Interstrand DNA crosslinks (ICLs) are a highly toxic form of DNA damage. ICL repair in both eukaryotes and bacteria involves unhooking of the two strands by specialized DNA glycosylases. We recently established that the...Interstrand DNA crosslinks (ICLs) are a highly toxic form of DNA damage. ICL repair in both eukaryotes and bacteria involves unhooking of the two strands by specialized DNA glycosylases. We recently established that the human pathogen Acinetobacter baumannii contains an ICL glycosylase (AlkX) that facilitates pathogenesis and protects the bacteria from DNA damage and acid stress. However, the physical basis for glycosylase-catalyzed ICL unhooking is unknown. Here, we describe a crystal structure of AlkX bound to DNA representing a product of the ICL unhooking reaction. Mutational analysis of ICL unhooking in vitro and A. baumannii sensitivity to the crosslinking agent mechlorethamine enable the identification of several AlkX motifs critical for ICL repair. We also find that a genetic variant from an antibiotic-resistant strain of the human pathogen Salmonella enterica reduces AlkX activity in vitro and increases A. baumannii sensitivity to DNA crosslinking. This work provides a structural basis for how bacterial ICL glycosylases recognize and repair DNA adducts and contributes additional evidence that ICL repair is important for fitness of human pathogens.
Shrama A, Zi Y, Pandit AS
… +16 more, Jha K, Sinha VK, Nagesh D, Shivanaiah B, Ravi V, Ghosh S, Khan D, Prabhashankar AB, Sumi TS, Rajpurohit S, Ningaraju S, Raghu S, Srivastava A, Singh M, Lin H, Sundaresan NR
Drawing to understand or explore concepts, complex relationships or cells enhances both creativity and analytical thinking in science. The same process also helps to design clearer, more effective conceptual figures for...Drawing to understand or explore concepts, complex relationships or cells enhances both creativity and analytical thinking in science. The same process also helps to design clearer, more effective conceptual figures for publications. [Image: see text]
Plant cells are connected to their neighbors via plasmodesmata facilitating the exchange of nutrients and signaling molecules. During immune responses, plasmodesmata close, but how this contributes towards a full immune...Plant cells are connected to their neighbors via plasmodesmata facilitating the exchange of nutrients and signaling molecules. During immune responses, plasmodesmata close, but how this contributes towards a full immune response is unknown. To investigate this, we develop two transgenic lines which allow to induce plasmodesmal closure independently of immune elicitors, using the over-active CALLOSE SYNTHASE3 allele icals3m and the C-terminus of PDLP1 to drive callose deposition at plasmodesmata. Induction of plasmodesmal closure increases the expression of stress responsive genes, salicylic acid accumulation and resistance to Pseudomonas syringae DC3000. More homogeneous plasmodesmal closure using icals3m also leads to the accumulation of starch and sugars, decreases leaf growth, as well as hypersusceptibility to Botrytis cinerea. Based on the profile of responses, we conclude that plasmodesmal closure activates stress signaling, raising questions about the signals mediating this response and whether these responses occur in all circumstances when plasmodesmata close.
Eukaryotic mRNAs typically encode a single functional polypeptide, a principle challenged by the discovery of widespread non-canonical peptide-coding ORFs within 5'UTRs. However, their functional significance at the prot...Eukaryotic mRNAs typically encode a single functional polypeptide, a principle challenged by the discovery of widespread non-canonical peptide-coding ORFs within 5'UTRs. However, their functional significance at the protein level remains underexplored. Using a four-layered pipeline, we identify 14 human transcripts predominantly transcribed in polycistronic forms, each encoding two conserved proteins. Focusing on the SLC35A4 transcript, we show that its 5'UTR encodes a mitochondrial inner membrane-localized microprotein that we name STREMI (SLC35A4 stress response regulating MICOS interactor). Sharing topology and motifs with the MICOS core subunit MIC10, STREMI regulates mitochondrial cristae morphogenesis in mice and human cells. Additionally, the STREMI-encoding uORF mediates stress-responsive translation of SLC35A4-a Golgi nucleotide sugar transporter-upregulating its translation during the integrated stress response. Evolutionary analyses indicate that these bicistronic transcripts likely arose through transcriptional readthrough following retroposition. We propose a mechanism of "gene symbiosis" that enables functional partitioning and coordinated translation of protein pairs from bicistronic transcripts.
The Hippo pathway is a tumor suppressor pathway, and most related studies have indicated that its inhibition leads to tumorigenesis. However, recent studies have suggested that the activated Hippo pathway can promote tum...The Hippo pathway is a tumor suppressor pathway, and most related studies have indicated that its inhibition leads to tumorigenesis. However, recent studies have suggested that the activated Hippo pathway can promote tumorigenesis in certain contexts. Here, we demonstrate that the activated Hippo pathway induces non-cell-autonomous tumorigenesis, characterized by tumor markers in the Drosophila wing epithelium. This suggests that Hippo-activated cells behave similarly to "oncogenic niche cells." We find that Hippo-activated cells induce Dronc-Wingless/Spitz signaling in the hinge/ventral notum region, which causes tumorigenesis. Moreover, we identify the amino acid transporters Sat1/2, which are implicated in amino acid incorporation and function redundantly with the growth factors Wingless and Spitz to facilitate non-cell-autonomous tumorigenesis.
The Hippo pathway is classically viewed as a tumor suppressor that limits tissue growth by inhibiting the transcriptional co-activator Yorkie/YAP. Accordingly, Hippo activation is expected to suppress proliferation and c...The Hippo pathway is classically viewed as a tumor suppressor that limits tissue growth by inhibiting the transcriptional co-activator Yorkie/YAP. Accordingly, Hippo activation is expected to suppress proliferation and can promote apoptosis. In this issue, Honda and colleagues challenge the prevailing unidirectional view of Hippo signaling as a purely tumor-suppressive pathway by showing that the outcome of Hippo activation is highly context-dependent in the wing disc (Honda et al, 2026). In the wing pouch, Hippo activation leads primarily to growth suppression, as expected. In contrast, in the hinge and ventral notum, Hippo-activated cells survive and act as “oncogenic niche” cells that stimulate tumorigenic proliferation in neighboring cells. This tumor-promoting effect is mediated by non-apoptotic activity of the initiator caspase Dronc, induction of Wnt and EGF signaling, and metabolic support provided by the amino-acid transporters Sat1 and Sat2, which together drive mTOR activation in nearby cells. These findings reveal how growth suppression in one cell population can paradoxically drive tumor growth in another, reframing Hippo activity as a regulator of tumor-promoting microenvironments.
Macropinocytosis and lysosomal degradation of extracellular protein constitute a nutrient acquisition pathway in Ras-driven cancers. By catabolizing albumin, the most abundant plasma protein, Ras-transformed cells sustai...Macropinocytosis and lysosomal degradation of extracellular protein constitute a nutrient acquisition pathway in Ras-driven cancers. By catabolizing albumin, the most abundant plasma protein, Ras-transformed cells sustain growth in environments where free amino acids are scarce. Under physiological conditions, however, albumin is normally protected from lysosomal degradation by the neonatal Fc receptor (FcRn), which recycles albumin back to the extracellular space. Here, by investigating how cancer cells overcome FcRn-mediated albumin recycling, we identify the Ras-Erk MAPK signaling pathway as a critical regulator of FcRn. Expression of constitutively active Ras variants or stimulation with growth factors represses FcRn transcription through activation of the MAPK pathway, leading to decreased FcRn protein abundance. Conversely, pharmacological inhibition of Ras-MAPK signaling de-represses FcRn expression. Restoring FcRn levels in Ras-transformed cells limits lysosomal albumin degradation and impairs the proliferation of cells that depend on albumin as an essential amino acid source. Thus, oncogenic Ras signaling promotes the nutritional utilization of albumin by suppressing FcRn, thereby supporting cancer cell adaptation to nutrient-poor environments.
Telomerase biogenesis is a multistep process requiring the coordinated action of several accessory factors. In the fission yeast Schizosaccharomyces pombe, the telomerase RNA TER1 undergoes spliceosome-mediated 3'-end pr...Telomerase biogenesis is a multistep process requiring the coordinated action of several accessory factors. In the fission yeast Schizosaccharomyces pombe, the telomerase RNA TER1 undergoes spliceosome-mediated 3'-end processing, followed by association with the Pof8/Bmc1/Thc1 complex, which facilitates binding of the Lsm2-8 complex. Lsm2-8 protects TER1 from nucleolytic degradation and promotes recruitment of the catalytic subunit Trt1. Here, we identify Pop6, Pop7, and Pop100, three subunits of the RNase P/MRP complex, as components of the active telomerase holoenzyme. These proteins associate with a stem-loop-stem structure near the TER1 pseudoknot that resembles the P3 domain found in RNase P/MRP RNAs. A single-nucleotide change within this P3-like loop disrupts Pop protein binding, resulting in reduced telomerase activity and severe telomere shortening. This mutation also impairs the assembly of key telomerase subunits and alters the folding of the template-pseudoknot region of TER1. Our findings reveal a critical role for Pop6, Pop7, and Pop100 in chaperoning TER1 into a conformation that promotes functional telomerase assembly and underscore the remarkable evolutionary plasticity of telomerase biogenesis.
Fasting initiates a coordinated metabolic response to preserve energy balance. As glycogen stores are depleted, the body transitions to mobilizing fatty acids from adipose tissue and generating ketone bodies in the liver...Fasting initiates a coordinated metabolic response to preserve energy balance. As glycogen stores are depleted, the body transitions to mobilizing fatty acids from adipose tissue and generating ketone bodies in the liver to sustain the function of vital organs. A network of hormonal signals and transcriptional programs coordinate these adaptations. Among these, the hepatokine fibroblast growth factor 21 (FGF21) is strongly upregulated during fasting and has been proposed as a key mediator of the fasting response. To investigate the physiological functions of FGF21, we study mice with hepatocyte-specific deletion of Fgf21. Although the liver is the primary source of circulating FGF21 during fasting, its absence in hepatocytes does not alter typical fasting-induced gene expression or key metabolic pathways such as hepatic gluconeogenesis, adipose tissue lipolysis, or ketone production. Instead, we uncover a distinct role for FGF21 in promoting protein appetite following a fast. These findings challenge the conventional view of hepatocyte-produced FGF21 as a fasting-acting hormone and reveal a more specialized function in guiding nutrient selection after energy depletion.
Flores-Garcia Y, Aguirre-Botero MC, Tripathi P
… +10 more, Locke E, Park M, Mathis-Torres S, Salgado-Jimenez B, Herrera-Arevalo S, Gladston A, Asady B, Coppens I, Amino R, Zavala F
Protection against infection by Plasmodium falciparum sporozoites is mediated in part by antibodies that recognize the repeated (NPNA)3 epitopes of the circumsporozoite protein (CSP). To evaluate the role that the antibo...Protection against infection by Plasmodium falciparum sporozoites is mediated in part by antibodies that recognize the repeated (NPNA)3 epitopes of the circumsporozoite protein (CSP). To evaluate the role that the antibody Fc region plays in neutralizing sporozoite infectivity, we assess the protective efficacy of Fab fragments obtained from protective human monoclonal antibodies and use antibodies bearing the LALA and KA mutations known to reduce Fc functions. To determine the impact of multiple-antibody binding to CSP on protection, we use sporozoites from genetically modified P. berghei strains expressing a CSP containing different numbers of (NPNA)3 epitopes. Our results indicate that Fab fragments and Fc-mutated antibodies have a protective efficacy comparable to intact antibodies, indicating a limited role, if any, of Fc functions in sporozoites in this model system. We also determine that antibody binding to multiple adjacent epitopes and the establishment of homotypic interactions between bound antibodies may not be necessary for protection, as binding to one epitope is sufficient to strongly reduce liver burden while only two separate epitopes are needed to achieve sterile protection.
Mitochondrial and lysosomal abnormalities co-occur in aging-related diseases with progressive tissue atrophy. It remains unclear whether these two pathogenic pathways affect tissue homeostasis independently, convergently...Mitochondrial and lysosomal abnormalities co-occur in aging-related diseases with progressive tissue atrophy. It remains unclear whether these two pathogenic pathways affect tissue homeostasis independently, convergently or epistatically. We show that mitochondrial protein import stress causes vacuolar damage in yeast, manifested by V-ATPase disassembly, and vacuolar deacidification and fragmentation. In a mouse model of mitochondrial protein import stress induced by overloading of the nuclear-encoded ANT1 protein, we observe progressive muscle atrophy independent of bioenergetic defects. Like in yeast mutants with severe vacuolar damage, genes involved in amino acid uptake/biosynthesis, one-carbon metabolism, lysosomal biogenesis and iron homeostasis are activated in the skeletal muscle of Ant1-transgenic mice. The affected muscles accumulate glycogen, lipofuscin and poorly processed multivesicular bodies. Despite activation of lysosomal repair and lysophagic pathways, autophagic flux is severely stalled. During aging, various proteolytic cathepsins are increasingly released from the lysosomal lumen into the cytosol. Together with proteasomal activation, this may contribute to unbalanced proteostasis, reduced myofiber size and skeletal muscle atrophy. Our study therefore discovered an evolutionarily conserved mitochondria-to-lysosome proteotoxic axis that affects tissue mass homeostasis during aging.
Neural progenitor cell (NPC) proliferation is fundamental for population expansion and brain development. G phase control determines the cell cycle duration of NPCs and thereby affects their proliferation efficiency. How...Neural progenitor cell (NPC) proliferation is fundamental for population expansion and brain development. G phase control determines the cell cycle duration of NPCs and thereby affects their proliferation efficiency. However, the molecular mechanisms governing G phase progression in NPCs remain unclear. Here, we show that AKT gain-of-function mutations and pharmacological inhibition exert opposing effects on NPC proliferation. Consistently, Emx1-Cre-mediated deletion of Akt1/2/3 in mice impairs NPC proliferation and disrupts cortical development. We find that AKT deficiency induces G phase arrest and prolongs the cell cycle of NPCs. Mechanistically, we demonstrate that AKT-mediated phosphorylation inhibits the activity of CRL4 E3 ubiquitin ligase to safeguard cyclin D2 (CCND2) stability. Specifically, AKT phosphorylates DDB1, the adaptor of CRL4, which disrupts its interaction with CCND2 and reduces its degradation. These findings reveal a post-translational mechanism impacting NPC cell cycle and cortical morphogenesis, providing insight into the etiology of malformations of cortical development.
Niven J, Kucuk S, Gope A
… +37 more, Certo M, Cassidy FC, Arana Echarri A, Ali S, Ladoukakis E, Vidali S, Macchi C, Amir SS, Bergin R, Davies S, Perkin OJ, Smith J, Cucchi D, Heneghan H, Wijesinghe S, Jenkins BJ, Baig S, Mahony C, Chidomere C, Sarkar S, Nicolaou A, Caamaño J, Croft A, Davies E, Thompson D, O'Shea D, Jones SW, Duggal NA, Ruscica M, Makarova M, Jones N, Da Silva Xavier G, Geberhiwot T, Turner JE, Hogan AE, Nedjai B, Mauro C
Obesity represents a major global healthcare crisis, with childhood obesity rising at an alarming rate. Children with obesity are highly likely to carry it into adulthood, bringing numerous associated health risks. Even...Obesity represents a major global healthcare crisis, with childhood obesity rising at an alarming rate. Children with obesity are highly likely to carry it into adulthood, bringing numerous associated health risks. Even more troubling is the emerging understanding of "obesity memory", which contributes to the frequent issue of weight regain. Here, we show that obesity imprints CD4 T cells through DNA methylation, leading to a long-time lag, spanning years, before adaptive immune homeostasis is restored after weight loss. Differential DNA methylation analysis highlights autophagy and immune senescence as potential key mechanisms underpinning this memory of obesity in CD4 T cells. In addition, particularly palmitate could be a key saturated fatty acid that can contribute to epigenetic alterations in CD4 T cells, potentially perpetuating this altered state. We identify molecular candidates (i.e., Stk26 and Cdkn1c) underpinning key cell functions (autophagy and immune senescence) that could be targeted to promote a return to immune homeostasis alongside weight loss. These findings raise the possibility that targeting such pathways could support the restoration of immune homeostasis alongside weight loss therapies.
The failure of negotiations to address plastic pollution and its impact on public health and the environment reflects deeper geopolitical fragmentation and a crisis of multilateralism. It highlights the need to strengthe...The failure of negotiations to address plastic pollution and its impact on public health and the environment reflects deeper geopolitical fragmentation and a crisis of multilateralism. It highlights the need to strengthen shared commitments across affective, normative, interest-based, and institutional dimensions to enable global action. [Image: see text]
Maintaining the germline fate requires tight post-transcriptional control of RNA function. Here, we investigate how primordial germ cell (PGC) identity is maintained in zebrafish and reveal that the conserved RNA-binding...Maintaining the germline fate requires tight post-transcriptional control of RNA function. Here, we investigate how primordial germ cell (PGC) identity is maintained in zebrafish and reveal that the conserved RNA-binding proteins Nanos3 and Dead End1 form a complex that safeguards PGC identity. Using transcriptomics and in vivo imaging-based analyses, we show that this complex controls the translational activation and localization of both nanos3 and dead end1 RNAs, establishing a positive feedback loop crucial for regulating their protein expression. These findings uncover a previously unknown layer of control over germline development, where a complex containing Nanos3, a protein associated with the inhibition of RNA translation, acts as an activator by interacting with an eIF3 complex protein to promote translation, thereby maintaining specific RNAs at the periphery of phase-separated germ cell granules. Disrupting the physical interaction between Nanos3 and Dead End1 leads to transdifferentiation of germ cells into somatic lineages. Overall, our findings identify a self-sustaining mechanism of translational activation in vivo, positioning the Nanos3-Dead End1 complex as a central effector of germline fate.
Histone modifications play critical roles in regulating chromatin dynamics and embryonic development. Among these, histone H4 lysine 20 mono-methylation (H4K20me1) is an essential epigenetic mark associated with gene exp...Histone modifications play critical roles in regulating chromatin dynamics and embryonic development. Among these, histone H4 lysine 20 mono-methylation (H4K20me1) is an essential epigenetic mark associated with gene expression and genome stability. However, the reprogramming and functional roles of H4K20me1 in early embryogenesis remain unclear. Here, we map genome-wide distributions of H4K20me1 in mouse, human, and zebrafish early embryos, revealing a broad distribution pattern along with species-specific features. H4K20me1 is predominantly enriched in gene bodies and undergoes dynamic erasure and reestablishment following fertilization. Functional perturbation of SET8, the only known H4K20me1 methyltransferase, results in developmental arrest, highlighting its necessity for embryogenesis. Mechanistically, H4K20me1 is crucial for zygotic genome activation (ZGA), where it regulates RNA synthesis and transcription, and promotes chromatin accessibility. Our findings provide insights into the dynamic reprogramming and regulatory functions of H4K20me1 in early developmental processes.
Cytomegaloviruses are highly adapted to their hosts through millions of years of co-evolution. Most human (H)CMV infections occur early in life when the virus enters via the mucosal surfaces of the respiratory or gastroi...Cytomegaloviruses are highly adapted to their hosts through millions of years of co-evolution. Most human (H)CMV infections occur early in life when the virus enters via the mucosal surfaces of the respiratory or gastrointestinal tract. These infections are usually asymptomatic, but coincide with critical phases of immune development, shaping long-term host immunity. In rare but clinically significant cases, CMV can invade protected sites, such as the central nervous system, leading to symptomatic disease. As the most abundant immune cells at barrier sites, myeloid cells support all stages of the viral life cycle: replication, dissemination, and latency. During the perinatal period, the myeloid compartment undergoes profound changes, including macrophage maturation, monocyte influx, and functional adaptation. CMV may exploit these developmental transitions to establish infection and to cross tissue barriers. This review discusses how CMV manipulates myeloid immune cells to establish postnatal infection, particularly via the respiratory tract, and explores strategies by which CMVs breach the placental barrier and access the fetal brain. The review integrates evidence from multiple CMV species, with emphasis on human and mouse data.
Wnt/β-catenin signaling regulates oocyte development in vertebrates. However, the dynamics of Wnt/β-catenin signaling in oocyte progression remain unclear. Here, we analyze oocytes across different developmental stages i...Wnt/β-catenin signaling regulates oocyte development in vertebrates. However, the dynamics of Wnt/β-catenin signaling in oocyte progression remain unclear. Here, we analyze oocytes across different developmental stages in zebrafish and find that the activity of Wnt/β-catenin signaling sharply increases when oocytes reach a size of 10 to 45 μm (stage IA to middle stage IB) and subsequently declines rapidly. In addition, we show that expression of the CST complex subunit Stn1 is enriched in germ cells. Stn1 interacts with the transcription factor Tcf/Lef, facilitates its association with promoters of germ cell-specific genes, thereby enhancing Wnt/β-catenin signaling activity in oocytes. Genetic deletion of stn1 leads to massive loss of oocytes prior to or during their development to stage IB, resulting in a male-like phenotype associated with infertility. Temporal activation of the Wnt/β-catenin signaling pathway partially restores germ cell loss and facilitates oocyte development to stage IB. Our findings highlight the importance of Wnt/β-catenin signaling in promoting the expression of germ cell-specific genes and provide novel insights into the physiological function of Stn1 in maintaining oocyte development in zebrafish.
This article highlights the benefits of preregistration in improving the reliability and transparency of in vitro studies. By preregistering their studies, researchers can make their findings more reproducible, paving th...This article highlights the benefits of preregistration in improving the reliability and transparency of in vitro studies. By preregistering their studies, researchers can make their findings more reproducible, paving the way for medical progress, and accelerating the replacement of animal experiments. [Image: see text]