Biology subjects

Cao, Q.

Publications and source records attributed to Cao, Q..

At least 91 records · Page 5Linked to original sources

bioRxiv2020

Plant-specific histone deacetylases are essential for early as well as late stages of Medicago nodule development

Legume and rhizobium can establish a nitrogen-fixing nodule symbiosis. Previous studies have shown that several transcription factors that play a role in (lateral) root development are also involved in nodule development. Chromatin remodelling factors, like transcription factors, are key players in regulating gene expression. However, it has not been studied whether chromatin remodelling genes that are essential for root development get involved in nodule development. Here we studied the role of Medicago histone deacetylases (MtHDTs) in nodule development. Their Arabidopsis orthologs have been shown to play a role in root development. The expression of MtHDTs is induced in nodule primordia and is maintained in nodule meristem and infection zone. Conditional knock-down of their expression in a nodule-specific way by RNAi blocks nodule primordium development. A few nodules still can be formed but their nodule meristems are smaller and rhizobial colonization of the cells derived from the meristem is markedly reduced. Although the HDTs are expressed during nodule and root development, transcriptome analyses indicate that HDTs control the development of these organs in a different manner. During nodule development the MtHDTs positively regulate 3-hydroxy-3-methylglutaryl coenzyme a reductase 1 (MtHMGR1). The decreased expression of MtHMGR1 is sufficient to explain the block of primordium formation. ONE SENTENCE SUMMARYPlant-specific histone deacetylases regulate the expression of 3-hydroxy-3-methylglutaryl-coenzyme A reductases to control root nodule development.

developmental biology↗

bioRxiv2020

Large-scale single-cell analysis reveals critical immune characteristics of COVID-19 patients

Dysfunctional immune response in the COVID-19 patients is a recurrent theme impacting symptoms and mortality, yet the detailed understanding of pertinent immune cells is not complete. We applied single-cell RNA sequencing to 284 samples from 205 COVID-19 patients and controls to create a comprehensive immune landscape. Lymphopenia and active T and B cell responses were found to coexist and associated with age, sex and their interactions with COVID-19. Diverse epithelial and immune cell types were observed to be virus-positive and showed dramatic transcriptomic changes. Elevation of ANXA1 and S100A9 in virus-positive squamous epithelial cells may enable the initiation of neutrophil and macrophage responses via the ANXA1-FPR1 and S100A8/9-TLR4 axes. Systemic upregulation of S100A8/A9, mainly by megakaryocytes and monocytes in the peripheral blood, may contribute to the cytokine storms frequently observed in severe patients. Our data provide a rich resource for understanding the pathogenesis and designing effective therapeutic strategies for COVID-19. HIGHLIGHTSO_LILarge-scale scRNA-seq analysis depicts the immune landscape of COVID-19 C_LIO_LILymphopenia and active T and B cell responses coexist and are shaped by age and sex C_LIO_LISARS-CoV-2 infects diverse epithelial and immune cells, inducing distinct responses C_LIO_LICytokine storms with systemic S100A8/A9 are associated with COVID-19 severity C_LI

genomics↗

bioRxiv2020

Development and validation of an open-source, disposable, 3D-printed in vitro environmental exposure system for Transwell culture inserts

Accessible in vitro models recapitulating the human airway that are amenable to study whole cannabis smoke exposure are needed for immunological and toxicological studies that inform public health policy and recreational cannabis use. In the present study, we developed and validated a novel 3D printed In Vitro Exposure System (IVES) that can be directly applied to study the effect of cannabis smoke exposure on primary human bronchial epithelial cells. Using commercially available design software and a 3D printer, we designed a four-chamber Transwell(R) insert holder for exposures to whole smoke. Software was used to model gas distribution, concentration gradients, velocity profile and shear stress within IVES. Following simulations, primary human bronchial epithelial cells cultured at air-liquid interface on Transwell(R) inserts were exposed to whole cannabis smoke. Following 24 hours, outcome measurements included cell morphology, epithelial barrier function, lactate dehydrogenase (LDH) levels, cytokine and gene expression. Whole smoke delivered through IVES possesses velocity profiles consistent with uniform gas distribution across the four chambers and complete mixing. Airflow velocity ranged between 1.0-1.5 m s-1 and generated low shear stresses (<< 1 Pa). Human airway epithelial cells exposed to cannabis smoke using IVES showed changes in cell morphology and disruption of barrier function without significant cytotoxicity. Cannabis smoke elevated IL-1 family cytokines and elevated CYP1A1 and CYP1B1 expression relative to control. IVES represents an accessible, open-source, exposure system that can be used to model varying types of cannabis smoke exposures with human airway epithelial cells grown under air-liquid interface culture conditions.

bioengineering↗

bioRxiv2020

LPA/PKD-1 signaling promotes development of arteriolar niche that supports self-renewal of breast cancer stem cells and stemness

Breast cancer stem cells (BCSCs) are essential for cancer growth, metastasis and recurrence. However, the regulatory mechanisms of self-renewal and interactions with the vascular niche within tumor microenvironment are currently under investigation. Here, we demonstrate that BCSCs are enriched within arteriolar niche within the tumor microenvironment of estrogen receptor positive (ER+) BC and bi-directionally interact with arteriolar endothelial cells (ECs). Mechanistically, this interaction is driven by the LPA/PKD-1 signaling pathway, which promotes arteriolar differentiation and self-renewal. Furthermore, this pathway directly promotes stemness features. These findings suggest that targeting LPA/PKD-1 signaling may disrupt the arteriolar niche within the tumor microenvironment and concomitantly eradicate BCSCs, thereby attenuating BC progression.

cancer biology↗

bioRxiv2020

PFRED: A computational platform for siRNA and antisense oligonucleotides design.

PFRED a software application for the design, analysis, and visualization of antisense oligonucleotides and siRNA is described. The software provides an intuitive user-interface for scientists to design a library of siRNA or antisense oligonucleotides that target a specific gene of interest. Moreover, the tool facilitates the incorporation of various design criteria that have been shown to be important for stability and potency. PFRED has been made available as an open-source project so the code can be easily modified to address the future needs of the oligonucleotide research community. A compiled version is available for downloading at https://github.com/pfred/pfred-gui/releases as a java Jar file. The source code and the links for downloading the precompiled version can be found at https://github.com/pfred.

bioinformatics↗

bioRxiv2020

Simultaneous transcriptome and methylome profiles of single mouse oocytes provide novel insights on maturation and aging

BackgroundAdvanced maternal aging has become a worldwide public health issue that contributes to female fertility decline and significant risk to embryo development. Despite transcriptional and epigenetic alterations reported in oocyte maturation and development, the dynamics of gene expression and DNA dynamics associated with aging remain elusive. Here we generated simultaneous transcriptome and methylome profiles of mouse oocytes during aging and maturation at single-cell and single-base resolution to examine key biological processes and identify the key targets for novel treatment options. ResultsWe report the dynamics in transcriptome and DNA methylome in mouse oocytes during maternal aging and oocyte maturation. Age-associated gene expression changes showed mitochondrial dysfunction in GV oocytes and defects of chromosome segregation and spindle assembly in MII oocytes. EIF2 signaling protein synthesis pathway was also impaired during aged oocyte maturation. Moreover, distinctive DNA methylation patterns were demonstrated during maternal aging in GV and MII oocytes. A positive correlation between gene expression and methylation in gene body was characterized. Furthermore, we identified several promising biomarkers, including IL-7, to assess oocyte quality, which are potential therapeutic targets for improve oocyte maturation. More importantly, we built the first mouse oocyte maturation and age prediction model using transcriptome data and validated its feasibility in published data. ConclusionsThis work provides a better understanding of molecular and cellular mechanisms during mouse oocyte aging, points a new direction of oocyte quality assessment, and paves the way for developing novel treatments to improve oocyte maturation and quality in the future.

genomics↗

bioRxiv2020

A novel copper-sensing two-component system for activating Dsb genes in bacteria

Copper is an essential element for biological systems but becomes toxic when present in excess. In Pseudomonas aeruginosa, an important human pathogen, the resistance to copper requires the induction of dsbDEG operon encoding proteins involved in disulfide-bond formation (Dsb). However, it is unknown how the copper stress induces the transcription of the operon. Here, we report that the exogenous copper induces the transcription of the dsbDEG operon through a new copper-sensing two-component system named DsbRS. The dsbRS is divergently transcribed from the dsbDEG operon, and the response regulator DsbR binds to the intergenic region between the operons. In the absence of copper, the sensor kinase DsbS acts as a phosphatase toward DsbR and thus blocks the transcription of the operons. However, in the presence of copper, the metal ion directly binds to the sensor domain of DsbS, for which the Cys82 residue plays a critical role. The copper-binding appears to inhibit the phosphatase activity of DsbS, leading to activation of DsbR. The copper resistance of the dsbRS knock-out mutant was restored by ectopic expression of the dsbDEG operon, confirming the critical role of the operon in the resistance to copper. Strikingly, cognates of dsbRS-dsbDEG pair are widely distributed across eubacteria. Also, a DsbR-binding site, which contains the consensus sequence 5-TAA-N7-TTAAT-3, is detected in the promoter region of dsbDEG homologs in those species. Thus, regulation of Dsb genes by DsbRS represents a novel mechanism by which bacterial cells cope with copper stress. ImportanceCopper is an essential redox active cofactor that becomes highly cytotoxic when present in excess. Therefore, in order to evade copper toxicity, bacteria must perceive copper stress and tightly regulate genes expression. In the present study, we identify a new copper-sensing two-component system (designated DsbRS) in Pseudomonas aeruginosa, an important human pathogen. We provide multiple lines of evidence that upon copper binding to the periplasmic domain of DsbS, its phosphatase activity is blocked, and the phosphorylated DsbR directly activates the transcription of a number of copper-induced genes including those involved in protein disulfide-bond formation (Dsb). This study suggests that regulation of Dsb genes by DsbRS may be an underappreciated regulatory mechanism by which bacteria sense and respond to copper.

microbiology↗

bioRxiv2020

MACMIC Reveals Dual Role of CTCF in Epigenetic Regulation of Cell Identity Genes

Numerous studies of relationship between epigenomic features have focused on their strong correlation across the genome, likely because such relationship can be easily identified by many established methods for correlation analysis. However, two features with little correlation may still colocalize at many genomic sites to implement important functions. There is no bioinformatic tool for researchers to specifically identify such feature pair. Here, we develop a method to identify feature pair in which two features have maximal colocalization but minimal correlation (MACMIC) across the genome. By MACMIC analysis of 3,385 feature pairs in 15 cell types, we reveal a dual role of CTCF in epigenetic regulation of cell identity genes. Although super-enhancers are associated with activation of target genes, only a subset of super-enhancers colocalized with CTCF regulate cell identity genes. At super-enhancers colocalized with CTCF, the CTCF is required for the active marker H3K27ac in cell type requiring the activation, and also required for the repressive marker H3K27me3 in other cell types requiring the repression. Our work demonstrates the biological utility of the MACMIC analysis and reveals a key role for CTCF in epigenetic regulation of cell identity.

bioinformatics↗

bioRxiv2020

Epigenetic Interaction between UTX and DNMT1 Regulates Diet-Induced Myogenic Remodeling in Brown Fat

Brown adipocytes share the same developmental origin with skeletal muscle. Here we find that a brown adipocyte-to-myocyte remodeling also exists in mature brown adipocytes, and is induced by prolonged high fat diet (HFD) feeding, leading to brown fat dysfunction. This process is regulated by the interaction of epigenetic pathways involving histone and DNA methylation. In mature brown adipocytes, the histone demethylase UTX maintains persistent demethylation of the repressive mark H3K27me3 at Prdm16 promoter, leading to high Prdm16 expression. PRDM16 then recruits DNA methyltransferase DNMT1 to Myod1 promoter, causing Myod1 promoter hypermethylation and suppressing its expression. The interaction between PRDM16 and DNMT1 coordinately serves to maintain brown adipocyte identity while repressing myogenic remodeling in mature brown adipocytes, thus promoting their active brown adipocyte thermogenic function. Suppressing this interaction by HFD feeding induces brown adipocyte-to-myocyte remodeling, which limits brown adipocyte thermogenic capacity and compromises diet-induced thermogenesis, leading to the development of obesity.

physiology↗

bioRxiv2020

Adipose tissue-derived neurotrophic factor 3 regulates sympathetic innervation and thermogenesis in adipose tissue

Activation of brown fat thermogenesis increases energy expenditure and alleviates obesity. Sympathetic nervous system (SNS) is important in brown/beige adipocyte thermogenesis. Here we discover a novel fat-derived “adipokine” neurotrophic factor neurotrophin 3 (NTF3) and its receptor Tropomyosin receptor kinase C (TRKC) as key regulators of SNS growth and innervation in adipose tissue. NTF3 is highly expressed in brown/beige adipocytes, and potently stimulates sympathetic neuron neurite growth. NTF3/TRKC regulates a plethora of pathways in neuronal axonal growth and elongation. Adipose tissue sympathetic innervation is significantly increased in mice with adipocyte-specific NTF3 overexpression, but profoundly reduced in mice with TRKC haploinsufficiency (TRKC+/-). Increasing NTF3 via pharmacological or genetic approach promotes beige adipocyte development, enhances cold-induced thermogenesis and protects against diet-induced obesity (DIO); whereas TRKC+/- mice or SNS TRKC deficient mice are cold intolerant and prone to DIO. Thus, NTF3 is an important fat-derived neurotrophic factor regulating SNS innervation, energy metabolism and obesity.Competing Interest StatementThe authors have declared no competing interest.View Full Text

physiology↗

bioRxiv2020

Cryo-EM structure and inhibitor design of human IAPP (amylin) fibrils

Human islet amyloid polypeptide (hIAPP, or amylin) is a 37 amino acid hormone secreted by pancreatic islet {beta}-cells. Aggregation of hIAPP into amyloid fibrils is found in more than 90% of Type-II Diabetes (T2D) patients and is considered to be associated with T2D pathology. Although different models have been proposed, the high resolution structure of hIAPP fibrils is unknown. Here we report the cryo-EM structure of recombinant full-length hIAPP fibrils. The fibril is composed of two symmetrically-related protofilaments with ordered residues 14-37 that meet at a 14-residue central hydrophobic core. Our hIAPP fibril structure (i) supports the previous hypothesis that residues 20-29, especially 23-29 are the primary amyloid core of hIAPP, (ii) suggests a molecular mechanism for the action of the hIAPP hereditary mutation S20G, (iii) explains why the 6 residue substitutions in rodent IAPP prevent aggregation, and (iv) suggests possible regions responsible for the observed hIAPP cross-seeding with {beta}-amyloid. Furthermore, we performed structure-based inhibitor design to generate potential hIAPP aggregation inhibitors via a capping strategy. Four of the designed candidates delay hIAPP aggregation in vitro, providing a starting point for the development of T2D therapeutics and proof-of-concept that the capping strategy can be used on full-length cryo-EM fibril structures.

biochemistry↗

bioRxiv2020

The cryoEM structure of the fibril-forming low-complexity domain of hnRNPA2 reveals distinct differences from pathogenic amyloid and shows how mutation converts it to the pathogenic form

hnRNPA2 is one of a group of human ribonucleoproteins (RNPs) involved in RNA metabolism which form fibrils both under cellular stress and in mutated form in neurodegenerative conditions. Previous work established that the C-terminal low-complexity domain (LCD) of hnRNPA2 fibrillizes under stress, and that missense mutations in this domain are found in the disease multisystem proteinopathy (MSP) with symptoms indistinguishable from ALS and FTD. However, little is known at the atomic level about the hnRNPA2 LCD structure that is involved in those processes and how disease mutations cause structural change. Here we present the cryo-electron microscopy (cryoEM) structure of hnRNPA2 LCD fibril core and demonstrate its capability to form a reversible hydrogel in vitro containing amyloid-like fibrils. Whereas these fibrils, like pathogenic amyloid, are formed from protein chains stacked into {beta}-sheets by backbone hydrogen bonds, they display distinct structural differences: the chains are kinked, enabling non-covalent cross-linking of fibrils and disfavoring formation of pathogenic steric zippers. Both their reversibility and energetic calculations suggest these fibrils are less stable than pathogenic amyloid. Moreover, the crystal structure of the disease-mutation-containing segment of hnRNPA2 suggests that the replacement fundamentally alters the fibril structure to a more stable energetic state. These findings illuminate how molecular interactions promote protein fibril networks and how mutation can transform fibril structure from functional to pathogenic form.

molecular biology↗

bioRxiv2020

The acetyltransferase Eco1 elicits cohesin dimerization during S phase

Sister chromatid cohesion is established by Eco1 in S phase. Nevertheless, the exact consequence of Eco1-catalyzed acetylation is unknown, and the cohesive state remains highly controversial. Here we show that self-interactions of cohesin subunits Scc1/Rad21 and Scc3 occur in a DNA replication-coupled manner in both yeast and human. Through cross-linking mass spectrometry and VivosX analysis of purified cohesin, we show that a subpopulation of cohesin may exist as dimers. Importantly, cohesin-cohesin interaction becomes significantly compromised when Eco1 is depleted. On the other hand, deleting either deacetylase Hos1 or Eco1 antagonist Wpl1/Rad61 results in an increase (e.g., from [~]20% to 40%) of cohesin dimers. These findings suggest that cohesin dimerization is controlled by common mechanisms as the cohesion cycle, thus providing an additional layer of regulation for cohesin to execute various functions such as sister chromatid cohesion, DNA repair, gene expression, chromatin looping and high-order organization. Author SummaryCohesin is a ring that tethers sister chromatids since their synthesis during S phase till their separation in anaphase. According to the single-ring model, one ring holds twin sisters. Here we show a conserved cohesin-cohesin interaction from yeast to human. A subpopulation of cohesin is dimerized concomitantly with DNA replication. Cohesin dimerization is dependent on the acetyltransferase Eco1 and counteracted by the anti-establishment factor Wpl1 and deacetylase Hos1. Approximately 20% of cellular cohesin complexes are measured to be dimers, close to the level of Smc3 acetylation by Eco1 in vivo. These findings provide evidence to support the double-ring model in sister chromatid cohesion.

biochemistry↗

bioRxiv2019

The inhibition of cellular toxicity of amyloid-beta by dissociated transthyretin

The protective effect of transthyretin (TTR) on cellular toxicity of amyloid-beta (A{beta}) has been previously reported. TTR is a tetrameric carrier of thyroxine in blood and cerebrospinal fluid, whose pathogenic aggregation causes systemic amyloidosis. In contrast, many reports have shown that TTR binds amyloid-beta (A{beta}), associated with Alzheimers disease, alters its aggregation, and inhibits its toxicity both in vitro and in vivo. In this study, we question whether TTR amyloidogenic ability and its anti-amyloid inhibitory effect are associated. Our results indicate that the dissociation of the TTR tetramer, required for its amyloid pathogenesis, is also necessary to prevent cellular toxicity from A{beta} oligomers. These findings suggest that the A{beta} binding site of TTR may be hidden in its tetrameric form. Aided by computational docking and peptide screening, we identified a TTR segment that is capable of altering A{beta} aggregation and toxicity, mimicking TTR cellular protection. This segment inhibits A{beta} oligomer formation and also promotes the formation of non-toxic, non-amyloid, amorphous aggregates which are more sensitive to protease digestion. This segment also inhibits seeding of A{beta} catalyzed by A{beta} fibrils extracted from the brain of an Alzheimers patient. Our results suggest that mimicking the inhibitory effect of TTR with peptide-based therapeutics represents an additional avenue to explore for the treatment of Alzheimers disease. Significance statementThe pathological landmarks of Alzheimers disease are the formation of amyloid plaques and neurofibrillary tangles. Amyloid plaques contain fibrous structures made of aggregated amyloid-beta (A{beta}). In 1982, Shirahama and colleagues observed the presence of transthyretin (TTR) in these plaques. TTR is a tetrameric protein whose aggregation causes transthyretin amyloidosis. However, TTR protects A{beta} from aggregating and causing toxicity to neurons. In this study, we show that the dissociation of TTR tetramers is required to inhibit cellular toxicity caused by A{beta}. In addition, we identified a minimum segment of TTR that inhibits A{beta} aggregation and cellular toxicity by the formation of amorphous aggregates that are sensitive to proteases, similar to the natural effect of TTR found by others in vivo.

biochemistry↗

bioRxiv2019

An integrative ENCODE resource for cancer genomics

ENCODE comprises thousands of functional genomics datasets, and the encyclopedia covers hundreds of cell types, providing a universal annotation for genome interpretation. However, for particular applications, it may be advantageous to use a customized annotation. Here, we develop such a custom annotation by leveraging advanced assays, such as eCLIP, Hi-C, and whole-genome STARR-seq on a number of data-rich ENCODE cell types. A key aspect of this annotation is comprehensive and experimentally derived networks of both transcription factors and RNA-binding proteins (TFs and RBPs). Cancer, a disease of system-wide dysregulation, is an ideal application for such a network-based annotation. Specifically, for cancer-associated cell types, we put regulators into hierarchies and measure their network change (rewiring) during oncogenesis. We also extensively survey TF-RBP crosstalk, highlighting how SUB1, a previously uncharacterized RBP, drives aberrant tumor expression and amplifies the effect of MYC, a well-known oncogenic TF. Furthermore, we show how our annotation allows us to place oncogenic transformations in the context of a broad cell space; here, many normal-to-tumor transitions move towards a stem-like state, while oncogene knockdowns show an opposing trend. Finally, we organize the resource into a coherent workflow to prioritize key elements and variants, in addition to regulators. We showcase the application of this prioritization to somatic burdening, cancer differential expression and GWAS. Targeted validations of the prioritized regulators, elements and variants using siRNA knockdowns, CRISPR-based editing, and luciferase assays demonstrate the value of the ENCODE resource.

genomics↗

bioRxiv2019

Serum-free culture system for spontaneous human mesenchymal stem cell spheroids formation

Human mesenchymal stem cells (hMSCs) are widely used in clinical research because of their multipotential, immunomodulatory, and reparative properties. Previous studies determined that hMSC spheroids from three-dimensional (3D) culture possess higher therapeutic efficacy than conventional hMSCs from monolayer (2D) culture. To date, various 3D culture methods have been developed to form hMSC spheroids, but most of them used culture medium containing fetal bovine serum (FBS), which is not suitable for further clinical use. Here, we demonstrate that dissociated single MSCs seeded in induced pluripotent stems medium (MiPS), adhere loosely to the dish and spontaneously migrate to form spheroids during day 3 to day 6. Through component deletion screening and complementation experiments, the knockout serum replacement (KSR) was identified as necessary and sufficient for hMSC spheroid formation. Transcriptome analysis showed that the overall expression profiles were highly similar between 2D culture with FBS and KSR derived spheroids. Interestingly, genes related to inflammatory response, immune response, and angiogenesis were up-regulated in spheroids at day 6, and qPCR results further validated the increased expression level of related genes, including STC1, CCL7, HGF, IL24, and TGFB3. When spheroids were re-plated in normal FBS medium, cells formed a typical spindle-shaped morphology, and FACS results showed that the recovered cells retained MSC-specific surface markers, such as CD73, CD90, and CD105. In summary, we developed a practical and convenient method to generate hMSC spheroids for clinical research and therapy.

cell biology↗

bioRxiv2019

Polycomb contraction differentially regulates terminal human hematopoietic differentiation programs

Lifelong production of the many types of mature blood cells from less differentiated progenitors is a hierarchically ordered process that spans multiple cell divisions. The nature and timing of the molecular events required to integrate the environmental signals, transcription factor activity, epigenetic modifications, and changes in gene expression involved are thus complex and still poorly understood. We now show that the more primitive types of human cells in this system display a unique repressive H3K27me3 signature that is retained by mature lymphoid cells but is lost in terminally differentiated monocytes and erythroblasts. Additional intervention data implicate that control of this chromatin state change is a requisite part of the process, whereby normal human hematopoietic progenitor cells make lymphoid and myeloid fate decisions.

cell biology↗

bioRxiv2019

Mck1 defines a key S-phase checkpoint effector in response to various degrees of replication threats

The S-phase checkpoint plays an essential role in regulation of the ribonucleotide reductase (RNR) activity to maintain the dNTP pools. How eukaryotic cells respond appropriately to different levels of replication threats remains elusive. Here, we have identified that a conserved GSK-3 kinase Mck1 cooperates with Dun1 in regulating this process. Deleting MCK1 sensitizes dun1{Delta} to hydroxyurea (HU) reminiscent of mec1{Delta} or rad53{Delta}. As a kinase at the downstream of Rad53, Mck1 does not participate in the post-translational regulation of RNR as Dun1 does, but Mck1 can release the Crt1 repressor from the promoters of RNR2/3/4 by phosphorylation. Meanwhile, Hug1, an Rnr2 inhibitor, is induced to fine-tune the dNTP levels. When cells suffer a more severe threat, Mck1 can inhibit the transcription of HUG1. Importantly, only a combined deletion of HUG1 and CRT1, can confer a dramatic boost of dNTP levels and the survival of mck1{Delta}dun1{Delta} or mec1{Delta} cells assaulted by a lethal dose of HU. These findings reveal the division-of-labor between Mck1 and Dun1 at the S-phase checkpoint pathway to fine-tune dNTP homeostasis.\n\nAuthor SummaryThe appropriate amount and balance of four dNTPs are crucial for all cells correctly copying and passing on their genetic material generation by generation. Eukaryotes have developed an alert and response system to deal with the disturbance. Here, we uncovered a second-level effector branch. It is activated by the upstream surveillance kinase cascade, which can induce the expression of dNTP-producing enzymes. It can also reduce the inhibitor of these enzymes to further boost their activity according to the degrees of threats. These findings suggest a multi-level response system to guarantee dNTP supply, which is essential to maintain genetic stability under various environmental challenges.

molecular biology↗