Activation of synoviolin promoter in rheumatoid synovial cells by a novel transcription complex of interleukin enhancer binding factor 3 and GA binding protein α

DNA and RNA Binding Proteins: From Motifs to Roles in Cancer

DNA and RNA binding proteins (DRBPs) are a broad class of molecules that regulate numerous cellular processes across all living organisms, creating intricate dynamic multilevel networks to control nucleotide metabolism and gene expression. These interactions are highly regulated, and dysregulation contributes to the development of a variety of diseases, including cancer. An increasing number of proteins with DNA and/or RNA binding activities have been identified in recent years, and it is important to understand how their activities are related to the molecular mechanisms of cancer. In addition, many of these proteins have overlapping functions, and it is therefore essential to analyze not only the loss of function of individual factors, but also to group abnormalities into specific types of activities in regard to particular cancer types. In this review, we summarize the classes of DNA-binding, RNA-binding, and DRBPs, drawing particular attention to the similarities and differences between these protein classes. We also perform a cross-search analysis of relevant protein databases, together with our own pipeline, to identify DRBPs involved in cancer. We discuss the most common DRBPs and how they are related to specific cancers, reviewing their biochemical, molecular biological, and cellular properties to highlight their functions and potential as targets for treatment.

Enhanced expression of synoviolin in peripheral blood from obese/overweight donors

Obesity is currently a major medical and societal issue. Synoviolin (SYVN1) is an E3 ubiquitin ligase involved in endoplasmic reticulum (ER) stress. Overexpression of Syvn1 has been found in genetically obese mice (ob/ob and db/db), and treatment with a Syvn1 inhibitor suppresses weight gain in some mouse models (C57BL/6J and db/db). However, SYVN1 expression in humans has not yet been elucidated. In the present study, 35 human volunteers were analyzed, and the expression level of SYVN1 mRNA in peripheral blood mononuclear cells (PBMCs) was detected using reverse transcription-quantitative polymerase chain reaction (RT-qPCR) analysis. Expression of SYVN1 mRNA was significantly increased in PBMCs from volunteers with a BMI ≥25.0, compared with volunteers with a BMI <25.0. In addition, PCR array and RT-qPCR of ER stress-responsive genes revealed that the expression of activating transcription factor 6 (ATF6), which plays an important role in the transcriptional activation of SYVN1, was increased in PBMCs from volunteers with a BMI ≥25.0. These results suggest that the ATF6-SYVN1 axis might be an important pathway in the progression of obesity.

High expression of interleukin-enhancer binding factor 3 predicts poor prognosis in patients with lung adenocarcinoma

Interleukin-enhancer binding factor 3 (ILF3) is a double-stranded RNA-binding protein that has been reported to contribute to the occurrence and progression of various malignant tumors. The aim of the present study was to evaluate the prognostic value of ILF3 and to apply this knowledge to avoid excessive medical treatment in patients with lung adenocarcinoma (LUAD). ILF3 expression in a discovery set consisting of tumor and peri-tumor tissue microarrays was analyzed using immunohistochemical methods. The mRNA level of ILF3 was subsequently analyzed in a validation set downloaded from The Cancer Genome Atlas. The Kaplan-Meier method, univariate and multivariate Cox analyses, decision curve analysis and nomogram models were used to evaluate the prognostic value of ILF3. ILF3 expression was upregulated in tumor tissues compared with peri-tumor tissues and was negatively associated with the overall survival time of patients with LUAD in the discovery and validation sets. Moreover, ILF3 expression was used for risk stratification in patients with tumor-node-metastasis stages II-IV and poor-to-moderate tumor differentiation. ILF3 expression was identified as an independent predictor of adverse prognosis for patients with LUAD in the discovery and validation sets. Finally, nomogram models for the 3- and 5 year survival time of patients with LUAD revealed that ILF3 expression may be used to improve the predictive accuracy of the prognosis and to avoid excessive medical treatment for certain patients with the disease. Overall, the data obtained in the current study revealed that high ILF3 expression was associated with poor prognosis, and demonstrated that ILF3, as a potential independent risk factor, may improve the hierarchical postoperative management of patients with LUAD.

GA-binding protein GABPβ1 is required for the proliferation of neural stem/progenitor cells

GA binding protein (GABP) is a ubiquitously expressed transcription factor that regulates the development of multiple cell types, including osteoblast, hematopoietic stem cells, B cells and T cells. However, so little is known about its biological function in the development of central nervous system. In this report, we show that GABP is highly expressed in neural stem/progenitor cells (NSPCs) and down-regulated in neurons, and that GABPβ1 is required for the proper proliferation of NSPCs. Knockdown of GABPα resulted in an elevated expression level of GABPβ1, and GABPβ1 down-regulation significantly decreased the proliferation of NSPCs, whereas GABPβ2 knockdown did not result in any changes in the proliferation of NSPCs. We observed that there was nearly a 21-fold increase of the GABPβ1S mRNA level in GABPβ1L KO NSPCs compared to WT cells, and knocking down of GABPβ1S in GABPβ1L KO NSPCs could further reduce their proliferation potential. We also found that knockdown of GABPβ1 promoted neuronal and astrocytic differentiation of NSPCs. Finally, we identified dozens of downstream target genes of GABPβ1, which are closely associated with the cell proliferation and differentiation. Collectively, our results suggest that both GABPβ1L and GABPβ1S play an essential role in regulating the proper proliferation and differentiation of NSPCs.

The NRF2‑PGC‑1β pathway activates kynurenine aminotransferase 4 via attenuation of an E3 ubiquitin ligase, synoviolin, in a cecal ligation/perforation‑induced septic mouse model

Sepsis‑associated encephalopathy (SAE) is a systemic inflammatory response syndrome of which the precise associated mechanisms remain unclear. Synoviolin (Syvn1) is an E3 ubiquitin ligase involved in conditions associated with chronic inflammation, including rheumatoid arthritis, obesity, fibrosis and liver cirrhosis. However, the role of Syvn1 in acute inflammation is not clear. The aim of the present study was to investigate the role of Syvn1 in a septic mouse model induced by cecal ligation/perforation (CLP). Metabolome analysis revealed that kynurenine (KYN), a key factor for the development of neuroinflammation, was increased in CLP‑induced septic mice. Notably, KYN was not detected in CLP‑induced septic Syvn1‑deficient mice. KYN is converted to kynurenic acid (KYNA) by kynurenine aminotransferases (KATs), which has a neuroprotective effect. The expression of KAT4 was significantly increased in Syvn1‑deficient mice compared to that in wild‑type mice. Promoter analysis demonstrated that Syvn1 knockdown induced the KAT4 promoter activity, as assessed by luciferase reporter activity, whereas Syvn1 overexpression repressed this activity in a dose‑dependent manner. Furthermore, the KAT4 promoter was significantly activated by the transcriptional factors, NF‑E2‑related factor 2 and peroxisome proliferator‑activated receptor coactivator 1β, which are targets of Syvn1‑induced degradation. In conclusion, the results of the current study demonstrates that the repression of Syvn1 expression induces the conversion of neurotoxic KYN to neuroprotective KYNA in a CLP‑induced mouse model of sepsis, and that Syvn1 is a potential novel target for the treatment of SAE.

Rheumatoid Arthritis, Immunosenescence and the Hallmarks of Aging

Age is the most important risk factor for the development of infectious diseases, cancer and chronic inflammatory diseases including rheumatoid arthritis (RA). The very act of living causes damage to cells. A network of molecular, cellular and physiological maintenance and repair systems creates a buffering capacity against these damages. Aging leads to progressive shrinkage of the buffering capacity and increases vulnerability. In order to better understand the complex mammalian aging processes, nine hallmarks of aging and their interrelatedness were recently put forward.

RA is a chronic autoimmune disease affecting the joints. Although RA may develop at a young age, the incidence of RA increases with age. It has been suggested that RA may develop as a consequence of premature aging (immunosenescence) of the immune system. Alternatively, premature aging may be the consequence of the inflammatory state in RA. In an effort to answer this chicken and egg conundrum, we here outline and discuss the nine hallmarks of aging, their contribution to the pre-aged phenotype and the effects of treatment on the reversibility of immunosenescence in RA.

Icariin induces synoviolin expression through NFE2L1 to protect neurons from ER stress-induced apoptosis

By suppressing neuronal apoptosis, Icariin is a potential therapeutic drug for neuronal degenerative diseases. The molecular mechanisms of Icariin anti-apoptotic functions are still largely unclear. In this report, we found that Icariin induces the expression of Synoviolin, an endoplasmic reticulum (ER)-anchoring E3 ubiquitin ligase that functions as a suppressor of ER stress-induced apoptosis. The nuclear factor erythroid 2-related factor 1 (NFE2L1) is responsible for Icariin-mediated Synoviolin gene expression. Mutation of the NFE2L1-binding sites in a distal region of the Synoviolin promoter abolished Icariin-induced Synoviolin promoter activity, and knockdown of NFE2L1 expression prevented Icariin-stimulated Synoviolin expression. More importantly, Icariin protected ER stress-induced apoptosis of PC12 cells in a Synoviolin-dependent manner. Therefore, our study reveals Icariin-induced Synoviolin expression through NFE2L1 as a previously unappreciated molecular mechanism underlying the neuronal protective function of Icariin.

Ilf3 and NF90 functions in RNA biology

Double-stranded RNA-binding proteins (DRBPs) are known to regulate many processes of RNA metabolism due, among others, to the presence of double-stranded RNA (dsRNA)-binding motifs (dsRBMs). Among these DRBPs, Interleukin enhancer-binding factor 3 (Ilf3) and Nuclear Factor 90 (NF90) are two ubiquitous proteins generated by mutually exclusive and alternative splicings of the Ilf3 gene. They share common N-terminal and central sequences but display specific C-terminal regions. They present a large heterogeneity generated by several post-transcriptional and post-translational modifications involved in their subcellular localization and biological functions. While Ilf3 and NF90 were first identified as activators of gene expression, they are also implicated in cellular processes unrelated to RNA metabolism such as regulation of the cell cycle or of enzymatic activites. The implication of Ilf3 and NF90 in RNA biology will be discussed with a focus on eukaryote transcription and translation regulation, on viral replication and translation as well as on noncoding RNA field.

Overexpression of SPACIA1/SAAL1, a newly identified gene that is involved in synoviocyte proliferation, accelerates the progression of synovitis in mice and humans

OBJECTIVE

To identify novel genes associated with dysregulated proliferation of activated synovial fibroblasts, which are involved in arthritic joint destruction.

METHODS

We performed transcriptome analysis to identify genes that were up-regulated in the foot joints of mice with collagen-induced arthritis (CIA). The effect of candidate genes on proliferation of synovial fibroblasts was screened using antisense oligodeoxynucleotides and small interfering RNAs (siRNAs). We characterized the expression and function of a novel gene, synoviocyte proliferation-associated in collagen-induced arthritis 1 (SPACIA1)/serum amyloid A-like 1 (SAAL1) using antibodies and siRNA and established transgenic mice to examine the effect of SPACIA1/SAAL1 overexpression in CIA.

RESULTS

Human and mouse SPACIA1/SAAL1 encoded 474 amino acid proteins that shared 80% homology. SPACIA1/SAAL1 was primarily expressed in the nucleus of rheumatoid arthritis (RA) synovial fibroblasts and was highly expressed in the hyperplastic lining of inflamed synovium. In addition, its expression level in RA- or osteoarthritis (OA)-affected synovial tissue was positively correlated with the thickness of the synovial lining. Furthermore, SPACIA1/SAAL1 siRNA inhibited the proliferation of synovial fibroblasts, especially tumor necrosis factor α-induced synovial fibroblasts, by blocking entry into the S phase without inducing apoptosis. Finally, transgenic mice overexpressing SPACIA1/SAAL1 exhibited early onset and rapid progression of CIA.

CONCLUSION

These results suggest that SPACIA1/SAAL1 is necessary for abnormal proliferation of synovial fibroblasts and its overexpression is associated with the progression of synovitis in mice and humans. Thus, therapy targeting SPACIA1/SAAL1 might have potential as an inhibitor of synovial proliferation in RA and/or OA.

E3 ubiquitin ligase synoviolin is involved in liver fibrogenesis

BACKGROUND AND AIM

Chronic hepatic damage leads to liver fibrosis, which is characterized by the accumulation of collagen-rich extracellular matrix. However, the mechanism by which E3 ubiquitin ligase is involved in collagen synthesis in liver fibrosis is incompletely understood. This study aimed to explore the involvement of the E3 ubiquitin ligase synoviolin (Syno) in liver fibrosis.

METHODS

The expression and localization of synoviolin in the liver were analyzed in CCl(4)-induced hepatic injury models and human cirrhosis tissues. The degree of liver fibrosis and the number of activated hepatic stellate cells (HSCs) was compared between wild type (wt) and Syno(+/-) mice in the chronic hepatic injury model. We compared the ratio of apoptosis in activated HSCs between wt and Syno(+/-) mice. We also analyzed the effect of synoviolin on collagen synthesis in the cell line from HSCs (LX-2) using siRNA-synoviolin and a mutant synoviolin in which E3 ligase activity was abolished. Furthermore, we compared collagen synthesis between wt and Syno(-/-) mice embryonic fibroblasts (MEF) using quantitative RT-PCR, western blotting, and collagen assay; then, we immunohistochemically analyzed the localization of collagen in Syno(-/-) MEF cells.

RESULTS

In the hepatic injury model as well as in cirrhosis, synoviolin was upregulated in the activated HSCs, while Syno(+/-) mice developed significantly less liver fibrosis than in wt mice. The number of activated HSCs was decreased in Syno(+/-) mice, and some of these cells showed apoptosis. Furthermore, collagen expression in LX-2 cells was upregulated by synoviolin overexpression, while synoviolin knockdown led to reduced collagen expression. Moreover, in Syno(-/-) MEF cells, the amounts of intracellular and secreted mature collagen were significantly decreased, and procollagen was abnormally accumulated in the endoplasmic reticulum.

CONCLUSION

Our findings demonstrate the importance of the E3 ubiquitin ligase synoviolin in liver fibrosis.