Stress-responsive Transcription Factor Research Articles

Transcription factors CpSPL5 and CpSPL8 negatively regulate salt tolerance in Codonopsis pilosula by inhibiting SOS pathway.

Environmental stresses such as salt and drought severely affect plant growth and development. SQUAMOSA-promoter binding protein-like (SPL) transcription factors (TFs) play critical roles in the regulation of diverse processes; however, reports describing the SPL regulation of plant responses to abiotic stress are relatively few. In this study, two stress-responsive TFs from Codonopsis pilosula (CpSPL5 and CpSPL8) are reported, which confer salt stress sensitivity. CpSPL5 and CpSPL8 are expressed in almost all tissues and localized in the nucleus, where the CpSPL5 transcript level is relatively higher than that of CpSPL8. Their expression levels are significantly suppressed in hairy roots treated with ABA, NaCl, PEG-6000, and under high temperature stress. Compared with the control, CpSPL5, or CpSPL8-overexpressed hairy roots increased salt stress sensitivity, and exhibited higher levels of O2- and MDA, as well as lower superoxide dismutase and peroxidase activities. Further, the CpSPL5 or CpSPL8 interference transgenic hairy roots enhanced salt tolerance and exhibited contrasting phenotype and antioxidant indices. Although all genotypes revealed significantly increased Na+ and decreased K+ contents under salt stress, the physiological indicators of CpSPL5 or CpSPL8-interference transgenic hairy roots could be partially restored, where CpSPL5 was more sensitive to salt stress than CpSPL8. A yeast one-hybrid and dual-luciferase assay revealed that CpSPL5 and CpSPL8 directly targeted and inhibited the expression of CpSOS2 in the salt overly sensitive (SOS) pathway, which promoted salt stress sensitivity. Our findings suggest that CpSPL5 and CpSPL8 served as negative regulators of salt tolerance, which indicate that members of the SPL family participate in the plant SOS pathway.

TMET-16. GABA PRODUCTION INDUCED BY IMIPRIDONES IS A TARGETABLE AND IMAGEABLE METABOLIC ALTERATION IN DIFFUSE MIDLINE GLIOMAS

Abstract Diffuse midline gliomas (DMGs) are lethal brain tumors in children. The imipridones ONC201 and ONC206 have emerged as promising therapies for DMG patients, but efficacy as monotherapy is limited. Another hurdle is the lack of biomarkers that report on drug-target engagement at an early timepoint after treatment. Here, using 1H-magnetic resonance spectroscopy (1H-MRS), which is a non-invasive method of quantifying metabolite pool sizes, we show that imipridones induce accumulation of gamma-aminobutyric acid (GABA) in patient-derived (BT245, SF8628) and syngeneic (26-B7, 26-C2) cells. Importantly, in vivo1H-MRS detects a significant increase in GABA within a week of ONC206 treatment, when anatomical alterations are absent, in mice bearing orthotopic BT245, SF8628 or 26-B7 xenografts. Mechanistic studies show that imipridones activate the mitochondrial protease ClpP and upregulate the stress-responsive transcription factor ATF4. ATF4, in turn, upregulates glutamate decarboxylase, the enzyme that synthesizes GABA, and downregulates GABA transaminase, which degrades GABA, leading to GABA accumulation in DMG cells and orthotopic tumors. Since GABA is known to regulate oxidative stress signaling and since imipridones induce oxidative stress, we assessed whether GABA influences oxidative stress in DMG cells. Our studies indicate that GABA induces expression of superoxide dismutase (SOD1), which scavenges superoxide radicals and, thereby, curbs apoptosis induced by imipridones. The biological effects of GABA are mediated via signaling cascades triggered by GABA receptors and we find that GABA acts in an autocrine manner via the GABAB receptor to upregulate SOD1. Importantly, the clinically translatable GABAB receptor antagonist SGS742 and the SOD1 inhibitor ATN-224 exacerbate oxidative stress and synergistically induce apoptosis in combination with imipridones in DMG cells. Furthermore, SGS742 is brain-penetrant and potentiates ONC206-induced apoptosis in mice bearing orthotopic SF8628 xenografts in vivo. Collectively, we identify GABA as a unique metabolic adaptation to imipridones that can be leveraged for imaging drug-target engagement and for enhancing response to therapy. Clinical translation of our studies will enable precision therapy and imaging for DMG patients.

Piwi mutant germ cells transmit a form of heritable stress that promotes longevity.

The C. elegans Argonaute protein PRG-1/Piwi and associated piRNAs protect metazoan genomes by silencing transposons and other types of foreign DNA. As prg-1 mutants are propagated, their fertility deteriorates prior to the onset of a reproductive arrest phenotype that resembles a starvation-induced stress response. We found that late-generation prg-1 mutants with substantially reduced fertility were long-lived, whereas early- or mid-generation prg-1 mutants had normal lifespans. Loss of the stress response transcription factor DAF-16 caused mid- or late-generation prg-1 mutants to live very short lives, whereas overexpression of DAF-16 enabled both mid- and late-generation prg-1 mutants to live long. Cytoplasmic P-bodies that respond to stress increased in long-lived late-generation prg-1 mutants and were transmitted to F1 but not F2 cross-progeny. Moreover, moderate levels of heritable stress shorten late-generation prg-1 mutant longevity when DAF-16 or P bodies are deficient. Together, these results suggest that the longevity of late-generation prg-1 mutants is a hormetic stress response. However, dauer larvae that occur in response to stress were not observed in late-generation prg-1 mutants. Small germ cell nucleoli that depended on germline DAF-16 were present in late-generation prg-1 mutants but were not necessary for their longevity. We propose that prg-1 mutant germ cells transmit a form of heritable stress, high levels of which promote longevity and strongly reduce fertility. The heritable stress transmitted by prg-1/Piwi mutant germ cells may be generally relevant to epigenetic inheritance of longevity.

Chromosome-scale genome assembly of Apocynum pictum, a drought-tolerant medicinal plant from the Tarim Basin.

Apocynum pictum Schrenk is a semishrub of the Apocynaceae family with a wide distribution throughout the Tarim Basin that holds significant ecological, medicinal, and economic values. Here, we report the assembly of its chromosome-level reference genome using Nanopore long-read, Illumina HiSeq paired-end, and high-throughput chromosome conformation capture sequencing. The final assembly is 225.32 Mb in length with a scaffold N50 of 19.64 Mb. It contains 23,147 protein-coding genes across 11 chromosomes, 21,148 of which (91.36%) have protein functional annotations. Comparative genomics analysis revealed that A. pictum diverged from the closely related species Apocynum venetum approximately 2.2 million years ago and has not undergone additional polyploidizations after the core eudicot WGT-γ event. Karyotype evolution analysis was used to characterize interchromosomal rearrangements in representative Apocynaceae species and revealed that several A. pictum chromosomes were derived entirely from single chromosomes of the ancestral eudicot karyotype. Finally, we identified 50 members of the well-known stress-responsive WRKY transcription factor family and used transcriptomic data to document changes in their expression at 2 stages of drought stress, identifying a number of promising candidate genes. Overall, this study provides high-quality genomic resources for evolutionary and comparative genomics of the Apocynaceae, as well as initial molecular insights into the drought adaptation of this valuable desert plant.

Elevated proline and melatonin alter the methylation pattern in the promoter of their biosynthesis genes in rice

Salt stress upregulates osmoprotectants proline and melatonin in plants, and their exogenous application under salt stress can protect them from stress. While melatonin-induced plant epigenetic reprogramming is known in plants, such a mechanism is yet to be identified in the case of proline. The studies conducted so far used proline and melatonin along with one or more stress factors to look into their stress-alleviating effects. We investigated the impact of externally applied proline and melatonin on the methylation of promoter sequences of proline and melatonin biosynthesis genes in 14-day-old rice plants using a combination of biochemical, bioinformatics, and molecular techniques. Our findings demonstrate that exogenously applied proline and melatonin elevate endogenous levels of these compounds in rice, mimicking stress conditions in plants, as the biochemical assays corroborated the activation of antioxidant systems, particularly ascorbate peroxidase (APX) and catalase (CAT). Bioinformatics analysis unveiled multiple stress-responsive transcription factor binding sites on gene promoters associated with proline and melatonin biosynthesis pathways. Restriction analysis using the isoschizomer pair MspI/HpaII revealed distinct cytosine methylations at the restriction sites on the promoters analyzed in plants treated with proline and melatonin compared to the control. Differential methylation identified in the promoter sequences were matching with the biosynthesis of proline and melatonin and also the antioxidant enzyme levels. These observations are consistent with previous transcriptome data of proline and melatonin biosynthesis genes, providing insights into underlying regulatory mechanisms of proline and melatonin biosynthesis, their role in epigenome control during abiotic stress, and the evolution of various stress-tolerant varieties.

Transcription factor SlSTOP1 regulates Small Auxin-Up RNA Genes for tomato root elongation under aluminum stress.

Aluminum (Al) stress, a prevalent constraint in acidic soils, inhibits plant growth by inhibiting root elongation through restricted cell expansion. The molecular mechanisms of Al-induced root inhibition, however, are not fully understood. This study aimed to elucidate the role of Small Auxin-up RNAs (SlSAURs), which function downstream of the key Al stress-responsive transcription factor SENSITIVE TO PROTON RHIZOTOXICITY 1 (SlSTOP1) and its enhancer STOP1-INTERACTING ZINC-FINGER PROTEIN 1 (SlSZP1), in modulating root elongation under Al stress in tomato (Solanum lycopersicum). Our findings demonstrated that tomato lines with knocked out SlSAURs exhibited shorter root lengths when subjected to Al stress. Further investigation into the underlying mechanisms revealed that SlSAURs interact with Type 2C Protein Phosphatases (SlPP2Cs), specifically D-clade Type 2C Protein Phosphatases (SlPP2C.Ds). This interaction was pivotal as it suppresses the phosphatase activity, leading to the degradation of SlPP2C.D's inhibitory effect on plasma membrane H+-ATPase. Consequently, this promoted cell expansion and root elongation under Al stress. These findings increase our understanding of the molecular mechanisms by which Al ions modulate root elongation. The discovery of the SlSAUR-SlPP2C.D interaction and its impact on H+-ATPase activity also provides a perspective on the adaptive strategies employed by plants to cope with Al toxicity, which may lead to the development of tomato cultivars with enhanced Al stress tolerance, thereby improving crop productivity in acidic soils.

The transcriptional response of cortical neurons to concussion reveals divergent fates after injury.

Traumatic brain injury (TBI) is a risk factor for neurodegeneration, however little is known about how different neuron types respond to this kind of injury. In this study, we follow neuronal populations over several months after a single mild TBI (mTBI) to assess long ranging consequences of injury at the level of single, transcriptionally defined neuronal classes. We find that the stress responsive Activating Transcription Factor 3 (ATF3) defines a population of cortical neurons after mTBI. We show that neurons that activate ATF3 upregulate stress-related genes while repressing many genes, including commonly used markers for these cell types. Using an inducible reporter linked to ATF3, we genetically mark damaged cells to track them over time. Notably, we find that a population in layer V undergoes cell death acutely after injury, while another in layer II/III survives long term and retains the ability to fire action potentials. To investigate the mechanism controlling layer V neuron death, we genetically silenced candidate stress response pathways. We found that the axon injury responsive kinase MAP3K12, also known as dual leucine zipper kinase (DLK), is required for the layer V neuron death. This work provides a rationale for targeting the DLK signaling pathway as a therapeutic intervention for traumatic brain injury. Beyond this, our novel approach to track neurons after a mild, subclinical injury can inform our understanding of neuronal susceptibility to repeated impacts.

Antisense transcription from stress-responsive transcription factors fine-tunes the cold response in Arabidopsis.

Transcription of antisense long noncoding RNAs (lncRNAs) occurs pervasively across eukaryotic genomes. Only a few antisense lncRNAs have been characterized and shown to control biological processes, albeit with idiosyncratic regulatory mechanisms. Thus, we largely lack knowledge about the general role of antisense transcription in eukaryotic organisms. Here, we characterized genes with antisense transcription initiating close to the poly(A) signal of genes (PAS genes) in Arabidopsis (Arabidopsis thaliana). We compared plant native elongation transcript sequencing (plaNET-seq) with RNA sequencing during short-term cold exposure and detected massive differences between the response in active transcription and steady-state levels of PAS gene-derived mRNAs. The cold-induced expression of transcription factors B-BOX DOMAIN PROTEIN28 (BBX28) and C2H2-TYPE ZINC FINGER FAMILY PROTEIN5 (ZAT5) was detected by plaNET-seq, while their steady-state level was only slightly altered due to high mRNA turnover. Knockdown of BBX28 and ZAT5 or of their respective antisense transcripts severely compromised plant freezing tolerance. Decreased antisense transcript expression levels resulted in a reduced cold response of BBX28 and ZAT5, revealing a positive regulatory role of both antisense transcripts. This study expands the known repertoire of noncoding transcripts. It highlights that native transcription approaches can complement steady-state RNA techniques to identify biologically relevant players in stress responses.

Unraveling the Role of MYB Transcription Factors in Abiotic Stress Responses: An Integrative Approach in Eugenia uniflora L.

Unraveling the Role of MYB Transcription Factors in Abiotic Stress Responses: An Integrative Approach in Eugenia uniflora L.

Arabidopsis WRKY1 promotes monocarpic senescence by integrative regulation of flowering, leaf senescence, and nitrogen remobilization

Monocarpic senescence, characterized by whole-plant senescence following a single flowering phase, is widespread in seed plants, particularly in crops, determining seed harvest time and quality. However, how external and internal signals are systemically integrated into monocarpic senescence remains largely unknown. Here, we report that the Arabidopsis thaliana transcription factor WRKY1 plays essential roles in multiple key steps of monocarpic senescence. WRKY1 expression is induced by age, salicylic acid (SA), and nitrogen (N) deficiency. Flowering and leaf senescence are accelerated in the WRKY1 overexpression lines but are delayed in the wrky1 mutants. The combined DNA affinity purification sequencing and RNA sequencing analyses uncover the direct target genes of WRKY1. Further studies show that WRKY1 coordinately regulates three processes in monocarpic senescence: (1) suppressing FLOWERING LOCUS C gene expression to initiate flowering, (2) inducing SA biosynthesis genes to promote leaf senescence, and (3) activating the N assimilation and transport genes to trigger N remobilization. In summary, our study reveals how one stress-responsive transcription factor, WRKY1, integrates flowering, leaf senescence, and N remobilization processes into monocarpic senescence, providing important insights into plant lifetime regulation.

Co-exposure to microplastic and plastic additives causes development impairment in zebrafish embryos

Since the run off of microplastic and plastic additives into the aquatic environment through the disposal of plastic products, we investigated the adverse effects of co-exposure to microplastics and plastic additives on zebrafish embryonic development. To elucidate the combined effects between microplastic mixtures composed of microplastics and plastic additives in zebrafish embryonic development, polystyrene (PS), bisphenol S (BPS), and mono-(2-ethylhexyl) phthalate (MEHP) were chosen as a target contaminant. Based on non-toxic concentration of each contaminant in zebrafish embryos, microplastic mixtures which is consisted of binary and ternary mixed forms were prepared. A strong phenotypic toxicity to zebrafish embryos was observed in the mixtures composed with non-toxic concentration of each contaminant. In particular, the mixture combination with ≤ EC10 values for BPS and MEHP showed a with a strong synergistic effect. Based on phenotypic toxicity to zebrafish embryos, change of transcription levels for target genes related to cell damage and thyroid hormone synthesis were analyzed in the ternary mixtures with low concentrations that were observed non-toxicity. Compared with the control group, cell damage genes linked to the oxidative stress response and thyroid hormone transcription factors were remarkably down-regulated in the ternary mixture-exposed groups, whereas the transcriptional levels of cyp1a1 and p53 were significantly up-regulated in the ternary mixture-exposed groups (P < 0.05). These results demonstrate that even at low concentrations, exposure to microplastic mixtures can cause embryonic damage and developmental malformations in zebrafish, depending on the mixed concentration-combination. Consequently, our findings will provide data to examine the action mode of zebrafish developmental toxicity caused by microplastic mixtures exposure composed with microplastics and plastic additives.

ATF4 as a Prognostic Marker and Modulator of Glutamine Metabolism in Oestrogen Receptor-Positive Breast Cancer.

ATF4, a stress-responsive transcription factor that upregulates adaptive genes, is a potential prognostic marker and modulator of glutamine metabolism in breast cancer. However, its exact role remains to be elucidated. ATF4 expression was evaluated at genomic and transcriptomic levels using METABRIC (n = 1,980), GeneMiner (n = 4,712), and KM-Plotter datasets. Proteomic expression was assessed via immunohistochemistry (n = 2,225) in the Nottingham Primary Breast Cancer Series. ATF4 genomic copy number (CN) variation and mRNA/protein in association with clinicopathological parameters, amino acid transporters (AATs), and patient outcome were investigated. Genomic, transcriptomic, and proteomic overexpression of ATF4 was associated with more aggressive ER-negative tumours. ATF4 mRNA and protein expression were significantly associated with increased expression of glutamine related AATs including SLC1A5 (p &lt; 0.01) and SLC7A11 (p &lt; 0.02). High ATF4 and SLC1A5 protein expression was significantly associated with shorter breast cancer-specific survival (p &lt; 0.01), especially in ER+ tumours (p &lt; 0.01), while high ATF4 and SLC7A11 protein expression was associated with shorter survival (p &lt; 0.01). These findings suggest a complex interplay between ATF4 and AATs in breast cancer biology and underscore the potential role for ATF4 as a prognostic marker in ER+ breast cancer, offering a unique opportunity for risk stratification and personalized treatment strategies.

Regulation of stress-responsive transcription factors of rice by CPPU, a synthetic cytokinin, during water deficit stress at protein level

Regulation of stress-responsive transcription factors of rice by CPPU, a synthetic cytokinin, during water deficit stress at protein level

Unravelling the biostimulant activity of a protein hydrolysate in lettuce plants under optimal and low N availability: a multi-omics approach.

The application of protein hydrolysates (PH) biostimulants is considered a promising approach to promote crop growth and resilience against abiotic stresses. Nevertheless, PHs bioactivity depends on both the raw material used for their preparation and the molecular fraction applied. The present research aimed at investigating the molecular mechanisms triggered by applying a PH and its fractions on plants subjected to nitrogen limitations. To this objective, an integrated transcriptomic-metabolomic approach was used to assess lettuce plants grown under different nitrogen levels and treated with either the commercial PH Vegamin® or its molecular fractions PH1(>10 kDa), PH2 (1-10 kDa) and PH3 (<1 kDa). Regardless of nitrogen provision, biostimulant application enhanced lettuce biomass, likely through a hormone-like activity. This was confirmed by the modulation of genes involved in auxin and cytokinin synthesis, mirrored by an increase in the metabolic levels of these hormones. Consistently, PH and PH3 upregulated genes involved in cell wall growth and plasticity. Furthermore, the accumulation of specific metabolites suggested the activation of a multifaceted antioxidant machinery. Notwithstanding, the modulation of stress-response transcription factors and genes involved in detoxification processes was observed. The coordinated action of these molecular entities might underpin the increased resilience of lettuce plants against nitrogen-limiting conditions. In conclusion, integrating omics techniques allowed the elucidation of mechanistic aspects underlying PH bioactivity in crops. Most importantly, the comparison of PH with its fraction PH3 showed that, except for a few peculiarities, the effects induced were equivalent, suggesting that the highest bioactivity was ascribable to the lightest molecular fraction.

From swamp to field: how genes from mangroves and its associates can enhance crop salinity tolerance.

Salinity stress is a critical challenge in crop production and requires innovative strategies to enhance the salt tolerance of plants. Insights from mangrove species, which are renowned for their adaptability to high-salinity environments, provides valuable genetic targets and resources for improving crops. A significant hurdle in salinity stress is the excessive uptake of sodium ions (Na+) by plant roots, causing disruptions in cellular balance, nutrient deficiencies, and hampered growth. Specific ion transporters and channels play crucial roles in maintaining a low Na+/K+ ratio in root cells which is pivotal for salt tolerance. The family of high-affinity potassium transporters, recently characterized in Avicennia officinalis, contributes to K+ homeostasis in transgenic Arabidopsis plants even under high-salt conditions. The salt overly sensitive pathway and genes related to vacuolar-type H+-ATPases hold promise for expelling cytosolic Na+ and sequestering Na+ in transgenic plants, respectively. Aquaporins contribute to mangroves' adaptation to saline environments by regulating water uptake, transpiration, and osmotic balance. Antioxidant enzymes mitigate oxidative damage, whereas genes regulating osmolytes, such as glycine betaine and proline, provide osmoprotection. Mangroves exhibit increased expression of stress-responsive transcription factors such as MYB, NAC, and CBFs under high salinity. Moreover, genes involved in various metabolic pathways, including jasmonate synthesis, triterpenoid production, and protein stability under salt stress, have been identified. This review highlights the potential of mangrove genes to enhance salt tolerance of crops. Further research is imperative to fully comprehend and apply these genes to crop breeding to improve salinity resilience.

An integrated approach to predict activators of NRF2 - the transcription factor for oxidative stress response

A variety of environmental and physiological conditions can cause oxidative stress that damage cellular components such as DNA, proteins and lipids. Oxidative stress is implicated in many human diseases including cancer, cardiovascular diseases, neurological diseases, inflammatory diseases, and aging. The nuclear factor erythroid 2–related factor 2 (NRF2) is a transcriptional factor that plays a key role in the cellular antioxidant defense system as it regulates transcription of antioxidant proteins and detoxifying enzymes. There is an urgent need to identify novel compounds that activate NRF2 and enhance antioxidant defense. We collected data from the high-throughput screening of NRF2 activators and identified molecular fragments (structural alerts) associated with the activation of NRF2. We also developed ten classification models using different types of molecular descriptors and machine learning techniques. Two approaches were used to establish the applicability domain of developed models: the structure-based approach and the distance to model approach. The best performing model that used message passing neural network (MPNN) technique showed accuracy of 87 % for the test set of chemicals within the distance to model of 0.3. The integrative approach using a combination of generated structural alerts and MPNN model was used to screen approved drugs collected in the DrugBank to identify potential NRF2 activators. Out of 2393 screened chemicals 138 compounds were predicted as NRF2 activators by both approaches. Analysis of these compounds showed that some drugs were already known activators of NRF2 while others are potentially novel activators.

ARV1 deficiency induces lipid bilayer stress and enhances rDNA stability by activating the unfolded protein response in Saccharomyces cerevisiae

The stability of ribosomal DNA (rDNA) is maintained through transcriptional silencing by the NAD+-dependent histone deacetylase Sir2 in Saccharomyces cerevisiae. Alongside proteostasis, rDNA stability is a crucial factor regulating the replicative lifespan (RLS) of S. cerevisiae. The unfolded protein response (UPR) is induced by misfolding of proteins or an imbalance of membrane lipid composition and is responsible for degrading misfolded proteins and restoring endoplasmic reticulum (ER) membrane homeostasis. Recent investigations have suggested that the UPR can extend the RLS of yeast by enhancing protein quality control mechanisms, but the relationship between the UPR and rDNA stability remains unknown. In this study, we found that the deletion of ARV1, which encodes an ER protein of unknown molecular function, activates the UPR by inducing lipid bilayer stress. In arv1Δ cells, the UPR and the cell wall integrity pathway are activated independently of each other, and the high osmolarity glycerol (HOG) pathway is activated in a manner dependent on Ire1, which mediates the UPR. Activated Hog1 translocates the stress response transcription factor Msn2 to the nucleus, where it promotes the expression of nicotinamidase Pnc1, a well-known Sir2 activator. Following Sir2 activation, rDNA silencing and rDNA stability are promoted. Furthermore, the loss of other ER proteins, such as Pmt1 or Bst1, and ER stress induced by tunicamycin or inositol depletion also enhance rDNA stability in a Hog1-dependent manner. Collectively, these findings suggest that the induction of the UPR enhances rDNA stability in S. cerevisiae by promoting the Msn2-Pnc1-Sir2 pathway in a Hog1-dependent manner.

Abstract 610: ClpP-dependent and -independent activation of HRI kinase by small molecules

Abstract HRI was initially identified as a kinase essential for maintaining heme-globin balance within red blood cells as well as for controlling the ISR in response to oxidative stress. HRI also responds to a broad range of stresses such as osmotic stress, heat shock, proteasome inhibition. The recently discovered unexpected functions of HRI include innate immunity, translational control of immune evasion in cancer by upregulating PD-L1, proteostasis, mitochondrial stress, inhibition of histone H3 lysine 27 (H3K27) demethylase (KDM6A) and iron deficiency. Importantly, recent evaluation of patient data uncovered high expression of HRI mRNA in a subset of epithelial tumors versus normal tissues. Elevated expression of HRI protein in these tumor cells lead to cell death when BIRC6 ubiquitin complex is inhibited, which mediates degradation of HRI and is required for the survival of the tumors. These further broaden the importance of this member of the eIF2α kinase family as a cancer therapeutic strategy. Dordaviprone (ONC201), an imipridone small molecule, binds to and activates mitochondrial protease ClpP leading to integrated stress response (ISR) and ATF4 transcription factor activation. PG3, a prodigiosin analog, induces ATF4 and pro-apoptotic PUMA. Our data indicate that PG3 activates ATF4 through ISR via eIF2α kinase HRI. ALAS1 (5'-aminolevulinate synthase 1) catalyzes the first rate-limiting step in heme (Iron-protoporphyrin) biosynthesis. ONC201 treatment leads to potent downregulation and inhibition of ALAS1, indicating that ONC201 inhibits heme biosynthesis. It is well known that reduced heme results in activation of the HRI kinase. We show that an inhibitor of heme biosynthesis or knockdown of ALAS1 results in HRI activation, while silencing of HRI or knockout of HRI gene potently inhibit the eIF2α phosphorylation and upregulation of ATF4, CHOP and PUMA by PG3 and imipridones. Knockdown of ClpP rescues ONC201-induced downregulation of ALAS1 which blocks ONC201-induced upregulation of CHOP. Also, silencing of ClpP significantly reduced PARP cleavage in HCT116 p53−/- and MDA-MB-468 cancer cells. Our studies identify a novel link between ClpP activation induced by ONC201 treatment and ATF4 upregulation, via the ClpP/ALAS1/HRI/ATF4 pathway. However, PG3 treatment did not lead to degradation of ALAS1, indicating that PG3 does not activate ClpP. PG3 potently induced cell apoptosis through ISR via HRI/ATF4/PUMA pathway independent of ClpP. We are further investigating the targets of PG3 and the signaling pathway that leads to PG3-induced activation of HRI. Our results suggest that different small molecule inducers of the ISR such as ONC201 and PG3 can achieve an anti-tumor effect through different pathways converging on kinase HRI ultimately leading to ATF4 activation and tumor cell death. Citation Format: Xiaobing Tian, Praveen Srinivasan, Wafik S. El-Deiry. ClpP-dependent and -independent activation of HRI kinase by small molecules [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 610.

Abstract 4295: Apoptotic DNase DFFB-induced DNA damage within cancer persister cells underlies acquired resistance to targeted therapies across multiple tumor types

Abstract Cancer acquired drug resistance contributes to a large proportion of patient deaths. A major obstacle to the development of effective therapies which prevent resistance is our lack of understanding of the relevant fundamental molecular adaptive processes. Here we report the discovery that tumor cells rely upon sublethal engagement of apoptotic death machinery and apoptotic DNase DFFB to acquire resistance to targeted therapies in multiple tumor types in cell culture and in vivo. We found that while DFFB wild type tumor cells readily acquire resistance to targeted therapies by escaping from the quiescent “persister” state into proliferating resistant cells, persister cells lacking functional DFFB remain indefinitely in a quiescent state on treatment. Mechanistically, we found that DFFB, which is activated by apoptotic caspases in surviving cancer persister cells, induces persistent DNA damage which promotes resistance through acquired mutations and nongenetic resistance through suppression of growth-arresting interferon signaling. During drug treatment acute interferon induction arises from sublethal mitochondrial outer membrane permeabilization and cytoplasmic exposure of mitochondrial nucleic acids which activate pattern recognition receptors. However, during longer treatments we found that DFFB knockout persister cells exhibit strikingly elevated levels of STAT1 and STAT2 and interferon stimulated gene sets. This interferon signaling is growth arresting because treatment of DFFB knockout persister cells with a JAK1/2 inhibitor rescues their ability to regrow. Furthermore, in DFFB wild type persister cells we found that DFFB-dependent DNA damage activates stress response transcription factor ATF3 which blocks the transcriptional activation of interferon stimulated genes following initial interferon induction. This is consistent with prior data in other contexts demonstrating that ATF3 is induced by DNA damage and that ATF3 directly binds to promoters of multiple interferon genes repressing their expression. These findings reveal that DFFB activation in persister cells prevents chronic interferon signaling and enables escape into proliferating drug resistant tumor cells. Therefore, DFFB-mediated interferon suppression represents a novel mechanism that is fundamental to acquired drug resistance. In addition, high expression of DFFB and ATF3 correlates with worse overall survival in a pan-cancer analysis and DFFB knockout mice develop normally indicating DFFB is a nonessential gene in normal tissue. Therefore, we propose that DFFB is a promising therapeutic target to prevent acquired resistance to targeted therapy. Citation Format: August Finley Williams, David A. Gervasio, Claire E. Turkal, Anna E. Stuhlfire, Michael X. Wang, Brandon E. Mauch, Ariel H. Nguyen, Michelle H. Paw, Mehrshad Hairani, Cooper P. Lathrop, Sophie H. Harris, Jennifer L. Page, Matthew J. Hangauer. Apoptotic DNase DFFB-induced DNA damage within cancer persister cells underlies acquired resistance to targeted therapies across multiple tumor types [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4295.

DNA-Binding with One Finger (Dof) Transcription Factor Gene Family Study Reveals Differential Stress-Responsive Transcription Factors in Contrasting Drought Tolerance Potato Species.

DNA-binding with one finger (Dof) proteins comprise a large family that play central roles in stress tolerance by regulating the expression of stress-responsive genes via the DOFCORE element or by interacting with other regulatory proteins. Although the Dof TF has been identified in a variety of species, its systemic analysis in potato (Solanum tuberosum L.) is lacking and its potential role in abiotic stress responses remains unclear. A total of 36 potential Dof genes in potato were examined at the genomic and transcriptomic levels in this work. Five phylogenetic groups can be formed from these 36 Dof proteins. An analysis of cis-acting elements revealed the potential roles of Dofs in potato development, including under numerous abiotic stress conditions. The cycling Dof factors (CDFs) might be the initial step in the abiotic stress response signaling cascade. In potato, five CDFs (StCDF1/StDof19, StCDF2/StDof4, StCDF3/StDof11, StCDF4/StDof24, and StCDF5/StDof15) were identified, which are homologs of Arabidopsis CDFs. The results revealed that these genes were engaged in a variety of abiotic reactions. Moreover, an expression analysis of StDof genes in two potato cultivars ('Long10' (drought tolerant) and 'DXY' (drought susceptible)) of contrasting tolerances under drought stress was carried out. Further, a regulatory network mediated by lncRNA and its target Dofs was established. The present study provides fundamental knowledge for further investigation of the roles of Dofs in the adaptation of potato to drought stress, aiming to provide insights into a viable strategy for crop improvement and stress-resistance breeding.