Monocyte Chemotactic Protein-induced Protein 1 and 4 Form a Complex but Act Independently in Regulation of Interleukin-6 mRNA Degradation

Regnase-2 inhibits glioblastoma cell proliferation

Regnase-2 (Reg-2/MCPIP2/ZC3H12B) is uniquely expressed at a high level in the healthy brain and down-regulated in samples from patients with glioma, reaching the lowest level in high-grade glioblastoma multiforme (GBM). This RNase is involved in the regulation of neuroinflammation through the degradation of IL-6 and IL-1 mRNAs, key pro-inflammatory cytokines for GBM pathology. Reg-2 is a strong inhibitor of the proliferation of human glioblastoma cell lines and blocks their potential to form colonies. Here, we describe that overexpression of Reg-2 stalls glioblastoma cells in the G1 phase of the cell cycle and reduces the level of transcripts implicated in cell cycle progression. These newly identified targets include CCND1, CCNE1, CCNE2, CCNA2, CCNB1, and CCNB2, encoding the cyclins as well as AURKA and PLK1, encoding two important mitosis regulators. By RNA immunoprecipitation we confirmed the direct interaction of Reg-2 with the investigated transcripts. We also tested mRNA regions involved in their interaction with Reg-2 on the example of CCNE2. Reg-2 interacts with the 3'UTR of CCNE2 in a dose-dependent manner. In conclusion, our results indicate that Reg-2 controls key elements in GBM biology by restricting neuroinflammation and inhibiting cancer cell proliferation.

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.

MCPIP1 Suppresses the NF-κB Signaling Pathway Through Negative Regulation of K63-Linked Ubiquitylation of TRAF6 in Colorectal Cancer

The abnormal activation of the nuclear factor-kappa B (NF-κB) signaling pathway is an important precipitating factor for the inception and development of colorectal cancer (CRC), one of the most common tumors worldwide. As a pro-apoptotic transcription factor, monocyte chemotactic protein-induced protein 1 (MCPIP1) has been closely associated with many tumor types. In the present study, the expression of MCPIP1 was firstly discovered reduced in CRC tissues and correlated with poor patient prognosis. The decreased expression was caused by promoter hypermethylation. Overexpressed MCPIP1 was found to inhibit the proliferative and migratory abilities of CRC cells, whereas knockdown of MCPIP1 produced the opposite result. The subsequent investigation demonstrated that MCPIP1 exerted its "anti-cancer" effect by suppression of the NF-κB signaling pathway through negative regulation of K63-linked ubiquitylation of TNF receptor associated factor 6 (TRAF6). Therefore, our results indicate a prognostic marker for CRC and a theoretical basis for MCPIP1 as a treatment.

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.

Regnase-1-related endoribonucleases in health and immunological diseases

Dynamic changes in gene expression are key factors in the development and activation of immune cells. RNA metabolism is one of the critical steps for the control of gene expression. Together with transcriptional regulation, mRNA decay by specific ribonucleases (RNases) plays a vital role in shaping gene expression. In addition to the canonical exoribonuclease-mediated mRNA degradation through the recognition of cis-elements in mRNA 3' untranslated regions by RNA-binding proteins (RBPs), endoribonucleases are involved in the control of mRNAs in immune cells. In this review, we gleam insights on how Regnase-1, an endoribonuclease necessary for regulating immune cell activation and maintenance of immune homeostasis, degrades RNAs involved in immune cell activation. Additionally, we provide insights on recent studies which uncover the role of Regnase-1-related RNases, including Regnase-2, Regnase-3, and Regnase-4, as well as N4BP1 and KHNYN, in immune regulation and antiviral immunity. As the dysregulation of immune mRNA decay leads to pathologies such as autoimmune diseases or impaired activation of immune responses, RNases are deemed as essential components of regulatory feedback mechanisms that modulate inflammation. Given the critical role of RNases in autoimmunity, RNases can be perceived as emerging targets in the development of novel therapeutics.

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.

Molecular Mechanisms of ZC3H12C/Reg-3 Biological Activity and Its Involvement in Psoriasis Pathology

The members of the ZC3H12/MCPIP/Regnase family of RNases have emerged as important regulators of inflammation. In contrast to Regnase-1, -2 and -4, a thorough characterization of Regnase-3 (Reg-3) has not yet been explored. Here we demonstrate that Reg-3 differs from other family members in terms of NYN/PIN domain features, cellular localization pattern and substrate specificity. Together with Reg-1, the most comprehensively characterized family member, Reg-3 shared IL-6, IER-3 and Reg-1 mRNAs, but not IL-1β mRNA, as substrates. In addition, Reg-3 was found to be the only family member which regulates transcript levels of TNF, a cytokine implicated in chronic inflammatory diseases including psoriasis. Previous meta-analysis of genome-wide association studies revealed Reg-3 to be among new psoriasis susceptibility loci. Here we demonstrate that Reg-3 transcript levels are increased in psoriasis patient skin tissue and in an experimental model of psoriasis, supporting the immunomodulatory role of Reg-3 in psoriasis, possibly through degradation of mRNA for TNF and other factors such as Reg-1. On the other hand, Reg-1 was found to destabilize Reg-3 transcripts, suggesting reciprocal regulation between Reg-3 and Reg-1 in the skin. We found that either Reg-1 or Reg-3 were expressed in human keratinocytes in vitro. However, in contrast to robustly upregulated Reg-1 mRNA levels, Reg-3 expression was not affected in the epidermis of psoriasis patients. Taken together, these data suggest that epidermal levels of Reg-3 are negatively regulated by Reg-1 in psoriasis, and that Reg-1 and Reg-3 are both involved in psoriasis pathophysiology through controlling, at least in part different transcripts.

The RNase MCPIP3 promotes skin inflammation by orchestrating myeloid cytokine response

CCCH zinc finger proteins resolve immune responses by degrading the mRNAs of inflammatory cytokines such as tumor necrosis factor (TNF) and interleukin (IL)-6. Here we report that one such family member, monocyte chemotactic protein-induced protein 3 (MCPIP3, also named ZC3H12C or Regnase-3), promotes skin inflammation by simultaneously enhancing TNF in macrophages and repressing IL-6 in plasmacytoid dendritic cells (pDCs). MCPIP3 is positively associated with psoriasis pathogenesis, and highly expressed by macrophages and pDCs. MCPIP3-deficient macrophages produce less TNF and IL-12p40. However, MCPIP3-deficient pDCs secrete significantly more IL-6. This enhanced intradermal IL-6 may alleviate imiquimod-induced skin inflammation. As a result, MCPIP3-deficient mice are protected from imiquimod-induced psoriasiform lesions. Furthermore, early exposure to pDC-derived IL-6 suppresses macrophage-derived TNF and IL-12p40. Mechanistically, MCPIP3 could directly degrade mRNAs of IL-6, Regnase-1, and IκBζ. In turn, Regnase-1 could degrade MCPIP3 mRNAs. Our study identifies a critical post-transcriptional mechanism that synchronizes myeloid cytokine secretion to initiate autoimmune skin inflammation.

Zinc finger proteins are involved in the resolution of immune responses and function by degrading mRNA of inflammatory cytokines. Here the authors show MCPIP3 promotes skin inflammation via modification of cytokine profiles in pDCs and macrophages.

Multifunctional RNase MCPIP1 and its Role in Cardiovascular Diseases

Monocyte chemoattractant protein-1 induced protein 1 (MCPIP1), one of the MCPIP family members, is characterized by the presence of both C-x8-C-x5-C-x3-H (CCCH)- type zinc finger and PilT-N-terminal domains. As a potent regulator of innate immunity, MCPIP1 exerts anti-inflammatory effects through its ribonuclease (RNase) and deubiquitinating enzyme activities to degrade cytokine mRNAs and inhibit nuclear factor- kappa B (NF-κB), respectively. MCPIP1 is expressed not only in immune cells but also in many other cell types, including cardiomyocytes, vascular endothelial cells (ECs) and smooth muscle cells (SMCs). Increasing evidence indicates that MCPIP1 plays a role in the regulation of cardiac functions and is involved in the processes of vascular diseases, such as ischemia-reperfusion (I/R) and atherosclerosis. To better understand the emerging roles of MCPIP1 in the cardiovascular system, we reviewed the current literature with respect to MCPIP1 functions and discussed its association with the pathogenesis of cardiovascular diseases and the implication as a therapeutic target.

Extracellular mRNA transported to the nucleus exerts translation-independent function

RNA in extracellular vesicles (EVs) are uptaken by cells, where they regulate fundamental cellular functions. EV-derived mRNA in recipient cells can be translated. However, it is still elusive whether “naked nonvesicular extracellular mRNA” (nex-mRNA) that are not packed in EVs can be uptaken by cells and, if so, whether they have any functions in recipient cells. Here, we show the entrance of nex-mRNA in the nucleus, where they exert a translation-independent function. Human nex-interleukin-1β (IL1β)-mRNA outside cells proved to be captured by RNA-binding zinc finger CCCH domain containing protein 12D (ZC3H12D)-expressing human natural killer (NK) cells. ZC3H12D recruited to the cell membrane binds to the 3′-untranslated region of nex-IL1β-mRNA and transports it to the nucleus. The nex-IL1β-mRNA in the NK cell nucleus upregulates antiapoptotic gene expression, migration activity, and interferon-γ production, leading to the killing of cancer cells and antimetastasis in mice. These results implicate the diverse actions of mRNA.

Nonvesicular extracellular RNA (nex-RNA) that are not packed in extracellular vesicles is detected outside the cell, but it is poorly understood. Here the authors report that nex-RNA is captured by a zinc finger protein and transported to the nucleus to enhance antimetastatic characters of the cell.

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.

How are MCPIP1 and cytokines mutually regulated in cancer-related immunity?

Cytokines are secreted by various cell types and act as critical mediators in many physiological processes, including immune response and tumor progression. Cytokines production is precisely and timely regulated by multiple mechanisms at different levels, ranging from transcriptional to post-transcriptional and posttranslational processes. Monocyte chemoattractant protein-1 induced protein 1 (MCPIP1), a potent immunosuppressive protein, was first described as a transcription factor in monocytes treated with monocyte chemoattractant protein-1 (MCP-1) and subsequently found to possess intrinsic RNase and deubiquitinase activities. MCPIP1 tightly regulates cytokines expression via various functions. Furthermore, cytokines such as interleukin 1 beta (IL-1B) and MCP-1 and inflammatory cytokines inducer lipopolysaccharide (LPS) strongly induce MCPIP1 expression. Mutually regulated MCPIP1 and cytokines form a complicated network in the tumor environment. In this review, we summarize how MCPIP1 and cytokines reciprocally interact and elucidate the effect of the network formed by these components in cancer-related immunity with aim of exploring potential clinical benefits of their mutual regulation.

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.

RNA Recognition and Immunity-Innate Immune Sensing and Its Posttranscriptional Regulation Mechanisms

RNA acts as an immunostimulatory molecule in the innate immune system to activate nucleic acid sensors. It functions as an intermediate, conveying genetic information to control inflammatory responses. A key mechanism for RNA sensing is discriminating self from non-self nucleic acids to initiate antiviral responses reliably, including the expression of type I interferon (IFN) and IFN-stimulated genes. Another important aspect of the RNA-mediated inflammatory response is posttranscriptional regulation of gene expression, where RNA-binding proteins (RBPs) have essential roles in various RNA metabolisms, including splicing, nuclear export, modification, and translation and mRNA degradation. Recent evidence suggests that the control of mRNA stability is closely involved in signal transduction and orchestrates immune responses. In this study, we review the current understanding of how RNA is sensed by host RNA sensing machinery and discuss self/non-self-discrimination in innate immunity focusing on mammalian species. Finally, we discuss how posttranscriptional regulation by RBPs shape immune reactions.

Deficiency of Prebiotic Fiber and Insufficient Signaling Through Gut Metabolite-Sensing Receptors Leads to Cardiovascular Disease

BACKGROUND

High blood pressure (BP) continues to be a major, poorly controlled but modifiable risk factor for cardiovascular death. Among key Western lifestyle factors, a diet poor in fiber is associated with prevalence of high BP. The impact of lack of prebiotic fiber and the associated mechanisms that lead to higher BP are unknown. Here we show that lack of prebiotic dietary fiber leads to the development of a hypertensinogenic gut microbiota, hypertension and its complications, and demonstrate a role for G-protein coupled-receptors (GPCRs) that sense gut metabolites.

METHODS

One hundred seventy-nine mice including C57BL/6J, gnotobiotic C57BL/6J, and knockout strains for GPR41, GPR43, GPR109A, and GPR43/109A were included. C57BL/6J mice were implanted with minipumps containing saline or a slow-pressor dose of angiotensin II (0.25 mg·kg^-1·d^-1). Mice were fed diets lacking prebiotic fiber with or without addition of gut metabolites called short-chain fatty acids ([SCFA)] produced during fermentation of prebiotic fiber in the large intestine), or high prebiotic fiber diets. Cardiac histology and function, BP, sodium and potassium excretion, gut microbiome, flow cytometry, catecholamines and methylation-wide changes were determined.

RESULTS

Lack of prebiotic fiber predisposed mice to hypertension in the presence of a mild hypertensive stimulus, with resultant pathological cardiac remodeling. Transfer of a hypertensinogenic microbiota to gnotobiotic mice recapitulated the prebiotic-deprived hypertensive phenotype, including cardiac manifestations. Reintroduction of SCFAs to fiber-depleted mice had protective effects on the development of hypertension, cardiac hypertrophy, and fibrosis. The cardioprotective effect of SCFAs were mediated via the cognate SCFA receptors GPR43/GPR109A, and modulated L-3,4-dihydroxyphenylalanine levels and the abundance of T regulatory cells regulated by DNA methylation.

CONCLUSIONS

The detrimental effects of low fiber Westernized diets may underlie hypertension, through deficient SCFA production and GPR43/109A signaling. Maintaining a healthy, SCFA-producing microbiota is important for cardiovascular health.

The role of deubiquitinating enzymes in gastric cancer

The epigenetic regulation of gene expression (via DNA methylation, histone modification and microRNA interference) contributes to a variety of diseases, particularly cancer. Protein deubiquitination serves a key role in the mechanism underlying histone modification, and consequently influences tumor development and progression. Improved characterization of the role of ubiquitinating enzymes has led to the identification of numerous deubiquitinating enzymes (DUBs) with various functions. Gastric cancer (GC) is a highly prevalent cancer type that exhibits a high mortality rate. Latest analysis about cancer patient revealed that GC is sixth deadliest cancer type, which frequently occur in male (7.2%) than female (4.1%). Complex associations between DUBs and GC progression have been revealed in multiple studies; however, the molecular mechanism underpinning the metastasis and recurrence of GC is yet to be elucidated. Generally, DUBs were upregulated in gastric cancer. The relation of DUBs and tumor size, classification and staging was observed in GC. Besides, 5-yar survival rate of patients with GC is effeccted by expression level of DUBs. Among the highly expressed DUBs, specifically six DUBs namely UCHs, USPs, OTUs, MJDs, JAMMs and MCPIPs effect on this survival rate. Consequently, the association between GC and DUBs has received increasing attention in recent years. Therefore, in the present review, literature investigating the association between DUBs and GC pathophysiology was analyzed and critically appraised.

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.

Involvement of PIN-like domain nucleases in tRNA processing and translation regulation

Transfer RNAs require essential maturation steps to become functional. Among them, RNase P removes 5' leader sequences of pre-tRNAs. Although RNase P was long thought to occur universally as ribonucleoproteins, different types of protein-only RNase P enzymes were discovered in both eukaryotes and prokaryotes. Interestingly, all these enzymes belong to the super-group of PilT N-terminal-like nucleases (PIN)-like ribonucleases. This wide family of enzymes can be subdivided into major subgroups. Here, we review recent studies at both functional and mechanistic levels on three PIN-like ribonucleases groups containing enzymes connected to tRNA maturation and/or translation regulation. The evolutive distribution of these proteins containing PIN-like domains as well as their organization and fusion with various functional domains is discussed and put in perspective with the diversity of functions they acquired during evolution, for the maturation and homeostasis of tRNA and a wider array of RNA substrates. © 2019 IUBMB Life, 2019 © 2019 IUBMB Life, 71(8):1117-1125, 2019.

Antineuroinflammation of Minocycline in Stroke

Accumulating research substantiates the statement that inflammation plays an important role in the development of stroke. Both proinflammatory and anti-inflammatory mediators are involved in the pathogenesis of stroke, an imbalance of which leads to inflammation. Anti-inflammation is a kind of hopeful strategy for the prevention and treatment of stroke. Substantial studies have demonstrated that minocycline, a second-generation semisynthetic antibiotic belonging to the tetracycline family, can inhibit neuroinflammation, inflammatory mediators and microglia activation, and improve neurological outcome. Experimental and clinical data have found the preclinical and clinical potential of minocycline in the treatment of stroke due to its anti-inflammation properties and anti-inflammation-induced pathogeneses, including antioxidative stress, antiapoptosis, inhibiting leukocyte migration and microglial activation, and decreasing matrix metalloproteinases activity. Hence, it suggests a great future for minocycline in the therapeutics of stroke that diminish the inflammatory progress of stroke.

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.

Intact NYN/PIN-Like Domain is Crucial for the Degradation of Inflammation-Related Transcripts by ZC3H12D

ZC3H12D belongs to a recently discovered family of proteins containing four members of which the most studied and best described is the RNase ZC3H12A (MCPIP1/Regnase-1). ZC3H12A is a crucial negative regulator of inflammation. It accelerates the turnover of transcripts of a spectrum of proinflammatory cytokines, as well as its own mRNA. The biological role of ZC3H12D is less clear, although it was shown that this member of ZC3H12 family is also involved in the regulation of inflammation. Here, we show that ZC3H12A and ZC3H12D recognize a set of common target mRNAs encoding proteins that play important roles in the course of the inflammation. Similarly to ZC3H12A, ZC3H12D participates in the 3'UTR-dependent regulation of the turnover of mRNAs encoding interleukin-6 (IL-6), tumor necrosis factor (TNF), and immediate early response 3 gene (IER3). The ZC3H12A mRNA is also among the identified ZC3H12D targets. Using the combination of immunofluorescence with single molecule RNA fluorescence in situ hybridization (smRNA FISH) we have shown that ZC3H12D protein interacts with the ZC3H12A transcript. The direct binding of these two molecules in vivo was further confirmed by RNA immunoprecipitation. Simultaneously, overexpression of ZC3H12D increases the turnover rate of transcripts containing ZC3H12A 3'UTR. Using reporter gene assays we have confirmed that the Asp95 residue present in the NYN/PIN-like domain is crucial for ZC3H12D biological activity. We have also revealed that ZC3H12D recognizes the same structural elements present in the 3'UTRs of the investigated transcripts, as ZC3H12A. J. Cell. Biochem. 118: 487-498, 2017. © 2016 Wiley Periodicals, Inc.