Although recent studies have shown that 2'3'-cyclic GMP-AMP synthase (cGAS) has both canonical cytoplasmic and non-canonical nuclear functions, the role of nuclear cGAS in cancer metastasis remains unclear. Here, we iden...Although recent studies have shown that 2'3'-cyclic GMP-AMP synthase (cGAS) has both canonical cytoplasmic and non-canonical nuclear functions, the role of nuclear cGAS in cancer metastasis remains unclear. Here, we identify a STING-independent mechanism by which nuclear cGAS activates Wnt/β-catenin signaling to promote metastasis in triple-negative breast cancer (TNBC). Protein kinase C alpha (PKCα) phosphorylates cGAS at Ser120, facilitating its nuclear translocation. Once in the nucleus, cGAS disrupts the interaction between β-catenin and tripartite motif-containing protein 33 (TRIM33), preventing β-catenin ubiquitination and promoting its stabilization, thereby activating Wnt/β-catenin signaling. PKCα thus acts as a key regulator of this non-canonical, cGAS-driven metastatic pathway. Therapeutic transactivator of transcription (TAT) peptides inhibiting cGAS phosphorylation significantly reduce metastasis. Clinically, elevated nuclear cGAS expression is associated with increased metastasis in TNBC cohorts. Together, these findings delineate a PKCα-cGAS-TRIM33 axis that regulates nuclear β-catenin stability and establish cGAS phosphorylation as a promising theragnostic target for TNBC metastasis.
Transposons can mobilize within the genome, and these events cause DNA breaks, gene mutations, and genome instability. As such, their aberrant activation is closely linked to cancer, neurodegenerative disorders, and othe...Transposons can mobilize within the genome, and these events cause DNA breaks, gene mutations, and genome instability. As such, their aberrant activation is closely linked to cancer, neurodegenerative disorders, and other pathologies. Despite this, the precise mechanisms that suppress transpositions during somatic development remain unclear. Here, by spatiotemporally monitoring transpositions with single-cell resolution, we identified a highly conserved suppression mechanism. We found that Cramp1 plays a critical role in silencing transposon mobility during both Drosophila hindgut regeneration and mouse embryonic erythropoiesis. The function of Cramp1 in controlling transposons is exclusively dependent on linker histone H1-mediated chromatin compaction. Cramp1 specifically binds to DNA sequences within the histone gene cluster, initiating H1 transcription. Subsequently, H1 proteins physically interact with and recruit Nsd to promote the establishment of H3K9 trimethylation (H3K36me2)-modified heterochromatin. Our findings highlight that, in the ongoing evolutionary arms race between hosts and transposons, core mechanisms have evolved to suppress transpositions during somatic development.
In a recent issue of Cell, Spiga et al. show that enterotoxigenic Bacteroides fragilis constructs a low-oxygen intestinal niche to fuel pathogen growth through aerobic respiration, promoting tumorigenesis and challenging...In a recent issue of Cell, Spiga et al. show that enterotoxigenic Bacteroides fragilis constructs a low-oxygen intestinal niche to fuel pathogen growth through aerobic respiration, promoting tumorigenesis and challenging the view that oxygen is strictly detrimental to obligate anaerobes.
Two recent publications in Science, DeWeirdt et al. and Mordret et al., deployed protein- and genomic-context language models to predict antiphage defense systems across thousands of bacterial genomes, experimentally val...Two recent publications in Science, DeWeirdt et al. and Mordret et al., deployed protein- and genomic-context language models to predict antiphage defense systems across thousands of bacterial genomes, experimentally validating dozens of systems and computationally identifying millions of additional putative defense proteins.
Stress granules are antiviral RNA condensates, but their core scaffold can be turned against the host. In this issue, Liu et al. show that alphavirus nsP3 redirects G3BP into proviral condensates that shelter viral RNA a...Stress granules are antiviral RNA condensates, but their core scaffold can be turned against the host. In this issue, Liu et al. show that alphavirus nsP3 redirects G3BP into proviral condensates that shelter viral RNA and promote its translation.
In this issue of Molecular Cell, Sohn et al. explore how endogenous dsRNAs influence organismal aging and identify an unexpected function of the aminoacyl-tRNA synthetase FARS-1/FARSA in regulating mitochondrial dsRNA ho...In this issue of Molecular Cell, Sohn et al. explore how endogenous dsRNAs influence organismal aging and identify an unexpected function of the aminoacyl-tRNA synthetase FARS-1/FARSA in regulating mitochondrial dsRNA homeostasis to balance longevity and innate immunity.
The myeloid translocation gene (Mtg) family of transcriptional corepressors is a frequent target of chromosomal translocations and deletions in cancer, yet the mechanisms underlying tumor suppression and transcriptional...The myeloid translocation gene (Mtg) family of transcriptional corepressors is a frequent target of chromosomal translocations and deletions in cancer, yet the mechanisms underlying tumor suppression and transcriptional repression are unclear. We employed a chemical-genetic system that enabled rapid degradation and recovery of Mtg16 to study both the maintenance and re-establishment of transcriptional repression. Nascent transcription and assay for transposase-accessible chromatin using sequencing (ATAC-seq) analyses showed that Mtg16 repressed highly accessible promoters and enhancers, including Lmo2, Myb, and Gfi1b. The highest confidence targets included these oncogenes, which were transcribed at low levels in the presence of Mtg16 and re-repressed upon its recovery. Proximity ligation assays showed that HEB associated with p300 in the absence of Mtg16, but endogenous levels of Mtg16 impaired this association. Repression was associated with decreased H3K27ac, but loss of H3K27ac also occurred at non-repressed sites. Strikingly, HDAC inhibition had little effect on the maintenance of repression but strongly impaired re-repression following Mtg16 restoration, revealing a selective requirement for HDACs during repression onset.
Synthetic lethality (SL) underlies the success of PARP1 inhibitors (PARPi) in treating homologous recombination (HR)-deficient cancers, yet their broader applicability beyond HR deficiency remains poorly defined. Here, w...Synthetic lethality (SL) underlies the success of PARP1 inhibitors (PARPi) in treating homologous recombination (HR)-deficient cancers, yet their broader applicability beyond HR deficiency remains poorly defined. Here, we performed an in vivo CRISPR screen that identifies FANCA deficiency as a driver of tumor progression and PARPi SL, validated across diverse human cancer models. Notably, FANCA loss does not impair HR but instead disrupts FEN1 recruitment to replication forks, leading to defective Okazaki fragment maturation, lagging-strand single-strand DNA gap accumulation, and RPA exhaustion upon PARPi treatment. Additionally, FANCA loss in oncogene-expressing cells promotes transcription-replication conflict (TRC) accumulation selectively on the lagging strand and sensitizes HR-proficient cells to PARPi, a phenotype reversible by RNA polymerase II inhibition or RNase H overexpression. Together, these findings identify FANCA deficiency as a context-specific PARPi vulnerability and establish FANCA as a key suppressor of TRCs required for genomic stability under oncogenic replication stress.
Understanding how pioneer transcription factors target nucleosomal DNA and initiate chromatin accessibility reveals the earliest events in cell fate changes. We integrated structural, biochemical, and genomic approaches...Understanding how pioneer transcription factors target nucleosomal DNA and initiate chromatin accessibility reveals the earliest events in cell fate changes. We integrated structural, biochemical, and genomic approaches to assess how the pioneer factor Ascl1-E12a heterodimer perturbs nucleosomes in vitro and in vivo to induce a neural cell fate. Two Ascl1-E12a heterodimers shift and unwrap 15 bp of nucleosomal DNA in a stepwise manner while eliciting solvent exchanges within the octamer. Nucleosome binding, but not free DNA binding, by Ascl1-E12a is enhanced by two types of associations with the nucleosome that differentially affect the kinetics of DNA unwrapping and shifting. Nucleosome association mutants of Ascl1 perturb chromatin opening on linker histone-compacted nucleosome arrays-independent of nucleosome remodelers-and targeting of closed chromatin in vivo, with consequent deficiencies in cellular reprogramming. Our findings establish that distinct associations with nucleosomes are essential for the pioneer factor Ascl1 to overcome chromatin barriers to reprogram cell fate.
Aberrant chromatin-associated condensates have emerged as drivers of transcriptional dysregulation in cancer, yet how extrinsic factors modulate their assembly and function remains poorly understood. Gain-of-function mut...Aberrant chromatin-associated condensates have emerged as drivers of transcriptional dysregulation in cancer, yet how extrinsic factors modulate their assembly and function remains poorly understood. Gain-of-function mutations in the chromatin reader ENL ("Eleven-nineteen-leukemia") drive oncogenesis by inducing condensate formation at select target loci. Here, we demonstrate that locally produced transcripts reinforce the nucleation, chromatin engagement, and oncogenic activity of mutant ENL condensates. Mutant ENL binds to RNA in part through a basic patch within its YEATS domain, and this interaction enhances condensate formation in vitro and in cells. Using a chemically inducible condensate displacement and renucleation system, we show that blocking ENL-RNA interactions or transcription impairs condensate reformation at endogenous targets. RNA binding preferentially enhances mutant ENL occupancy and transcriptional bursting at condensate-permissive loci. In mouse models, disrupting RNA binding suppresses mutant ENL-driven oncogenic transcription and leukemogenesis. These findings reveal how chromatin-associated oncogenic proteins hijack local transcripts to reinforce condensate nucleation and drive tumorigenesis.
Anerillas C, Altés G, Gresova K
… +26 more, Tsitsipatis D, Mazan-Mamczarz K, Banarjee R, Cunningham ASG, Salamini-Montemurri M, Yang JH, Munk R, Rossi M, Piao Y, Olinger B, Strassheim Q, Martindale JL, Fan J, Cui CY, De S, Rutherford DV, Hao Y, Li Z, Roberts J, Qi YA, Abdelmohsen K, de Cabo R, Herman AB, Maragkakis M, Basisty N, Gorospe M
There is an urgent need to comprehensively catalog senescence markers across cell types in an organism in order to characterize senescent-cell heterogeneity. Here, we profiled the transcriptomes and proteomes in 14 diffe...There is an urgent need to comprehensively catalog senescence markers across cell types in an organism in order to characterize senescent-cell heterogeneity. Here, we profiled the transcriptomes and proteomes in 14 different primary human cell types undergoing over 30 senescence paradigms to create a senescence catalog we termed "SenCat." We found that while senescent cells from all primary cell types did not share a single unique marker, they did activate shared specific metabolic and damage-response pathways implicated in tissue repair. Moreover, machine-learning-refined SenCat signatures enabled senescence scoring and identification across multiple human and mouse datasets, both at bulk and single-cell levels. In sum, SenCat represents a much-needed resource to identify senescence across multiple cell types and tissues in the body.
The large serine recombinase Bxb1 catalyzes recombination between DNA molecules containing compatible attP and attB sequences, offering broad applications in genome engineering and gene therapies. Here, we present cryo-e...The large serine recombinase Bxb1 catalyzes recombination between DNA molecules containing compatible attP and attB sequences, offering broad applications in genome engineering and gene therapies. Here, we present cryo-electron microscopy structures of the Bxb1-attP-attB synaptic complex in four distinct functional states during its recombination cycle. Notably, the Bxb1 complex structures in the pre-, mid-, and post-strand-exchange states explain how the attP- and attB-bound Bxb1 dimers are assembled into a tetrameric synaptic complex and how an approximately 180° rotation occurs between the left and right dimers after DNA cleavage, thereby enabling DNA strand exchange and religation. Furthermore, we engineered Bxb1 variants with altered DNA preferences and enhanced recombination activity, which improved programmable gene integration in human cells. Overall, our findings advance the mechanistic understanding of large serine recombinases and provide a structural framework for future engineering of Bxb1-mediated genome integration technologies.
TRIM21 is an exceptionally versatile ubiquitin ligase that can be directed by antibodies to target oligomeric protein scaffolds, viral capsids, and proteopathic aggregates for intracellular degradation. How the cell degr...TRIM21 is an exceptionally versatile ubiquitin ligase that can be directed by antibodies to target oligomeric protein scaffolds, viral capsids, and proteopathic aggregates for intracellular degradation. How the cell degrades these typically resistant substrates remains poorly understood. To address this, we used TRIM21 viral restriction to create a genome-wide phenotypic screen for antibody-dependent capsid degradation. We identify an antimicrobial selective macroautophagy pathway in mammalian cells, which we term "antibody-directed xenophagy" (ADX). We show that this mechanism restricts structurally diverse pathogens, including adenovirus and Salmonella. Using quantitative microscopy, we demonstrate that TRIM21 rapidly intercepts antibody-pathogen complexes, leading to ubiquitin ligase activation. Following this, selective autophagy adaptors are recruited, and viral cargoes are delivered to lysosomes. This process reduces Salmonella pathology and bacterial tissue invasion in mice. We propose that TRIM21 evolved through competition with pathogens to induce autophagy of diverse and complex substrates, potentially explaining its versatility for targeted protein degradation.
Like mitochondria themselves, research on this organelle can take many shapes and sizes. This month, to coincide with the Cell Press Symposia: Multifaceted Mitochondria, we are highlighting the diversity of the global mi...Like mitochondria themselves, research on this organelle can take many shapes and sizes. This month, to coincide with the Cell Press Symposia: Multifaceted Mitochondria, we are highlighting the diversity of the global mitochondria community with contributions from researchers at all career stages published across Cell Metabolism, Molecular Cell, Cell Reports, and Trends in Endocrinology and Metabolism. Together, these voices showcase the central role of mitochondrial research in metabolism, inflammation, cell biology, and much more.
In this issue of Molecular Cell, Berquez et al. reveal that MHC-I is degraded from within the endoplasmic reticulum (ER) by a ubiquitin-driven autophagy pathway involving co-operation of a cytoplasmic and an ER-phagy car...In this issue of Molecular Cell, Berquez et al. reveal that MHC-I is degraded from within the endoplasmic reticulum (ER) by a ubiquitin-driven autophagy pathway involving co-operation of a cytoplasmic and an ER-phagy cargo receptor.
In this issue, Zhang and Cañari-Chumpitaz et al. find that RNA polymerase (RNAP) preferentially binds to the apices of supercoiled DNA plectonemes, which facilitates promoter escape but imposes a torsional trade-off duri...In this issue, Zhang and Cañari-Chumpitaz et al. find that RNA polymerase (RNAP) preferentially binds to the apices of supercoiled DNA plectonemes, which facilitates promoter escape but imposes a torsional trade-off during elongation. In the presence of torsional blocks, it generates twin supercoiling domains and drives cooperative transcription.
In this issue of Molecular Cell, Mallory et al. use single-molecule DNA methyltransferase footprinting to provide an unprecedented view of the chromatin and transcriptional state of reporter plasmid molecules in human ce...In this issue of Molecular Cell, Mallory et al. use single-molecule DNA methyltransferase footprinting to provide an unprecedented view of the chromatin and transcriptional state of reporter plasmid molecules in human cells.
Biguanides, including metformin, the world's most prescribed oral hypoglycemic, extend health span and lifespan in vertebrates and invertebrates. Given the widespread use and apparent safety of metformin, it is assumed t...Biguanides, including metformin, the world's most prescribed oral hypoglycemic, extend health span and lifespan in vertebrates and invertebrates. Given the widespread use and apparent safety of metformin, it is assumed that its effects are not associated with toxicity, except when in marked excess. Here, we determine that accumulation of damaging reducing equivalents is an unanticipated toxicity associated with biguanides, defense against which requires post-transcriptional protection of de novo lipogenesis. We demonstrate that biguanide treatment during impaired lipogenesis drives NADPH toxicity, leading to catastrophic elevation of NADH/GSH reducing equivalents and accelerated death across metazoans. Multiple NADPH-generating interventions require de novo lipogenesis to prevent markedly shortened survival, indicating that this defense mechanism is broadly leveraged. We propose that fatty acid biosynthesis is a tunable rheostat that can minimize biguanide-induced reductive stress while maximizing its pro-longevity outcomes and can serve as an exploitable vulnerability in reductive stress-sensitive cancers.
Topoisomerase II (TOP2) poisons, such as etoposide, are potent antineoplastic drugs that also cause significant secondary toxicity to postmitotic cells. Proliferating mammalian cells express two TOP2 isoforms, TOP2A and...Topoisomerase II (TOP2) poisons, such as etoposide, are potent antineoplastic drugs that also cause significant secondary toxicity to postmitotic cells. Proliferating mammalian cells express two TOP2 isoforms, TOP2A and TOP2B, whereas postmitotic cells only express TOP2B. Selectively targeting TOP2A, but not TOP2B, could thus prevent secondary toxicity in postmitotic cells. Here we report that the heat shock transcription factor, HSF1, facilitates the catalytic engagement of TOP2B on chromatin. Purified HSF1 stimulates the DNA cleavage and relaxation activity of TOP2B. Atomic force microscopy revealed that HSF1 enhances the binding of TOP2B across a range of DNA conformations. Intriguingly, HSF1 preferentially stimulates TOP2B over TOP2A, and knockdown or inhibition of HSF1 reduces the levels of catalytically engaged TOP2B but not TOP2A. Moreover, HSF1 inhibitors suppress the cytotoxicity of TOP2 poisons toward postmitotic cells without compromising their ability to kill cancer cells, revealing a strategy for minimizing the side-effects of TOP2 poison-based chemotherapy.
The IS110 elements employ RNA-guided transposases using bridge-RNA to coordinate donor and target DNA recognition and integration via donor- and target-binding loops, which offers promise for DSB-free genome editing. How...The IS110 elements employ RNA-guided transposases using bridge-RNA to coordinate donor and target DNA recognition and integration via donor- and target-binding loops, which offers promise for DSB-free genome editing. However, their transposition mechanism remains unclear, with prior inconsistent observations. Using an IS110 element from Caloranaerobacter azorensis, we show that IS110 transposons utilize two independent transposition pathways. The first depends on bridge-RNA (bRNA) and excises the element via top-strand excision and rejoining, which corresponds to the initial step of the canonical copy-out model and revisits the earlier cut-out model. Integration occurs predominantly through top-strand insertion, which suggests an alternative to the Holliday junction-mediated dual-strand mechanism. The second involves cooperation between a truncated target-binding loop RNA and bRNA, which enables direct top-strand transfer to a new target via two sequential reactions. Both pathways preserve the original transposon copy. These findings redefine the mechanistic understanding of IS110 transposition and reconcile prior discrepancies, thus offering an insight into programmable, RNA-guided genome modification.