Search Results (311)

Suppressors of cytokine signaling (SOCSs) are negative feedback regulators of the JAK-STAT pathway and are often exploited by viruses to evade host antiviral immunity. Unlike other SOCS members, the role of SOCS2 in viral infection remains poorly understood. Here, we report that overexpression of silkworm SOCS2 isoforms, SOCS2L and SOCS2S, promotes Bombyx mori nucleopolyhedrovirus (BmNPV) replication at multiple stages, including viral DNA replication, late gene (VP39) transcription, and virion egress, while their knockdown suppresses these processes. Overexpression of SH2 domain mutants (R123Q in SOCS2S, R142Q in SOCS2L) reduced viral DNA replication to baseline and VP39 expression below baseline, drastically decreased infectious progeny titers, but unexpectedly increased viral DNA release to wild-type levels, suggesting that the SH2 domain may differentially regulate distinct steps of viral replication. Furthermore, SOCS2 isoforms, alone or cooperatively with BmNPV, modulate the mRNA levels of SOCS-STAT network members in an isoform-, dose-, and target-specific manner. Collectively, this study reveals for the first time the multiple proviral functions of silkworm SOCS2 isoforms, with differential effects on distinct stages of the viral life cycle, and highlights their potential as transcriptional modulators exploited by viruses for immune evasion. Full article

Hepatocellular carcinoma (HCC) is the most common type of liver cancer, and accounts for over 800,000 deaths worldwide, making it a major global health concern. Unfortunately, despite major advances in systemic treatments, such as the introduction of atezolizumab and bevacizumab, patient objective response rates fall below 30%. HCC most commonly develops against a background of chronic liver disease and cirrhosis, although single gene mutations can also drive HCC development, progression, and metastasis. Around 25% of HCC patient tumours carry mutations in TP53, the gene encoding the tumour-suppressor protein p53. p53 is a central regulator of genomic stability, cell-cycle arrest, apoptosis, senescence, and metabolic homeostasis, and its dysfunction is a frequent event in hepatocarcinogenesis. Accumulating evidence highlights the critical role of p53 in liver fibrosis, inflammation, and shaping of the HCC tumour microenvironment (TME). This review summarizes the role of p53 and its negative regulators Mdm2 and MdmX in HCC development and progression, with an emphasis on how p53 shapes the TME in favour of tumour progression. We also evaluate current and emerging p53-targeted therapeutic strategies, including Mdm2/MdmX inhibitors, mutant p53 reactivators, and rational combinations with immunotherapies. Finally, we discuss major challenges in translating p53-based therapies to the clinic, such as tumour heterogeneity, underlying liver dysfunction, and the development of therapeutic resistance. A deeper understanding of p53 biology in chronic liver disease may unlock new avenues for effective HCC prevention and treatment. Full article

Interleukin (IL)-1β is a pro-inflammatory cytokine implicated in sterile inflammation and tumor development. Investigating the role of MAPKAP kinase 2 (MK2) in IL-1β processing, we found that Il1b mRNA and IL-1β protein levels were elevated in resting MK2-knockout (KO) macrophages and in the serum of MK2/3 double-KO mice. This was linked to activation of the non-canonical NF-κB pathway in the absence of MK2 or its activator, p38α. Rescue by MK2, its kinase-inactive mutant MK2K79R, or p38α suppressed this pathway and reduced Il1b expression. We also observed decreased basal protein levels of tumor suppressor p53 in MK2- or p38α-deficient cells. Mechanistically, p53 interacts with caspase-3, promoting cleavage of RelB, thereby inhibiting non-canonical NF-κB signaling and subsequent Il1b and TP53 expression. These findings explain elevated basal IL-1β levels in MK2-KO macrophages and uncover a new autoregulatory mechanism of TP53 expression. Additionally, they reveal a new mechanism that contributes to the long-discussed link between cancer and inflammation, wherein the tumor suppressor p53 inhibits cytokine production in parallel. Full article

Mitogen-activated protein kinase kinase kinase 1 (MAP3K1) possesses dual enzymatic functions, i.e., kinase and E3 ubiquitin ligase activities, orchestrating proliferation, survival, apoptosis, DNA damage response, and immune modulation. Recent genomic and mechanistic studies have revealed MAP3K1’s paradoxical, context-dependent roles as both an oncogene and a tumor suppressor. We discuss MAP3K1’s multidomain architecture, featuring an N-terminal RING and PHD domain (E3 ligase activity), a TOG domain (microtubule dynamics), and a C-terminal kinase domain, enabling the integration of c-jun N-terminal kinase (JNK), p38 mitogen-activated protein kinase (p38 MAPK), extracellular signal-regulated kinase (ERK), and nuclear factor kappa B (NF-κB) signaling pathways. MAP3K1 functions as a molecular switch balancing survival and apoptosis, with caspase-3 cleavage at Asp878 activating pro-apoptotic JNK/p38 signaling. Genomic analyses across >35 cancer types reveal MAP3K1 alterations at frequencies of <1–14%, highest in breast and endometrial cancers. These alterations show tissue specificity: loss-of-function mutations predominate in hormone receptor-positive breast cancer with a favorable prognosis, whereas gain-of-function mutations in melanoma activate oncogenic ERK signaling. MAP3K1 mutations predict response to mitogen-activated protein kinase kinase (MEK) and phosphoinositide 3-kinase (PI3K) inhibitors, with mutant cancers showing higher MEK inhibitor response than wild-type tumors. Despite substantial progress, critical gaps remain regarding MAP3K1’s E3 ligase substrates, context-dependent activity determinants, and therapeutic strategies. Addressing these through inhibitor development, biomarker validation, and mechanistic studies will accelerate potential clinical translation of MAP3K1 biology. Full article

Chromatin remodelers play essential roles in modulating nucleosome structure and enabling dynamic transcriptional control. Arabidopsis calmodulin-binding transcription activators CAMTA1/2/3 negatively regulate plant immunity by suppressing the expression of biosynthesis genes of major defence hormones salicylic acid (SA) and N-hydroxy-pipecolic acid (NHP). The autoimmunity of the camta2/3 mutant is partially suppressed by loss of the NHP biosynthesis enzyme SAR deficient 4 (SARD4). During a forward genetic screen with the mildly autoimmune camta2/3 sard4 mutant, we identified chromatin-remodelling factor 5 (chr5) as its partial suppressor. The chr5 single mutants displayed decreased SA biosynthesis and compromised basal immunity. Further RNA-sequencing with chr5 defined immune-related genes that were downregulated in the mutants, including those involved in SA and NHP biosynthesis and signalling, PTI and ETI pathways. Our analysis highlights the roles of CHR5 in immune-specific chromatin remodelling events, contributing to transcriptional reprogramming during plant defence responses. Full article

Constitutively active KRAS mutations are highly prevalent in lung cancers, but the direct role of its downstream phosphatidylinositol 3-kinase (PI3K) pathway in tumor progression remains unclear. A previous study established the requirement for PIK3CA, the alpha catalytic isoform, in lung tumor development in mouse models with an intact Trp53 tumor suppressor. In this study, we further investigated the requirement of PIK3CA for tumor growth both in vitro and in vivo. We first generated a “KPA” cell line by genetically deleting Pik3ca from a murine lung adenocarcinoma “KP” cell line harboring oncogenic Kras^G12D and lacking Trp53. We also examined the requirement for STK11, a tumor suppressor and metabolic regulator frequently co-mutated with KRAS in lung cancer. We found that Pik3ca is not required for cell survival and growth in vitro, even under anchorage-independent conditions, but reduced the growth rate by 15%. We next orthotopically implanted KP and KPA cells into syngeneic mice and found that PIK3CA is absolutely required for tumor progression, even in the absence of Trp53. Implantation of KP cells, or a “KPS” cell line lacking the Stk11 gene, led to rapid tumor growth and death of all host animals. In contrast, mice implanted with KPA cells all survived with no detectable lung tumors. The gene expression profiles from cultured cell lines suggest oxidative stress as a potential vulnerability of KPA cells. Indeed, we found KPA cells were more sensitive to hydrogen peroxide and diethyl maleate-induced oxidative stress as compared to KP and KPS cells. Together, these results indicate that PIK3CA is not required for lung cancer cell growth induced by mutant KRAS in vitro but is essential for in vivo progression and growth. Full article

Background: The turnaround of the tumor suppressor p53 protein, the guardian of the genome, is closely regulated to ensure avoidance of its untimely activation, which could lead to the demise of normal cells. Cancer cells often display mutations in the gene TP53 encoding for p53, which interferes with its normal function. Methods: The genomic series of colorectal cancer from the Cancer Genome Atlas (TCGA) was interrogated to discover genomic alterations and determine the mRNA expression of enzymes affecting p53 ubiquitination in colorectal cancers with wild-type and mutant TP53. Results: Genomic alterations of p53-regulating E3 ubiquitin ligases were uncommon in colorectal cancers, the most frequent being mutations in RCHY1. Several p53-regulating E3 ligases were well expressed in subsets of colorectal cancers, two of which, MDM2 and TRIM24, displayed higher mRNA expressions than the normal colorectal epithelia. The former was particularly upregulated in TP53 wild-type colorectal cancers, and the latter was upregulated in both wild-type and mutant TP53 cancers. Upregulation of TRIM24 in TP53 mutant cancers was observed independently of the type of mutations (gain-of-function or other). Among E3 ligases used in proteolysis-targeting chimeras (PROTACs), VHL was upregulated together with its E2-conjugating enzyme UBE2S in colorectal cancers. Conclusions: This survey of p53-targeting ubiquitin ligases provides a roadmap for potential therapeutic strategies working by promoting the destruction of the mutant protein or reactivating its normal function in TP53-mutated colorectal cancers and promoting p53 function by preventing degradation in TP53 wild-type cancers. Full article

The p53 tumor suppressor protein plays a central role in maintaining genomic stability by regulating cell cycle arrest, apoptosis, and DNA repair under cellular stress. Mouse double minute 2 (MDM2), an E3 ubiquitin ligase, negatively regulates p53 via direct binding and proteasomal degradation. Overexpression or amplification of MDM2 can disrupt this pathway and promote tumorigenesis, even in cancers with wild-type p53. This review outlines the structural features of MDM2, particularly its N-terminal hydrophobic pocket and C-terminal RING domain, and their roles in p53 regulation. We further examine the pathological effects of MDM2 dysregulation and SNPs linked to increased cancer risk. Recent progress in small molecule MDM2 inhibitors is discussed, with a focus on non-covalent agents such as rhein-derived anthraquinone analogs, including AQ-101, which demonstrate promising anti-cancer activity with reduced toxicity. These findings support the continued development of non-covalent MDM2 inhibitors as a novel therapeutic approach for cancers involving both wild-type and mutant p53. Full article

PCIF1 is primarily recognized as an RNA methyltransferase that mediates N⁶-methylation of cap-proximal adenosine (m⁶Am) and plays diverse roles in gene expression. In this study, we uncover a novel role for PCIF1 as a crucial negative regulator of type I interferon (IFN) induction, a pathway critical for antiviral immunity whose dysregulation leads to inflammatory and autoimmune diseases. We demonstrate that PCIF1 deficiency robustly enhances the poly(I:C)-induced type I IFN response, accompanied by augmented STAT1 activation and interferon-stimulated gene (ISG) expression. Mechanistically, PCIF1 suppresses IFNB1 transcription by attenuating IRF3 phosphorylation and nuclear translocation, as shown by increased nascent IFNB1 mRNA synthesis and promoter activity in PCIF1-deficient cells, without affecting the mRNA stability. Crucially, this suppressive function was independent of PCIF1’s canonical RNA methyltransferase activity, as both wild-type PCIF1 and a methyltransferase-inactive mutant effectively attenuated type I IFN induction. Collectively, our findings establish PCIF1 as a novel methyltransferase-independent suppressor of type I IFN responses, revealing its previously unrecognized non-catalytic function. This discovery offers critical insights into the multifaceted regulation of innate immunity and highlights PCIF1’s non-catalytic function as a promising therapeutic target for modulating antiviral responses and inflammatory diseases. Full article

Nucleotide-binding and leucine-rich repeat receptors (NLRs) play an important role in plant innate immunity. Previous reports indicate that SUT1 (SUPPRESSOR OF TOPP4 1) is required for the autoimmune response mediated by TYPE ONE PROTEIN PHOSPHATASE 4 (TOPP4) mutation topp4-1 (namely TOPP4^T246M) in Arabidopsis. We observed that co-expression of SUT1 with TOPP4 mutant versions, instead of wild-type TOPP4, produced robust cell death in N. benthamiana. The YFP-labeled SUT1 was localized on the plasma membrane (PM), and Gly2, Cys4, and Ser6 are crucial amino acid sites for its PM localization and function. Further dissection proclaimed that the function and localization of SUT1 are influenced by mutations in conserved specific residues. These findings may provide a new perspective for elucidating the activation mechanism of SUT1. Full article

Potyvirus genomes are expressed as a single large open reading frame, which is translated into a polyprotein that is post-translationally cleaved by three virus-encoded proteases into 10 functional proteins. Several of these potyviral proteins, including nuclear inclusion protein b (NIb), are multifunctional. Here, using the classic GFP silencing in Nicotiana benthamiana gfp-transgenic plants, we show that potato virus Y (PVY) NIb, in addition to its canonical role as the viral RNA-dependent RNA polymerase (RdRP), functions as a suppressor of RNA silencing. Mutational analyses reveal a previously unreported NIb nuclear localization signal (NLS) consisting of a triple-lysine motif. NIb suppression of RNA silencing activity was lost when the NLS was mutated, suggesting that nuclear localization is required for NIb suppression of RNA silencing activity. Analysis of sequenced GFP siRNAs revealed three reproducible hotspot regions at ≈175 nt, ≈320–330 nt, and a broader 3′-proximal region spanning ≈560–700 nt that contains multiple local maxima. These data show differences in the positional distribution of siRNAs between samples expressing NIb and those expressing NIb^Del3×2, the NIb null mutant that does not suppress RNA silencing. However, the positional distribution of GFP-derived small RNAs across the transgene differed modestly between NIb and NIb^Del3×2, while both treatments showed the same three reproducible hotspot regions. Furthermore, NIb was found to interact with four key RNA silencing pathway proteins—AGO4, HSP70, HSP90, and SGS3. Except for HSP90, each of these proteins showed degradation products that were absent in NIb mutants that did not suppress RNA silencing. These findings support a role for NIb in countering host defense during virus infection. Full article

Mutations in TP53 inhibit p53 protective behaviors including cell cycle arrest, DNA damage repair protein recruitment, and apoptosis. The ubiquity of p53 in genome-stabilizing functions leads to an aberrant tumor microenvironment in TP53-mutated myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML). Profound immunosuppression mediated by myeloid-derived suppressor cells, the upregulation of cytokines and cell-surface receptors on leukemic cells, the suppression of native immune regulator cells, and metabolic aberrations in the bone marrow are features of the TP53-mutated AML/MDS marrow microenvironment. These localized changes in the bone marrow microenvironment (BMME) explain why traditional therapies for MDS/AML, including chemotherapeutics and hypomethylating agents, are not as effective in TP53-mutated myeloid neoplasms and demonstrate the dire need for new treatments in this patient population. The unique pathophysiology of TP53-mutated disease also provides new therapeutic approaches which are being studied, including intracellular targets (MDM2, p53), cell-surface protein biologics (immune checkpoint inhibitors, BiTE therapy, and antibody–drug conjugates), cell therapies (CAR-T, NK-cell), signal transduction pathways (Hedgehog, Wnt, NF-κB, CCRL2, and HIF-1α), and co-opted biologic pathways (cholesterol synthesis and glycolysis). In this review, we will discuss the pathophysiologic anomalies of the tumor microenvironment in TP53-mutant MDS/AML, the hypothesized mechanisms of chemoresistance it imparts, and how novel therapies are leveraging diverse therapeutic targets to address this critical area of need. Full article

p53 has long been studied as a major regulator in cellular pathways, resulting in a plethora of information on the structure and function of this protein as a frequently mutated tumor suppressor. Recent studies have demonstrated how the p53 transcription activation domain (TAD) interacts with the BH3-binding pocket of BCL-2 to regulate cell survival/death. While the in vitro studies on p53 and BCL-2 have frequently used truncated and stabilized proteins of p53 to ensure crystallization, these mutated proteins are not naturally observed in cells. Thus, it becomes important to find a way in silico to simulate how a full-length monomer with the unaltered sequence of wild-type (WT) or missense mutant (MT) p53 interacts with BCL-2. Our objective is to provide a predictive insight into how p53 monomers might interact with BCL-2 through the combination of previously published algorithms. Using pre-established computational techniques in silico, the interactions between p53 variants and BCL-2 were compared to existing crystals to ensure the validity of the current method, and the affinities were predicted to explore the strength of these interactions. Here, we found that this protocol was able to replicate some of the amino acid interactions identified in the previous literature, as well as identify affinities between each WT/MT p53 and BCL-2. Most major MT p53 variants are predicted to directly interact with BCL-2, but have a decrease in affinity compared to WT p53, suggesting a potential increase in BCL-2 survival activity. Together, the method described here can potentially be useful as a predictive workflow to inform future studies in vitro and in vivo. Full article

Fine particulate matter (PM2.5) is a major air pollutant linked to lung cancer progression. In Southeast Asia, seasonal smoke-haze produces biomass-derived PM2.5, yet its acute effects on genetically diverse lung tumours remain unclear. We investigate how Chiang Mai haze-derived PM2.5 impacts oxidative stress and gene expression in three non-small-cell lung cancer (NSCLC) cell lines: A549 (KRAS-mutant), NCI-H1975 (EGFR-mutant), and NCI-H460 (KRAS/PIK3CA-mutant). Cells were exposed to PM2.5 (0–200 µg/mL) and assessed for viability (MTT), reactive oxygen species (ROS; H₂O₂, •OH) and malondialdehyde (MDA) levels, mitochondrial-associated fluorescence, and whole-transcriptome responses. Acute exposure caused dose- and time-dependent viability loss, with A549 and NCI-H1975 more sensitive than NCI-H460. ROS profiling normalized to viable cells revealed genotype-specific oxidative patterns: cumulative increases in A549, sharp reversible spikes in NCI-H1975, and modest changes in NCI-H460. MitoTracker intensity trended downward without significance, with subtle fluorescence changes and particulate uptake. RNA-seq identified robust induction of xenobiotic metabolism (CYP1A1, CYP1B1), oxidative/metabolic stress mediators (GDF15, TIPARP), and tumour-associated genes (FOSB, VGF), alongside repression of tumour suppressors (FAT1, LINC00472). Pathway enrichment analyses highlighted oxidative stress, IL-17, NF-κB, and immune checkpoint signaling. Together, biomass haze-derived PM2.5 from Northern Thailand drives genotype-dependent oxidative stress and transcriptional remodeling in NSCLC cells. Full article

Mutations in the POU1F1 gene cause defects in the expression of the genes encoding thyroid-stimulating hormone (TSH)-β subunit, growth hormone (GH), and prolactin (PRL). Here, we characterized 15 missense and nonsense mutations. Protein stability was reduced in the P14L, P24L, F135C, K145X, F233S and E250X mutants. Transactivation by 15 mutants in the TSHβ promoter was moderately correlated with that of the PRL promoter. Based on their transcriptional activity, we classified them into three groups: group I, equivalent to the wild type; group II, partial; and group III, substantially lost. A review of case reports on four patients with group II mutations revealed that TSH deficiency manifested after recombinant GH therapy. A transcription factor, GATA2, is the main activator in the TSHβ gene, while POU1F1 protects its function from inhibition by the suppressor region (SR). We found that the SR is critical for the pathogenesis of TSH deficiency. The transactivation of the TSHβ promoter by the K216E mutant was equivalent to that of wild-type POU1F1; however, that of the PRL promoter was low, while the opposite was found in the R271W mutant. The functional property of K216E suggests that the interaction of POU1F1 with GATA2 may not always be necessary for the activation of the TSHβ promoter. Full article