Protein inhibitor of activated STAT1 (PIAS1) alleviates cerebral infarction and inflammation after cerebral ischemia in rats

Background

Ischemic stroke is a severe disorder with high incidence, disability rate and mortality. Multiple pathogenesis mechanisms are involved in ischemic stroke, such as inflammation and neuronal cell apoptosis. Protein inhibitor of activated signal transducer and activators of transcription 1 (PIAS1) plays a crucial role in various biological processes, including inflammation. PIAS1 is also downregulated in ischemia-reperfusion injury and involved in the disease processes. However, the role of PIAS1 in cerebral ischemia is unclear.

Methods

Sprague-Dawley (SD) rats were induced with middle cerebral artery occlusion (MCAO). The role and mechanisms of PIAS1 in ischemic cerebral infarction were explored by Longa test, 2,3,5-triphenyltetrazolium chloride (TTC) staining, Morris water maze (MWM) test, hematoxylin-eosin (HE) staining, quantification of brain water content, reverse transcription-quantitative polymerase chain reaction (RT-qPCR), enzyme-linked immunosorbent assay (ELISA), terminal deoxynucleotidyl transferase deoxyuridine triphosphate (dUTP) nick end labeling (TUNEL), Western blot and immunofluorescence assays.

Results

The expression of PIAS1 in MCAO-induced rat was declined compared to sham rats. Overexpression of PIAS1 reduced the Longa neurological scores, the percent of infarction area, the pathological abnormality, the escape latency of swimming and the percent of brain water content, and increased the number of platform crossings and time in the target quadrant in the MCAO-induced rats. Besides, overexpression of PIAS1 decreased the MCAO-induced the contents of IL-1β, IL-6 and TNF-α, but further elevated the concentrations of IL-10 in both sera and brain tissues. Moreover, overexpression of PIAS1 reversed the MCAO-induced apoptosis rate and the relative protein level of Bax, cleaved caspase3 and Bcl-2. Overexpression of PIAS1 also reversed the level of proteins involved in NF-κB pathway.

Conclusion

PIAS1 reduced inflammation and apoptosis, thereby alleviating ischemic cerebral infarction in MCAO-induced rats through regulation NF-κB pathway.

SUMOylation of the m6A reader YTHDF2 by PIAS1 promotes viral RNA decay to restrict EBV replication

YTH N6-methyladenosine RNA-binding protein F2 (YTHDF2) is a member of the YTH protein family that binds to N6-methyladenosine (m6A)-modified RNA, regulating RNA stability and restricting viral replication, including Epstein-Barr virus (EBV). PIAS1 is an E3 small ubiquitin-like modifier (SUMO) ligase known as an EBV restriction factor, but its role in YTHDF2 SUMOylation remains unclear. In this study, we investigated the functional regulation of YTHDF2 by PIAS1. We found that PIAS1 promotes the SUMOylation of YTHDF2 at three specific lysine residues (K281, K571, and K572). Importantly, PIAS1 synergizes with wild-type YTHDF2, but not a SUMOylation-deficient mutant, to limit EBV lytic replication. Mechanistically, YTHDF2 lacking SUMOylation exhibits reduced binding to EBV transcripts, leading to increased viral mRNA stability. Furthermore, PIAS1 mediates SUMOylation of YTHDF2's paralogs, YTHDF1 and YTHDF3, to restrict EBV replication. These results collectively uncover a unique mechanism whereby YTHDF family proteins control EBV replication through PIAS1-mediated SUMOylation, highlighting the significance of SUMOylation in regulating viral mRNA stability and EBV replication.IMPORTANCEm6A RNA modification pathway plays important roles in diverse cellular processes and viral life cycle. Here, we investigated the relationship between PIAS1 and the m6A reader protein YTHDF2, which is involved in regulating RNA stability by binding to m6A-modified RNA. We found that both the N-terminal and C-terminal regions of YTHDF2 interact with PIAS1. We showed that PIAS1 promotes the SUMOylation of YTHDF2 at three specific lysine residues. We also demonstrated that PIAS1 enhances the anti-EBV activity of YTHDF2. We further revealed that PIAS1 mediates the SUMOylation of other YTHDF family members, namely, YTHDF1 and YTHDF3, to limit EBV replication. These findings together illuminate an important regulatory mechanism of YTHDF proteins in controlling viral RNA decay and EBV replication through PIAS1-mediated SUMOylation.

Multi-omics integration identifies cell-state-specific repression by PBRM1-PIAS1 cooperation

PBRM1 is frequently mutated in cancers of epithelial origin. How PBRM1 regulates normal epithelial homeostasis, prior to cancer initiation, remains unclear. Here, we show that PBRM1's gene regulatory roles differ drastically between cell states, leveraging human skin epithelium (epidermis) as a research platform. In progenitors, PBRM1 predominantly functions to repress terminal differentiation to sustain progenitors' regenerative potential; in the differentiation state, however, PBRM1 switches toward an activator. Between these two cell states, PBRM1 retains its genomic binding but associates with differential interacting proteins. Our targeted screen identified the E3 SUMO ligase PIAS1 as a key interactor. PIAS1 co-localizes with PBRM1 on chromatin to directly repress differentiation genes in progenitors, and PIAS1's chromatin binding drastically diminishes in differentiation. Furthermore, SUMOylation contributes to PBRM1's repressive function in progenitor maintenance. Thus, our findings highlight PBRM1's cell-state-specific regulatory roles influenced by its protein interactome despite its stable chromatin binding.

SUMOylation and coupling of eNOS mediated by PIAS1 contribute to maintenance of vascular homeostasis

Endothelial dysfunction (ED) is commonly considered a crucial initiating step in the pathogenesis of numerous cardiovascular diseases. The coupling of endothelial nitric oxide synthase (eNOS) is important in maintaining normal endothelial functions. However, it still remains elusive whether and how eNOS SUMOylation affects the eNOS coupling. In the study, we investigate the roles and possible action mechanisms of protein inhibitor of activated STAT 1 (PIAS1) in ED. Human umbilical vein endothelial cells (HUVECs) treated with palmitate acid (PA) in vitro and ApoE-/- mice fed with high-fat diet (HFD) in vivo were constructed as the ED models. Our in vivo data show that PIAS1 alleviates the dysfunction of vascular endothelium by increasing nitric oxide (NO) level, reducing malondialdehyde (MDA) level, and activating the phosphatidylinositol 3-kinase-protein kinase B-endothelial nitric oxide synthase (PI3K-AKT-eNOS) signaling in ApoE-/- mice. Our in vitro data also show that PIAS1 can SUMOylate eNOS under endogenous conditions; moreover, it antagonizes the eNOS uncoupling induced by PA. The findings demonstrate that PIAS1 alleviates the dysfunction of vascular endothelium by promoting the SUMOylation and inhibiting the uncoupling of eNOS, suggesting that PIAS1 would become an early predictor of atherosclerosis and a new potential target of the hyperlipidemia-related cardiovascular diseases.

SUMOylation of SMAD4 by PIAS1 in Conjunction with Vimentin Upregulation Promotes Migration Potential in Non-Small Cell Lung Cancer

BACKGROUND

The expression of vimentin as a marker of epithelial-to-mesenchymal transition (EMT) has been speculated to be associated with tissue heterogeneity and metastases of non-small cell lung cancer (NSCLC).

METHODS

This study utilized in vitro co-immunoprecipitation with small interfering RNAs (siRNAs) against protein inhibitors of STAT system type 1 (PIAS1) or SMAD4 in transforming growth factor-beta (TGF-β) signaling pathway in combination with SUMOylation assay.

RESULTS

We successfully demonstrated that PIAS1 enhanced SUMOylation of SMAD4 by forming a complex PIAS1-SUMO1-SMAD4 protein complex. This, in accordance with subsequently increased production of vimentin microfilaments, led to enhanced migration ability of non-small cell lung cancer (NSCLC) A549 line, observed from wound healing assay.

CONCLUSIONS

Our results further supported the positive correlation of SUMOylated SMAD4 mediated by PIAS1 and downstream overexpression of vimentin. In addition, the observation that overexpression of vimentin in this certain cell line was not necessarily linked with accelerated relative wound closure raised concerns that further exploration will be needed to confirm if the causal relationship exists between vimentin expression and the metastases of NSCLC, and if so, to what extent vimentin contributes to it.

SUMOylation of the m6A reader YTHDF2 by PIAS1 promotes viral RNA decay to restrict EBV replication

YTHDF2 is a member of the YTH protein family that binds to N6-methyladenosine (m6A)-modified RNA, regulating RNA stability and restricting viral replication, including Epstein-Barr virus (EBV). PIAS1 is an E3 SUMO ligase known as an EBV restriction factor, but its role in YTHDF2 SUMOylation remains unclear. In this study, we investigated the functional regulation of YTHDF2 by PIAS1. We found that PIAS1 promotes the SUMOylation of YTHDF2 at three specific lysine residues (K281, K571, and K572). Importantly, PIAS1 enhances the antiviral activity of YTHDF2, and SUMOylation-deficient YTHDF2 shows reduced anti-EBV activity. Mechanistically, YTHDF2 lacking SUMOylation exhibits reduced binding to EBV transcripts, leading to increased viral mRNA stability. Furthermore, PIAS1 mediates SUMOylation of YTHDF2's paralogs, YTHDF1 and YTHDF3. These results collectively uncover a unique mechanism whereby YTHDF2 controls EBV replication through PIAS1-mediated SUMOylation, highlighting the significance of SUMOylation in regulating viral mRNA stability and EBV replication.

NRIP1 aggravates lung injury caused by Pseudomonas aeruginosa in mice by increasing PIAS1 ubiquitination

Recently, evidence has shown that nuclear receptor interacting protein 1 (NRIP1) is involved in acute lung injury (ALI) progression, but the specific mechanism remains unclear. Pseudomonas aeruginosa (PA)-treated TC-1 cells were transfected with pcDNA-NRIP1 or si-NRIP1, and we found that overexpression of NRIP1 inhibited cell viability and promoted cell apoptosis and secretion of inflammatory factors, and transfection of si-NRIP1 reversed these effects. Furthermore, online bioinformatics analysis and co-immunoprecipitation assay results indicated that NRIP1 could bind to Ubiquitin Conjugating Enzyme E2I (UBE2I), and promoted UBE2I expression. Next, the PA-treated TC-1 cells were transfected with si-NRIP1 alone or together with pcDNA-UBE2I, and we observed that transfection with si-NRIP1 inhibited UBE2I expression, promoted cell viability, and reduced cell apoptosis and inflammatory factor secretion, which could be reversed by UBE2I overexpression. Moreover, UBE2I could bind to protein inhibitor of activated signal transducer and activators of transcription 1 (PIAS1). Overexpression of NRIP1 promoted UBE2I expression and inhibited PIAS1 expression, and NRIP1 promoted PIAS1 ubiquitination and degradation by UBE2I. The PA-treated TC-1 cells were transfected with si-UBE2I alone or together with si-PIAS1, and the results indicated that transfection of si-UBE2I had the same effect as transfection of si-NRIP1. Finally, our in vivo findings indicated that the expression of NRIP1 and UBE2I was decreased, and PIAS1 expression was increased, in the lung tissues of mice with NRIP1 knocked-down, and the inflammatory infiltration in the lung tissue was reduced. In conclusion, our study demonstrates that NRIP1 aggravates PA-induced lung injury in mice by promoting PIAS1 ubiquitination.

Grass carp (Ctenopharyngodon idellus) PIAS1 inhibits innate immune response via interacting with STAT1

Protein inhibitor of activated signal transducer and activator of transcription (PIAS) family protein involved in gene transcriptional regulation acts as negative regulator in Janus kinase-signal transducer and activator of transcription (JAK/STAT) signaling pathway. But until now, the roles of PIAS in fish are not clear. In this study, we identified the two mammalian PIAS1 orthologs from Ctenopharyngodon idellus, namely CiPIAS1a and CiPIAS1b, respectively. They can respond to the stimulation from Polyribocytidylic acid (Poly I:C), Grass Carp Reovirus (GCRV) and Lipopolysaccharides (LPS) respectively, so we suggested that they could participate in interferon (IFN)-mediated antiviral and antibacterial immune response. The subcellular localization and nuclear cytoplasm extraction showed that CiPIAS1a and CiPIAS1b were mainly distributed in the nucleus. In addition, Co-IP showed that they separately inhibited the phosphorylation of STAT1 via interacting with it, which leads to the reduction of IFN1 expression.

PIAS1 Regulates Hepatitis C Virus-Induced Lipid Droplet Accumulation by Controlling Septin 9 and Microtubule Filament Assembly

Chronic hepatitis C virus (HCV) infection often leads to fibrosis and chronic hepatitis, then cirrhosis and ultimately hepatocellular carcinoma (HCC). The processes of the HVC life cycle involve intimate interactions between viral and host cell proteins and lipid metabolism. However, the molecules and mechanisms involved in this tripartite interaction remain poorly understood. Herein, we show that the infection of HCC-derived Huh7.5 cells with HCV promotes upregulation of the protein inhibitor of activated STAT1 (PIAS1). Reciprocally, PIAS1 regulated the expression of HCV core protein and HCV-induced LD accumulation and impaired HCV replication. Furthermore, PIAS1 controlled HCV-promoted septin 9 filament formation and microtubule polymerization. Subsequently, we found that PIAS1 interacted with septin 9 and controlled its assembly on filaments, which thus affected septin 9-induced lipid droplet accumulation. Taken together, these data reveal that PIAS1 regulates the accumulation of lipid droplets and offer a meaningful insight into how HCV interacts with host proteins.

Linking nuclear matrix-localized PIAS1 to chromatin SUMOylation via direct binding of histones H3 and H2A.Z

As a conserved posttranslational modification, SUMOylation has been shown to play important roles in chromatin-related biological processes including transcription. However, how the SUMOylation machinery associates with chromatin is not clear. Here, we present evidence that multiple SUMOylation machinery components, including SUMO E1 proteins SAE1 and SAE2 and the PIAS (protein inhibitor of activated STAT) family SUMO E3 ligases, are primarily associated with the nuclear matrix rather than with chromatin. We show using nuclease digestion that all PIAS family proteins maintain nuclear matrix association in the absence of chromatin. Of importance, we identify multiple histones including H3 and H2A.Z as directly interacting with PIAS1 and demonstrate that this interaction requires the PIAS1 SAP (SAF-A/B, Acinus, and PIAS) domain. We demonstrate that PIAS1 promotes SUMOylation of histones H3 and H2B in both a SAP domain– and an E3 ligase activity–dependent manner. Furthermore, we show that PIAS1 binds to heat shock–induced genes and represses their expression and that this function also requires the SAP domain. Altogether, our study reveals for the first time the nuclear matrix as the compartment most enriched in SUMO E1 and PIAS family E3 ligases. Our finding that PIAS1 interacts directly with histone proteins also suggests a molecular mechanism as to how nuclear matrix–associated PIAS1 is able to regulate transcription and other chromatin-related processes.

CDKN2A deregulation in fatty liver disease and its accelerative role in the process of lipogenesis

Previous literature has indicated that cyclin-dependent kinase inhibitor 2 A (CDKN2A) is upregulated, while the Protein Inhibitor of Activated STAT1 (PIAS1) is downregulated in the liver tissues of obese mice. The current study aimed to investigate the relationship between CDKN2A and PIAS1 in the lipogenesis of fatty liver disease. In the C57BL/6J db/db mouse model and hepatocyte model of fatty liver, the expression pattern of CDKN2A, PIAS1, Protein arginine methyltransferase 1 (PRMT1) and CASP8 and FADD-like apoptosis regulator (CFLAR) was characterized by RNA quantitative and Western blot analysis. The lipogenesis-related genes (Srebp1c and Fas) in the liver tissues and cells were employed in the assessment of lipogenesis in response to gain- or loss-of-function of CDKN2A, PIAS1, PRMT1, and CFLAR, while triglyceride and fat content were evaluated in relation to fat accumulation. Western blot analysis was conducted to determine c-Jun amino-terminal kinase (JNK) phosphorylation, while the ubiquitination of CFLAR and SUMOylation of PIAS1 was examined by immunoprecipitation. PIAS1 and CFLAR were downregulated, while CDKN2A, PRMT1, and phosphorylation of JNK was elevated in the tissues and cells of the fatty liver models. Our results suggested that CDKN2A enhanced the SUMOylation of PIAS1 to reduce the expression of PIAS1. PRMT1 downregulated CFLAR by triggering its ubiquitination, while CFLAR repressed phosphorylation of JNK. The in vitro and in vivo results indicated that CDKN2A silencing prevented lipogenesis and fat accumulation by impairing the PRMT1-dependent ubiquitination of CFLAR and blocking the phosphorylation of JNK. Taken together, the central observations of our study demonstrate that targeting CDKN2A contributes to the suppression of lipogenesis and fat accumulation in fatty liver disease. The findings of our study highlight the potential of CDKN2A as a promising target against fatty liver.

PIAS1 potentiates the anti-EBV activity of SAMHD1 through SUMOylation

BACKGROUND

Sterile alpha motif and HD domain 1 (SAMHD1) is a deoxynucleotide triphosphohydrolase (dNTPase) that restricts the infection of a variety of RNA and DNA viruses, including herpesviruses. The anti-viral function of SAMHD1 is associated with its dNTPase activity, which is regulated by several post-translational modifications, including phosphorylation, acetylation and ubiquitination. Our recent studies also demonstrated that the E3 SUMO ligase PIAS1 functions as an Epstein-Barr virus (EBV) restriction factor. However, whether SAMHD1 is regulated by PIAS1 to restrict EBV replication remains unknown.

RESULTS

In this study, we showed that PIAS1 interacts with SAMHD1 and promotes its SUMOylation. We identified three lysine residues (K469, K595 and K622) located on the surface of SAMHD1 as the major SUMOylation sites. We demonstrated that phosphorylated SAMHD1 can be SUMOylated by PIAS1 and SUMOylated SAMHD1 can also be phosphorylated by viral protein kinases. We showed that SUMOylation-deficient SAMHD1 loses its anti-EBV activity. Furthermore, we demonstrated that SAMHD1 is associated with EBV genome in a PIAS1-dependent manner.

CONCLUSION

Our study reveals that PIAS1 synergizes with SAMHD1 to inhibit EBV lytic replication through protein-protein interaction and SUMOylation.

Small heterodimer partner (SHP) aggravates ER stress in Parkinson's disease-linked LRRK2 mutant astrocyte by regulating XBP1 SUMOylation

Background

Endoplasmic reticulum (ER) stress is a common feature of Parkinson’s disease (PD), and several PD-related genes are responsible for ER dysfunction. Recent studies suggested LRRK2-G2019S, a pathogenic mutation in the PD-associated gene LRRK2, cause ER dysfunction, and could thereby contribute to the development of PD. It remains unclear, however, how mutant LRRK2 influence ER stress to control cellular outcome. In this study, we identified the mechanism by which LRRK2-G2019S accelerates ER stress and cell death in astrocytes.

Methods

To investigate changes in ER stress response genes, we treated LRRK2-wild type and LRRK2-G2019S astrocytes with tunicamycin, an ER stress-inducing agent, and performed gene expression profiling with microarrays. The XBP1 SUMOylation and PIAS1 ubiquitination were performed using immunoprecipitation assay. The effect of astrocyte to neuronal survival were assessed by astrocytes-neuron coculture and slice culture systems. To provide in vivo proof-of-concept of our approach, we measured ER stress response in mouse brain.

Results

Microarray gene expression profiling revealed that LRRK2-G2019S decreased signaling through XBP1, a key transcription factor of the ER stress response, while increasing the apoptotic ER stress response typified by PERK signaling. In LRRK2-G2019S astrocytes, the transcriptional activity of XBP1 was decreased by PIAS1-mediated SUMOylation. Intriguingly, LRRK2-GS stabilized PIAS1 by increasing the level of small heterodimer partner (SHP), a negative regulator of PIAS1 degradation, thereby promoting XBP1 SUMOylation. When SHP was depleted, XBP1 SUMOylation and cell death were reduced. In addition, we identified agents that can disrupt SHP-mediated XBP1 SUMOylation and may therefore have therapeutic activity in PD caused by the LRRK2-G2019S mutation.

Conclusion

Our findings reveal a novel regulatory mechanism involving XBP1 in LRRK2-G2019S mutant astrocytes, and highlight the importance of the SHP/PIAS1/XBP1 axis in PD models. These findings provide important insight into the basis of the correlation between mutant LRRK2 and pathophysiological ER stress in PD, and suggest a plausible model that explains this connection.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12929-021-00747-1.

The E3 Ligase PIAS1 Regulates p53 Sumoylation to Control Stress-Induced Apoptosis of Lens Epithelial Cells Through the Proapoptotic Regulator Bax

Protein sumoylation is one of the most important post-translational modifications regulating many biological processes (Flotho A & Melchior F. 2013. Ann Rev. Biochem. 82:357–85). Our previous studies have shown that sumoylation plays a fundamental role in regulating lens differentiation (Yan et al., 2010. PNAS, 107(49):21034-9.; Gong et al., 2014. PNAS. 111(15):5574–9). Whether sumoylation is implicated in lens pathogenesis remains elusive. Here, we present evidence to show that the protein inhibitor of activated STAT-1 (PIAS1), a E3 ligase for sumoylation, is implicated in regulating stress-induced lens pathogenesis. During oxidative stress-induced cataractogenesis, expression of PIAS1 is significantly altered at both mRNA and protein levels. Upregulation and overexpression of exogenous PIAS1 significantly enhances stress-induced apoptosis. In contrast, silence of PIAS1 with CRISPR/Cas9 technology attenuates stress-induced apoptosis. Mechanistically, different from other cells, PIAS1 has little effect to activate JNK but upregulates Bax, a major proapoptotic regulator. Moreover, Bax upregulation is derived from the enhanced transcription activity of the upstream transcription factor, p53. As revealed previously in other cells by different laboratories, our data also demonstrate that PIAS1 promotes SUMO1 conjugation of p53 at K386 residue in lens epithelial cells and thus enhances p53 transcription activity to promote Bax upregulation. Silence of Bax expression largely abrogates PIAS1-mediated enhancement of stress-induced apoptosis. Thus, our results demonstrated that PIAS1 promotes oxidative stress-induced apoptosis through positive control of p53, which specifically upregulates expression of the downstream proapoptotic regulator Bax. As a result, PIAS1-promoted apoptosis induced by oxidative stress is implicated in lens pathogenesis.

Functional genomics study of protein inhibitor of activated STAT1 in mouse hippocampal neuronal cells revealed by RNA sequencing

Protein inhibitor of activated STAT1 (PIAS1), a small ubiquitin-like modifier (SUMO) E3 ligase, was considered to be an inhibitor of STAT1 by inhibiting the DNA-binding activity of STAT1 and blocking STAT1-mediated gene transcription in response to cytokine stimulation. PIAS1 has been determined to be involved in modulating several biological processes such as cell proliferation, DNA damage responses, and inflammatory responses, both in vivo and in vitro. However, the role played by PIAS1 in regulating neurodegenerative diseases, including Alzheimer’s disease (AD), has not been determined. In our study, significantly different expression levels of PIAS1 between normal controls and AD patients were detected in four regions of the human brain. Based on a functional analysis of Pias1 in undifferentiated mouse hippocampal neuronal HT-22 cells, we observed that the expression levels of several AD marker genes could be inhibited by Pias1 overexpression. Moreover, the proliferation ability of HT-22 cells could be promoted by the overexpression of Pias1. Furthermore, we performed RNA sequencing (RNA-seq) to evaluate and quantify the gene expression profiles in response to Pias1 overexpression in HT-22 cells. As a result, 285 significantly dysregulated genes, including 79 upregulated genes and 206 downregulated genes, were identified by the comparison of Pias1/+ cells with WT cells. Among these genes, five overlapping genes, including early growth response 1 (Egr1), early growth response 2 (Egr2), early growth response 3 (Egr3), FBJ osteosarcoma oncogene (Fos) and fos-like antigen 1 (Fosl1), were identified by comparison of the transcription factor binding site (TFBS) prediction results for STAT1, whose expression was evaluated by qPCR. Three cell cycle inhibitors, p53, p18 and p21, were significantly downregulated with the overexpression of Pias1. Analysis of functional enrichment and expression levels showed that basic region leucine zipper domain-containing transcription factors including zinc finger C2H2 (zf-C2H2), homeobox and basic/helix-loop-helix (bHLH) in several signaling pathways were significantly involved in PIAS1 regulation in HT-22 cells. A reconstructed regulatory network under PIAS1 overexpression demonstrated that there were 43 related proteins, notably Nr3c2, that directly interacted with PIAS1.

miR-182-5p and miR-96-5p Target PIAS1 and Mediate the Negative Feedback Regulatory Loop between PIAS1 and STAT3 in Endometrial Cancer

The expressions and roles of protein inhibitor of activated STAT (PIAS) proteins, a group of proteins with STAT inhibition and SUMOylation E3 ligase activity, are rarely revealed in endometrial cancer (EC). In this study, we analyzed the expressions of PIASs and their relationships with clinical features by mining online data through web servers, including UALCAN and Gene Expression Profiling Interactive Analysis (GEPIA) in EC. The expressions of PIASs in EC tissues were further validated by immunohistochemistry (IHC). The online analyses revealed only PIAS1 was consistently downregulated both at mRNA and protein level in EC, which was validated by the IHC. Subsequently, the mechanism of PIAS1 downregulation was explored with online tools like UALCAN, cBioPortal, LinkedOmics, and the Encyclopedia of RNA Interactomes (ENCORI). The results indicated that the mutation rate of PIAS1 was extremely low and not associated with PIAS1 expression. The promoter methylation level of PIAS1 was comparable between normal and EC tissues. miR-182-5p and miR-96-5p with negative association with PIAS1 in EC were predicted to target PIAS1. Dual luciferase reporter assay confirmed miR-182-5p and miR-96-5p could target PIAS1 in EC. MiR-182-5p and miR-96-5p inhibitors could upregulate PIAS1 in EC cells. Moreover, ectopic PIAS1 expression and STAT3 inhibitor treatment significantly inhibited STAT3's activity and the levels of miR-182-5p and miR-96-5p in EC cells. Collectively, our findings revealed PIAS1 was downregulated in EC, which was caused by upregulation of miR-182-5p and miR-96-5p, and PIAS1 downregulation further activated STAT3 and increased the expression of miR-182-5p and miR-96-5p, confirming miR-182-5p and miR-96-5p mediated the negative feedback regulatory loop between PIAS1 and STAT3 in EC.

An in vitro Förster resonance energy transfer-based high-throughput screening assay identifies inhibitors of SUMOylation E2 Ubc9

SUMOylation is one of the posttranslational modifications that mediate cellular activities such as transcription, DNA repair, and signal transduction and is involved in the cell cycle. However, only a limited number of small molecule inhibitors have been identified to study its role in cellular processes. Here, we report a Förster resonance energy transfer (FRET) high-throughput screening assay based on the interaction between E2 Ubc9 and E3 PIAS1. Of the 3200 compounds screened, 34 (1.1%) showed higher than 50% inhibition and 4 displayed dose-response inhibitory effects. By combining this method with a label-free surface plasmon resonance (SPR) assay, false positives were excluded leading to discovering WNN0605-F008 and WNN1062-D002 that bound to Ubc9 with K_D values of 1.93 ± 0.62 and 5.24 ± 3.73 μM, respectively. We examined the effect of the two compounds on SUMO2-mediated SUMOylation of RanGAP1, only WNN0605-F008 significantly inhibited RanGAP1 SUMOylation, whereas WNN1062-D002 did not show any inhibition. These compounds, with novel chemical scaffolds, may serve as the initial material for developing new SUMOylation inhibitors.

SUMO E3 ligase PIAS1 is a potential biomarker indicating stress susceptibility

Prior studies suggest that individual differences in stress responses contribute to the pathogenesis of neuropsychiatric disorders. In the present study, we investigated the role of small ubiquitin-like modifier (SUMO) E3 ligase protein inhibitor of activated STAT1 (PIAS1) in mediating stress responses to chronic social defeat stress (CSDS). We found that mRNA and protein levels of PIAS 1 were decreased in the hippocampus of high-susceptibility (HS) mice but not in low-susceptibility (LS) mice after CSDS. Local overexpression of PIAS1 in the hippocampus followed by CSDS exposure promoted stress resilience by attenuating social avoidance and improving anxiety-like behaviors. Viral-mediated gene transfer to generate a conditional knockdown of PIAS1 in the hippocampus promoted social avoidance and stress vulnerability after subthreshold microdefeat. HS mice displayed decreased levels of glucocorticoid receptor (GR) expression, and GR SUMOylation in the hippocampus was associated with stress vulnerability. Furthermore, cytokine/chemokine levels were changed predominantly in the hippocampus of HS mice. These results suggest that hippocampal PIAS1 plays a role in the regulation of stress susceptibility by post-translational modification of GRs.

Hypermethylation of miR-181b in monocytes is associated with coronary artery disease and promotes M1 polarized phenotype via PIAS1-KLF4 axis

Background

Dysregulated microRNAs are involved in the macrophage polarization and atherosclerotic development. Apart from microRNAs, alteration in DNA methylation is considered as one of the most frequent epigenetic changes. The purpose of the research is to investigate the altered methylation status of miR-181b in the circulating monocytes from patients with coronary artery disease (CAD) and explore the underlying mechanisms.

Methods

We examined the methylation status of miR-181b in purified circulating monocytes from patients with CAD and healthy controls. We then transfected monocytes with miR-181b mimics and determined the role of miR-181b on the phenotypic switch of macrophages and inflammatory response. DNA methylation levels determined by MethyLight PCR and pyrosequencing at the promoter of miR-181b significantly increased in CAD patients. Based on TargetScan database, we identified PIAS1 as the target gene of miR-181b and explored the interaction of miR-181b and PIAS1 by Dual-Luciferase assay, quantitative PCR and immunoblots. We also investigated the role of miR-181b and PIAS1 on macrophage polarization and inflammation.

Results

Hypermethylation at the promoter of miR-181b directly contributed to the decrease of miR-181b activity and expression. Overexpression of miR-181b reduced M1 polarization and facilitated M2 polarization determined by quantitative PCR. While knockdown of PIAS1 induced KLF4 degradation and SUMOylation in monocytes, miR-181b mimics reverse the KLF4 SUMOylation via suppression of PIAS1. Moreover, KLF4 SUMOylation by PIAS1 reversed M1 polarization induced by depletion of miR-181b in monocytes.

Conclusions

Hypermethylation of miR-181b induces M1 polarization and promotes atherosclerosis through activation of PIAS1 and KLF4 SUMOylation in macrophages.

High expression of miR-483-5p aggravates sepsis-induced acute lung injury

Sepsis-induced acute lung injury (ALI) has high morbidity and mortality rates, and there remains a need for therapeutic methods to improve the outcome of ALI patients. miR-483-5p is an important regulator for the development of various diseases such as sepsis. Nevertheless, it is not known whether miR-483-5p has an effect on sepsis-induced ALI. To explore this issue, this study used cecal ligation and puncture (CLP)-treated mice and lipopolysaccharide (LPS)-treated pulmonary microvascular endothelial cells (PMVECs) cells to simulate the models of sepsis-induced ALI in vivo and in vitro. Pathological and histological changes of lungs from sepsis-induced ALI mice were detected by Hematoxylin-eosin staining. The detection levels of caspase-3, interleukin (IL)-6 and IL-1β were used to reflect the effect of miR-483-5p on apoptosis and inflammation of sepsis-induced ALI. The detection level of lactate dehydrogenase (LDH) in PMVECs cells was used to reflect the severe extent of sepsis-induced injury. The expression of miR-483-5p in lung tissues of sepsis-induced ALI mice was determined by qRT-PCR. In addition, the interaction of miR-483-5p with PIAS1 was identified and validated by Targetscan website and luciferase reporter assay, respectively. The results showed that miR-483-5p was up-regulated in the lung tissues of sepsis-induced ALI mice. Knockdown of miR-483-5p effectively ameliorated lung injury in mice with sepsis-induced ALI and inhibited inflammation and apoptosis of LPS-treated PMVECs cells. Furthermore, in vitro experiment revealed that PIAS1 was a potential target of miR-483-5p. Moreover, miR-483-5p could suppress PIAS1 expression to aggravate inflammation and apoptosis of LPS-treated PMVECs cells. These findings suggest miR-483-5p is a potential therapeutic and diagnostic biomarker for sepsis-induced ALI and provide a new insight for understanding the molecular mechanism of sepsis-induced ALI.

Melatonin Induction of APP Intracellular Domain 50 SUMOylation Alleviates AD through Enhanced Transcriptional Activation and Aβ Degradation

The amyloid precursor protein (APP) intracellular domain (AICD) is implicated in the pathogenesis of Alzheimer’s disease (AD), but post-translational modification of AICD has rarely been studied and its role in AD is unknown. In this study, we examined the role and molecular mechanism of AICD SUMOylation in the pathogenesis of AD. We found that AICD is SUMO-modified by the SUMO E3 ligase protein inhibitor of activated STAT1 (PIAS1) in the hippocampus at Lys-43 predominantly, and that knockdown of PIAS1 decreases endogenous AICD SUMOylation. AICD SUMOylation increases AICD association with its binding protein Fe65 and increases AICD nuclear translocation. Furthermore, AICD SUMOylation increases AICD association with cyclic AMP-responsive element binding protein (CREB) and p65 and their DNA binding for transcriptional activation of neprilysin (NEP) and transthyretin (TTR), two major Aβ-degrading enzymes, respectively. Consequently, AICD SUMOylation decreases the Aβ level, Aβ oligomerization, and amyloid plaque deposits. It also rescues spatial memory deficits in APP/PS1 mice. Conversely, blockade of AICD SUMOylation at Lys-43 produces the opposite effects. Melatonin is identified as an endogenous stimulus that induces AICD SUMOylation. It also decreases the Aβ level and rescues reduction of PIAS1, NEP, and TTR expression in APP/PS1 mice. In this study, we demonstrate that AICD SUMOylation functions as a novel endogenous defense mechanism to combat AD.

Protein inhibitor of activated STAT1 (PIAS1) inhibits IRF8 activation of Epstein-Barr virus lytic gene expression

Epstein-Barr virus (EBV), a major human oncogenic pathogen, establishes life-long persistent infections. In latently infected B lymphocytes, the virus persists as an episome in the nucleus. Periodic reactivation of latent virus is controlled by both viral and cellular factors. Our recent studies showed that interferon regulatory factor 8 (IRF8) is required for EBV lytic reactivation while protein inhibitor of activated STAT1 (PIAS1) functions as an EBV restriction factor to block viral reactivation. Here, we show that IRF8 directly binds to the EBV genome and regulates EBV lytic gene expression together with PU.1 and EBV transactivator RTA. Furthermore, our study reveals that PIAS1 antagonizes IRF8/PU.1-mediated lytic gene activation through binding to and inhibiting IRF8. Together, our study establishes IRF8 as a transcriptional activator in promoting EBV reactivation and defines PIAS1 as an inhibitor of IRF8 to limit lytic gene expression.

Localization Patterns of Sumoylation Enzymes E1, E2 and E3 in Ocular Cell Lines Predict Their Functional Importance

PURPOSE

It is well established now that protein sumoylation acts as an important regulatory mechanism mediating control of ocular development through regulation of multiple transcription factors. Yet the functional mechanisms of each factor modulated remain to be further explored using the available in vitro systems. In this regard, various ocular cell lines including HLE, FHL124, αTN4-1, N/N1003A and ARPE-19 have been demonstrated to be useful for biochemical and molecular analyses of normal physiology and pathogenesis. We have recently examined that these cell lines express a full set of sumoylation enzymes E1, E2 and E3. Following this study, here we have examined the localization of these enzymes and determined their differential localization patterns in these major ocular cell lines.

METHODS

The 5 major ocular cell lines were cultured in Dulbecco's modified Eagle's medium (DMEM) containing fetal bovine serum (FBS) or rabbit serum (RBS) and 1% Penicillin- Streptomycin. The localization of the 3 major sumoylation enzymes in the 5 major ocular cell lines were determined with immunohistochemistry. The images were captured with a Zeiss LSM 880 confocal microscope.

RESULTS

we have obtained the following results: 1) The sumoylation enzymes SAE1, UBC9 and PIAS1 are distributed in both nucleus and cytoplasm, with a much higher level concentrated in the nucleus and the neighboring cellular organelle zone in all cell lines; 2) The sumoylation enzyme UBA2 was highly concentrated in both cytoplasm membrane, cytoskeleton and nucleus of all cell lines; 3) The ligase E3, RanBP2 was exclusively localized in the nucleus with homogeneous distribution.

CONCLUSIONS

Our results for the first time established the differential localization patterns of the three types of sumoylation enzymes in 5 major ocular cell lines. Our establishment of the differential localization patterns of the three types of sumoylation enzymes in these cell lines help to predict their functional importance of sumoylation in the vision system. Together, our results demonstrate that these cell lines can be used for assay systems to explore the functional mechanisms of sumoylation mediating ocular development and pathogenesis.

Analysis of the Differential Expression Patterns of Sumoylation Enzymes E1, E2 and E3 in Ocular Cell Lines

PURPOSE

Protein sumoylation is a well established regulatory mechanism to control many cellular processes such as chromatin structure dynamics, transcriptional regulation of gene expression, cell proliferation and differentiation, cell transformation and carcinogenesis, autophagy and senescence. In the vertebrate vision system, we and others have revealed that sumoylation plays important roles in regulating differentiation of several ocular tissues during eye development. To further elucidate the functional mechanisms of sumoylation, in vitro assay systems are needed. Currently, the five major cell lines including αTN4-1, FHL124, HLE, N/N1003A and ARPE-19 have been extensively used to test the biochemical and molecular aspects of normal vision physiology and various disease processes. Thus, we conducted the study on the expression patterns of the three types of sumoylation enzymes, the activating enzymes SAE1 and UBA2, the conjugating enzyme UBC9, and the ligating enzymes such as RanBP2 and PIAS1 in these ocular cell lines.

METHODS

The 5 major ocular cell lines were cultured in Dulbecco's modified Eagle's medium (DMEM) containing fetal bovine serum (FBS) or rabbit serum (RBS) and 1% Penicillin- Streptomycin. The mRNA levels were analysed with qRT-PCR. The protein levels were determined with western blot analysis and quantitated with Image J.

RESULTS

we have obtained the following results: 1) For the mRNAs encoding E1 SAE1 and UBA2, E2 UBC9 and E3 PIAS1, the highest level of expression was observed in αTN4-1 cells; For the mRNA encoding RanBP2, the highest level of expression was detected in N/N1003A cells; 2) In contrast to the mRNA expression patterns, a similar level of the SAE1 protein was observed in the all five cell lines, and so is true with UBA2 protein in all cells except for N/N1003A where over fourfold of enrichment in UBA2 protein was observed compared with other cell lines; 3) A similar level of UBC9 protein was also detected in all cells except for N/N1003A where more than one-fold of decrease in UBC9 level was found compared with other cell lines; 4) For E3 ligases, we did not identify the regular PIAS1 band in N/N1003A cells, the remaining cells have a level of PIAS1 with difference of less than 0.6-fold; all cells except for FHL124 cells have a similar level of RanBP2, and a 70% drop in RanBP2 was observed in FHL124 cell.

CONCLUSIONS

Our determination of the differential expression patterns of the three types of sumoylation enzymes in the 5 ocular cell lines help to understand sumoylation functions in vertebrate eye.

Effect of miR-181a-5p targeting PIAS1 on cerulein-induced acute pancreatitis-induced acinar cell injury

BACKGROUND

Acute inflammation caused by acute pancreatitis (AP) is extremely harmful to people's health and can be life-threatening in severe cases. Its pathogenesis is complex and not fully understood. MiRNAs have been involved in the pathogenesis of AP. It was found that miR-181a-5p can inhibit cancer cell migration, invasion, and angiogenesis. MiR-181a-5p can also inhibit gastric cancer cell proliferation, invasion, metastasis, and epithelial mesenchymal transition. Inhibition of miR-181a-5p expression inhibits cell proliferation and invasion by negatively targeting INPP5A, and enhances apoptosis of cervical cancer cells. In addition, miR-181a inhibits the growth of pancreatic cancer cell lines, reduces their migration, and increases their apoptosis. However, the effect and mechanism of miR-181a-5p on the proliferation and apoptosis of AP are still unclear.

AIM

To investigate the effect of miR-181a-5p on acinar cell injury in AP and the potential mechanism involved.

METHODS

An AP model was constructed by treating rat pancreatic acinar AR42J and MPC-83 cells with 100 nmol/L caerulein. Different groups of cells were included: Con group (normal cells), caerulein group (treated with caerulein), miR-NC group (transfected with miR-NC), miR-181a-5p group (transfected with miR-181a-5p mimic), anti-miR-NC group (transfected with anti-miR-NC), anti-miR-181a-5p group (transfected with anti-miR-181a-5p), caerulein + anti-miR-NC group (caerulein treatment after transfection with anti-miR-NC), caerulein + anti-miR-181a-5p group (caerulein treatment after transfection with anti-miR-181a-5p), caerulein + pcDNA group (caerulein treatment after transfection with pcDNA), caerulein + pcDNA-PIAS1 group (caerulein treatment after transfection with pcDNA-PIAS1), caerulein + anti-miR-181a-5p + si-NC group (caerulein treatment after anti-miR-181a-5p and si-NC co-transfection), and caerulein + anti-miR-181a-5p + si-PIAS1 group (caerulein treatment after anti-miR-181a-5p and si-PIAS1 co-transfection). Cell transfections were performed by the liposome method. The expression of TNF-α and IL-6 in AR42J and MPC-83 cells treated with caerulein was detected by enzyme-linked immunosorbent assay. qRT-PCR was used to detect miR-181a-5p and PIAS1 mRNA in AR42J and MPC-83 cells treated with cerulein. Western blot was used to detect protein expression. Flow cytometry was used to detect apoptosis. Dual luciferase reporter gene assay was used to detect fluorescence activity.

RESULTS

After treatment of AR42J and MPC-83 cells with caerulein, the expression of TNF-α and IL-6 was significantly increased, the expression level of miR-181a-5p was significantly increased, and the expression of PIAS1 mRNA and protein was significantly decreased. Inhibition of miR-181a-5p expression and overexpression of PIAS1 inhibited the expression of TNF-α and IL-6 and inhibited cell apoptosis. MiR-181a-5p negatively regulated the expression of PIAS1, and inhibition of PIAS1 expression reversed the inhibitory effect of miR-181a-5p on apoptosis of AR42J and MPC-83 cells treated with caerulein.

CONCLUSION

Inhibition of miR-181a-5p expression inhibits caerulein-induced AP-induced acinar cell injury via mechanisms that may be related to the targeted regulation of PIAS1. Our findings may provide new targets and new ideas for the diagnosis and treatment of AP.

Biochemical characterization of SUMO-conjugating enzymes by in vitro sumoylation assays

The small ubiquitin-related modifier (SUMO) is a protein of ~10kDa that is covalently conjugated to its substrate proteins in an enzymatic process called sumoylation. This posttranslational modification is an essential regulatory mechanism that plays crucial roles in many cellular pathways. It allows rapid adaptation to environmental changes by switching protein functions due to alternate complex assemblies, changes in intracellular localization, enzymatic activity, or stability. SUMO conjugation is executed by the hierarchical action of E1, E2, and E3 enzymes. Both E2 and E3 enzymes contribute to substrate specificity but with E3 ligases being the more important for this. E1 and E2 activities are essential for all sumoylation reactions but usually-with a few exceptions-modify substrates only inefficiently. Hence, most substrates require the additional action of an E3 ligase or a cofactor. Here, we describe methods to distinguish a bona fide E3 ligase from a cofactor activity by using in vitro sumoylation assays.

Altered Expression Patterns of the Sumoylation Enzymes E1, E2 and E3 Are Associated with Glucose Oxidase- and UVA-Induced Cataractogenesis

PURPOSE

Protein sumoylation is a well established regulatory mechanism that regulates chromatin structure and dynamics, cell proliferation and differentiation, stress response and cell apoptosis. In the vertebrate eye, we and others have shown that sumoylation plays an indispensable role in regulating eye development. During stress induction and aging process, the ocular tissues gradually loss their normality and develop major ocular diseases such as cataract and aging-related macular degeneration. We have recently demonstrated that sumoylation actively regulates differentiation of lens cells, whether this process is implicated in lens pathogenesis remains to be investigated. In this study, we have demonstrated that transparent mouse lenses treated with glucose oxidase and UVA irradiation undergo in vitro cataract formation, and associated with this process, the expression patterns of the 3 sumoylation enzymes have been found significantly altered.

METHODS

Four-week-old C57BL/6J mice were used in our experiment. Lenses were carefully excised from eyes and cultured in M199 medium (Sigma 3769) for at least 12 hours. Transparent lenses (without surgical damage) were selected for experimentation. The lenses were exposed to UVA for 60 min or treated with 30 mU/mL glucose oxidase (GO, MP Biomedicals, 1673) to induce cataract formation. The mRNA levels were analysed with qRT-PCR. The protein levels were determined with western blot analysis and quantitated with Image J.

RESULTS

we have obtained the following results: 1) Both GO treatment and UVA irradiation can induce cataract formation in the in vitro cultured mouse lenses; 2) With GO treatment, the mRNAs and proteins for the 5 sumoylation enzymes were all significantly downregulated; 3) With UVA irradiation, the changes in the expression patterns of the mRNAs and proteins for the SAE1, UBA2 , UBC9 and PIAS1 were opposite, while the mRNAs were upregulated either significantly (for SAE1, UBA2 and UBC9) or slightly (PIAS1), the proteins for all 4 sumoylation enzymes were downregulated; For RanBP2, the UVA induced changes in both mRNA and protein are consist with the GO treatment.

CONCLUSION

Under GO and UVA irradiation conditions, the expression levels of both mRNA and protein for the three major sumoylation enzymes were significantly changed. Our results suggest that altered expression patterns of the sumoylation enzymes are associated with oxidative stressinduced cataractogenesis.

Analysis of Sumoylation

Protein regulation by reversible attachment of SUMO (small ubiquitin-related modifier) plays an important role in several cellular processes such as transcriptional regulation, nucleo-cytoplasmic transport, cell-cycle progression, meiosis, and DNA repair. However, most sumoylated proteins are of marginal abundance at steady state levels, which is due to strict regulation and/or rapid turnover of modification and de-modification. Consequently, analysis of protein sumoylation in vivo is very challenging. Nonetheless, a novel method was established that allows detection of sumoylated proteins at endogenous levels from vertebrate cells and tissues. This approach involves the enrichment of sumoylated proteins by immunoprecipitation followed by peptide elution. After endogenous substrate sumoylation is verified, addressing its functional consequences is the next logical step. This requires SUMO site mapping that benefits from larger quantities of modified protein. Here, we shortly describe strategies to achieve efficient in vitro sumoylation of many substrates.

SUMOylation of PCNA by PIAS1 and PIAS4 promotes template switch in the chicken and human B cell lines

DNA damage tolerance (DDT) releases replication blockage caused by damaged nucleotides on template strands employing two alternative pathways, error-prone translesion DNA synthesis (TLS) and error-free template switch (TS). Lys164 of proliferating cell nuclear antigen (PCNA) is SUMOylated during the physiological cell cycle. To explore the role for SUMOylation of PCNA in DDT, we characterized chicken DT40 and human TK6 B cells deficient in the PIAS1 and PIAS4 small ubiquitin-like modifier (SUMO) E3 ligases. DT40 cells have a unique advantage in the phenotypic analysis of DDT as they continuously diversify their immunoglobulin (Ig) variable genes by TLS and TS [Ig gene conversion (GC)], both relieving replication blocks at abasic sites without accompanying by DNA breakage. Remarkably, PIAS1 ^-/- /PIAS4 ^-/- cells displayed a multifold decrease in SUMOylation of PCNA at Lys164 and over a 90% decrease in the rate of TS. Likewise, PIAS1 ^-/- /PIAS4 ^-/- TK6 cells showed a shift of DDT from TS to TLS at a chemosynthetic UV lesion inserted into the genomic DNA. The PCNA ^K164R/K164R mutation caused a ∼90% decrease in the rate of Ig GC and no additional impact on PIAS1 ^-/- /PIAS4 ^-/- cells. This epistatic relationship between the PCNA ^K164R/K164R and the PIAS1 ^-/- /PIAS4 ^-/- mutations suggests that PIAS1 and PIAS4 promote TS mainly through SUMOylation of PCNA at Lys164. This idea is further supported by the data that overexpression of a PCNA-SUMO1 chimeric protein restores defects in TS in PIAS1 ^-/- /PIAS4 ^-/- cells. In conclusion, SUMOylation of PCNA at Lys164 promoted by PIAS1 and PIAS4 ensures the error-free release of replication blockage during physiological DNA replication in metazoan cells.

Targeted Ubiquitin-Proteasomal Proteolysis Pathway in Chronic Social Defeat Stress

Stressful events promote psychopathogenic changes that might contribute to the development of mental illnesses. Some individuals tend to recover from the stress response, while some do not. However, the molecular mechanisms of stress resilience during stress are not well-characterized. Here, we identify proteomic changes in the hippocampus using proteomic technique to examine mice following chronic social defeat stress. We showed that small ubiquitin-like modifier (SUMO)-1 expression was significantly decreased in susceptible mice following chronic social defeat stress. We also examined a protein inhibitor of activated signal transducer of transcription (PIAS)1 levels, an E3 SUMO-protein ligase protein inhibitor of activated STAT1, which is known to interact with SUMO-1. PIAS1 was shown to be profoundly decreased and monoamine oxidase (MAO)-A increased in the hippocampus of susceptible mice following chronic social defeat stress. Furthermore, the manipulated PIAS1 expression in the hippocampus also has an influence on glucocorticoid receptor (GR) translocation. We also found that knockdown of PIAS1 expression in the hippocampus then subject to submaximal stress increased GR to glucocorticoid response element (GRE)-binding site on the MAO-A promoter. The present study raises the possibility of different levels of PIAS1 between individuals in response to chronic social defeat stress and that such differences may contribute to the susceptibility to stress.

PIAS1 protects against myocardial ischemia-reperfusion injury by stimulating PPARγ SUMOylation

Background

Myocardial ischemia-reperfusion injury (IRI) has become one of the most serious complications after reperfusion therapy in patients with acute myocardial infarction. Small ubiquitin-like modification (SUMOylation) is a reversible process, including SUMO E1-, E2-, and E3-mediated SUMOylation and SUMO-specific protease-mediated deSUMOylation, with the latter having been shown to play a vital role in myocardial IRI previously. However, little is known about the function and regulation of SUMO E3 ligases in myocardial IRI.

Results

In this study, we found dramatically decreased expression of PIAS1 after ischemia/reperfusion (I/R) in mouse myocardium and H9C2 cells. PIAS1 deficiency aggravated apoptosis and inflammation of cardiomyocytes via activating the NF-κB pathway after I/R. Mechanistically, we identified PIAS1 as a specific E3 ligase for PPARγ SUMOylation. Moreover, H9C2 cells treated with hypoxia/reoxygenation (H/R) displayed reduced PPARγ SUMOylation as a result of down-regulated PIAS1, and act an anti-apoptotic and anti-inflammatory function through repressing NF-κB activity. Finally, overexpression of PIAS1 in H9C2 cells could remarkably ameliorate I/R injury.

Conclusions

Collectively, our findings demonstrate the crucial role of PIAS1-mediated PPARγ SUMOylation in protecting against myocardial IRI.

Electronic supplementary material

The online version of this article (10.1186/s12860-018-0176-x) contains supplementary material, which is available to authorized users.

B Cell Receptor Activation and Chemical Induction Trigger Caspase-Mediated Cleavage of PIAS1 to Facilitate Epstein-Barr Virus Reactivation

Epstein-Barr virus (EBV) in tumor cells is predominately in the latent phase, but the virus can undergo lytic reactivation in response to various stimuli. However, the cellular factors that control latency and lytic replication are poorly defined. In this study, we demonstrated that a cellular factor, PIAS1, restricts EBV lytic replication. PIAS1 depletion significantly facilitated EBV reactivation, while PIAS1 reconstitution had the opposite effect. Remarkably, we found that various lytic triggers promote caspase-dependent cleavage of PIAS1 to antagonize PIAS1-mediated restriction and that caspase inhibition suppresses EBV replication through blocking PIAS1 cleavage. We further demonstrated that a cleavage-resistant PIAS1 mutant suppresses EBV replication upon B cell receptor activation. Mechanistically, we demonstrated that PIAS1 acts as an inhibitor for transcription factors involved in lytic gene expression. Collectively, these results establish PIAS1 as a key regulator of EBV lytic replication and uncover a mechanism by which EBV exploits apoptotic caspases to antagonize PIAS1-mediated restriction.

Smad4 SUMOylation is essential for memory formation through upregulation of the skeletal myopathy gene TPM2

Background

Smad4 is a critical effector of TGF-β signaling that regulates a variety of cellular functions. However, its role in the brain has rarely been studied. Here, we examined the molecular mechanisms underlying the post-translational regulation of Smad4 function by SUMOylation, and its role in spatial memory formation.

Results

In the hippocampus, Smad4 is SUMOylated by the E3 ligase PIAS1 at Lys-113 and Lys-159. Both spatial training and NMDA injection enhanced Smad4 SUMOylation. Inhibition of Smad4 SUMOylation impaired spatial learning and memory in rats by downregulating TPM2, a gene associated with skeletal myopathies. Similarly, knockdown of TPM2 expression impaired spatial learning and memory, while TPM2 mRNA and protein expression increased after spatial training. Among the TPM2 mutations associated with skeletal myopathies, the TPM2E122K mutation was found to reduce TPM2 expression and impair spatial learning and memory in rats.

Conclusions

We have identified a novel role of Smad4 SUMOylation and TPM2 in learning and memory formation. These results suggest that patients with skeletal myopathies who carry the TPM2E122K mutation may also have deficits in learning and memory functions.

Electronic supplementary material

The online version of this article (doi:10.1186/s12915-017-0452-9) contains supplementary material, which is available to authorized users.

Sumoylation and Its Contribution to Cancer

Post-translational modifications play an important role in regulating protein activity by altering their functions. Sumoylation is a highly dynamic process which is tightly regulated by a fine balance between conjugating and deconjugating enzyme activities. It affects intracellular localization and their interaction with their binding partners, thereby changing gene expression. Consequently, these changes in turn affect signaling mechanisms that regulate many cellular functions, such as cell growth, proliferation, apoptosis , DNA repair , and cell survival. It is becoming apparent that deregulation in the SUMO pathway contributes to oncogenic transformation by affecting sumoylation/desumoylation of many oncoproteins and tumor suppressors. Loss of balance between sumoylation and desumoylation has been reported in a number of studies in a variety of disease types including cancer. This chapter summarizes the mechanisms and functions of the deregulated SUMO pathway affecting oncogenes and tumor suppressor genes.

Kr-POK (ZBTB7c) regulates cancer cell proliferation through glutamine metabolism

Kr-POK (ZBTB7c) is a kidney cancer-related POK transcription factor that not only represses transcription of CDKN1A but also increases expression of FASN. However, precisely how Kr-POK affects cell metabolism by controlling gene expression in response to an energy source in rapidly proliferating cells remains unknown. In this study, we characterized the molecular and functional features of Kr-POK in the context of tumor growth and glutamine metabolism. We found that cells expressing Kr-POK shRNA exhibited more severe cell death than control cells in glucose-deprived medium, and that knockdown of Kr-POK decreased glutamine uptake. Glutamine is critical for tumor cell proliferation. Glutaminase (GLS1), which is activated by p-STAT1, catalyzes the initial reaction in the pathway of glutaminolysis. Kr-POK interacts with PIAS1 to disrupt the interaction between PIAS1 and p-STAT1, and free p-STAT1 can activate GLS1 transcription through an interaction with p300. Kr-POK can be also sumoylated by PIAS1, facilitating Kr-POK degradation by the ubiquitin-mediated proteasomal pathway. Finally, we showed that repression of Kr-POK inhibited tumor growth in vivo in a xenograft model by repressing GLS1 expression. Taken together, our data reveal that Kr-POK activates GLS1 transcription and increases glutamine uptake to support rapid cancer cell proliferation.

Identification of novel NF-κB transcriptional targets in TNFα-treated HeLa and HepG2 cells

Identification of target genes of NF-κB is critical for deeply understanding its biological functions. Here, we identified five novel NF-κB target genes. Firstly, we found that 20 NF-κB potential target genes (PTGs) identified by ChIP-Seq and Genechip assay were enriched into the KEGG term of Pathways in cancer, 16 of them were enriched into the KEGG pathways of small cell lung cancer, chronic myeloid leukemia, basal cell carcinoma, pancreatic cancer, and colorectal cancer. Among these PTGs, there are many documented NF-κB target genes. Therefore, NF-κB may play important role in cancer progression by transcriptionally regulating these genes. Apart from the known target genes, we also found some novel PTGs including CYCS, MITF, FZD1, FZD8, and PIAS1. We subsequently demonstrated whether NF-κB transcriptionally control the five PTGs. The ChIP-Seq assay revealed that NF-κB/p65 bound to these genes in TNFα-treated HeLa. The bioinformatic analysis indicated that the NF-κB binding regions (i.e., ChIP-Seq peaks) contained κB sites and NF-κB/RelA DNA-binding motif. The ChIP-qPCR assay also confirmed that NF-κB bound to these regions in both TNFα-treated HeLa and HepG2 cells. The reporter construct showed that NF-κB could regulate luciferase expression via its binding region. Finally, qPCR and Western blot assay demonstrated that NF-κB indeed regulated the expression of these genes in the TNFα-treated HeLa and HepG2 cells. In a word, CYCS, MITF, FZD1, FZD8, and PIAS1 were identified as bona fide NF-κB target genes. These findings provide more insights into the role of NF-κB in cancers.

Leukemogenic kinase FIP1L1-PDGFRA and a small ubiquitin-like modifier E3 ligase, PIAS1, form a positive cross-talk through their enzymatic activities

Fusion tyrosine kinases play a crucial role in the development of hematological malignancies. FIP1L1‐PDGFRA is a leukemogenic fusion kinase that causes chronic eosinophilic leukemia. As a constitutively active kinase, FIP1L1‐PDGFRA stimulates downstream signaling molecules, leading to cellular proliferation and the generation of an anti‐apoptotic state. Contribution of the N‐terminal FIP1L1 portion is necessary for FIP1L1‐PDGFRA to exert its full transforming activity, but the underlying mechanisms have not been fully characterized. We identified PIAS1 as a FIP1L1‐PDGFRA association molecule by yeast two‐hybrid screening. Our analyses indicate that the FIP1L1 portion of FIP1L1‐PDGFRA is required for efficient association with PIAS1. As a consequence of the association, FIP1L1‐PDGFRA phosphorylates PIAS1. Moreover, the kinase activity of FIP1L1‐PDGFRA stabilizes PIAS1. Therefore, PIAS1 is one of the downstream targets of FIP1L1‐PDGFRA. Moreover, we found that PIAS1, as a SUMO E3 ligase, sumoylates and stabilizes FIP1L1‐PDGFRA. In addition, suppression of PIAS1 activity by a knockdown experiment resulted in destabilization of FIP1L1‐PDGFRA. Therefore, FIP1L1‐PDGFRA and PIAS1 form a positive cross‐talk through their enzymatic activities. Suppression of sumoylation by ginkgolic acid, a small molecule compound inhibiting a SUMO E1‐activating enzyme, also destabilizes FIP1L1‐PDGFRA, and while the tyrosine kinase inhibitor imatinib suppresses FIP1L1‐PDGFRA‐dependent cell growth, ginkgolic acid or siRNA of PIAS1 has a synergistic effect with imatinib. In conclusion, our results suggest that sumoylation by PIAS1 is a potential target in the treatment of FIP1L1‐PDGFRA‐positive chronic eosinophilic leukemia.

c-Myc is targeted to the proteasome for degradation in a SUMOylation-dependent manner, regulated by PIAS1, SENP7 and RNF4

c-Myc is the most frequently overexpressed oncogene in tumors, including breast cancer, colon cancer and lung cancer. Post-translational modifications comprising phosphorylation, acetylation and ubiquitylation regulate the activity of c-Myc. Recently, it was shown that c-Myc-driven tumors are strongly dependent on the SUMO pathway. Currently, the relevant SUMO target proteins in this pathway are unknown. Here we show that c-Myc is a target protein for SUMOylation, and that SUMOylated c-Myc is subsequently ubiquitylated and degraded by the proteasome. SUMO chains appeared to be dispensable for this process, polymerization-deficient SUMO mutants supported proteolysis of SUMOylated c-Myc. These results indicate that multiple SUMO monomers conjugated to c-Myc could be sufficient to direct SUMOylated c-Myc to the ubiquitin-proteasome pathway. Knocking down the SUMO-targeted ubiquitin ligase RNF4 enhanced the levels of SUMOylated c-Myc, indicating that RNF4 could recognize a multi-SUMOylated protein as a substrate in addition to poly-SUMOylated proteins. Knocking down the SUMO E3 ligase PIAS1 resulted in reduced c-Myc SUMOylation and increased c-Myc transcriptional activity, indicating that PIAS1 mediates c-Myc SUMOylation. Increased SUMOylation of c-Myc was noted upon knockdown of the SUMO protease SENP7, indicating that it also could regulate a multi-SUMOylated protein in addition to poly-SUMOylated proteins. C-Myc lacks KxE-type SUMOylation consensus motifs. We used mass spectrometry to identify 10 SUMO acceptor lysines: K52, K148, K157, K317, K323, K326, K389, K392, K398 and K430. Intriguingly, mutating all 10 SUMO acceptor lysines did not reduce c-Myc SUMOylation, suggesting that SUMO acceptor lysines in c-Myc act promiscuously. Our results provide novel insight into the complexity of c-Myc post-translational regulation.

PIAS1 binds p300 and behaves as a coactivator or corepressor of the transcription factor c-Myb dependent on SUMO-status

The PIAS proteins (Protein Inhibitor of Activated STATs) constitute a family of multifunctional nuclear proteins operating as SUMO E3 ligases and being involved in a multitude of interactions. They participate in a range of biological processes, also beyond their well-established role in the immune system and cytokine signalling. They act both as transcriptional corepressors and coactivators depending on the context. In the present work, we investigated mechanisms by which PIAS1 causes activation or repression of c-Myb dependent target genes. Analysis of global expression data shows that c-Myb and PIAS1 knockdowns affect a subset of common targets, but with a dual outcome consistent with a role of PIAS1 as either a corepressor or coactivator. Our mechanistic studies show that PIAS1 engages in a novel interaction with the acetyltransferase and coactivator p300. Interaction and ChIP analysis suggest a bridging function where PIAS1 enhances p300 recruitment to c-Myb-bound sites through interaction with both proteins. In addition, the E3 activity of PIAS1 enhances further its coactivation. Remarkably, the SUMO status of c-Myb had a decisive role, indicating a SUMO-dependent switch in the way PIAS1 affects c-Myb, either as a coactivator or corepressor. Removal of the two major SUMO-conjugation sites in c-Myb (2KR mutant), which enhances its activity significantly, turned PIAS1 into a corepressor. Also, p300 was less efficiently recruited to chromatin by c-Myb-2KR. We propose that PIAS1 acts as a "protein inhibitor of activated c-Myb" in the absence of SUMOylation while, in its presence, PIAS behaves as a "protein activator of repressed c-Myb".

A Fluorescent In Vitro Assay to Investigate Paralog-Specific SUMO Conjugation

Protein modification with the small ubiquitin-related modifier SUMO is a potent regulatory mechanism implicated in a variety of biological pathways. In vitro sumoylation reactions have emerged as a versatile tool to identify and characterize novel SUMO enzymes as well as their substrates. Here, we present detailed protocols for the purification and fluorescent labeling of mammalian SUMO paralogs for their application in sumoylation assays. These assays provide a fast readout for in vitro SUMO chain formation activity of E3 ligases in a paralog-specific manner. Finally, we critically analyze the application of fluorescent SUMO proteins to study substrate modification in vitro revealing also the drawbacks of the system.

Androgen receptor- and PIAS1-regulated gene programs in molecular apocrine breast cancer cells

We have analyzed androgen receptor (AR) chromatin binding sites (ARBs) and androgen-regulated transcriptome in estrogen receptor negative molecular apocrine breast cancer cells. These analyses revealed that 42% of ARBs and 39% androgen-regulated transcripts in MDA-MB453 cells have counterparts in VCaP prostate cancer cells. Pathway analyses showed a similar enrichment of molecular and cellular functions among AR targets in both breast and prostate cancer cells, with cellular growth and proliferation being among the most enriched functions. Silencing of the coregulator SUMO ligase PIAS1 in MDA-MB453 cells influenced AR function in a target-selective fashion. An anti-apoptotic effect of the silencing suggests involvement of the PIAS1 in the regulation of cell death and survival pathways. In sum, apocrine breast cancer and prostate cancer cells share a core AR cistrome and target gene signature linked to cancer cell growth, and PIAS1 plays a similar coregulatory role for AR in both cancer cell types.

RSRC1 SUMOylation enhances SUMOylation and inhibits transcriptional activity of estrogen receptor β

The transcription factor estrogen receptor β (ERβ) plays roles in the central nervous, endocrine, cardiovascular, and immune systems. ERβ can be SUMOylated. However, the underlying mechanism remains unclear. Here, we show that RSRC1/SRrp53 interacts with ERβ and SUMOylation of RSRC1 is required for regulation of PIAS1-mediated ERβ SUMOylation. RSRC1 promotes ERβ SUMOylation through enhanced interaction between ERβ and PIAS1. RSRC1 represses ERβ transcriptional activity through regulation of ERβ SUMOylation. By establishing RSRC1 as a novel cofactor for SUMOylation, our data provide insight into regulation of ERβ SUMOylation and indicate that SUMOylation of one protein can regulate another protein SUMOylation.

CREB SUMOylation by the E3 ligase PIAS1 enhances spatial memory

cAMP-responsive element binding protein (CREB) phosphorylation and signaling plays an important role in long-term memory formation, but other posttranslational modifications of CREB are less known. Here, we found that CREB1Δ, the short isoform of CREB, could be sumoylated by the small ubiquitin-like modifier (SUMO) E3 ligase protein inhibitor of activated STAT1 (PIAS1) at Lys271 and Lys290 and PIAS1 SUMOylation of CREB1Δ increased the expression level of CREB1Δ. CREB1Δ could also be sumoylated by other PIAS family proteins, but not by the E3 ligases RanBP2 and Pc2 or by the E2 ligase Ubc9. Furthermore, water maze training increased the level of endogenous CREB SUMOylation in rat CA1 neurons determined by in vitro SUMOylation assay, but this effect was not observed in other brain areas. Moreover, transduction of Lenti-CREBWT to rat CA1 area facilitated, whereas transduction of Lenti-CREB double sumo-mutant (CREBK271RK290R) impaired, spatial learning and memory performance. Transduction of Lenti-CREBWT-SUMO1 fusion vector to rat CA1 area showed a more significant effect in enhancing spatial learning and memory and CREB SUMOylation. Lenti-CREBWT transduction increased, whereas Lenti-CREBK271RK290R transduction decreased, CREB DNA binding to the brain-derived neurotrophic factor (bdnf) promoter and decreased bdnf mRNA expression. Knock-down of PIAS1 expression in CA1 area by PIAS1 siRNA transfection impaired spatial learning and memory and decreased endogenous CREB SUMOylation. In addition, CREB SUMOylation was CREB phosphorylation dependent and lasted longer. Therefore, CREB phosphorylation may be responsible for signal transduction during the early phase of long-term memory formation, whereas CREB SUMOylation sustains long-term memory.

PIAS1 and STAT-3 impair the tumoricidal potential of IFN-γ-stimulated mouse dendritic cells generated with IL-15

Primarily defined by their antigen-presenting property, dendritic cells (DCs) are being implemented as cancer vaccines in immunotherapeutic interventions. DCs can also function as direct tumor cell killers. How DC cytotoxic activity can be efficiently harnessed and the mechanisms controlling this nonconventional property are not fully understood. We report here that the tumoricidal potential of mouse DCs generated from myeloid precursors with GM-CSF and IL-15 (IL-15 DCs) can be triggered with the Toll-like receptor (TLR) 4 ligand lipopolysaccharide to a similar extent compared with that of their counterparts, conventionally generated with IL-4 (IL-4 DCs). The mechanism of tumor cell killing depends on the induction of iNOS expression by DCs. In contrast, interferon (IFN)-γ induces the cytotoxic activity of IL-4 but not IL-15 DCs. Although the IFN-γ-STAT-1 signaling pathway is overall functional in IL-15 DCs, IFN-γ fails to induce iNOS expression in these cells. iNOS expression is negatively controlled in IFN-γ-stimulated IL-15 DCs by the cooperation between the E3 SUMO ligase PIAS1 and STAT-3, and can be partially restored with PIAS1 siRNA and STAT-3 inhibitors.

A novel role for the SUMO E3 ligase PIAS1 in cancer metastasis

Tumor metastasis contributes to the grave morbidity and mortality of cancer, but the mechanisms underlying tumor cell invasiveness and metastasis remain incompletely understood. Here, we report that expression of the SUMO E3 ligase PIAS1 suppresses TGFβ-induced activation of the matrix metalloproteinase MMP2 in human breast cancer cells. We also find that knockdown of endogenous PIAS1 or inhibition of its SUMO E3 ligase activity stimulates the ability of TGFβ to induce an aggressive phenotype in three-dimensional breast cancer cell organoids. Importantly, inhibition of the SUMO E3-ligase activity of PIAS1 in breast cancer cells promotes metastases in mice in vivo. Collectively, our findings define a novel and critical role for the SUMO E3 ligase PIAS1 in the regulation of the invasive and metastatic potential of malignant breast cancer cells. These findings advance our understanding of cancer invasiveness and metastasis with potential implications for the development of biomarkers and therapies in breast cancer.

The biophysical and biochemical properties of the autoimmune regulator (AIRE) protein

AIRE (for autoimmune regulator) is a multidomain protein that performs a fundamental function in the thymus and possibly in the secondary lymphoid organs: the regulation, especially in the sense of activation, of the process of gene transcription in cell lines deputed to the presentation of self-antigens to the maturing T lymphocytes. The apoptosis of the elements bearing T-cell receptors with critical affinity for the exhibited self-antigens prevents the escape of autoreactive clones and represents a simple and efficient mechanism of deletional self-tolerance. However, AIRE action relies on an articulated complex of biophysical and biochemical properties, in most cases attributable to single subspecialized domains. Here a thorough review of the matter is presented, with a privileged look at the pathogenic changes of AIRE that interfere with such properties and lead to the impairment in its chief function.

Pleiotropic effects of methionine adenosyltransferases deregulation as determinants of liver cancer progression and prognosis

Downregulation of liver-specific MAT1A gene, encoding S-adenosylmethionine (SAM) synthesizing isozymes MATI/III, and upregulation of widely expressed MAT2A, encoding MATII isozyme, known as MAT1A:MAT2A switch, occurs in hepatocellular carcinoma (HCC). Being inhibited by its reaction product, MATII isoform upregulation cannot compensate for MATI/III decrease. Therefore, MAT1A:MAT2A switch contributes to decrease in SAM level in rodent and human hepatocarcinogenesis. SAM administration to carcinogen-treated rats prevents hepatocarcinogenesis, whereas MAT1A-KO mice, characterized by chronic SAM deficiency, exhibit macrovesicular steatosis, mononuclear cell infiltration in periportal areas, and HCC development. This review focuses upon the pleiotropic changes, induced by MAT1A/MAT2A switch, associated with HCC development. Epigenetic control of MATs expression occurs at transcriptional and post-transcriptional levels. In HCC cells, MAT1A/MAT2A switch is associated with global DNA hypomethylation, decrease in DNA repair, genomic instability, and signaling deregulation including c-MYC overexpression, rise in polyamine synthesis, upregulation of RAS/ERK, IKK/NF-kB, PI3K/AKT, and LKB1/AMPK axis. Furthermore, decrease in MAT1A expression and SAM levels results in increased HCC cell proliferation, cell survival, and microvascularization. All of these changes are reversed by SAM treatment in vivo or forced MAT1A overexpression or MAT2A inhibition in cultured HCC cells. In human HCC, MAT1A:MAT2A and MATI/III:MATII ratios correlate negatively with cell proliferation and genomic instability, and positively with apoptosis and global DNA methylation. This suggests that SAM decrease and MATs deregulation represent potential therapeutic targets for HCC. Finally, MATI/III:MATII ratio strongly predicts patients' survival length suggesting that MAT1A:MAT2A expression ratio is a putative prognostic marker for human HCC.

PIAS1 negatively modulates virus triggered type I IFN signaling by blocking the DNA binding activity of IRF3

During viral infection, production of proinflammatory cytokines including type I interferons (IFNs) is under stringent control to avoid detrimental overreaction. The protein inhibitor of activated STAT (PIAS) family proteins have been recognized as anti-inflammatory molecules by restraining type I IFN induced amplifying signaling. Here we identified PIAS1 as an important negative regulator of virus-triggered type I IFN signaling. Overexpression of PIAS1 repressed virus-or RIG-I like receptor stimulated type I IFN transcription, whereas knockdown of PIAS1 expression augmented virus-induced production of type I IFNs. PIAS1 with a mutation in the SAP domain retained the inhibitory function in virus-induced IFN transcription, but abolished the inhibition in IFN-stimulated signaling. SUMO E3 ligase activity dead mutant PIAS1/C350S still had the comparable inhibitory function with WT PIAS1. Further study indicated that PIAS1 interacted with IRF3 and inhibited the DNA binding activity of IRF3. The C-terminal region of PIAS1 around a cluster of acidic amino acids is critical for the interaction with IRF3 and the inhibitory functions of PIAS1. Therefore, these results unveil PIAS1 functions both at the virus-induced early signaling stage and IFN stimulated amplifying stage with distinct mechanisms. PIAS1 is important in maintaining proper amounts of type I IFNs and restrains its magnitude when the antiviral response intensifies.