Bioscience Reports最新文献

The two murine double minute (MDM) family members, MDM2 and MDMX, are a well-established negative regulator of p53 activity. Under DNA damage conditions, MDM2 and MDMX are phosphorylated near their RING domains (serine 395 at MDM2 and serine 403 at MDMX) and switch to act as p53 positive regulators. MDMX binds to TP53 mRNA and acts as a chaperone for RNA structure, enabling MDM2 to bind. This interaction enhances TP53 mRNA translation, leading to increased p53 protein production. While the biological significance of this interaction has been described, the specific features of the MDMX-RNA interaction remain poorly understood. We used various MDMX protein constructs to characterize binding to TP53 mRNA and identified that the interaction mediated by the RING domain is modulated by the presence of other domains. Hydrogen-deuterium exchange mass spectrometry (HDX-MS) and binding assays in high salt conditions and various pH demonstrate that the whole protein participates in RNA interaction, with the C-terminal domain likely providing the contact with RNA by electrostatic forces. We show that protein structural changes induced by the chelating agent EDTA or the reducing agent TCEP enhance RNA binding by promoting partial structural destabilization of the protein. Our findings suggest that the MDMX/TP53 mRNA interaction is complex, with the RING domain binding to RNA and being supported by the entire protein, which acts as a scaffold for the RNA interaction. These results contribute to a better understanding of MDMX's role in TP53 mRNA binding and provide valuable insights for future investigation of the MDM2-MDMX-TP53 mRNA complex, which is crucial for p53 stabilization and activation under DNA-damaging conditions.

Apolipoprotein B mRNA editing catalytic subunit 3B (A3B), a nuclear enzyme that catalyzes cytidine-to-uridine (C-to-U) editing in single-stranded DNA (ssDNA), contributes to genetic diversity in many cancers. A3B is induced or activated by DNA damage owing to a variety of factors; however, the mechanisms by which A3B accesses ssDNA within the genome remain unclear. In this study, we showed that in unstimulated cells, A3B is retained in the nucleoplasm in an RNA-dependent manner. Upon DNA damage induced by camptothecin or actinomycin D (Act D), both targeting topoisomerase I, or by 1-methyl-3-nitro-1-nitrosoguanidine (MNNG), an alkylating agent that generates apurinic/apyrimidinic sites, A3B accumulates at the nucleolar rim and interior. Using confocal microscopy, we assessed the colocalization of A3B with drug-induced R-loops. A3B accumulation was abolished by RNase H treatment, implicating R-loops in its localization. However, the S9.6 antibody, commonly used to detect DNA/RNA hybrids, did not identify R-loop-specific signals in the nucleolus, leaving the direct involvement of R-loops in A3B accumulation unresolved. Conversely, immunoprecipitation-mass spectrometry with data-independent acquisition (IP-MS DIA) revealed increased interactions between A3B and RNA helicases such as DDX17 and DDX21, which are known R-loop-binding proteins, following MNNG or Act D treatment. Our results demonstrate that A3B-induced secondary DNA damage occurs in the nucleolus after DNA damage, providing new insights into the acquisition of cancer diversity involving A3B and the DNA damage response in the nucleolus.

Polysaccharides have gained considerable attention recently because of their anti-tumor and immunoregulatory properties. Its activity depends on the type of fungus that produces it, the extraction method, and the molecular weight.

Materials and methods: This study evaluated the anti-tumor and immunoregulatory properties of Ganoderma parvulum (GP)-derived polysaccharides.

Results: GP crude polysaccharides inhibited mice's lymphoma without cytotoxicity. In vitro studies showed that exopolysaccharides (GEPS) and intrapolysaccharides (GIPS) of G. parvulum inhibited the proliferation of tumor cells, but no cell death was observed. Significantly, GEPS and GIPS increased the production of nitric oxide, TNF-α, MCP-1, and an increase in IL-1β, IL-18, and Caspase-1, while NLRP3 was down-regulated. Also, it decreases the production of IL-10 and IL-6.

Conclusion: These observations suggest that GP-derived polysaccharides may exert anti-tumor activity primarily by activating the host's immune system via macrophage stimulation.

FGR proto-oncogene (Fgr), a member of the Src family kinases, has garnered attention for its potential involvement in apoptotic signaling, yet its role in cardiovascular diseases, particularly acute myocardial infarction (AMI), remains unexplored. This study sought to investigate whether elevated left ventricular Fgr expression alleviates myocardial injury in the infarcted area and whether this protective mechanism is mediated by modulating phosphoinositide 3-kinase (PI3K)/Akt phosphorylation. The transcriptome-wide association study was initially utilized to screen for susceptibility genes in the left ventricle, with findings validated using bulk-RNA sequencing data from a rat model of left anterior descending coronary artery (LAD) ligation; subsequently, human spatial transcriptomics combined with single-nucleus RNA sequencing data confirmed differential expression of Fgr and PI3K/Akt in the infarcted region. Fgr knockdown via siRNA in H9C2 cells and pharmacological inhibition with TL02-59 in rats were conducted to assess cellular survival and cardiac function, respectively. Fgr emerged as a common candidate gene identified through multi-omics data analysis, with its up-regulation confirmed both in vivo and in vitro. Fgr silencing in an in vitro oxygenglucose deprivation model significantly reduced cell survival and suppressed PI3K/Akt phosphorylation, whereas TL02-59 administration in rats subjected to LAD ligation impaired post-infarction cardiac function while concurrently inhibiting PI3K/Akt phosphorylation levels. This study demonstrates that Fgr is markedly up-regulated in AMI and exerts cardioprotective effects, possibly through modulation of PI3K/Akt signaling phosphorylation, thereby underscoring its potential as a therapeutic target.

Proteome, the molecular product of regulatory diktat of the cellular machinery, predicts the behaviour and progression of cancers. Designing effective molecular therapies based on proteins with comprehensive patient stratification remains the mainstay of every translational research. Research on the proteome involves a) identification of biomarkers that, with utmost sensitivity and specificity, reveal significant insights into the disease state and b) understanding the mechanistic underpinnings and rewiring of cellular signaling pathways that drive a particular cancerous pathology. In this review, we give a comprehensive description of the evolution of mass spectrometer-based methods, including labeling strategies available to study the proteome and post-translational modifications in response to various perturbations. We summarize their utility in understanding complex processes of cancers, advance research on cancer therapy by decoding novel biomarkers, identify therapy resistance drivers, and enhance spatial attributes of tumor microenvironment by single-cell proteomics. Finally, some of the challenges in the currently used methods have been discussed.