Aberrant ribosome biogenesis activates c-Myc and ASK1 pathways resulting in p53-dependent G1 arrest

Lnc-SNHG5 Promoted Hepatocellular Carcinoma Progression Through the RPS3-NFκB Pathway

Background

We planned to explore the underlying mechanism and clinical significance of lnc-SNHG5 and RPS3 in hepatocellular carcinoma in this current study.

Methods

The expression of Lnc-SNHG5 and RPS3 in HCC tissues and several cell lines were affirmed, respectively, using UALCAN, TIMER, TCGA and RT-qPCR assay. Cell proliferation ability was detected by colony formation assay and CCK8 assay. Cell apoptosis was monitored by flow cytometry assay. Next, the RPS3 expression levels and the related proteins in NFκB pathway were examined using Western blot analysis. The role of lnc-SNHG5 and RPS3 in vivo was identified by subcutaneous tumor bearing experiment.

Results

Lnc-SNHG5 was significantly increased in hepatocellular carcinoma tissues and in hepatocellular carcinoma cells. Further investigation showed that up-regulated lnc-SNHG5 promoted cell viability and cell proliferation ability of SMMC-7721 cells by regulating the cell apoptosis, while down-regulation of lnc-SNHG5 revealed opposite results in QGY-7703 cells. In terms of mechanism, we found that lnc-SNHG5 interacted with RPS3. Lnc-SNHG5 regulated the NFκB pathway through RPS3 in vitro and in vivo.

Conclusion

This study suggested that lnc-SNHG5 expression was signally up-regulated in hepatocellular carcinoma, and lnc-SNHG5 promoted the malignant phenotypes in vitro and in vivo via directly regulating RPS3-NFκB pathway. Lnc-SNHG5 might be a target for molecular targeted therapy, a potential and novel diagnostic marker for HCC patients.

Maintaining Genome Integrity: Protein Kinases and Phosphatases Orchestrate the Balancing Act of DNA Double-Strand Breaks Repair in Cancer

DNA double-strand breaks (DSBs) are the most lethal DNA damages which lead to severe genome instability. Phosphorylation is one of the most important protein post-translation modifications involved in DSBs repair regulation. Kinases and phosphatases play coordinating roles in DSB repair by phosphorylating and dephosphorylating various proteins. Recent research has shed light on the importance of maintaining a balance between kinase and phosphatase activities in DSB repair. The interplay between kinases and phosphatases plays an important role in regulating DNA-repair processes, and alterations in their activity can lead to genomic instability and disease. Therefore, study on the function of kinases and phosphatases in DSBs repair is essential for understanding their roles in cancer development and therapeutics. In this review, we summarize the current knowledge of kinases and phosphatases in DSBs repair regulation and highlight the advancements in the development of cancer therapies targeting kinases or phosphatases in DSBs repair pathways. In conclusion, understanding the balance of kinase and phosphatase activities in DSBs repair provides opportunities for the development of novel cancer therapeutics.

Molecular etiology of defective nuclear and mitochondrial ribosome biogenesis: Clinical phenotypes and therapy

Ribosomopathies are rare congenital disorders associated with defective ribosome biogenesis due to pathogenic variations in genes that encode proteins related to ribosome function and biogenesis. Defects in ribosome biogenesis result in a nucleolar stress response involving the TP53 tumor suppressor protein and impaired protein synthesis leading to a deregulated translational output. Despite the accepted notion that ribosomes are omnipresent and essential for all cells, most ribosomopathies show tissue-specific phenotypes affecting blood cells, hair, spleen, or skin. On the other hand, defects in mitochondrial ribosome biogenesis are associated with a range of clinical manifestations affecting more than one organ. Intriguingly, the deregulated ribosomal function is also a feature in several human malignancies with a selective upregulation or downregulation of specific ribosome components. Here, we highlight the clinical conditions associated with defective ribosome biogenesis in the nucleus and mitochondria with a description of the affected genes and the implicated pathways, along with a note on the treatment strategies currently available for these disorders.

The role of the nucleolus in regulating the cell cycle and the DNA damage response

The nucleolus has long been perceived as the site for ribosome biogenesis, but numerous studies suggest that the nucleolus carefully sequesters crucial proteins involved in multiple cellular functions. Among these, the role of nucleolus in cell cycle regulation is the most evident. The nucleolus is the first responder of growth-related signals to mediate normal cell cycle progression. The nucleolus also senses different cellular stress insults by activating diverse pathways that arrest the cell cycle, promote DNA repair, or initiate apoptosis. Here, we review the emerging concepts on how the ribosomal and nonribosomal nucleolar proteins mediate such cellular effects.

SIAH1-mediated RPS3 ubiquitination contributes to chemosensitivity in epithelial ovarian cancer

The E3 ligase SIAH1 is deregulated in human cancers and correlated with poor prognosis, but its contributions to chemoresistance in epithelial ovarian cancer (EOC) are not evident. Herein we found that SIAH1 was decreased in EOC tumour tissues and cell lines and negatively correlated with the RPS3 levels. SIAH1 overexpression suppressed tumour cell growth, colony formation, invasion, metastasis, and cisplatin resistance in vivo and in vitro. SIAH1 promoted RPS3 ubiquitination and degradation using the RING-finger domain, and these steps were required for RPS3 localization to the cytoplasm, which led to subsequent NF-κB inactivation and thereby conferred chemosensitivity. Moreover, ectopic expression of RPS3 or depletion of RPS3 ubiquitination mediated by SIAH1 via the K214R mutant significantly impaired cisplatin-induced tumour suppression in cells stably expressing SIAH1. Together, our findings reveal a tumour suppressor function of SIAH1 and provide evidence showing that the SIAH1-RPS3-NF-κB axis may act as an appealing strategy for tackling treatment resistance in EOC.

RNA-Seq based transcriptome analysis in oral lichen planus

Objectives

Oral lichen planus (OLP) is a T cell-mediated autoimmune disease recognized as an oral potential malignant disorder (OPMD) with the precise mechanism unknown. This study focused on the transcriptional profiles of OLP to elucidate its potential pathogenesis.

Methods

We conducted RNA sequencing on matched 6 OLP tissues and 6 normal oral mucosal tissues. Gene Ontology (GO) enrichment analysis, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway and weighted gene co-expression network analysis (WGCNA) were performed on differentially expressed genes (DEGs). We utilized qRT-PCR to validated the top dysregulated genes and hub genes in another 10 pairs of specimens.

Results

A total of 153 DEGs (p-values< 0.05) were detected from RNA-Seq. According to GO and KEGG analysis, the dysregulated genes were mainly related to T cell related pathway and Wnt signaling. Based on the WGCNA analysis, 5 modules with high intramodular connectivity and hub genes in each module were gained.

Conclusions

RNA-Seq and bioinformatic methods offered a valuable understanding of the biological pathways and key genes in the regulation of OLP. The identified DEGs and hub genes categorized into 2 groups including T cell regulation and inflammation and Wnt signaling pathway may serve as potential novel molecular targets for therapy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s41065-021-00202-z.

Effect of Graphene and Graphene Oxide on Airway Barrier and Differential Phosphorylation of Proteins in Tight and Adherens Junction Pathways

Via inhalation we are continuously exposed to environmental and occupational irritants which can induce adverse health effects, such as irritant-induced asthma (IIA). The airway epithelium forms the first barrier encountered by these agents. We investigated the effect of environmental and occupational irritants on the airway epithelial barrier in vitro. The airway epithelial barrier was mimicked using a coculture model, consisting of bronchial epithelial cells (16HBE) and monocytes (THP-1) seeded on the apical side of a permeable support, and human lung microvascular endothelial cells (HLMVEC) grown on the basal side. Upon exposure to graphene (G) and graphene oxide (GO) in a suspension with fetal calf serum (FCS), ammonium persulfate (AP), sodium persulfate (SP) and hypochlorite (ClO⁻), the transepithelial electrical resistance (TEER) and flux of fluorescent labelled dextran (FD4-flux), was determined. Exposure to graphene nanoparticles (GNPs) induced an immediate negative effect on the epithelial barrier, whereas ClO⁻ only had a negative impact after 24 h of exposure. AP and SP did not affect the barrier properties. The tight junctions (TJ) network showed less connected zonula occludens 1 (ZO-1) and occludin staining in GNP-exposed cocultures. Functional analysis of the phosphoproteomic data indicated that proteins in the adherens junction (AJ) and TJ pathways showed an altered phosphorylation due to GNP exposure. To conclude, the negative effect of GNPs on the epithelial barrier can be explained by the slightly altered the TJ organization which could be caused by alterations in the phosphorylation level of proteins in the AJ and TJ pathway.

Cisplatin-Resistant Gastric Cancer Cells Promote the Chemoresistance of Cisplatin-Sensitive Cells via the Exosomal RPS3-Mediated PI3K-Akt-Cofilin-1 Signaling Axis

Cisplatin is an important agent in first-line chemotherapy against gastric cancer (GC). However, consequential drug resistance limits its effectiveness for the treatment of GC. In this study, a cisplatin resistant gastric cancer cell line SGC7901R was determined by LC-MS/MS with increased exosomal levels of RPS3 protein. SGC7901R cell-derived exosomes were readily taken up by cisplatin-sensitive SGC7901S cells, thus triggering off a phenotype of chemoresistance in the receptor cells. Subsequently, it was demonstrated that exosomal RPS3 was essential for inducing chemoresistance of receptor cells as shown by the acquisition of this phenotype in SGC7901S cells with enforced expression of RPS3. Further mechanism study demonstrated that cisplatin-resistant gastric cancer cell-derived exosomal RPS3 enhanced the chemoresistance of cisplatin-sensitive gastric cancer cells through the PI3K-Akt-cofilin-1 signaling pathway. All these findings demonstrated that cisplatin-resistant gastric cancer cells communicate with sensitive cells through the intercellular delivery of exosomal RPS3 and activation of the PI3K-Akt-cofilin-1 signaling pathway. Targeting exosomal RPS3 protein in cisplatin-resistant gastric cancer cells may thus be a promising strategy to overcome cisplatin resistance in gastric cancer.

Ribosomal protein S3 selectively affects colon cancer growth by modulating the levels of p53 and lactate dehydrogenase

Ribosomal protein S3 (RPS3) is a component of the 40S ribosomal subunit. It is known to function in ribosome biogenesis and as an endonuclease. RPS3 has been shown to be over expressed in colon adenocarcinoma but its role in colon cancer is still unknown. In this study, we aim at determining the expression levels of RPS3 in a colon cancer cell line Caco-2 compared to a normal colon mucosa cell line NCM-460 and study the effects of targeting this protein by siRNA on cellular behavior. RPS3 was found to be expressed in both cell lines. However, siRNA treatment showed a more protruding effect on Caco-2 cells compared to NCM-460 cells. RPS3 knockdown led to a significant decrease in the proliferation, survival, migration and invasion and an increase in the apoptosis of Caco-2 cells. Western blot analysis demonstrated that these effects correlated with an increase in the level of the tumor suppressor p53 and a decrease in the level and activity of lactate dehydrogenase (LDH), an enzyme involved in the metabolism of cancer cells. No significant effect was shown in normal colon NCM-460 cells. Targeting p53 by siRNA did not affect RPS3 levels indicating that p53 may be a downstream target of RPS3. However, the concurrent knockdown of RPS3 and p53 showed no change in LDH level in Caco-2 cells suggesting an interesting interplay among the three proteins. These findings might present RPS3 as a selective molecular marker in colon cancer and an attractive target for colon cancer therapy.

Ribosomal protein S3 is a novel negative regulator of non-homologous end joining repair of DNA double-strand breaks

DNA double-strand breaks (DSBs) are one of the most serious types of DNA damage. However, multiple repair pathways are present in cells to ensure rapid and appropriate repair of DSBs. Pathway selection depends on several factors including cell type, cell cycle phase, and damage severity. Ribosomal protein S3 (rpS3), a component of the 40S small ribosomal subunit, is a multi-functional protein primarily involved in protein synthesis. rpS3 is also involved in the mediation of various extra-ribosomal pathways, including DNA damage processing and the stress response. Here, we report that rpS3 is a novel negative regulator of non-homologous end joining (NHEJ)-mediated repair of DSBs. We found that rpS3 interacts with the Ku heterodimers of the DNA-dependent protein kinase (DNA-PK) complex and slows down NHEJ ligation reactions, ultimately triggering p53-dependent cell death following treatment with high-dose ionizing radiation. After DSB formation, DNA-PK phosphorylates rpS3, which consequently reduces the binding of rpS3 to the Ku complex. We hypothesized that rpS3 may play a role in DSB repair by repressing NHEJ, while inducing other repair pathways, and by initiating DSB-induced cell death in response to severe DNA damage.

JNK activation induced by ribotoxic stress is initiated from 80S monosomes but not polysomes

Translation is a costly, but inevitable, cell maintenance process. To reduce unnecessary ATP consumption in cells, a fine-tuning mechanism is needed for both ribosome biogenesis and translation. Previous studies have suggested that the ribosome functions as a hub for many cellular signals such as ribotoxic stress response, mammalian target of rapamycin (mTOR), and ribosomal S6 kinase (RSK) signaling. Therefore, we investigated the relationship between ribosomes and mitogen-activated protein kinase (MAPK) activation under ribotoxic stress conditions and found that the activation of c-Jun N-terminal kinases (JNKs) was suppressed by ribosomal protein knockdown but that of p38 was not. In addition, we found that JNK activation is driven by the association of inactive JNK in the 80S monosomes rather than the polysomes. Overall, these data suggest that the activation of JNKs by ribotoxic stress is attributable to 80S monosomes. These 80S monosomes are active ribosomes that are ready to initiate protein translation, rather than polysomes that are already acting ribosomes involved in translation elongation.

RNA-binding protein RPS3 contributes to hepatocarcinogenesis by post-transcriptionally up-regulating SIRT1

Although several studies indicate that RNA-binding proteins (RBPs) contribute to key steps in a variety of physiological processes and cancer, the detailed biological functions and mechanisms remain to be determined. By performing bioinformatics analysis using well-established hepatocellular carcinoma (HCC) datasets, we identified a set of HCC progression-associated RBPs (HPARBPs) and found that the global expression of HPARBPs was significantly correlated with patient prognosis. Among the 42 HPARBPs, human ribosomal protein S3 (RPS3) was one of the most abundant genes whose role remains uncharacterized in HCC. Gain- and loss-of-function analyses demonstrated that RPS3 promoted HCC tumorigenesis both in vitro and in vivo. Mechanistically, we revealed that silent information regulator 1 (SIRT1) was a critical target of RPS3 and was essential for sustaining the RPS3-induced malignant phenotypes of HCC cells. RPS3 stabilized SIRT1 mRNA by binding to AUUUA motifs in the 3448–3530 region of the 3′ untranslated region (UTR) of SIRT1 mRNA. In addition, we found that (5-formylfuran-2-yl) methyl 4-hydroxy-2-methylenebutanoate (FMHM) inhibited HCC progression by repressing the RPS3/SIRT1 pathway. Our study unveils a novel extra-ribosomal role of RPS3 in facilitating hepatocarcinogenesis via the post-transcriptional regulation of SIRT1 expression and proposes that the RPS3/SIRT1 pathway serves as a potential therapeutic target in HCC.

ASK1 modulates the expression of microRNA Let7A in microglia under high glucose in vitro condition

Hyperglycemia results in oxidative stress and leads to neuronal apoptosis in the brain. Diabetes studies show that microglia participate in the progression of neuropathogenesis through their involvement in inflammation in vivo and in vitro. In high-glucose-induced inflammation, apoptosis signal regulating kinase 1 (ASK1) triggers the release of apoptosis cytokines and apoptotic gene expression. MicroRNA-Let7A (miR-Let7A) is reported to be a regulator of inflammation. In the present study, we investigated whether miR-Let7A regulates the function of microglia by controlling ASK1 in response to high-glucose-induced oxidative stress. We performed reverse transcription (RT) polymerase chain reaction, Taqman assay, real-time polymerase chain reaction, and immunocytochemistry to confirm the alteration of microglia function. Our results show that miR-Let7A is associated with the activation of ASK1 and the expression of anti-inflammatory cytokine (interleukin (IL)-10) and Mycs (c-Myc and N-Myc). Thus, the relationship between Let-7A and ASK1 could be a novel target for enhancing the beneficial function of microglia in central nervous system (CNS) disorders.

Ribosomal protein S3 regulates GLI2-mediated osteosarcoma invasion

It has been reported that GLI2 promotes proliferation, migration, and invasion of mesenchymal stem cell and osteosarcoma cells. To examine the molecular mechanisms of GLI2-mediated osteosarcoma metastasis, we performed a microarray analysis. The gene encoding ribosomal protein S3 (RPS3) was identified as a target of GLI2. Real-time PCR revealed that RPS3 was upregulated in osteosarcoma cell lines compared with normal osteoblast cells. Knockdown of GLI2 decreased RPS3 expression, whereas forced expression of a constitutively active form of GLI2 upregulated the expression of RPS3. RPS3 knockdown by siRNA decreased the migration and invasion of osteosarcoma cells. Although forced expression of constitutively active GLI2 increased the migration of human mesenchymal stem cells, knockdown of RPS3 reduced the up-regulated migration. In contrast, forced expression of RPS3 increased migration and invasion of osteosarcoma cells. Moreover, reduction of migration by GLI2 knockdown was rescued by forced expression of RPS3. Immunohistochemical analysis showed that RPS3 expression was increased in primary osteosarcoma lesions with lung metastases compared with those without. These findings indicate that GLI2-RPS3 signaling may be a marker of invasive osteosarcoma and a therapeutic target for patients with osteosarcoma.

Ribosomal protein S3 is secreted as a homodimer in cancer cells

Protein secretion is a general phenomenon by which cells communicate with the extracellular environment. Secretory proteins, including hormones, enzymes, toxins, and antimicrobial peptides have various functions in extracellular environments. Here, we determined that ribosomal protein S3 (rpS3) is homodimerized and secreted in several cancer cell lines such as HT1080 (human fibrosarcoma) and MPC11 (mouse plasmacytoma). Moreover, we found that the secreted rpS3 protein increased in doxorubicin-resistant MPC11 cells compared to that in MPC11 cells. In addition, we also detected that the level of secreted rpS3 increased in more malignant cells, which were established with continuous exposure of cigarette smoke condensate. These findings suggest that the secreted rpS3 protein is an indicator of malignant tumors.

p53 as an intervention target for cancer and aging

p53 is well known for suppressing tumors but could also affect other aging processes not associated with tumor suppression. As a transcription factor, p53 responds to a variety of stresses to either induce apoptosis (cell death) or cell cycle arrest (cell preservation) to suppress tumor development. Yet, the effect p53 has on the non-cancer aspects of aging is complicated and not well understood. On one side, p53 could induce cellular senescence or apoptosis to suppress cancer but as an unintended consequence enhance the aging process especially if these responses diminish stem and progenitor cell populations. But on the flip side, p53 could reduce growth and growth-related stress to enable cell survival and ultimately delay the aging process. A better understanding of diverse functions of p53 is essential to elucidate its influences on the aging process and the possibility of targeting p53 or p53 transcriptional targets to treat cancer and ameliorate general aging.

Cytoplasmic ribosomal protein S3 (rpS3) plays a pivotal role in mitochondrial DNA damage surveillance

Ribosomal protein S3 (rpS3) is known to play critical roles in ribosome biogenesis and DNA repair. When cellular ROS levels increase, the mitochondrial genes are highly vulnerable to DNA damage. Increased ROS induces rpS3 accumulation in the mitochondria for DNA repair while significantly decreasing the cellular protein synthesis. For the entrance into the mitochondria, the accumulation of rpS3 was regulated by interaction with HSP90, HSP70, and TOM70. Pretreatment with geldanamycin, which binds to the ATP pocket of HSP90, significantly decreased the interaction of rpS3 with HSP90 and stimulated the accumulation of rpS3 in the mitochondria. Furthermore, cellular ROS was decreased and mtDNA damage was rescued when levels of rpS3 were increased in the mitochondria. Therefore, we concluded that when mitochondrial DNA damages accumulate due to increased levels of ROS, rpS3 accumulates in the mitochondria to repair damaged DNA due to the decreased interaction between rpS3 and HSP90 in the cytosol.

Ribosomal protein S3 localizes on the mitotic spindle and functions as a microtubule associated protein in mitosis

The human ribosomal protein S3 (rpS3) has multi-functions such as translation, DNA repair and apoptosis. These multiple functions are regulated by post-translational modifications including phosphorylation, methylation and sumoylation. We report here a novel function of rpS3 that is involved in mitosis. When we examined localization of ribosomal proteins in mitosis, we found that rpS3 specifically localizes on the mitotic spindle. Depletion of the rpS3 proteins caused mitotic arrest during the metaphase. Furthermore, the shape of the spindle and chromosome movement in the rpS3 depleted cell was abnormal. Microtubule (MT) polymerization also decreased in rpS3 depleted cells, suggesting that rpS3 is involved in spindle dynamics. Therefore, we concluded that rpS3 acts as a microtubule associated protein (MAP) and regulates spindle dynamics during mitosis.

5-Fluorouracil signaling through a calcium-calmodulin-dependent pathway is required for p53 activation and apoptosis in colon carcinoma cells

5-Fluorouracil (5-FU) is an anti-metabolite that is in clinical use for treatment of several cancers. In cells, it is converted into three distinct fluoro-based nucleotide analogs, which interfere with DNA synthesis and repair, leading to genome impairment and, eventually, apoptotic cell death. Current knowledge states that in certain cell types, 5-FU-induced stress is signaling through a p53-dependent induction of tumor necrosis factor-receptor oligomerization required for death-inducing signaling complex formation and caspase-8 activation. Here we establish a role of calcium (Ca(2+)) as a messenger for p53 activation in response to 5-FU. Using a combination of pharmacological and genetic approaches, we show that treatment of colon carcinoma cells stimulates entry of extracellular Ca(2+) through long lasting-type plasma membrane channels, which further directs posttranslational phosphorylation of at least three p53 serine residues (S15, S33 and S37) by means of calmodulin (CaM) activity. Obstructing this pathway by the Ca(2+)-chelator BAPTA (1,2-bis(o-aminophenoxy)ethane- N,N,N',N'-tetraacetic acid) or by inhibitors of CaM efficiently reduces 5-FU-induced caspase activities and subsequent cell death. Moreover, ectopic expression of p53 S15A in HCT116 p53(-/-) cells confirmed the importance of a Ca(2+)-CaM-p53 axis in 5-FU-induced extrinsic apoptosis. The fact that a widely used therapeutic drug, such as 5-FU, is operating via this pathway could provide new therapeutic intervention points, or specify new combinatorial treatment regimes.