Asymmetrical arginine dimethylation of histone H4 by 8-oxog/OGG1/PRMT1 is essential for oxidative stress-induced transcription activation

TRIM25 promotes glioblastoma cell growth and invasion via regulation of the PRMT1/c-MYC pathway by targeting the splicing factor NONO

BACKGROUND

Ubiquitination plays an important role in proliferating and invasive characteristic of glioblastoma (GBM), similar to many other cancers. Tripartite motif 25 (TRIM25) is a member of the TRIM family of proteins, which are involved in tumorigenesis through substrate ubiquitination.

METHODS

Difference in TRIM25 expression levels between nonneoplastic brain tissue samples and primary glioma samples was demonstrated using publicly available glioblastoma database, immunohistochemistry, and western blotting. TRIM25 knockdown GBM cell lines (LN229 and U251) and patient derived GBM stem-like cells (GSCs) GBM#021 were used to investigate the function of TRIM25 in vivo and in vitro. Co-immunoprecipitation (Co-IP) and mass spectrometry analysis were performed to identify NONO as a protein that interacts with TRIM25. The molecular mechanisms underlying the promotion of GBM development by TRIM25 through NONO were investigated by RNA-seq and validated by qRT-PCR and western blotting.

RESULTS

We observed upregulation of TRIM25 in GBM, correlating with enhanced glioblastoma cell growth and invasion, both in vitro and in vivo. Subsequently, we screened a panel of proteins interacting with TRIM25; mass spectrometry and co-immunoprecipitation revealed that NONO was a potential substrate of TRIM25. TRIM25 knockdown reduced the K63-linked ubiquitination of NONO, thereby suppressing the splicing function of NONO. Dysfunctional NONO resulted in the retention of the second intron in the pre-mRNA of PRMT1, inhibiting the activation of the PRMT1/c-MYC pathway.

CONCLUSIONS

Our study demonstrates that TRIM25 promotes glioblastoma cell growth and invasion by regulating the PRMT1/c-MYC pathway through mediation of the splicing factor NONO. Targeting the E3 ligase activity of TRIM25 or the complex interactions between TRIM25 and NONO may prove beneficial in the treatment of GBM.

OGG1 as an Epigenetic Reader Affects NFκB: What This Means for Cancer

8-oxoguanine glycosylase 1 (OGG1), which was initially identified as the enzyme that catalyzes the first step in the DNA base excision repair pathway, is now also recognized as a modulator of gene expression. What is important for cancer is that OGG1 acts as a modulator of NFκB-driven gene expression. Specifically, oxidant stress in the cell transiently halts enzymatic activity of substrate-bound OGG1. The stalled OGG1 facilitates DNA binding of transactivators, such as NFκB to their cognate sites, enabling the expression of cytokines and chemokines, with ensuing recruitment of inflammatory cells. Recently, we highlighted chief aspects of OGG1 involvement in regulation of gene expression, which hold significance in lung cancer development. However, OGG1 has also been implicated in the molecular underpinning of acute myeloid leukemia. This review analyzes and discusses how these cells adapt through redox-modulated intricate connections, via interaction of OGG1 with NFκB, which provides malignant cells with alternative molecular pathways to transform their microenvironment, enabling adjustment, promoting cell proliferation, metastasis, and evading killing by therapeutic agents.

Targeting PRMT1-mediated SRSF1 methylation to suppress oncogenic exon inclusion events and breast tumorigenesis

PRMT1 plays a vital role in breast tumorigenesis; however, the underlying molecular mechanisms remain incompletely understood. Herein, we show that PRMT1 plays a critical role in RNA alternative splicing, with a preference for exon inclusion. PRMT1 methylome profiling identifies that PRMT1 methylates the splicing factor SRSF1, which is critical for SRSF1 phosphorylation, SRSF1 binding with RNA, and exon inclusion. In breast tumors, PRMT1 overexpression is associated with increased SRSF1 arginine methylation and aberrant exon inclusion, which are critical for breast cancer cell growth. In addition, we identify a selective PRMT1 inhibitor, iPRMT1, which potently inhibits PRMT1-mediated SRSF1 methylation, exon inclusion, and breast cancer cell growth. Combination treatment with iPRMT1 and inhibitors targeting SRSF1 phosphorylation exhibits an additive effect of suppressing breast cancer cell growth. In conclusion, our study dissects a mechanism underlying PRMT1-mediated RNA alternative splicing. Thus, PRMT1 has great potential as a therapeutic target in breast cancer treatment.

Excessive iron inhibits insulin secretion via perturbing transcriptional regulation of SYT7 by OGG1

Although iron overload is closely related to the occurrence of type 2 diabetes mellitus (T2DM), the specific mechanism is unclear. Here, we found that excessive iron inhibited the secretion of insulin (INS) and impaired islet β cell function through downregulating Synaptotagmin 7 (SYT7) in iron overload model in vivo and in vitro. Our results further demonstrated that 8-oxoguanine DNA glycosylase (OGG1), a key protein in the DNA base excision repair, was an upstream regulator of SYT7. Interestingly, such regulation could be suppressed by excessive iron. Ogg1-null mice, iron overload mice and db/db mice exhibit reduced INS secretion, weakened β cell function and subsequently impaired glucose tolerance. Notably, SYT7 overexpression could rescue these phenotypes. Our data revealed an intrinsic mechanism by which excessive iron inhibits INS secretion through perturbing the transcriptional regulation of SYT7 by OGG1, which suggested that SYT7 was a potential target in clinical therapy for T2DM.

Stimuli-Responsive Double Single-Atom Catalysts for Parallel Catalytic Therapy

Tumor microenvironment (TME)-induced nanocatalytic therapy is a trending strategy for tumor-targeting therapy, but the low catalytic efficiency remains to limit its therapeutic effect. The single-atom catalysts (SACs) appear as a novel type of nanozymes that possesses incredible catalytic activity. Here, we developed PEGylated manganese/iron-based SACs (Mn/Fe PSACs) by coordinating single-atom Mn/Fe to nitrogen atoms in hollow zeolitic imidazolate frameworks (ZIFs). Mn/Fe PSACs catalyze cellular hydrogen peroxide (H₂O₂) converting to hydroxyl radical (•OH) through a Fenton-like reaction; it also enhances the decomposition of H₂O₂ to O₂ that continuously converts to cytotoxic superoxide ion (•O₂^-) via oxidase-like activity. Mn/Fe PSACs can reduce the depletion of reactive oxygen species (ROS) by consuming glutathione (GSH). Here, we demonstrated the Mn/Fe PSACs-mediated synergistic antitumor efficacy among in vitro and in vivo experiments. This study proposes new promising single-atom nanozymes with highly efficient biocatalytic sites and synergistic therapeutic effects, which will give birth to abundant inspirations in ROS-related biological applications in broad biomedical fields.

Histone H4K20 monomethylation enables recombinant nucleosome methylation by PRMT1 in vitro

Protein arginine methyltransferases (PRMTs) catalyze the transfer of methyl groups to specific arginine residues of histones and nonhistone proteins. There are nine members in the PRMT family (PRMT1 to PRMT9), and PRMT1 is a dominant member catalyzing majority of arginine methylation in the cell. However, none of the PRMTs is active with recombinant nucleosome as substrate in vitro. Here, we report the discovery of the first in class novel crosstalk between histone H4 lysine 20 (H4K20) monomethylation on nucleosome by SETD8 and histone H4 arginine 3 (H4R3) methylation by PRMT1 in vitro. Full kinetic characterization and mass spectrometry analysis indicated that PRMT1 is only active with recombinant nucleosomes monomethylated at H4K20 by SETD8. These data suggests that the level of activity of PRMT1 could potentially be regulated selectively by SETD8 in various pathways, providing a new approach for discovery of selective regulators of PRMT1 activity.

OGG1 inhibition suppresses African swine fever virus replication

African swine fever virus (ASFV) is an important pathogen that causes a highly contagious and lethal disease in swine, for which neither a vaccine nor treatment is available. The DNA repair enzyme 8-oxoguanine DNA glycosylase 1 (OGG1), which excises the oxidative base lesion 8-oxo-7,8-dihydroguanine (8-oxoG), has been linked to the pathogenesis of different diseases associated with viral infections. However, the role of OGG1-base excision repair (BER) in ASFV infection has been poorly investigated. Our study aimed to characterize the alteration of host reactive oxygen species (ROS) and OGG1 and to analyse the role of OGG1 in ASFV infection. We found that ASFV infection induced high levels and dynamic changes in ROS and 8-oxoG and consistently increased the expression of OGG1. Viral yield, transcription level, and protein synthesis were reduced in ASFV-infected primary alveolar macrophages (PAMs) treated by TH5487 or SU0268 inhibiting OGG1. The expression of BER pathway associated proteins of ASFV was also suppressed in OGG1-inhibited PAMs. Furthermore, OGG1 was found to negatively regulate interferon β (IFN-β) production during ASFV infection and IFN-β could be activated by OGG1 inhibition with TH5487 and SU0268, which blocked OGG1 binding to 8-oxoG. Additionally, the interaction of OGG1 with viral MGF360-14-L protein could disturb IFN-β production to further affect ASFV replication. These results suggest that OGG1 plays the crucial role in successful viral infection and OGG1 inhibitors SU0268 or TH5487 could be used as antiviral agents for ASFV infection.

Brain-targeted antigen-generating nanoparticles improve glioblastoma prognosis

The exploration of multifunctional nanomedicine has prompted interest in improving glioblastoma (GBM) prognosis. In this study, we constructed tumor microenvironment (TME)-responsive magnetic therapeutic nanoparticles (BK@MTNPs) as a multifunctional drug delivery platform. It contains the following components. [Des-arg(Sheets et al., 2020 [9])]bradykinin (BK), which contributes to the transient opening of the blood-brain barrier (BBB) and targeting of GBM cells; nanoparticles (NPs) encapsulated in MTNPs, which act as an in vivo magnetic resonance (MR) imaging agent; crizotinib, which is an inhibitor of protein kinase c-Met; and the immune drug anti-PDL1 antibody. These components were loaded into BK@MTNPs for complete tumoricidal effects. Abundant glutathione in the TME can promote BK@MTNP degradation by interrupting the disulfide bonds between cysteine residues. Such BK@MTNPs support a synergistic tumoricidal effect by inducing DNA damage, activating the transcription of the tumor suppressor gene PTEN, inhibiting glioblastoma stem cell function, activating cytotoxic T lymphocytes, and reprogramming tumor-associated macrophages. BK@MTNPs showed a significant increase in antitumor activity compared with free drugs in vitro. Furthermore, in mice bearing orthotopic GBM, treatment with BK@MTNPs resulted in marked tumor inhibition and greatly extended survival time with minimal side effects. This study demonstrates the advantages of chemo-immunotherapeutic NPs accumulated in the GBM area and their effective inhibition of GBM growth, thus establishing a delivery platform to promote antitumor immunity against GBM.

OGG1 contributes to hepatocellular carcinoma by promoting cell cycle-related protein expression and enhancing DNA oxidative damage repair in tumor cells

Background

This study aimed to analyze the expression of 8‐oxoguanine DNA glycosylase (OGG1) in patients with hepatocellular carcinoma (HCC) and its effect on prognosis by bioinformatics techniques and to determine its possible carcinogenic mechanism through data mining.

Methods

The difference in OGG1 expression between healthy people and HCC patients was searched and analyzed by TCGA and GEO databases, and the effect of OGG1 on prognosis was judged by survival analysis. Meanwhile, the possible molecular mechanism of OGG1 in the tumorigenesis and development of HCC was explored by GO analysis, KEGG analysis, immune infiltration analysis, protein–protein interaction network, promoter methylation analysis, and so forth. Quantitative polymerase chain reaction (qPCR) was used to examine the gene expression in 36 pairs of HCC tissues and adjacent tissues.

Results

The expression of OGG1 in HCC patients was higher than that in healthy people, and the overexpression of OGG1 might stimulate cell proliferation by increasing the activity of cell cycle‐related proteins.

Conclusion

The alteration of OGG1 was significantly correlated with the tumorigenesis and development of HCC. OGG1 is expected to be a new biomarker for evaluating the prognosis of HCC and a new target for the treatment of HCC.

Chromatin Structure and Dynamics: Focus on Neuronal Differentiation and Pathological Implication

Chromatin structure is an essential regulator of gene expression. Its state of compaction contributes to the regulation of genetic programs, in particular during differentiation. Epigenetic processes, which include post-translational modifications of histones, DNA methylation and implication of non-coding RNA, are powerful regulators of gene expression. Neurogenesis and neuronal differentiation are spatio-temporally regulated events that allow the formation of the central nervous system components. Here, we review the chromatin structure and post-translational histone modifications associated with neuronal differentiation. Studying the impact of histone modifications on neuronal differentiation improves our understanding of the pathophysiological mechanisms of chromatinopathies and opens up new therapeutic avenues. In addition, we will discuss techniques for the analysis of histone modifications on a genome-wide scale and the pathologies associated with the dysregulation of the epigenetic machinery.

Genomic Uracil and Aberrant Profile of Demethylation Intermediates in Epigenetics and Hematologic Malignancies

DNA of all living cells undergoes continuous structural and chemical alterations resulting from fundamental cellular metabolic processes and reactivity of normal cellular metabolites and constituents. Examples include enzymatically oxidized bases, aberrantly methylated bases, and deaminated bases, the latter largely uracil from deaminated cytosine. In addition, the non-canonical DNA base uracil may result from misincorporated dUMP. Furthermore, uracil generated by deamination of cytosine in DNA is not always damage as it is also an intermediate in normal somatic hypermutation (SHM) and class shift recombination (CSR) at the Ig locus of B-cells in adaptive immunity. Many of the modifications alter base-pairing properties and may thus cause replicative and transcriptional mutagenesis. The best known and most studied epigenetic mark in DNA is 5-methylcytosine (5mC), generated by a methyltransferase that uses SAM as methyl donor, usually in CpG contexts. Oxidation products of 5mC are now thought to be intermediates in active demethylation as well as epigenetic marks in their own rights. The aim of this review is to describe the endogenous processes that surround the generation and removal of the most common types of DNA nucleobase modifications, namely, uracil and certain epigenetic modifications, together with their role in the development of hematological malignances. We also discuss what dictates whether the presence of an altered nucleobase is defined as damage or a natural modification.