AP-1 Transcription Factor Research Articles

Exploiting YES1-driven EGFR expression improves the efficacy of EGFR inhibitors.

Epidermal growth factor receptor (EGFR) is a highly expressed driver of many cancers, yet the utility of EGFR inhibitors is limited to cancers that harbor sensitizing mutations in the EGFR gene due to dose limiting toxicities. Rather than conventionally blocking the kinase activity of EGFR, we sought to reduce its transcription as an alternative approach to broaden the therapeutic window for EGFR inhibitors targeting wildtype or mutant EGFR. We found that YES1 is highly expressed in triple negative breast cancer (TNBC) and drives cell growth by elevating EGFR levels. Mechanistically, YES1 stimulates EGFR expression by signaling to JNK and stabilizing the AP-1 transcription factor, c-Jun. This effect extends beyond TNBC as YES1 also sustains EGFR expression in non-small cell lung cancer (NSCLC) cells, including those that harbor the EGFR gatekeeper mutation, T790M. The novel ability of YES1 to regulate the expression of wildtype and mutant EGFR mRNA and protein provides a potential therapeutic opportunity of utilizing YES1 blockade to broadly increase the efficacy of EGFR inhibitors. Indeed, we found synergy within in vitro and in vivo models of TNBC and NSCLC, even in the absence of EGFR activating mutations. Together, these data provide a rationale for blocking YES1 activity as an approach for improving the efficacy of EGFR-targeting drugs in cancers that have generally been refractory to such inhibitors. Implications: YES1 sustains EGFR expression, revealing a therapeutic vulnerability for increasing the efficacy of EGFR inhibitors by lowering the threshold for efficacy in tumors driven by wildtype or mutant receptor.

WDR26 depletion alters chromatin accessibility and gene expression profiles in mammalian cells.

WD-repeat containing protein 26 (WDR26) is an essential component of the CTLH E3 ligase complex. Mutations in WDR26 lead to Skraban-Deardorff, an intellectual disability syndrome with clinical features resembling other disorders arising from defects in transcriptional regulation and chromatin structure. However, the role of WDR26 and its associated CTLH complex in regulating chromatin or transcription has not been elucidated. Here, we assessed how loss of WDR26 affects chromatin accessibility and gene expression. Transcriptome analysis of WDR26 knockout HeLa cells revealed over 2000 differentially expressed genes, while ATAC-Seq analysis showed over 32,000 differentially accessible chromatin regions, the majority mapping to intergenic and intronic regions and 13 % mapping to promoters. Above all, we found that WDR26 loss affected expression of genes regulated by AP-1 and NF-1 transcription factors and resulted in dramatic changes in their chromatin accessibility. Overall, our analyses implicate WDR26 and the CTLH complex in chromatin regulation.

Adaptation responses to salt stress in the gut of Poecilia reticulata

ABSTRACT Osmoregulation is essential for the survival of aquatic organisms, particularly teleost fish facing osmotic challenges in environments characterized by variable salinity. While the gills are known for ion exchange, the intestine’s role in water and salt absorption is gaining attention. Here, we investigated the adaptive responses of the intestine to salinity stress in guppies (Poecilia reticulata), observing significant morphological and transcriptomic alterations. Guppies showed superior salt tolerance compared to zebrafish (Danio rerio). Increasing salinity reduced villus length and intestinal diameter in guppies, while zebrafish exhibited damage to villus structure and loss of goblet cells. Transcriptomic analysis identified key genes involved in osmoregulation, tissue remodeling, and immune modulation. Upregulated genes included the solute carrier transporters slc2al and slc3al, which facilitate ion and water transport, as well as a transcription factor AP-1 subunit and phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit beta, both of which participate in tissue repair and growth responses. In contrast, many genes related to the innate immune system (such as Tnfaip6) were downregulated, suggesting a shift toward the prioritization of osmoregulatory functions over immune responses. Interestingly, the differential expression of adaptation genes was linked to variations in epigenetic modifications and transcription factor activity. Transcription factors crucial for adapting to salt stress, such as bhlhe40, cebpd, and gata6, were progressively upregulated in guppies but remained downregulated in zebrafish. Our findings highlight the intricate mechanisms of adaptation to salinity stress in P. reticulata, providing insights into osmoregulatory mechanisms involving the intestine in aquatic organisms.

Using the AP1 Transcription Factor FOSL1 to Assess the Exacerbation of Psoriasis.

The transcription factor AP1 plays a crucial role in the proliferation, apoptosis, and terminal differentiation of epidermal keratinocytes. This study aimed to clarify whether the subunit of AP1, FOSL1 protein, can be used to assess the exacerbation of psoriasis by evaluating its changes in protein and mRNA levels in cultured epidermal keratinocytes and skin specimens of the patients prescribed with bathwater PUVA (Psoralen and UVA) therapy. This study aimed to investigate FOSL1, a subunit of the transcription factor AP-1, as a potential biomarker for psoriasis by examining its protein and mRNA expression in skin specimens from patients undergoing bathwater PUVA (Psoralen and UVA) therapy and cultured epidermal keratinocytes. The distribution of FOSL1 in patients' skin was explored by immunohistochemistry. Changes in gene and protein expression were quantitatively assessed by qPCR and ELISA, respectively. Immunohistochemistry analysis revealed that FOSL1 accumulated in lesional skin. The expression of FOSL1 significantly increased during disease flare-ups but decreased following the treatment with bathwater PUVA therapy. Furthermore, silencing FOSL1 led to a marked reduction in the expression of ten FOSL1 target genes associated with the disease. Our study suggests that FOSL1 shows potential as a biomarker for psoriasis. This is supported by two key findings: first, the expression of FOSL1 correlates with disease activity, and second, its expression is linked to changes in the expression of genes previously implicated in the pathogenesis of psoriasis, namely MMP1, MMP9, IVL, CCNA2, CCL2, HMOX1, PLAU, PLAUR, and THBD.

House dust mite induced mucosal barrier dysfunction and type 2 inflammatory responses via the MAPK/AP-1/IL-24 Signaling pathway in allergic rhinitis.

The epithelial barrier, previously regarded only as a physical defense, is now understood to play a vital role in immune responses and the regulation of inflammation. Allergic rhinitis (AR) is a prevalent chronic inflammatory condition of the nasal mucosa, with House Dust Mite (HDM) identified as a significant inhalant allergen that can impair this barrier. IL-24 has emerged as a key cytokine in allergic diseases, involved in maintaining epithelial cell homeostasis. Nevertheless, the underlying mechanisms of these effects remain inadequately understood. This study explores HDM-induced IL-24 secretion and mucosal barrier impairment using patient and animal tissue samples. Our results confirm that HDM sensitization triggers inflammatory changes in the nasal cavity, with IL-24 acting as a key mediator of type 2 inflammation and AR severity. HDM enhances IL-24 secretion via the P38 MAPK pathway and transcription factor AP-1, while IL-24 downregulates occludin and ZO-1 expression through the STAT1/STAT3 signaling pathway, compromising barrier function and increasing permeability. Furthermore, IL-24 promotes IL-33 secretion, further exacerbating the inflammatory response in AR. These findings clarify the mechanisms of epithelial barrier disruption in HDM-sensitized allergic rhinitis and suggest that modulating the IL-24 signaling pathway may serve as a promising therapeutic strategy to restore barrier integrity in AR.

Transcription factor AP-2 Beta, a potential target of repetitive Transspinal magnetic stimulation in spinal cord injury treatment, reduced inflammation and alleviated spinal cord injury.

Spinal cord injury (SCI) is a neurodegenerative disease, with a high disability rate. According to the results of mRNA-seq, transcription factor AP-2 Beta (TFAP2B) is a potential target of repetitive Transspinal Magnetic Stimulation (rTSMS) in SCI treatment. Our results demonstrated that rTSMS significantly improved motor function and promoted neuronal survival post-SCI. The result showed that TFAP2B was downregulated following SCI, while significant upregulation after rTSMS treatment, suggesting its pivotal role in neuronal repair. Overexpression of TFAP2B improved Basso Beattie and Bresnahan (BBB) score and athletic ability, and decreased cell apoptosis in SCI rats. Additionally, overexpression of TFAP2B reduced the expression of Iba1 and GFAP in spinal cord, and the expression of PDGFrβ was also reduced in SCI rats after TFAP2B overexpression. Knockdown of TFAP2B reverses the effect of rTSMS treatment in SCI. We found that rTSMS alleviate osteoporosis caused by SCI, resulting in increased BMD, BV/TV, and Tb.Th. rTSMS treatment lowered the RANKL/OPG ratio. In all, our study illustrated TFAP2B is a downstream target of rTSMS for the treatment of SCI, and overexpression of TFAP2B enhanced the therapeutic effect of rTSMS.

Gasoline exhaust particles induce MMP1 expression via Nox4-derived ROS-ATF3-linked pathway in human umbilical vein endothelial cells.

Gasoline exhaust particles (GEP) are risk factors for cardiovascular disease. Activating transcription factor 3 (ATF3) is a transcription factor known to form a heterodimer with AP-1 transcription factors for its target gene expression. However, the involvement of ATF3 in GEP-induced gene expression in human umbilical vein endothelial cells (HUVECs) has not been investigated. In this study, we found that GEP, at IC50 value of 59μg/ml, induced the expression of ATF3, which led to the expression of matrix metalloproteinase 1 (MMP1) in HUVECs. GEP induce an interaction between c-Jun and ATF3, and c-Jun depletion attenuates GEP-induced MMP1 expression. Depletion of NADPH oxidase 4 (Nox4) suppressed GEP-induced reactive oxygen species (ROS) generation and the subsequent upregulation of ATF3 and MMP1, suggesting that Nox4-derived ROS play a role as upstream regulators of GEP-induced ATF3 expression and MMP1 upregulation. Furthermore, Nox4 depletion attenuated the interaction between ATF3 and c-Jun and their binding to the AP-1 binding site of the MMP1 promoter. Taken together, these findings demonstrate that GEP induce the expression of MMP1 by generating Nox4-dependent ROS, which subsequently increase ATF3 expression and its interaction with c-Jun. This leads to their binding to the promoter region of MMP1 and its transcription. These findings suggest that Nox4-derived ROS and ATF3 are critical for GEP-induced MMP1 expression.

Phosphorylation of endothelial histone H3.3 serine 31 by PKN1 links flow-induced signaling to proatherogenic gene expression.

Atherosclerotic lesions develop preferentially in arterial regions exposed to disturbed blood flow, where endothelial cells acquire an inflammatory phenotype. How disturbed flow induces endothelial cell inflammation is incompletely understood. Here we show that histone H3.3 phosphorylation at serine 31 (H3.3S31) regulates disturbed-flow-induced endothelial inflammation by allowing rapid induction of FOS and FOSB, required for inflammatory gene expression. We identified protein kinase N1 (PKN1) as the kinase responsible for disturbed-flow-induced H3.3S31 phosphorylation. Disturbed flow activates PKN1 in an integrin α5β1-dependent manner and induces its translocation into the nucleus, and PKN1 is also involved in the phosphorylation of the AP-1 transcription factor JUN. Mice with endothelium-specific PKN1 loss or endothelial expression of S31 phosphorylation-deficient H.3.3 mutants show reduced endothelial inflammation and disturbed-flow-induced vascular remodeling in vitro and in vivo. Together, we identified a pathway whereby disturbed flow through PKN1-mediated histone phosphorylation and FOS/FOSB induction promotes inflammatory gene expression and vascular inflammation.

Targeting Senescent Stemlike Subpopulations in Philadelphia Chromosome-Like Acute Lymphoblastic Leukemia.

Philadelphia chromosome-like B-cell acute lymphoblastic leukemia (Ph-like ALL) is driven by genetic alterations that induce constitutive kinase signaling and is associated with chemoresistance and high relapse risk in children and adults. Preclinical studies in the most common CRLF2-rearranged/JAK pathway-activated Ph-like ALL subtype have shown variable responses to JAK inhibitor-based therapies, suggesting incomplete oncogene addiction and highlighting a need to elucidate alternative biologic dependencies and therapeutic vulnerabilities, while the ABL-class Ph-like ALL subtype appears preferentially sensitive to SRC/ABL- or PDGFRB-targeting inhibitors. Which patients may be responsive versus resistant to tyrosine kinase inhibitor (TKI)-based precision medicine approaches remains a critical knowledge gap. Using bulk and single-cell multiomics analyses, we profiled residual cells from CRLF2-rearranged or ABL1-rearranged Ph-like ALL patient-derived xenograft models treated in vivo with targeted inhibitors to identify TKI-resistant subpopulations and potential mechanisms of therapeutic escape. We detected a specific MYC dependency in Ph-like ALL cells and defined a new leukemia cell subpopulation with senescence-associated stem cell-like features regulated by AP-1 transcription factors. This dormant ALL subpopulation was effectively eradicated by dual pharmacologic inhibition of BCL-2 and JAK/STAT or SRC/ABL pathways, a clinically-relevant therapeutic strategy. Single cell-derived molecular signatures of this senescence and stem/progenitor-like subpopulation further predicted poor clinical outcomes associated with other high-risk genetic subtypes of childhood B-ALL and thus may have broader prognostic applicability beyond Ph-like ALL.

Transcriptomic Insights into Post-Spawning Death and Muscle Atrophy in Ayu (Plecoglossus altivelis).

In semelparous species like the ayu (Plecoglossus altivelis), spawning is followed by rapid physiological decline and death; yet, the underlying molecular mechanisms remain largely unexplored. This study examines transcriptomic changes in ayu skeletal muscle before and after spawning, with a focus on key genes and pathways contributing to muscle atrophy and metabolic dysfunction. Through RNA sequencing and DEG analysis, we identified over 3000 DEGs, and GSEA and KEGG pathway analysis revealed significant downregulation of energy metabolism and protein degradation. In post-spawning ayu, a rapid decrease in body weight was observed, accompanied by a decline in the expression of myosin heavy chain genes, which are major muscle protein genes, and gene expression changes indicative of muscle atrophy. Decreased expression of AP-1 transcription factors associated with muscle development and aging was also evident. PPI network analysis identified carbohydrate catabolism protein gapdh may be the key factor that led to muscle atrophy and accelerated aging in ayu. Our study revealed that after spawning, the ayu muscle tissue undergoes strong metabolic disorders and cellular stress responses, providing special insights into the mechanisms through the post-spawning death of ayu.

EFFECT OF TRANSCRIPTION FACTOR MODULATORS ON THE NITRIC OXIDE SYSTEM PARAMETERS IN THE BLOOD OF RATS UNDER LIPOPOLYSACCHARIDE-INDUCED SYSTEMIC INFLAMMATORY RESPONSE

The study aimed to investigate the effect of transcription factor modulators on nitric oxide (NO) system parameters in the blood of rats under lipopolysaccharide (LPS)-induced systemic inflammatory response (SIR). The experiment was conducted on 42 male Wistar rats weighing 180–220 g, divided into 6 groups (7 animals per group): Group 1 included intact rats (Control I); Group 2 involved rats, which underwent LPS-induced systemic inflammatory response (SIR) modeling (Control II). In the remaining groups, transcription factor modulators were administered under SIR modeling: Group 3 received the anticancer drug bortezomib (used to treat multiple myeloma and mantle cell lymphoma), an NF-κB inhibitor (via proteasome suppression); Group 4 received the anticancer agent SR 11302 (investigated as a potential treatment for lung cancer), an inhibitor of the transcription factor AP-1; Group 5 received dimethyl fumarate, a specific activator of the Nrf2–ARE signaling pathway; Group 6 was administered with quercetin, a flavonoid that acts as an NF-κB inhibitor and an Nrf2 pathway activator. The results showed that LPS-induced SIR significantly increased total NOS and iNOS activity while reducing cNOS and arginase activity in blood serum. This indicates the development of nitrosative stress and impaired L-arginine metabolism in rats. The use of NF-κB inhibitors (bortezomib) and AP-1 inhibitors (SR 11302), as well as Nrf2 activators (dimethyl fumarate and quercetin) reduced iNOS activity and partially normalized cNOS activity, demonstrating their anti-inflammatory and metabolic effects. The most effective agents for correcting nitrosative stress in SIR were bortezomib and SR 11302, which reduced iNOS activity to near-intact levels and partially restored the functional activity of cNOS. Most transcription factor modulators (bortezomib, dimethyl fumarate, quercetin) partially restored arginase activity, highlighting their potential role in correcting impaired L-arginine metabolism. However, the AP-1 inhibitor (SR 11302) further decreased arginase activity compared to the LPS-induced group, suggesting possible inhibition of compensatory enzyme mechanisms and an exacerbation of metabolic imbalance. The findings confirm the key roles of the NF-κB, AP-1, and Nrf2 signaling pathways in regulating nitrosative stress, offering promising pharmacological targets for correcting inflammatory and metabolic disturbances.

Transcriptome and miRNAome analyses uncover the regulatory role of miR6155 in trichome development of tobacco

BackgroundGlandular trichomes, which act as the first barrier against damage induced by insects and disease, can produce specialized metabolites that play important roles during plant development. However, the role played by microRNAs (miRNAs), which regulate many plant physiological processes, during trichome development is not unraveled in detail.ResultsIn this study, we performed RNA sequencing (RNA-Seq) and small RNA sequencing assessments of tobacco trichome, leaf minus trichome (leaf-trichome), and leaf tissue to improve our understanding of the miRNA mechanisms regulating trichome development. Totally, we identified 270 differentially expressed miRNAs (DEMs) and 10,430 differentially expressed genes (DEGs) between trichome and leaf-trichome tissues. DEM targets were mainly associated with plant hormone signal transduction, plant–pathogen interactions, and the biosynthesis of secondary metabolites. Of these, 1233 miRNA–mRNA pairs were identified with reverse expression patterns. Next, we used dual-luciferase reporter (LUC) assays to reveal that several potential targets were significantly inhibited by corresponding miRNAs, including the transcription factors (TF) NAC021, AP2, MYB36, WRKY6 and TIFY10B. Further analysis showed that miR6155-WRKY6 might perform vital roles in trichome development, and that overexpression of miR6155 resulted in decreased trichome density.ConclusionsTaken together, these findings demonstrate that miRNAs may be involved in trichome development in tobacco, and they may advance our understanding of the regulation of trichome development mediated by miRNA and can help to improve genetic engineering of trichome regulation in plants.Graphical

E3 ubiquitin ligase ITCH-mediated proteasomal degradation of WBP2 sensitizes breast cancer cells to chemotherapy through restraining AMOTL2/c-JUN axis.

Our study had demonstrated that WW domain-binding protein 2 (WBP2) conferred chemoresistance in breast cancer (BC). However, the underlying mechanism remains unclear. Herein, a decreased expression of itchy E3 ubiquitin protein ligase (ITCH) was observed in drug-resistant BC tissues which negatively regulated the expression of WBP2. However, ligase-deficient ITCH C830A mutant missed this function. WBP2 upregulation-initiated the chemoresistance to doxorubicin was reversed by exogenous ITCH, which was not affected by ITCH C830A mutant. In in vivo model, exogenous ITCH obstructed WBP2-mediated chemoresistance, which was destroyed by the proteasome inhibitor (MG132). Upon RNA sequencing, the excessive activations of angiomotin-like 2 (AMOTL2) and c-JUN (Jun proto-oncogene, AP-1 transcription factor subunit) were screened in WBP2-overexpressed BC cells. Additionally, AMOTL2 and endonuclear phosphorylated c-JUN were at a high level in chemoresistant BC tumors and WBP2-overexpressed BC cells. Mechanistically, exogenous ITCH transfection prevented the activation of AMOTL2/c-JUN induced by WBP2 overexpression, which was restored by MG132-mediated inhibition on ITCH activation. The increase of multiple drug-resistant proteins caused by WBP2 upregulation were restrained by AMOTL2 knockdown or c-JUN antagonist, respectively. Our findings present how ITCH/WBP2 signaling functions to link the intricate AMOTL2/c-JUN signaling networks in chemoresistant BC cells. Targeting WBP2 combined with c-JUN inhibitors may be a potential option to overcome chemoresistance in breast cancer patients.

FAM96B negatively regulates FOSL1 to modulate the osteogenic differentiation and regeneration of periodontal ligament stem cells via ferroptosis

BackgroundPeriodontal ligament stem cell (PDLSC)-based therapy is one of the methods to assist bone regeneration. Understanding the functional regulation of PDLSCs and the mechanisms involved is a crucial issue in bone regeneration. This study aimed to explore the roles of the family with sequence similarity 96 member B (FAM96B) in the functional regulation of PDLSCs.MethodsTo assess the osteogenic differentiation of PDLSCs, the alkaline phosphatase (ALP) activity assay, Alizarin red staining, quantitative calcium analysis, and osteogenic marker detection were conducted. Transplantation PDLSCs under the dorsum of nude mice and into the rat calvarial defects were also performed. Then, FAM96B-overexpressed PDLSCs were used for RNA-sequencing and bioinformatic analysis. To evaluate the ferroptosis of PDLSCs, cytosolic reactive oxygen species (ROS), expression of glutathione peroxidase 4 (GPX4), mitochondrial morphology and functions including the mitochondrial ROS, mitochondria membrane potential, and mitochondrial respiration were detected.ResultsThe osteogenic indicators ALP activity, level of mineralization, and osteocalcin expression were decreased in PDLSCs by FAM96B, which demonstrated that FAM96B inhibited the osteogenic differentiation of PDLSCs. FAM96B knockdown promoted the new bone formation of PDLSCs subcutaneously transplanted to the dorsum of nude mice. Then, related biological functions were detected by the RNA-sequencing and the ferroptosis was focused. FAM96B enhanced the cytosolic ROS level and inhibited the expression of GPX4 and mitochondrial functions in PDLSCs. Hence, FAM96B promoted the ferroptosis of PDLSCs. Meanwhile, we found that FAM96B inhibition upregulated the target gene FOS like 1, AP-1 transcription factor subunit (FOSL1) expression and FOSL1 promoted the osteogenic differentiation of PDLSCs in vitro. FOSL1 also promoted the new bone formation of PDLSCs transplanted subcutaneously to the dorsum of nude mice and transplanted into rat calvarial defects. Then, the inhibitory effect of FOSL1 on the ferroptosis was confirmed.ConclusionsFAM96B depletion promoted the osteogenic differentiation and suppressed the ferroptosis of PDLSCs. FAM96B negatively regulated the downstream gene FOSL1 and FOSL1 promoted the osteogenic differentiation of PDLSCs via the ferroptosis. Hence, our findings provided a foundation for understanding the FAM96B-FOSL1 axis acting as a target for MSC mediated bone regeneration.

TFAP2A Promotes Cell Progression and Suppresses Ferroptosis in Lung Adenocarcinoma via Activating Transcription of CST1.

Lung adenocarcinoma (LUAD) is a common type of lung cancer with complicated pathological mechanism. Transcription Factor AP-2 Alpha (TFAP2A) and Cysteine protease inhibitor 1 (CST1) are upregulated genes in LUAD samples, accordingly, we focused on clarifying the role of TFAP2A/CST1 axis in LUAD. Expression analysis was performed using real-time quantitative polymerase chain reaction and western blot. Cellular behaviors were detected by colony formation assay, EdU assay, wound healing assay and flow cytometry. Ferroptosis was assessed by oxidative indicators, Fe2+ level and related proteins. TFAP2A and CST1 interaction was analyzed via ChIP assay and dual-luciferase reporter assay. TFAP2A function in vivo was evaluated by xenograft tumor assay. CST1 was overexpressed in LUAD samples and cells. Downregulation of CST1 inhibited proliferation, migration but it promoted apoptosis and ferroptosis of LUAD cells. TFAP2A interacted with the promoter of CST1 to up-regulate CST1 expression. TFAP2A regulated the malignant behaviors and ferroptosis of LUAD cells by targeting CST1. TFAP2A affected LUAD tumor growth via mediating CST1. All these data proved that TFAP2A/CST1 axis contributed to proliferation, migration while it suppressed apoptosis and ferroptosis in LUAD.

A KSHV RNA-binding protein promotes FOS to inhibit nuclease AEN and transactivate RGS2 for AKT phosphorylation.

Kaposi's sarcoma-associated herpesvirus (KSHV) encodes an RNA-binding protein ORF57 in lytic infection. Using an optimized CLIP-seq in this report, we identified ORF57-bound transcripts from 544 host protein-coding genes. By comparing with the RNA-seq profiles from BCBL-1 cells with latent and lytic KSHV infection and from HEK293T cells with and without ORF57 expression, we identified FOS RNA as one of the major ORF57-specific RNA targets. FOS dimerizes with JUN as a transcription factor AP-1 involved in cell proliferation, differentiation, and transformation. Knockout of the ORF57 gene from the KSHV genome led BAC16-iSLK cells incapable of FOS expression in KSHV lytic infection. The dysfunctional KSHV genome in FOS expression could be rescued by Lenti-ORF57 virus infection. ORF57 protein does not regulate FOS translation but binds to the 13-nt RNA motif near the FOS RNA 5' end and prolongs FOS mRNA half-life 7.7 times longer than it is in the absence of ORF57. This binding of ORF57 to FOS RNA is likely competitive to the binding of host nuclease AEN (ISG20L1) of which physiological RNase activity remains unknown. KSHV infection inhibits the expression of AEN, but not exosomal RNA helicase MTR4. FOS expression mediated by ORF57 inhibits AEN transcription through FOS binding to AEN promoter but transactivates RGS2, a regulator of G-protein-coupled receptors. FOS binds a conserved AP-1 site in the RGS2 promoter and enhances RGS2 expression to phosphorylate AKT. Altogether, we have discovered that KSHV ORF57 specifically binds and stabilizes FOS RNA to increase FOS expression, thereby disturbing host gene expression and inducing pathogenesis during KSHV lytic infection.IMPORTANCEWe discovered that FOS, a heterodimer component of oncogenic transcription factor AP-1, is highly elevated in KSHV-infected cells by expression of a viral lytic RNA-binding protein, ORF57, which binds a 13-nt RNA motif near the FOS RNA 5' end to prolong FOS RNA half-life. This binding of ORF57 to FOS RNA is competitive to the binding of host RNA destabilizer(s). KSHV infection inhibits expression of host nuclease AEN, but not MTR4. FOS inhibits AEN transcription by binding to the AEN promoter but transactivates RGS2 by binding to a conserved AP-1 site in the RGS2 promoter, thereby enhancing RGS2 expression and phosphorylation of AKT. Thus, KSHV lytic infection controls the expression of a subset of genes for signaling, cell cycle progression, and proliferation to potentially contribute to viral oncogenesis.

Muramyl dipeptide potentiates Staphylococcus aureus lipoteichoic acid-induced nitric oxide production via TLR2/NOD2/PAFR signaling pathways.

Lipoteichoic acid (LTA) and peptidoglycan (PGN) are considered as key virulence factors of Staphylococcus aureus, which is a representative sepsis-causing Gram-positive pathogen. However, cooperative effect of S. aureus LTA and PGN on nitric oxide (NO) production is still unclear despite the pivotal roles of NO in initiation and progression of sepsis. We here evaluated the cooperative effects of S. aureus LTA (SaLTA) and muramyl dipeptide (MDP), the minimal structure of PGN, on NO production in both a mouse macrophage-like cell line, RAW 264.7 and mouse bone marrow-derived macrophages (BMMs). Although MDP alone did not affect NO production, MDP potently enhanced SaLTA-induced NO production via the expression of inducible NO synthases. The enhanced NO production was ameliorated in BMMs from TLR2-, CD14-, MyD88-, and NOD2-deficient mice. Moreover, the augmented SaLTA-induced NO production by MDP was attenuated by inhibitors specific for PAFR and MAP kinases. Furthermore, MDP also potently increased SaLTA-induced activities of STAT1, NF-κB, and AP-1 transcription factors, and specific inhibitors for these transcription factors suppressed the elevated NO production. Collectively, these results demonstrated that MDP potentiates SaLTA-induced NO production via TLR2/NOD2/PAFR, MAP kinases signaling axis, resulting in the activation of NF-κB, AP-1 and STAT1 transcription factors.

FC03 T17 polarization of skin-homing (CLA-positive) T cells is maintained by activation-dependent, AP-1-mediated chromatin remodelling

Abstract Background T cells undergo polyclonal expansion in psoriasis and PsA, with persistence of ‘driver clones’ after effective treatment (JCI 127:4031; JI 172:1935). A recent study found roughly equally sized compartments of clonally expanded and polyclonal Th17 and Tc17 cells in psoriasis (Science 371:364). Memory T17 cells undergo monocyte-dependent expansion in CD3/CD28-activated PBMC cultures (PNAS 104:17034; JID 139:1245). Methods We stimulated PBMC from 85 psoriatic and 68 controls for 1 day with anti-CD3/CD28 Dynabeads (24 h), or without beads (0 h), followed on Day 0 or Day 1 by flow sorting (CD3+CD45RO+, CD4/CD8 × CLA+/CLA- × 0/24 h), RNA-seq and ATAC-seq. Results CD3/CD28 activation provoked marked (>100-fold) upregulation of the T17 signature transcripts IL17A, IL17F, IL22, and CCL22, and of the T1 signature transcript IFNG. However, stratified analysis of CLAP vs. CLAN in activated T cells revealed 2.9- to 12.1-fold upregulation of the four T17 signature mRNAs, without a corresponding increase in IFNG. Notably, IL17A and IL17F were overexpressed in activated T cells from psoriatic vs. control donors (each 1.9-fold, P = 4.7E−4). Occupancy analysis of 702 transcription factor (TF) motifs using CENTIPEDE revealed remarkable correlations between activation (CLAN at 24 vs. 0 h) and skin-homing status (CLAP vs. CLAN at 0 h) [Spearman’s rho = 0.94 for CD4 and 0.93 for CD8; rho(expected)∼0.5]. Compared with CLAP/CLAN, correlations with activation were much weaker for CD8/CD4, the other dimension in our 2 × 2 × 2 study design (rho = 0.41 for CLAN and 0.29 for CLAP). AP-1 motifs were significantly enriched among CLAP vs. CLAN differentially occupied motifs (P < 2.2E−16 for CD4 and CD8, Fisher’s exact). Discussion CLAP are effector memory T cells (Tem) arising after injury/infection of skin (or tonsils), whereas CLAN are central memory T cells (Tcm) that may arise in the skin, lung, or gut (JID 130:362; STM 7:269). Our results support findings that human Th17 cells are long-lived Tem (STM 3:104) and that Tem are more responsive than Tcm due to increased TF occupancy driven by AP-1 TFs (Commun Biol 6:363). Our results nominate repetitive activation of memory T cells (whether clonally via TCR activation or polyclonally via cytokines) as a mechanism for increased responsiveness of CLAP/Tem vs. CLAN/Tcm. They also advance a plausible explanation for the presence of polyclonal T cells in psoriasis lesions (‘chromatin memory’ of secondarily activated T cells), suggesting a molecular basis of the Koebner phenomenon (heterologous activation of poised chromatin, Nature 580:475), and provide a rationale for implementing highly effective treatment early in the course of psoriasis (to prevent expansion of memory T cells, clonal or not, with chromatin poised for T17 reactivation).

TFAP2C is a key regulator of intrauterine trophoblast cell invasion and deep hemochorial placentation.

Transcription factor AP-2 gamma (TFAP2C) has been identified as a key regulator of the trophoblast cell lineage and hemochorial placentation. The rat possesses deep placentation characterized by extensive intrauterine trophoblast cell invasion, which resembles human placentation. Tfap2c is expressed in multiple trophoblast cell lineages, including invasive trophoblast cells situated within the uterine-placental interface of the rat placentation site. Global genome-editing was used to explore the biology of Tfap2c in rat placenta development. Homozygous global disruption of Tfap2c resulted in prenatal lethality. Heterozygous global disruption of Tfap2c was associated with diminished invasive trophoblast cell infiltration into the uterus. The role of TFAP2C in the invasive trophoblast cell lineage was explored using Cre-lox conditional mutagenesis. Invasive trophoblast cell-specific disruption of Tfap2c resulted in inhibition of intrauterine trophoblast cell invasion and intrauterine and postnatal growth restriction. The invasive trophoblast cell lineage was not impaired following conditional monoallelic disruption of Tfap2c. In summary, TFAP2C contributes to the progression of distinct stages of placental development. TFAP2C is a driver of early events in trophoblast cell development and reappears later in gestation as an essential regulator of the invasive trophoblast cell lineage. A subset of TFAP2C actions on trophoblast cells are dependent on gene dosage.

Celecoxib paradoxically induces COX-2 expression and astrocyte activation through the ERK/JNK/AP-1 signaling pathway in the cerebral cortex of rats.

Previous studies have shown that celecoxib or NSAID may paradoxically induce cyclooxygenase-2 (COX-2) expression and trigger inflammation-like responses in airway smooth muscle cells and renal mesangial cells. Despite the extensive research on celecoxib, its atypical biological effect on the induction of COX-2 in astroglial cells within the central nervous system (CNS) remains unexplored. In the present study, we investigated the impact of celecoxib on COX-2 and Glial Fibrillary Acidic Protein (GFAP) expression and explored the mechanisms underlying celecoxib-regulated COX-2 expression in cortical astrocytes of rats. Cortical astrocytes were treated with celecoxib (20 μM) for 24 hours, resulting in a significant increase in COX-2 expression and up-regulation of GFAP, a marker of astrocyte activation, and the COX-2 induced by celecoxib is functionally active in prostaglandin E2 (PGE2) synthesis. Celecoxib also enhanced LPS-induced COX-2 expression, but its ability to inhibit PGE2 synthesis decreased at higher concentrations. Celecoxib induced phosphorylation of Extracellular signal-regulated Kinase (ERK) and c-Jun N-terminal Kinase (JNK) but not p38 Mitogen-Activated Protein Kinase (p38 MAPK), and inhibition of activity of ERK and JNK by U0126 and SP600125 effectively blocked COX-2 and GFAP induction by celecoxib. Celecoxib increased the accumulation of transcription factor AP-1 (composed of phosphorylated c-Jun and c-fos) in the nucleus. Inhibition of AP-1 activity with SR11302 significantly prevented celecoxib-induced COX-2 and GFAP expression. Additionally, the inhibiting activity of ERK and JNK can effectively suppress AP-1 expression and activity induced by celecoxib. These findings demonstrated that celecoxib induces COX-2 expression and astrocyte activation through the ERK/JNK/AP-1 signaling pathway, highlighting its potential effect in modulating inflammatory responses in the central nervous system.