RNF20 to chromosomal breaks upon DNA damage. Disruption of the RPA-RNF20 interaction or depletion of RNF20 increases mitotic lagging chromosomes and chromosome bridges and impairs BRCA1 and RAD51 loading and homologous recombination repair, leading to elevated chromosome breaks, genome instability, and sensitivities to DNA-damaging agents. Mechanistically, the RPA-RNF20 pathway promotes local H2Bub, H3K4 dimethylation, and subsequent SNF2H recruitment, ensuring proper Aurora B kinase activation at centromeres and efficient loading of repair proteins at DNA breaks. Thus, the RPA-RNF20-SNF2H cascade plays a broad role in preserving genome stability by coupling H2Bub to chromosome segregation and DNA repair.

Galectin-7 Induction by EHMT2 Inhibition Enhances Immunity in Microsatellite Stability Colorectal Cancer.

BACKGROUND & AIMS: Although immunotherapy shows substantial advancement in colorectal cancer (CRC) with microsatellite instability high, it has limited efficacy for CRC with microsatellite stability (MSS). Identifying combinations that reverse immune suppression and prime MSS tumors for current immunotherapy approaches remains an urgent need. METHODS: An in vitro CRISPR screen was performed using coculture models of primary tumor cells and autologous immune cells from MSS CRC patients to identify epigenetic targets that could enhance immunotherapy efficacy in MSS tumors. RESULTS: We revealed EHMT2, a histone methyltransferase, as a potential target for MSS CRC. EHMT2 inhibition transformed the immunosuppressive microenvironment of MSS tumors into an immunomodulatory one by altering cytokine expression, leading to T-cell-mediated cytotoxicity activation and improved responsiveness to anti-PD1 treatment. We observed galectin-7 up-regulation upon EHMT2 inhibition, which converted a "cold" MSS tumor environment into a T-cell-inflamed one. Mechanistically, CHD4 repressed galectin-7 expression by recruiting EHMT2 to form a cotranscriptional silencing complex. Galectin-7 administration enhanced anti-PD1 efficacy in MSS CRC, serving as a potent adjunct cytokine therapy. CONCLUSIONS: Our findings suggest that targeting the EHMT2/galectin-7 axis could provide a novel combination strategy for immunotherapy in MSS CRC.

SIRT1 deacetylates WEE1 and sensitizes cancer cells to WEE1 inhibition.

The cell-cycle checkpoint kinase WEE1 is emerging as a therapeutic target for cancer treatment. However, how its catalytic activity is regulated remains poorly understood, and reliable biomarkers for predicting response to WEE1 inhibitor remain to be identified. Here we identify an evolutionarily conserved segment surrounding its Lys177 residue that inhibits WEE1 activity through an intermolecular interaction with the catalytic kinase domain. Upon DNA damage, CHK1-dependent phosphorylation of WEE1 at Ser642 primes GCN5-mediated acetylation at Lys177, resulting in dissociation of the inhibitory segment from the kinase domain and subsequent activation of WEE1 and cell-cycle checkpoints. Conversely, SIRT1 associates with and deacetylates WEE1, which maintains it in an inactive state. Consequently, SIRT1 deficiency induces WEE1 hyperacetylation and activation, rendering cancer cells resistant to WEE1 inhibition. These results suggest that SIRT1 expression level and abundance of WEE1 Lys177 acetylation in tumor cells can serve as useful biomarkers for predicting WEE1 inhibitor sensitivity or resistance.

The FLIP-FIGNL1 complex regulates the dissociation of RAD51/DMC1 in homologous recombination and replication fork restart.

Recruitment of RAD51 and/or DMC1 recombinases to single-strand DNA is indispensable for homology search and strand invasion in homologous recombination (HR) and for protection of nascent DNA strands at stalled replication forks. Thereafter RAD51/DMC1 dissociate, actively or passively, from these joint molecules upon DNA repair or releasing from replication stress. However, the mechanism that regulates RAD51/DMC1 dissociation and its physiological importance remain elusive. Here, we show that a FLIP-FIGNL1 complex regulates RAD51 and DMC1 dissociation to promote meiotic recombination and replication fork restart in mammals. Mice lacking FLIP are embryonic lethal, while germline-specific deletion of FLIP leads to infertility in both males and females. FLIP-null meiocytes are arrested at a zygotene-like stage with massive RAD51 and DMC1 foci, which frequently co-localize with SHOC1 and TEX11. Furthermore, FLIP interacts with FIGNL1. Depletion of FLIP or FIGNL1 in cell lines destabilizes each other and impairs RAD51 dissociation. Thus, the active dissociation of RAD51/DMC1 by the FLIP-FIGNL1 complex is a crucial step required for HR and replication fork restart, and represents a conserved mechanism in somatic cells and germ cells.