Hsa_circ_0001944 regulates apoptosis by regulating the binding of PARP1 and HuR in leukemia and malignant transformed cells induced by hydroquinone

Hsa_circ_0000479 promotes gastric cancer progression by inhibiting BTRC-mediated ubiquitination of G3BP1

An increasing number of studies have shown that circular RNAs (circRNAs) are key regulators of cancer development and progression. RNA-binding proteins (RBPs) play critical roles in the regulation of biological activities, such as RNA synthesis, selective splicing, modification, translocation, and translation; therefore, research on the interactions of circRNAs with RBPs is key to identifying potential targets for cancer treatment. However, the biological roles and mechanisms of circRNAs in gastric cancer (GC) remain largely unknown. We identified differentially expressed circRNAs in GC by analysing Gene Expression Omnibus (GEO) datasets. Concurrently, in vitro functional assays and in vivo animal studies were performed to explore the biological role of circRNAs in GC. We performed western blotting (WB) of labelled proteins, salvage assays, mass spectrometry (MS), and RNA sequencing to investigate the mechanism of circRNAs in GC to explore their effects on GC cell proliferation and metastasis and to validate their potential value as therapeutic targets. Upregulated expression of cyclic RNA EPSTI1 (circEPSTI1; hsa_circ_0000479) was found in GC tissues and was associated with a poor clinical prognosis. hsa_circ_0000479 promotes the proliferation and migration of GC cells in vitro and in vivo. Notably, hsa_circ_0000479 interacts with Ras-GTPase-activated protein-binding protein 1 (G3BP1) in GC cells and inhibits the degradation of G3BP1 via the ubiquitin‒proteasome pathway, whereas hsa_circ_0000479 blocks the binding of G3BP1 to the E3 ligase BTRC. Mechanistic studies suggest that hsa_circ_0000479 promotes GC progression by competitively inhibiting the G3BP1 ubiquitination-mediated degradation facilitated by BTRC. Our results reveal the molecular mechanism by which hsa_circ_0000479 promotes GC progression through BTRC-mediated competitive binding to G3BP1 to inhibit its ubiquitination-mediated degradation, which provides a new theoretical basis for the targeted treatment of GC and elucidates the potential of hsa_circ_0000479-G3BP1-BTRC as a therapeutic target in GC. These findings provide a new direction for the treatment of patients with GC.

Circular RNA circ_0004470 accelerates the occurrence of lung cancer by promoting DNA damage and cell cycle arrest

Defects in the DNA damage response are associated with tumorigenesis, and circular RNAs (circRNAs) can also affect the occurrence and progression of cancer by regulating gene expression. However, the relationship between DNA damage in lung cancer and circRNAs remains unexplored. In this study, circ_0004470 was significantly upregulated in various lung cancer cells (H446, A549, H1299) as well as in carcinogenic animal models and clinical lung cancer samples. Circ_0004470 promoted DNA damage and cell cycle S phase arrest in human pulmonary bronchial epithelial cells, inhibited DNA repair, and accelerated malignant transformation in response to continuous DNA damage-inducing stimulation. Circ_0004470 inhibited DNA repair and cell cycle progression by binding specifically to the nucleotide excision repair complex Xeroderma pigmentosum group C-complementing protein and damage-specific DNA binding protein 1, thus interacting with the DNA damage response process and accelerating the accumulation of DNA damage. These findings suggest that circRNAs are involved in regulating genetic damage-associated lung cancer and provide insight into the mechanism by which circ_0004470 affects the DNA damage response during carcinogenesis.

Circular RNAs as key regulators in cancer hallmarks: New progress and therapeutic opportunities

Circular RNAs (circRNAs) have emerged as critical regulators in cancer biology, contributing to various cancer hallmarks, including cell proliferation, apoptosis, metastasis, and drug resistance. Defined by their covalently closed loop structure, circRNAs possess unique characteristics like high stability, abundance, and tissue-specific expression. These non-coding RNAs function through mechanisms such as miRNA sponging, interactions with RNA-binding proteins (RBPs), and modulating transcription and splicing. Advances in RNA sequencing and bioinformatics tools have enabled the identification and functional annotation of circRNAs across different cancer types. Clinically, circRNAs demonstrate high specificity and sensitivity in samples, offering potential as diagnostic and prognostic biomarkers. Additionally, therapeutic strategies involving circRNA mimics, inhibitors, and delivery systems are under investigation. However, their precise mechanisms remain unclear, and more clinical evidence is needed regarding their roles in cancer hallmarks. Understanding circRNAs will pave the way for novel diagnostic and therapeutic approaches, potentially improving patient outcomes.

Serum CircNIPSNAP3A is Associated with Metabolic Disorders, Atherosclerosis and Severity of Coronary Artery Disease in a Chinese Population

The relationships of serum circNIPSNAP3A and circHIPK3 with metabolic disorders, atherosclerosis and severity of coronary artery disease (CAD) remain to be clarified. Three hundred and thirty-eight subjects were categorized into normal coronary artery, atherosclerosis and CAD groups. Clinical data including anthropometric indexes, medical history, and physiological and biochemical parameters were collected. Serum circNIPSNAP3A and circHIPK3 were determined by quantitative real-time PCR. CAD severity was evaluated by clinical manifestation, electrocardiogram and coronary angiography. Both CAD and atherosclerosis groups had a higher serum level of circNIPSNAP3A than the normal coronary artery group (P < 0.05 for all). The subjects with a high percentage (> 66th percentile) of circNIPSNAP3A had higher mean levels of triglycerides, uric acid and homocysteine, and lower mean levels of high-density lipoprotein cholesterol and apolipoprotein AI than those with a low percentage (< 33rd percentile) of circNIPSNAP3A. Notably, circNIPSNAP3A is significantly and independently associated with CAD, and subjects with a high percentage of circNIPSNAP3A had more diseased coronary branches and a higher incidence of acute coronary syndrome than those with a low percentage of circNIPSNAP3A. Regarding circHIPK3, subjects with a medium or high percentage of circHIPK3 had a lower mean level of apolipoprotein AI than those with a low percentage of circHIPK3, but no significant differences in the incidence and severity of CAD among the < 33rd, 33rd-66th, and > 66th percentiles of circHIPK3 were detected. Serum circNIPSNAP3A is related to cardiovascular risk factors and CAD severity, and may be a potential prognostic marker and/or therapeutic target for CAD.

DNMT1 regulates hypermethylation and silences hsa_circ_401351 in hydroquinone-induced malignant TK6 cells

BACKGROUND

Benzene and its metabolite hydroquinone (HQ) are widely used in daily life, and long-term exposure to benzene or HQ can induce acute myeloid leukemia (AML). Circular RNAs (circRNAs) are mostly produced by reverse splicing of gene exon mRNA precursors. The modulation of circRNA expression is connected to leukemia progression; however, the molecular mechanism is still unknown.

MATERIALS AND METHODS

In this study, the cells were divided into four groups: PBS control group (PBS-TK6), TK6 malignantly transformed cells induced by 10.0 μmol/L HQ (HQ-TK6), and HQ-TK6 cells treated with 5 μmol/L 5-AzaC (DNA methyltransferase inhibitor) for 24 h (HQ + 5-AzaC). HQ-TK6 cells were treated with 200 nmol/L TSA (histone deacetylation inhibitor) for 24 h (HQ + TSA). qRT-PCR was used to identify the differential hsa_circ_401351 expression between the four groups. We further determined the hsa_circ_401351 promoter methylation level with methylation-specific PCR. DNMT1 and DNMT3b were knocked down by CRISPR/Cas9 to elucidate the specific molecular mechanism of hsa_circ_401351 in HQ-TK6 cells. CCK-8 and flow cytometry detected cell proliferation and apoptosis, respectively, after hsa_circ_401351 was overexpressed in HQ-TK6 cells.

RESULTS

Compared with the PBS-TK6 group, the expression of hsa_circ_401351 was found to be lower in the HQ-TK6 group. Nevertheless, treatment with 5-AzaC or TSA increased hsa_circ_401351 expression, with the upregulation being more pronounced in the TSA group. The expression of hsa_circ_401351 in the DNMT1 knockdown group was dramatically increased by 50% compared to that in the control group, and the DNA methylation level of the hsa_circ_401351 promoter region was decreased. When hsa_circ_401351 was overexpressed, HQ-TK6 cell proliferation was significantly slowed after 48 h compared with the control group. Flow cytometry showed that cells were mainly arrested in G1 phase, and apoptosis was significantly enhanced. Similarly, qRT-PCR and Western blot data showed significant reductions in Caspase-3 mRNA and protein production, and Bcl-2 mRNA levels were also elevated.

CONCLUSIONS

Overall, our research showed that elevated DNMT1 expression in HQ-TK6 cells increased methylation levels and decreased expression of the hsa_circ_401351 promoter region, limiting its ability to suppress HQ-TK6 cell growth and enhance apoptosis.

Non-coding RNAs: A new frontier in benzene-mediated toxicity

One of the most frequent environmental contaminants, benzene is still widely used as an industrial solvent around the world, especially in developing nations, posing a serious occupational risk. While the processes behind the toxicity of benzene grounds are not fully understood, it is generally accepted that its metabolism, which involves one or more reactive metabolites, is crucial to its toxicity. In order to evaluate the many ways that benzene could influence gene regulation and thus have an impact on human health, new methodologies have been created. The pathophysiology of the disorder may result from epigenetic reprogramming caused by exposure to benzene, including changes in non-coding RNA (ncRNA) markers, according to recent studies. We are interested in the identification of hazardous regulatory ncRNAs, the identification of these ncRNAs' targets, and the comprehension of the significance of these interactions in the mechanisms behind benzene toxicity. Hence, the focus of recent research is on long non-coding RNAs (lncRNAs), circular RNAs (circRNAs) and microRNAs (miRNAs), and some of the more pertinent articles are also discussed.

Exploring the interplay between PARP1 and circRNA biogenesis and function

PARP1 (poly-ADP-ribose polymerase 1) is a multidomain protein with a flexible and self-folding structure that allows it to interact with a wide range of biomolecules, including nucleic acids and target proteins. PARP1 interacts with its target molecules either covalently via PARylation or non-covalently through its PAR moieties induced by auto-PARylation. These diverse interactions allow PARP1 to participate in complex regulatory circuits and cellular functions. Although the most studied PARP1-mediated functions are associated with DNA repair and cellular stress response, subsequent discoveries have revealed additional biological functions. Based on these findings, PARP1 is now recognized as a major modulator of gene expression. Several discoveries show that this multifunctional protein has been intimately connected to several steps of mRNA biogenesis, from transcription initiation to mRNA splicing, polyadenylation, export, and translation of mRNA to proteins. Nevertheless, our understanding of PARP1's involvement in the biogenesis of both coding and noncoding RNA, notably circular RNA (circRNA), remains restricted. In this review, we outline the possible roles of PARP1 in circRNA biogenesis. A full examination of the regulatory roles of PARP1 in nuclear processes with an emphasis on circRNA may reveal new avenues to control dysregulation implicated in the pathogenesis of several diseases such as neurodegenerative disorders and cancers. This article is categorized under: RNA Interactions with Proteins and Other Molecules > Protein-RNA Interactions: Functional Implications Regulatory RNAs/RNAi/Riboswitches > Regulatory RNAs RNA Processing > Splicing Regulation/Alternative Splicing.

Hexavalent chromium [Cr(VI)]-induced ribosomal DNA copy number variation and DNA damage responses and their associations with nucleolar protein HRAS in humans and cells

The carcinogenicity of hexavalent chromium [Cr(VI)] and its compounds has been widely recognized, yet the mechanism of genetic damage is still not fully understood. The ribosomal DNA (rDNA) copy number is recently considered a potential marker of cancer-associated stress. To investigate the roles of rDNA copy number variation (CNV) in DNA damage responses (DDRs) induced by Cr(VI) and the potential mechanism from nucleolar protein HRAS, a cross-sectional study in Cr(Ⅵ)-exposed workers and an in vitro experiment using HeLa cells were conducted. Our results showed increased levels of rDNA CNV, DDRs, and HRAS expression in Cr(VI)-exposed workers. Generalized linear regression analyses showed that Cr(VI) exposure was significantly positively associated with increased levels of rDNA CNV, DDRs, and HRAS expression in Cr(VI)-exposed workers. Moreover, there were pairwise associations between rDNA CNV, DDRs, and HRAS levels. Mediation analyses found that rDNA CNV significantly mediated the association between Cr(VI) exposure and DDRs. The in vitro experiments further confirmed that Cr(VI) treatment induced increased levels of rDNA CNV, DDRs, and HRAS expression in HeLa cells. Cr(VI)-induced rDNA CNV, ATM activation, and apoptosis damage were then strongly enhanced by HRAS depletion with siRNA in vitro, suggesting the important role of HRAS in CNV and DDRs caused by Cr(VI). The combined results of the human and cell line studies indicated that Cr(VI) exposure might enhance rDNA CNV by regulation of HRAS expression, which leads to Cr(VI)-induced genetic damage.