ZC3H12D attenuated inflammation responses by reducing mRNA stability of proinflammatory genes

RNA Metabolism Governs Immune Function and Response

Inflammation is a complex process that protects our body from various insults such as infection, injury, and stress. Proper inflammation is beneficial to eliminate the insults and maintain organ homeostasis, however, it can become detrimental if uncontrolled. To tightly regulate inflammation, post-transcriptional mechanisms governing RNA metabolism play a crucial role in monitoring the expression of immune-related genes, such as tumor necrosis factor (TNF) and interleukin-6 (IL-6). These mechanisms involve the coordinated action of various RNA-binding proteins (RBPs), including the Regnase family, Roquin, and RNA methyltransferases, which are responsible for mRNA decay and/or translation regulation. The collaborative efforts of these RBPs are essential in preventing aberrant immune response activation and consequently safeguarding against inflammatory and autoimmune diseases. This review provides an overview of recent advancements in our understanding of post-transcriptional regulation within the immune system and explores the specific roles of individual RBPs in RNA metabolism and regulation.

Transcriptional repression of lncRNA and miRNA subsets mediated by LRF during erythropoiesis

Non-coding RNA (ncRNA) species, mainly long non-coding RNAs (lncRNAs) and microRNAs (miRNAs) have been currently imputed for lesser or greater involvement in human erythropoiesis. These RNA subsets operate within a complex circuit with other epigenetic components and transcription factors (TF) affecting chromatin remodeling during cell differentiation. Lymphoma/leukemia-related (LRF) TF exerts higher occupancy on DNA CpG rich sites and is implicated in several differentiation cell pathways and erythropoiesis among them and also directs the epigenetic regulation of hemoglobin transversion from fetal (HbF) to adult (HbA) form by intervening in the γ-globin gene repression. We intended to investigate LRF activity in the evolving landscape of cells' commitment to the erythroid lineage and specifically during HbF to HbA transversion, to qualify this TF as potential repressor of lncRNAs and miRNAs. Transgenic human erythroleukemia cells, overexpressing LRF and further induced to erythropoiesis, were subjected to expression analysis in high LRF occupancy genetic loci-producing lncRNAs. LRF abundance in genetic loci transcribing for studied lncRNAs was determined by ChIP-Seq data analysis. qPCRs were performed to examine lncRNA expression status. Differentially expressed miRNA pre- and post-erythropoiesis induction were assessed by next-generation sequencing (NGS), and their promoter regions were charted. Expression levels of lncRNAs were correlated with DNA methylation status of flanked CpG islands, and contingent co-regulation of hosted miRNAs was considered. LRF-binding sites were overrepresented in LRF overexpressing cell clones during erythropoiesis induction and exerted a significant suppressive effect towards lncRNAs and miRNA collections. Based on present data interpretation, LRF's multiplied binding capacity across genome is suggested to be transient and associated with higher levels of DNA methylation. KEY MESSAGES: During erythropoiesis, LRF displays extensive occupancy across genetic loci. LRF significantly represses subsets of lncRNAs and miRNAs during erythropoiesis. Promoter region CpG islands' methylation levels affect lncRNA expression. MiRNAs embedded within lncRNA loci show differential regulation of expression.

Tfl deletion induces extraordinary Cxcl13 secretion and cachexia in VavP-Bcl2 transgenic mice

STATEMENT OF SIGNIFICANCE

Loss of TFL, found in several types of lymphoma, induces excessive CXCL13 secretion through RNA dysregulation contributing to body weight loss and early death in lymphoma model mice. Follicular lymphoma (FL) is associated with overexpressed BCL-2 and other genetic aberrations, including 6q-. We identified a novel gene on 6q25, "Transformed follicular lymphoma (TFL)," from a transformed FL. TFL regulates several cytokines via mRNA degradation, which has been suggested to underlie resolving inflammation. Fluorescence in situ hybridization revealed a deletion of TFL occurred in 13.6% of various B-cell lymphoma samples. We developed VavP-bcl2 transgenic, TFL deficit mice (Bcl2-Tg/Tfl -/-) to seek how TFL affects disease progression in this lymphoma model. While Bcl2-Tg mice developed lymphadenopathy and died around 50 weeks, Bcl2-Tg/Tfl -/- mice lost body weight around 30 weeks and died about 20 weeks earlier than Bcl2-Tg mice. Furthermore, we found a unique B220-IgM+ cell population in the bone marrow of Bcl2-Tg mice. cDNA array in this population revealed that Cxcl13 mRNA in Bcl2-Tg/Tfl -/- mice expressed significantly higher than Bcl2-Tg mice. In addition, bone marrow extracellular fluid and serum showed an extremely high Cxcl13 concentration in Bcl2-Tg/Tfl -/- mice. Among bone marrow cells, the B220-IgM+ fraction was the main producer of Cxcl13 in culture. A reporter assay demonstrated TFL regulates CXCL-13 via induction of 3'UTR mRNA degradation in B lineage cells. These data suggest Tfl regulates Cxcl13 in B220-IgM+ cells in the bone marrow, and a very high concentration of serum Cxcl13 arising from these cells may contribute to early death in lymphoma-bearing mice. Since several reports have suggested the association of CXCL13 expression with lymphoma, these findings provide new insights into cytokine regulation via TFL in lymphoma.

The evolution and immunomodulatory role of Zc3h12 proteins in zebrafish (Danio rerio)

Zc3h12 family is an important RNA-binding protein family regulating mRNA of inflammatory cytokines in mammals. However, there are few studies on their post-transcriptional level regulation of inflammatory cytokines in fish. Here, we investigated the evolution of zebrafish Zc3h12 family and explored their immunomodulatory role. Phylogenetic and syntenic analysis indicated the number of zc3h12 family members had increased ranging from a single member in invertebrates to a single copy of four members in mammals. As the most evolutionarily diverse group of vertebrates, the number of zc3h12 family members was more complex and diverse in the teleost, each member experienced different fates and followed different rules in multiple rounds of whole-genome duplication events. Thereinto, zebrafish contained three zc3h12 genes, among which zc3h12aa and zc3h12ab were duplicated from the same gene. Zebrafish Zc3h12 family could recognize the 3'-UTR regions of inflammatory cytokines through binding to the specific RNA secondary structure and negatively regulate their expression. Deletion of either Zc3h12 domains or mutation of the key amino acid in RNAase domain attenuated their modulatory effect, suggesting both domain and RNAase activity are important to the immunomodulatory role. These results elucidated the evolution of Zc3h12 family and uncovered Zc3h12-mediated post-transcriptional regulation of cytokines in zebrafish.

RNA sequence analysis of nasopharyngeal swabs from asymptomatic and mildly symptomatic patients with COVID-19

OBJECTIVES

The characterization of asymptomatic and mildly symptomatic patients with COVID-19 by observing changes in gene expression profile and possible bacterial coinfection is relevant to be investigated. We aimed to identify transcriptomic and coinfection profiles in both groups of patients.

METHODS

A ribonucleic acid (RNA) sequence analysis on nasopharyngeal swabs were performed using a shotgun sequencing pipeline. Differential gene analysis, viral genome assembly, and metagenomics analysis were further performed using the retrieved data.

RESULTS

Both groups of patients underwent a cilia modification and mRNA splicing. Modulations in macroautophagy, epigenetics, and cell cycle processes were observed specifically in the asymptomatic group. Modulation in the RNA transport was found specifically in the mildly symptomatic group. The mildly symptomatic group showed modulation in the RNA transport and upregulation of autophagy regulator genes and genes in the complement system. No link between viral variants and disease severity was found. Microbiome analysis revealed the elevation of Streptococcus pneumoniae and Veillonella parvula proportion in symptomatic patients.

CONCLUSION

A reduction in the autophagy influx and modification in the epigenetic profile might be involved in halting the disease progression. A global dysregulation of RNA processing and translation might cause more severe outcomes in symptomatic individuals. Coinfection by opportunistic microflora should be taken into account when assessing the possible outcome of SARS-CoV-2 infection.

Long non-coding RNA FOXP4-AS1 facilitates the biological functions of hepatocellular carcinoma cells via downregulating ZC3H12D by mediating H3K27me3 through recruitment of EZH2

BACKGROUND

Some studies have reported the effect of long non-coding RNA forkhead box P4 antisense RNA 1 (lncRNA FOXP4-AS1) on hepatocellular carcinoma (HCC). Here, we aimed to discuss the effects of FOXP4-AS1/enhancer of zeste homolog 2 (EZH2)/trimethylation of lysine 27 on histone H3 (H3K27me3)/zinc finger CCCH-type containing 12D (ZC3H12D) axis on HCC.

METHODS

The expression of FOXP4-AS1, EZH2, and ZC3H12D, and abundance of H3K27me3 in HCC tissues and cells were tested. The relationship between FOXP4-AS1 expression and prognosis of HCC patients was analyzed. The biological functions of HCC cells were detected via loss- and gain-of-function assays. The tumor weight and volume in vivo were tested. The interaction between FOXP4-AS1 and EZH2 as well as that between EZH2 and H3K27me3 was verified.

RESULTS

FOXP4-AS1 and EZH2 expression and H3K27me3 abundance were enhanced while ZC3H12D expression was depressed in HCC tissues and cells. Knockdown of FOXP4-AS1 suppressed biological functions of HCC cells as well as the weight and volume of HCC transplanted tumor. Depleting ZC3H12D reversed the effect of downregulated FOXP4-AS1 on HCC cells. FOXP4-AS1 suppressed ZC3H12D expression via mediating H3K27me3 by recruitment of EZH2.

CONCLUSION

The key findings of the present study demonstrate that FOXP4-AS1 suppresses ZC3H12D expression via mediating H3K27me3 by recruitment of EZH2, thus promoting the progression of HCC.

Monocyte Chemotactic Protein-Induced Protein 1 (MCPIP-1): A Key Player of Host Defense and Immune Regulation

Inflammatory response is a host-protective mechanism against tissue injury or infections, but also has the potential to cause extensive immunopathology and tissue damage, as seen in many diseases, such as cardiovascular diseases, neurodegenerative diseases, metabolic syndrome and many other infectious diseases with public health concerns, such as Coronavirus Disease 2019 (COVID-19), if failure to resolve in a timely manner. Recent studies have uncovered a superfamily of endogenous chemical molecules that tend to resolve inflammatory responses and re-establish homeostasis without causing excessive damage to healthy cells and tissues. Among these, the monocyte chemoattractant protein-induced protein (MCPIP) family consisting of four members (MCPIP-1, -2, -3, and -4) has emerged as a group of evolutionarily conserved molecules participating in the resolution of inflammation. The focus of this review highlights the biological functions of MCPIP-1 (also known as Regnase-1), the best-studied member of this family, in the resolution of inflammatory response. As outlined in this review, MCPIP-1 acts on specific signaling pathways, in particular NFκB, to blunt production of inflammatory mediators, while also acts as an endonuclease controlling the stability of mRNA and microRNA (miRNA), leading to the resolution of inflammation, clearance of virus and dead cells, and promotion of tissue regeneration via its pleiotropic effects. Evidence from transgenic and knock-out mouse models revealed an involvement of MCPIP-1 expression in immune functions and in the physiology of the cardiovascular system, indicating that MCPIP-1 is a key endogenous molecule that governs normal resolution of acute inflammation and infection. In this review, we also discuss the current evidence underlying the roles of other members of the MCPIP family in the regulation of inflammatory processes. Further understanding of the proteins from this family will provide new insights into the identification of novel targets for both host effectors and microbial factors and will lead to new therapeutic treatments for infections and other inflammatory diseases.

Post-transcriptional regulation of immunological responses by Regnase-1-related RNases

Regulation of messenger RNA (mRNA) decay plays a crucial role in the control of gene expression. Canonical mRNA decay pathways are initiated by deadenylation and decapping, and are followed by exonucleolytic degradation. However, recent studies revealed that endoribonucleolytic cleavage also mediates mRNA decay, and both exoribonucleolytic and endoribonucleolytic decay pathways are important for the regulation of immune responses. Regnase-1 functions as an endoribonuclease to control immunity by damping mRNAs. Particularly, Regnase-1 controls cytokines and other inflammatory mediators by recognizing their mRNAs via stem-loop structures present in the 3' untranslated regions. Regnase-1 was found to be critical for human inflammatory diseases such as ulcerative colitis and idiopathic pulmonary fibrosis. Furthermore, a set of Regnase-1-related RNases contribute to immune regulation as well as antiviral host defense. In this review, we provide an overview of recent findings as to immune-related RNA-binding proteins (RBPs) with an emphasis on stem-loop-mediated mRNA decay via Regnase-1 and related RNases and discuss how the function of these RBPs is regulated and contributes to inflammatory disorders.

Zc3h12d, a Novel of Hypomethylated and Immune-Related for Prognostic Marker of Lung Adenocarcinoma

Background

Zc3h12d is a negative regulator which plays a crucial role in immune modulation. However, the role of zc3h12d in lung adenocarcinoma (LUAD) remains unclear. We aim to explore the prognostic of zc3h12d and investigate the relationship between zc3h12d expression and immune infiltration in LUAD.

Methods

TIMER site was used to analyze the expression of zc3h12d in LUAD. The zc3h12d protein levels in patient tissue samples were detected by immunohistochemistry staining assays. Meanwhile, based on UALCAN database and samples' data from our cohort, we explored the relationship of clinicopathological features and zc3h12d expression to determine the clinical effect of zc3h12d in LUAD. Several databases including GEPIA, Kaplan-Meier plotter and our samples' data were used to explore the prognostic value of zc3h12d in LUAD. Cox regression analysis was established to further evaluate the prognostic value of zc3h12d in LUAD. In addition, zc3h12d promoter methylation was analyzed by UALCAN database. Genetic alteration analysis was observed in the cBioPortal web. GO and KEGG analyses were conducted to elucidate the underlying mechanisms. Finally, the correlation between zc3h12d and tumor-infiltrating immune cells in LUAD was investigated by TIMER database. The B cells level was investigated by flow cytometry analysis of peripheral blood from our LUAD cohort.

Results

Zc3h12d expression was significantly higher in LUAD, compared with adjacent normal tissues. The clinical data from the UALCAN database demonstrated that zc3h12d expression was closely related with cancer stage and nodal metastasis. However, patient sample detection revealed that zc3h12d expression was closely related to pathological N (p = 0.0431) and grade (p = 0.004). Moreover, low zc3h12d expression was associated with poorer overall survival in LUAD. We analyzed the methylation level of zc3h12d in LUAD and found that the methylation levels of zc3h12d promoter in LUAD were significantly reduced. In addition, zc3h12d genetic alterations, including deep deletion, could be found in LUAD. GO and KEGG pathway analysis results indicated that zc3h12d has a certain value in immune infiltration. We investigated the expression of zc3h12d in tumor-immune interactions. It was found that zc3h12d might be associated with the immune infiltration and markers of infiltrating immune cells of LUAD. The results of patient sample detection confirmed that B cells level was significantly lower in the patients with low zc3h12d expression than those in the patients with high zc3h12d expression.

Conclusion

zc3h12d might be considered as a potential biomarker for determining prognosis and immune-related therapeutic target in LUAD.

Cell-intrinsic mechanisms to restrain inflammatory responses in T lymphocytes

A mechanistic understanding of the regulatory circuits that control the effector responses of memory T helper lymphocytes, and in particular their ability to produce pro-inflammatory cytokines, may lead to effective therapeutic interventions in all immune-related diseases. Activation of T lymphocytes induces robust immune responses that in most cases lead to the complete eradication of invading pathogens or tumor cells. At the same time, however, such responses must be both highly controlled in magnitude and limited in time to avoid unnecessary damage. To achieve such sophisticated level of control, T lymphocytes have at their disposal an array of transcriptional and post-transcriptional regulatory mechanisms that ensure the acquisition of a phenotype that is tailored to the incoming stimulus while restraining unwarranted activation, eventually leading to the resolution of the inflammatory response. Here, we will discuss some of these cell-intrinsic mechanisms that control T cell responses and involve transcription factors, microRNAs, and RNA-binding proteins. We will also explore how the same mechanisms can be involved both in anti-tumor responses and in autoimmunity.

miR-128-3p serves as an oncogenic microRNA in osteosarcoma cells by downregulating ZC3H12D

Osteosarcoma is the second leading cause of cancer-associated mortality worldwide in children and adolescents. ZC3H12D has been shown to negatively regulate Toll-like receptor signaling and serves as a possible tumor suppressor gene. MicroRNAs (miRNAs/miRs) are known to play an important role in the proliferation of human osteosarcoma cells. However, whether miRNAs can affect tumor development by regulating the expression of ZC3H12D has not yet been investigated. The aim of the present study was to investigate the role of miR128-3p in regulating ZC3H12D expression, as well as its function in tumor cell proliferation, apoptosis, and metastasis. Reverse transcription-quantitative PCR, western blotting and dual luciferase reporter assays were performed to analyze the regulation of ZC3H12D expression by miR-128-3p. MTT, colony formation and flow cytometry assays were also used to analyze the effect of miR-128-3p on cell proliferation and apoptosis. A wound healing assay was performed to investigate the cell migration ability. The results demonstrated that miR-128-3p directly targeted ZC3H12D and downregulated its expression, thereby promoting cell proliferation and migration. miR-128-3p overexpression also improved resistance to cisplatin in MG-63 and 143B cell lines, supporting the hypothesis that miR-128-3p may function as an oncogene in osteosarcoma cells. The potential clinical significance of miR-128-3p as a biomarker and therapeutic target provides rationale for further investigation into the miR-128-3p-mediated molecular pathway and how it is associated with osteosarcoma development.

Application for proteomics analysis technology in studying animal-derived traditional Chinese medicine: A review

Different therapeutically active ingredients, from plants, animals, and mineral sources, are prescribed as traditional Chinese medicines (TCM). TCMs, from animal sources, are rich in proteins and peptides. Different advanced proteomics technologies, such as two-dimensional gel electrophoresis (2-DE), multi-dimensional liquid chromatography (MDLC), matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF-MS), and isobaric tags for relative and absolute quantitation (iTRAQ), have been applied to analyze TCMs, from animal sources. This paper reviews the common proteomic techniques for analyzing animal - derived TCMs. Various scientific studies have reported the application of proteomics for locating drug targets, identifying active components, and elucidating the mechanisms of action of animal - derived TCMs. However, these researches are still at the preliminary stage. This review has also discussed the existing challenges and future directions in this field of research.

The immunomodulatory role of Regnase family RNA-binding proteins

RNA-binding proteins regulate RNA fate and govern post-transcriptional gene regulation. A new family of RNA-binding proteins is represented by regulatory RNases (Regnase, also known as Zc3h12 or MCPIP), which have emerged as important players in immune homoeostasis. Four members, Regnase1-4, have been identified to date. Here we summarize recent findings on the role of Regnase in the regulation of RNA biology and its consequences for cell functions and inflammatory processes.

ZC3H12B/MCPIP2, a new active member of the ZC3H12 family

ZC3H12B is the most enigmatic member of the ZC3H12 protein family. The founding member of this family, Regnase-1/MCPIP1/ZC3H12A, is a well-known modulator of inflammation and is involved in the degradation of inflammatory mRNAs. In this study, for the first time, we characterized the properties of the ZC3H12B protein. We show that the biological role of ZC3H12B depends on an intact NYN/PIN RNase domain. Using RNA immunoprecipitation, experiments utilizing actinomycin D and ELISA, we show that ZC3H12B binds interleukin-6 (IL-6) mRNA in vivo, regulates its turnover, and results in reduced production of IL-6 protein upon stimulation with IL-1β. We verified that regulation of IL-6 mRNA stability occurs via interaction of ZC3H12B with the stem-loop structure present in the IL-6 3'UTR. The IL-6 transcript is not the only target of ZC3H12B. ZC3H12B also interacts with other known substrates of Regnase-1 and ZC3H12D, such as the 3'UTRs of IER3 and Regnase-1, and binds IER3 mRNA in vivo. Using immunofluorescence, we examined the localization of ZC3H12B within the cell. ZC3H12B forms small, granule-like structures in the cytoplasm that are characteristic of proteins involved in mRNA turnover. The overexpression of ZC3H12B inhibits proliferation by stalling the cell cycle in the G2 phase. This effect of ZC3H12B is also NYN/PIN dependent. The analysis of the ZC3H12B mRNA level reveals its highest expression in the human brain and the neuroblastoma cell line SH-SY5Y, although the factors regulating its expression remain elusive. Down-regulation of ZC3H12B in SH-SY5Y cells by specific shRNAs results in up-regulation of ZC3H12B-target mRNAs.

Biliverdin administration regulates the microRNA-mRNA expressional network associated with neuroprotection in cerebral ischemia reperfusion injury in rats

Inflammatory response has an important role in the outcome of cerebral ischemia reperfusion injury (CIR). Biliverdin (BV) administration can relieve CIR in rats, but the mechanism remains unknown. The aim of the present study was to explore the expressional network of microRNA (miRNA)-mRNA in CIR rats following BV administration. A rat middle cerebral artery occlusion model with BV treatment was established. After neurobehavior was evaluated by neurological severity scores (NSS), miRNA and mRNA expressional profiles were analyzed by microarray technology from the cerebral cortex subjected to ischemia and BV administration. Then, bioinformatics prediction was used to screen the correlation between miRNA and mRNA, and 20 candidate miRNAs and 33 candidate mRNAs were verified by reverse transcription-quantitative polymerase chain reaction. Furthermore, the regulation relationship between ETS proto-oncogene 1 (Ets1) and miRNA204-5p was examined by luciferase assay. A total of 86 miRNAs were differentially expressed in the BV group compared with the other groups. A total of 10 miRNAs and 26 candidate genes were identified as a core 'microRNA-mRNA' regulatory network that was linked with the functional improvement of BV administration in CIR rats. Lastly, the luciferase assay results confirmed that miRNA204-5p directly targeted Ets1. The present findings suggest that BV administration may regulate multiple miRNAs and mRNAs to improve neurobehavior in CIR rats, by influencing cell proliferation, apoptosis, maintaining ATP homeostasis, and angiogenesis.

LncRNA Expression in CD4+ T Cells in Neurosyphilis Patients

Recent studies have shown that several long noncoding RNAs (lncRNAs) are involved in regulating the immune response to cope with pathogenic invasion. To date, the roles of lncRNAs in the CD4+ T cell response to Treponema pallidum (T. pallidum) infection in neurosyphilis patients remain unknown. The mRNA and lncRNA expression profiles of CD4+ T cells that were isolated from neurosyphilis patients and healthy controls were analyzed by microarray. A total of 2258 lncRNAs and 1728 mRNAs were identified as over-expressed or under-expressed, respectively (fold change > 1.5) in the CD4+ T cells of neurosyphilis patients compared to the healthy controls. The lncRNA-mRNA co-expression network showed that 59 lncRNAs showed significant differences along with significantly different mRNAs. Among the 59 gene pairs, the LOC79999 mRNA was positively correlated with the RP11-160E2.16, RP11-160E2.11, and RP11-160E2.19 lncRNAs, and the NKX1-1 mRNA was positively correlated with the RP11-1398P2.1, RP11-160E2.19, and XLOC_003422 lncRNAs. The following five mRNAs were correlated with two differential lncRNAs: DUSP16, AP000349.1, FAM115C, TIMM8A, and SMCHD1. Gene Ontology (GO) analysis revealed that the differentially expressed coding genes were mainly involved in biological processes and the top 4 terms that associated with above-mentioned differentially expressed coding genes were as follows: defense response to fungus, defense response to bacterium, killing of cells of other organism and disruption of cells of another organism. A subsequent pathway analysis was also conducted, and several pathways, including the T cell receptor, MAPK, and TGF-beta signaling pathways, were associated with the differentially expressed mRNAs. This study reveals the differential expression profiles of lncRNAs in the CD4+ T cell response to the T. pallidum infection in neurosyphilis patients. LncRNAs are involved in key biological processes that comprise the CD4+ T cell response to the T. pallidum infection.

Endonuclease Regnase-1/Monocyte chemotactic protein-1-induced protein-1 (MCPIP1) in controlling immune responses and beyond

The activation of inflammatory cells is controlled at transcriptional and posttranscriptional levels. Posttranscriptional regulation modifies mRNA stability and translation, allowing for elaborate control of proteins required for inflammation, such as proinflammatory cytokines, prostaglandin synthases, cell surface co-stimulatory molecules, and even transcriptional modifiers. Such regulation is important for coordinating the initiation and resolution of inflammation, and is mediated by a set of RNA-binding proteins (RBPs), including Regnase-1, Roquin, Tristetraprolin (TTP), and AU-rich elements/poly(U)-binding/degradation factor 1 (AUF1). Among these, Regnase-1, also known as Zc3h12a and Monocyte chemotactic protein-1-induced protein-1 (MCPIP1), acts as an endoribonuclease responsible for the degradation of mRNAs involved in inflammatory responses. Conversely, the RBPs Roquin and TTP trigger exonucleolytic degradation of mRNAs by recruiting the CCR4-NOT deadenylase complex. Regnase-1 specifically recognizes stem-loop structures present in 3'-untranslated regions of cytokine mRNAs, and directly degrades the mRNAs in a translation- and ATP-dependent RNA helicase upframeshift 1 (UPF1)-dependent manner that is reminiscent of nonsense-mediated decay. Regnase-1 regulates the activation of innate and acquired immune cells, and is critical for maintaining immune homeostasis as well as preventing over-activation of the immune system under inflammatory conditions. Furthermore, recent studies have revealed that Regnase-1 and its family members are involved not only in immunity but also in various biological processes. In this article, I review molecular mechanisms of Regnase-1-mediated mRNA decay and its physiological roles. WIREs RNA 2018, 9:e1449. doi: 10.1002/wrna.1449 This article is categorized under: RNA Interactions with Proteins and Other Molecules > Protein-RNA Interactions: Functional Implications RNA Turnover and Surveillance > Regulation of RNA Stability RNA in Disease and Development > RNA in Disease.

ZC3H12A/MCPIP1/Regnase-1-related endonucleases: An evolutionary perspective on molecular mechanisms and biological functions

The mammalian Zc3h12a/MCPIP1/Regnase-1, an extensively studied regulator of inflammatory response, is the founding member of a ribonuclease family, which includes proteins related by the presence of the so-called Zc3h12a-like NYN domain. Recently, several related proteins have been described in Caenorhabditis elegans, allowing comparative evaluation of molecular functions and biological roles of these ribonucleases. We discuss the structural features of these proteins, which endow some members with ribonuclease (RNase) activity while others with auxiliary or RNA-independent functions. We also consider their RNA specificity and highlight a common role for these proteins in cellular defense, which is remarkable considering the evolutionary distance and fundamental differences in cellular defense mechanisms between mammals and nematodes.

RNA-binding proteins in immune regulation: a focus on CCCH zinc finger proteins

Nearly 60 CCCH zinc finger proteins have been identified in humans and mice. These proteins are involved in the regulation of multiple steps of RNA metabolism, including mRNA splicing, polyadenylation, transportation, translation and decay. Several CCCH zinc finger proteins, such as tristetraprolin (TTP), roquin 1 and MCPIP1 (also known as regnase 1), are crucial for many aspects of immune regulation by targeting mRNAs for degradation and modulation of signalling pathways. In this Review, we focus on the emerging roles of CCCH zinc finger proteins in the regulation of immune responses through their effects on cytokine production, immune cell activation and immune homeostasis.