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Paneth cells at the bottom of small intestinal crypts secrete antimicrobial peptides, enzymes, and growth factors and contribute to pathogen clearance and maintenance of the stem cell niche. Loss of Paneth cells and their dysfunction occur commonly in various pathologies, but the mechanism underlying the control of Paneth cell function remains largely unknown. Here, we identified microRNA-195 (miR-195) as a repressor of Paneth cell development and activity by altering SOX9 translation via interaction with RNA-binding protein HuR. Tissue-specific transgenic expression of miR-195 (miR195-Tg) in the intestinal epithelium decreased the levels of mucosal SOX9 and reduced the numbers of lysozyme-positive (Paneth) cells in mice. Ectopically expressed SOX9 in the intestinal organoids derived from miR-195-Tg mice restored Paneth cell development ex vivo. miR-195 did not bind to Sox9 mRNA but it directly interacted with HuR and prevented HuR binding to Sox9 mRNA, thus inhibiting SOX9 translation. Intestinal mucosa from mice that harbored both Sox9 transgene and ablation of the HuR locus exhibited lower levels of SOX9 protein and Paneth cell numbers than those observed in miR-195-Tg mice. Inhibition of miR-195 activity by its specific antagomir improved Paneth cell function in HuR-deficient intestinal organoids. These results indicate that interaction of miR-195 with HuR regulates Paneth cell function by altering SOX9 translation in the small intestinal epithelium.NEW & NOTEWORTHY Our results indicate that intestinal epithelial tissue-specific transgenic miR-195 expression decreases the levels of SOX9 expression, along with reduced numbers of Paneth cells. Ectopically expressed SOX9 in the intestinal organoids derived from miR-195-Tg mice restores Paneth cell development ex vivo. miR-195 inhibits SOX9 translation by preventing binding of HuR to Sox9 mRNA. These findings suggest that interaction between miR-195 and HuR controls Paneth cell function via SOX9 in the intestinal epithelium.

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CD8+ T cells kill target cells by releasing cytotoxic molecules and proinflammatory cytokines, such as TNF and IFN-γ. The magnitude and duration of cytokine production are defined by posttranscriptional regulation, and critical regulator herein are RNA-binding proteins (RBPs). Although the functional importance of RBPs in regulating cytokine production is established, the kinetics and mode of action through which RBPs control cytokine production are not well understood. Previously, we showed that the RBP ZFP36L2 blocks the translation of preformed cytokine encoding mRNA in quiescent memory T cells. Here, we uncover that ZFP36L2 regulates cytokine production in a time-dependent manner. T cell-specific deletion of ZFP36L2 (CD4-cre) had no effect on T-cell development or cytokine production during early time points (2-6 h) of T-cell activation. In contrast, ZFP36L2 specifically dampened the production of IFN-γ during prolonged T-cell activation (20-48 h). ZFP36L2 deficiency also resulted in increased production of IFN-γ production in tumor-infiltrating T cells that are chronically exposed to antigens. Mechanistically, ZFP36L2 regulates IFN-γ production at late time points of activation by destabilizing Ifng mRNA in an AU-rich element-dependent manner. Together, our results reveal that ZFP36L2 employs different regulatory nodules in effector and memory T cells to regulate cytokine production.

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Achieving optimally balanced gene expression within synthetic operons requires regulatory elements capable of providing a spectrum of expression levels. In this study, we investigate the expression of gfp reporter gene in tobacco chloroplasts, guided by variants of the plastid atpH 5' UTR, which harbors a binding site for PPR10, a protein that activates atpH at the posttranscriptional level. Our findings reveal that endogenous tobacco PPR10 confers distinct levels of reporter activation when coupled with the tobacco and maize atpH 5' UTRs in different design contexts. Notably, high GFP expression was not coupled to the stabilization of monocistronic gfp transcripts in dicistronic reporter lines, adding to the evidence that PPR10 activates translation via a mechanism that is independent of its stabilization of monocistronic transcripts. Furthermore, the incorporation of a tRNA upstream of the UTR nearly abolishes gfp mRNA (and GFP protein), presumably by promoting such rapid RNA cleavage and 5' exonucleolytic degradation that PPR10 had insufficient time to bind and protect gfp RNA, resulting in a substantial reduction in GFP accumulation. When combined with a mutant atpH 5' UTR, the tRNA leads to an exceptionally low level of transgene expression. Collectively, this approach allows for tuning of reporter gene expression across a wide range, spanning from a mere 0.02-25% of the total soluble cellular protein. These findings highlight the potential of employing cis-elements from heterologous species and expand the toolbox available for plastid synthetic biology applications requiring multigene expression at varying levels.

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ArcZ is a small regulatory RNA conserved in Enterobacterales It is an Hfq-dependent RNA that is cleaved by RNase E in a processed form of 55-60 nucleotides. This processed form is highly conserved for controlling the expression of target mRNAs. ArcZ expression is induced by abundant oxygen levels and reaches its peak during the stationary growth phase. This control is mediated by the oxygen-responsive two-component system ArcAB, leading to the repression of arcZ transcription under low-oxygen conditions in most bacteria in which it has been studied. ArcZ displays multiple targets, and it can control up to 10% of a genome and interact directly with more than 300 mRNAs in Escherichia coli and Salmonella enterica ArcZ displays a multifaceted ability to regulate its targets through diverse mechanisms such as RNase recruitment, modulation of ribosome accessibility on the mRNA, and interaction with translational enhancing regions. By influencing stress response, motility, and virulence through the regulation of master regulators such as FlhDC or RpoS, ArcZ emerges as a major orchestrator of cell physiology within Enterobacterales.

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Type I toxin-antitoxin systems (T1TAs) are bipartite bacterial loci encoding a growth-inhibitory toxin and an antitoxin small RNA (sRNA). In many of these systems, the transcribed toxin mRNA is translationally inactive, but becomes translation-competent upon ribonucleolytic processing. The antitoxin sRNA targets the processed mRNA to inhibit its translation. This two-level control mechanism prevents cotranscriptional translation of the toxin and allows its synthesis only when the antitoxin is absent. Contrary to this, we found that the timP mRNA of the timPR T1TA locus does not undergo enzymatic processing. Instead, the full-length timP transcript is both translationally active and can be targeted by the antitoxin TimR. Thus, tight control in this system relies on a noncanonical mechanism. Based on the results from in vitro binding assays, RNA structure probing, and cell-free translation experiments, we suggest that timP mRNA adopts mutually exclusive structural conformations. The active form uniquely possesses an RNA pseudoknot structure which is essential for translation initiation. TimR preferentially binds to the active conformation, which leads to pseudoknot destabilization and inhibited translation. Based on this, we propose a model in which "structural processing" of timP mRNA enables tight inhibition by TimR in nonpermissive conditions, and TimP synthesis only upon TimR depletion.

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Posttranscriptional regulation comprises those mechanisms occurring after the initial copy of the DNA sequence is transcribed into an intermediate RNA molecule (i.e., messenger RNA) until such a molecule is used as a template to generate a protein. A subset of these posttranscriptional regulatory mechanisms essentially are destined to process the immature mRNA toward its mature form, conferring the adequate mRNA stability, providing the means for pertinent introns excision, and controlling mRNA turnover rate and quality control check. An additional layer of complexity is added in certain cases, since discrete nucleotide modifications in the mature RNA molecule are added by RNA editing, a process that provides large mature mRNA diversity. Moreover, a number of posttranscriptional regulatory mechanisms occur in a cell- and tissue-specific manner, such as alternative splicing and noncoding RNA-mediated regulation. In this chapter, we will briefly summarize current state-of-the-art knowledge of general posttranscriptional mechanisms, while major emphases will be devoted to those tissue-specific posttranscriptional modifications that impact on cardiac development and congenital heart disease.

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The RNA chaperone Hfq acts as a global regulator of numerous biological processes, such as carbon/nitrogen metabolism and environmental adaptation in plant-associated diazotrophs; however, its target RNAs and the mechanisms underlying nitrogen fixation remain largely unknown. Here, we used enhanced UV cross-linking immunoprecipitation coupled with high-throughput sequencing to identify hundreds of Hfq-binding RNAs probably involved in nitrogen fixation, carbon substrate utilization, biofilm formation, and other functions. Collectively, these processes endow strain A1501 with the requisite capabilities to thrive in the highly competitive rhizosphere. Our findings revealed a previously uncharted landscape of Hfq target genes. Notable among these is nifM, encoding an isomerase necessary for nitrogenase reductase solubility; amtB, encoding an ammonium transporter; oprB, encoding a carbohydrate porin; and cheZ, encoding a chemotaxis protein. Furthermore, we identified more than 100 genes of unknown function, which expands the potential direct regulatory targets of Hfq in diazotrophs. Our data showed that Hfq directly interacts with the mRNA of regulatory proteins (RsmA, AlgU, and NifA), regulatory ncRNA RsmY, and other potential targets, thus revealing the mechanistic links in nitrogen fixation and other metabolic pathways. IMPORTANCE: Numerous experimental approaches often face challenges in distinguishing between direct and indirect effects of Hfq-mediated regulation. New technologies based on high-throughput sequencing are increasingly providing insight into the global regulation of Hfq in gene expression. Here, enhanced UV cross-linking immunoprecipitation coupled with high-throughput sequencing was employed to identify the Hfq-binding sites and potential targets in the root-associated Pseudomonas stutzeri A1501 and identify hundreds of novel Hfq-binding RNAs that are predicted to be involved in metabolism, environmental adaptation, and nitrogen fixation. In particular, we have shown Hfq interactions with various regulatory proteins' mRNA and their potential targets at the posttranscriptional level. This study not only enhances our understanding of Hfq regulation but, importantly, also provides a framework for addressing integrated regulatory network underlying root-associated nitrogen fixation.

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The spinocerebellar ataxias (SCA) comprise a group of inherited neurodegenerative diseases. Machado-Joseph Disease (MJD) or spinocerebellar ataxia 3 (SCA3) is the most common autosomal dominant form, caused by the expansion of CAG repeats within the ataxin-3 (ATXN3) gene. This mutation results in the expression of an abnormal protein containing long polyglutamine (polyQ) stretches that confers a toxic gain of function and leads to misfolding and aggregation of ATXN3 in neurons. As a result of the neurodegenerative process, SCA3 patients are severely disabled and die prematurely. Several screening approaches, e.g., druggable genome-wide and drug library screenings have been performed, focussing on the reduction in stably overexpressed ATXN3(polyQ) protein and improvement in the resultant toxicity. Transgenic overexpression models of toxic ATXN3, however, missed potential modulators of endogenous ATXN3 regulation. In another approach to identify modifiers of endogenous ATXN3 expression using a CRISPR/Cas9-modified SK-N-SH wild-type cell line with a GFP-T2A-luciferase (LUC) cassette under the control of the endogenous ATXN3 promotor, four statins were identified as potential activators of expression. We here provide an overview of the high throughput screening approaches yet performed to find compounds or genomic modifiers of ATXN3(polyQ) toxicity in different SCA3 model organisms and cell lines to ameliorate and halt SCA3 progression in patients. Furthermore, the putative role of cholesterol in neurodegenerative diseases (NDDs) in general and SCA3 in particular is discussed.

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Development is a chain reaction in which one event leads to another until the completion of a life cycle. Phase transitions are milestone events in the cycle of life. LEAFY COTYLEDON1 (LEC1), ABA INSENSITIVE3 (ABI3), FUSCA3 (FUS3), and LEC2 proteins, collectively known as LAFL, are master transcription factors (TFs) regulating seed and other developmental processes. Since the initial characterization of the LAFL genes, more than three decades of active research has generated tremendous amounts of knowledge about these TFs, whose roles in seed development and germination have been comprehensively reviewed. Recent advances in cell biology with genetic and genomic tools have allowed the characterization of the LAFL regulatory networks in previously challenging tissues at a higher throughput and resolution in reference species and crops. In this review, we provide a holistic perspective by integrating advances at the epigenetic, transcriptional, posttranscriptional, and protein levels to exemplify the spatiotemporal regulation of the LAFL networks in Arabidopsis seed development and phase transitions, and we briefly discuss the evolution of these TF networks.

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Maintaining immune homeostasis is instrumental for host health. Immune cells, such as T cells, are instrumental for the eradication of pathogenic bacteria, fungi and viruses. Furthermore, T cells also play a major role in the fight against cancer. Through the formation of immunological memory, a pool of antigen-experienced T cells remains in the body to rapidly protect the host upon reinfection or retransformation. In order to perform their protective function, T cells produce cytolytic molecules, such as granzymes and perforin, and cytokines such as interferon γ and tumor necrosis factor α. Recently, it has become evident that posttranscriptional regulatory events dictate the kinetics and magnitude of cytokine production by murine and human CD8+ T cells. Here, the recent literature regarding the role posttranscriptional regulation plays in maintaining immune homeostasis of antigen-experienced CD8+ T cells is reviewed.

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Messenger ribonucleoprotein particles (mRNPs) are vital for tissue-specific gene expression via mediating posttranscriptional regulations. However, proteomic profiling of proteins in mRNPs, i.e., mRNA-associated proteins (mRAPs), has been challenging at the tissue level. Herein, we report the development of formaldehyde cross-linking-based mRNA-associated protein profiling (FAXRAP), a chemical strategy that enables the identification of mRAPs in both cultured cells and intact mouse organs. Applying FAXRAP, tissue-specific mRAPs were systematically profiled in the mouse liver, kidney, heart, and brain. Furthermore, brain mRAPs in Parkinson's disease (PD) mouse model were investigated, which revealed a global decrease of mRNP assembly in the brain of mice with PD. We envision that FAXRAP will facilitate uncovering the posttranscriptional regulation networks in various biological systems.

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3' untranslated regions (3' UTRs) are critical elements of messenger RNAs, as they contain binding sites for RNA-binding proteins (RBPs) and microRNAs that affect various aspects of the RNA life cycle including transcript stability and cellular localization. In response to T cell receptor activation, T cells undergo massive expansion during the effector phase of the immune response and dynamically modify their 3' UTRs. Whether this serves to directly regulate the abundance of specific mRNAs or is a secondary effect of proliferation remains unclear. To study 3'-UTR dynamics in T helper cells, we investigated division-dependent alternative polyadenylation (APA). In addition, we generated 3' end UTR sequencing data from naive, activated, memory, and regulatory CD4+ T cells. 3'-UTR length changes were estimated using a nonnegative matrix factorization approach and were compared with those inferred from long-read PacBio sequencing. We found that APA events were transient and reverted after effector phase expansion. Using an orthogonal bulk RNA-seq data set, we did not find evidence of APA association with differential gene expression or transcript usage, indicating that APA has only a marginal effect on transcript abundance. 3'-UTR sequence analysis revealed conserved binding sites for T cell-relevant microRNAs and RBPs in the alternative 3' UTRs. These results indicate that poly(A) site usage could play an important role in the control of cell fate decisions and homeostasis.

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CsrA is an RNA-binding protein that regulates processes critical for growth and survival, including central carbon metabolism, motility, biofilm formation, stress responses, and expression of virulence factors in pathogens. Transcriptomics studies in Escherichia coli suggested that CsrA repressed genes involved in surviving extremely acidic conditions. Here, we examine the effects of disrupting CsrA-dependent regulation on the expression of genes and circuitry for acid stress survival and demonstrate CsrA-mediated repression at multiple levels. We show that this repression is critical for managing the trade-off between growth and survival; overexpression of acid stress genes caused by csrA disruption enhances survival under extreme acidity but is detrimental for growth under mildly acidic conditions. In vitro studies confirmed that CsrA binds specifically to mRNAs of structural and regulatory genes for acid stress survival, causing translational repression. We also found that translation of the top-tier acid stress regulator, evgA, is coupled to that of a small leader peptide, evgL, which is repressed by CsrA. Unlike dedicated acid stress response genes, csrA and its sRNA antagonists, csrB and csrC, did not exhibit a substantial response to acid shock. Furthermore, disruption of CsrA regulation of acid stress genes impacted host-microbe interactions in Caenorhabditis elegans, alleviating GABA deficiencies. This study expands the known regulon of CsrA to genes of the extreme acid stress response of E. coli and highlights a new facet of the global role played by CsrA in balancing the opposing physiological demands of stress resistance with the capacity for growth and modulating host interactions.IMPORTANCETo colonize/infect the mammalian intestinal tract, bacteria must survive exposure to the extreme acidity of the stomach. E. coli does this by expressing proteins that neutralize cytoplasmic acidity and cope with molecular damage caused by low pH. Because of the metabolic cost of these processes, genes for surviving acid stress are tightly regulated. Here, we show that CsrA negatively regulates the cascade of expression responsible for the acid stress response. Increased expression of acid response genes due to csrA disruption improved survival at extremely low pH but inhibited growth under mildly acidic conditions. Our findings define a new layer of regulation in the acid stress response of E. coli and a novel physiological function for CsrA.

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Thermospermine (Tspm) is a polyamine found to play a crucial role in xylem development in Arabidopsis thaliana. Tspm promotes the translation of the SACL genes by counteracting the activity of a cis element in their 5'-leader region that suppresses the translation of the main ORF. Here we describe a method to test the Tspm-dependent translational regulation of the 5'-leader of the SACL mRNAs in Nicotiana benthamiana leaves and A. thaliana mesophyll protoplasts with a dual luciferase assay. The dual luciferase reporter system is used to assess gene expression and is based on the detection of the Firefly luciferase luminescence driven by a specific promoter. However, it can also be used to evaluate the cis elements found in 5'-leader that influence the translation of the main ORF in a transcript. We have used a modified version of the pGreenII 0800 LUC plasmid carrying a double 35S promoter, followed by a poly-linker sequence in phase with the Firefly luciferase gene (pGreen2x35SLUC) where the full 5'-leader sequence of SACL3 was cloned. This construct was used for Agrobacterium tumefaciens infiltration of N. benthamiana leaves and for transfection of A. thaliana mesophyll protoplasts, followed by mock or Tspm treatments. The resulting translation of the Firefly luciferase in these organisms and conditions was then tested by measuring luminescence with the dual luciferase assay and a luminometer. These experiments have allowed us to quantify the positive effect of Tspm in the translation of SACL3 transcripts.

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Post-transcriptional regulation, by small RNAs (sRNAs) as well as the global Carbon Storage Regulator A (CsrA) protein, play critical roles in bacterial metabolic control and stress responses. The CsrA protein affects selective sRNA-mRNA networks, in addition to regulating transcription factors and sigma factors, providing additional avenues of cross talk between other stress-response regulators. Here, we expand the known set of sRNA-CsrA interactions and study their regulatory effects. In vitro binding assays confirm novel CsrA interactions with ten sRNAs, many of which are previously recognized as key regulatory nodes. Of those 10 sRNA, we identify that McaS, FnrS, SgrS, MicL, and Spot42 interact directly with CsrA in vivo. We find that the presence of CsrA impacts the downstream regulation of mRNA targets of the respective sRNA. In vivo evidence supports enhanced CsrA McaS-csgD mRNA repression and showcases CsrA-dependent repression of the fucP mRNA via the Spot42 sRNA. We additionally identify SgrS and FnrS as potential new sRNA sponges of CsrA. Overall, our results further support the expanding impact of the Csr system on cellular physiology via CsrA impact on the regulatory roles of these sRNAs.

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MKT1 is a pleiotropic stress response gene identified by several quantitative trait studies with MKT189G as a causal variant, contributing to growth advantage in multiple stress environments. MKT1 has been shown to regulate HO endonuclease posttranscriptionally via the Pbp1-Pab1 complex. RNA-binding protein Puf3 modulates a set of nuclear-encoded mitochondrial transcripts whose expression was found to be affected by MKT1 alleles. This study attempts to relate the MKT1 allele-derived growth advantage with the stability of Puf3 targets during stress and elucidate the roles of Pbp1 and Puf3 in this mechanism. Our results showed that the growth advantage of the MKT189G allele in cycloheximide and H2 O2 was PBP1-dependent, whereas in 4-nitroquinoline 1-oxide, the growth advantage was dependent on both PUF3 and PBP1. We compared the messenger RNA decay kinetics of a set of Puf3 targets in multiple stress environments to understand the allele-specific regulation by MKT1. In oxidative stress, the MKT189G allele modulated the differential expression of nuclear-encoded mitochondrial genes in a PBP1- and PUF3-dependent manner. Additionally, MKT189G stabilised Puf3 targets, namely, COX17, MRS1 and RDL2, in an allele and stress-specific manner. Our results showed that COX17, MRS1 and RDL2 had a stress-specific response in stress environments, with the MKT189G allele contributing to better growth; this response was both PBP1- and PUF3-dependent. Our results indicate that the common allele, MKT189G , regulates stress responses by differentially stabilising Puf3-target mitochondrial genes, which allows for the strain's better growth in stress environments.

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The conserved family of RNA-binding proteins (RBPs), IGF2BPs, plays an essential role in posttranscriptional regulation controlling mRNA stability, localization, and translation. Mammalian cells express three isoforms of IGF2BPs: IGF2BP1-3. IGF2BP3 is highly overexpressed in cancer cells, and its expression correlates with a poor prognosis in various tumors. Therefore, revealing its target RNAs with high specificity in healthy tissues and in cancer cells is of crucial importance. Photoactivatable-ribonucleoside-enhanced crosslinking and immunoprecipitation (PAR-CLIP) identifies the binding sites of RBPs on their target RNAs at nucleotide resolution in a transcriptome-wide manner. Here, we optimized the PAR-CLIP protocol to study RNA targets of endogenous IGF2BP3 in a human colorectal carcinoma cell line. To this end, we first established an immunoprecipitation protocol to obtain highly pure endogenous IGF2BP3-RNA complexes. Second, we modified the protocol to use highly sensitive infrared (IR) fluorescent dyes instead of radioactive probes to visualize IGF2BP3-crosslinked RNAs. We named the modified method "IR-PAR-CLIP." Third, we compared RNase cleavage conditions and found that sequence preferences of the RNases impact the number of the identified IGF2BP3 targets and introduce a systematic bias in the identified RNA motifs. Fourth, we adapted the single adapter circular ligation approach to increase the efficiency in library preparation. The optimized IR-PAR-CLIP protocol revealed novel RNA targets of IGF2BP3 in a human colorectal carcinoma cell line. We anticipate that our IR-PAR-CLIP approach provides a framework for studies of other RBPs.

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Bacteria live in complex polymicrobial communities and are constantly competing for resources. The type VI secretion system (T6SS) is a widespread antagonistic mechanism used by Gram-negative bacteria to gain an advantage over competitors. T6SSs translocate toxic effector proteins inside target prokaryotic cells in a contact-dependent manner. In addition, some T6SS effectors can be secreted extracellularly and contribute to the scavenging scarce metal ions. Bacteria deploy their T6SSs in different situations, categorizing these systems into offensive, defensive and exploitative. The great variety of bacterial species and environments occupied by such species reflect the complexity of regulatory signals and networks that control the expression and activation of the T6SSs. Such regulation is tightly controlled at the transcriptional, posttranscriptional and posttranslational level by abiotic (e.g. pH, iron) or biotic (e.g. quorum-sensing) cues. In this review, we provide an update on the current knowledge about the regulatory networks that modulate the expression and activity of T6SSs across several species, focusing on systems used for interbacterial competition.

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Thiamin (vitamin B1) plays a vital role in cellular energy metabolism/ATP production. Pancreatic acinar cells (PACs) obtain thiamin from circulation and convert it to thiamin pyrophosphate (TPP) in the cytoplasm. TPP is then taken up by the mitochondria via a carrier-mediated process that involves the mitochondrial TPP transporter (MTPPT; encoded by the gene SLC25A19). We have previously characterized different aspects of the mitochondrial carrier-mediated TPP uptake process, but nothing is known about its possible regulation at the posttranscriptional level. We address this issue in the current investigations focusing on the role of miRNAs in this regulation. First, we subjected the human (and rat) 3'-untranslated region (3'-UTR) of the SLC25A19 to three in-silico programs, and all have identified putative binding sites for miR-122-5p. Transfecting pmirGLO-hSLC25A19 3'-UTR into rat PAC AR42J resulted in a significant reduction in luciferase activity compared with cells transfected with pmirGLO-empty vector. Mutating as well as truncating the putative miR-122-5p binding sites in the hSLC25A19 3'-UTR led to abrogation of inhibition in luciferase activity in PAC AR42J. Furthermore, transfecting/transducing PAC AR42J and human primary PACs with mimic of miR-122-5p led to a significant inhibition in the level of expression of the MTPPT mRNA and protein as well as in mitochondrial carrier-mediated TPP uptake. Conversely, transfecting PAC AR42J with an inhibitor of miR-122-5p increased MTPPT expression and function. These findings show, for the first time, that expression and function of the MTPPT in PACs are subject to posttranscriptional regulation by miR-122-5p.NEW & NOTEWORTHY This study shows that the expression and function of mitochondrial TPP transporter (MTPPT) are subject to posttranscriptional regulation by miRNA-122-5p in pancreatic acinar cells.

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AT-rich interactive domain 5a (Arid5a) is a member of the arid family of proteins, which contain a helix-turn-helix domain and an ability to bind to nucleic acids. Current evidence suggests that Arid5a performs dual functions as a transcription factor and an RNA-binding protein in immune, nonimmune, and/ or tumor cells depending on its cellular localization. The contribution of Arid5a to the development of inflammation, autoimmunity, and obesity through its transcriptional and posttranscriptional regulatory functions has broadly been reviewed. Recent studies have indeed revealed an association of Arid5a with cancers, including breast, pancreatic, colorectal, and lung cancers and glioma. Notably, Arid5a affects various aspects of cellular homeostasis, including invasion, metastasis, epithelial-to-mesenchymal transition, immune evasion, adipogenesis and M1-like tumor-associated macrophage (TAM)-to-M2-like TAM transition. This review aims to summarize current knowledge of Arid5a from a cancer perspective and highlights recent advances in Arid5a-related cancer research. This review may improve the understanding of Arid5a-mediated molecular mechanisms and their relevance to cancers.