The SUMOylation of zinc-fingers and homeoboxes 1 (ZHX1) by Ubc9 regulates its stability and transcriptional repression activity

Acupuncture for radicular pain: a review of analgesic mechanism

Radicular pain, a common and complex form of neuropathic pain, presents significant challenges in treatment. Acupuncture, a therapy originating from ancient traditional Chinese medicine and widely utilized for various pain types, including radicular pain, has shown promising outcomes in the management of lumbar radicular pain, cervical radicular pain, and radicular pain due to spinal stenosis. Despite its efficacy, the exact mechanisms through which acupuncture achieves analgesia are not fully elucidated and are the subject of ongoing research. This review sheds light on the current understanding of the analgesic mechanisms of acupuncture for radicular pain, offering valuable perspectives for both clinical application and basic scientific research. Acupuncture is postulated to relieve radicular pain by several mechanisms: peripherally, it reduces muscle spasms, lessens mechanical pressure on nerve roots, and improves microcirculation; at the molecular level, it inhibits the HMGB1/RAGE and TLR4/NF-κB signaling pathways, thereby decreasing the release of pro-inflammatory cytokines; within the spinal cord, it influences synaptic plasticity; and centrally, it modulates brain function, particularly affecting the medial prefrontal cortex, anterior cingulate cortex, and thalamus within the default mode network. By acting across these diverse biological domains, acupuncture presents an effective treatment modality for radicular pain, and deepening our understanding of the underlying mechanisms regarding analgesia for radicular pain is crucial for enhancing its clinical efficacy and advancement in pain management.

Post-translational Modification Control of HBV Biological Processes

Hepatitis B virus infection remains a global healthy issue that needs to be urgently solved. Novel strategies for anti-viral therapy are based on exploring the effective diagnostic markers and therapeutic targets of diseases caused by hepatitis B virus (HBV) infection. It is well-established that not only viral proteins themselves but also key factors from the host control the biological processes associated with HBV, including replication, transcription, packaging, and secretion. Protein post-translational modifications (PTMs), such as phosphorylation, acetylation, methylation, and ubiquitination, have been shown to control protein activity, regulate protein stability, promote protein interactions and alter protein subcellular localization, leading to the modulation of crucial signaling pathways and affected cellular processes. This review focuses on the functions and effects of diverse PTMs in regulating important processes in the HBV life cycle. The potential roles of PTMs in the pathogenesis of HBV-associated liver diseases are also discussed.

Small ubiquitin-related modifier 1 is involved in hepatocellular carcinoma progression via mediating p65 nuclear translocation

Small ubiquitin-related modifier (SUMO) proteins participate in a post-translational modification called SUMOylation and regulate a variety of intracellular processes, such as targeting proteins for nuclear import. The nuclear transport of p65 results in the activation of NF-κB, and p65 contains several SUMO interacting motifs (SIMs). However, the relationship between p65 and SUMO1 in hepatocellular carcinoma (HCC) remains unclear. In this study, we demonstrated the potential roles of SUMO1 in HCC via the regulation of p65 subcellular localization. We found that either SUMO1- or p65-positive immunoreactivity was remarkably increased in the nuclei of tumor tissues in HCC patients compared with non-tumor tissues, and further analysis suggested a correlation between SUMO1- and nuclear p65-positive immunoreactivities (R = 0.851, P = 0.002). We also verified the interaction between p65 and SUMO1 in HCC by co-immunoprecipitation. TNF-α and hypoxia increased SUMO1 protein levels and enhanced SUMO1-modified p65 SUMOylation. Moreover, the knockdown of SUMO1 decreased p65 nuclear translocation and inhibited NF-κB transcriptional activity. Further the results of this study revealed that the knockdown of SUMO1 suppressed the proliferation and migration of hepatoma cells. These results suggest that SUMO1 contributes to HCC progression by promoting p65 nuclear translocation and regulating NF-κB activity.

Regulation of transcription factors by sumoylation

Transcription factors (TFs) are among the most frequently detected targets of sumoylation, and effects of the modification have been studied for about 200 individual TFs to date. TF sumoylation is most often associated with reduced target gene expression, which can be mediated by enhanced interactions with corepressors or by interference with protein modifications that promote transcription. However, recent studies show that sumoylation also regulates gene expression by controlling the levels of TFs that are associated with chromatin. SUMO can mediate this by modulating TF DNA-binding activity, promoting clearance of TFs from chromatin, or indirectly, by influencing TF abundance or localization.

ZHX1 Promotes the Proliferation, Migration and Invasion of Cholangiocarcinoma Cells

Zinc-fingers and homeoboxes 1 (ZHX1) is a transcription repressor that has been associated with the progressions of hepatocellular carcinoma, gastric cancer, and breast cancer. However, the functional roles of ZHX1 in cholangiocarcinoma (CCA) have not been determined. We investigated the expression and roles of ZHX1 during the proliferation, migration, and invasion of CCA cells. In silico analysis and immunohistochemical studies showed amplification and overexpression of ZHX1 in CCA tissues. Furthermore, ZHX1 knockdown using specific siRNAs decreased CCA cell proliferation, migration, and invasion, whereas ZHX1 overexpression promoted all three characteristics. In addition, results suggested EGR1 might partially mediate the effect of ZHX1 on the proliferation of CCA cells. Taken together, these results show ZHX1 promotes CCA cell proliferation, migration, and invasion, and present ZHX1 as a potential target for the treatment of CCA.

The Key Regulator for Language and Speech Development, FOXP2, is a Novel Substrate for SUMOylation

Transcription factor forkhead box protein P2 (FOXP2) plays an essential role in the development of language and speech. However, the transcriptional activity of FOXP2 regulated by the post-translational modifications remains unknown. Here, we demonstrated that FOXP2 is clearly defined as a SUMO target protein at the cellular levels as FOXP2 is covalently modified by both SUMO1 and SUMO3. Furthermore, SUMOylation of FOXP2 was significantly decreased by SENP2 (a specific SUMOylation protease). We further showed that FOXP2 is selectively SUMOylated in vivo on a phylogenetically conserved lysine 674 but the SUMOylation does not alter subcellular localization and stability of FOXP2. Interestingly, we observed that human etiological FOXP2 R553H mutation robustly reduces its SUMOylation potential as compared to wild-type FOXP2. In addition, the acidic residues downstream the core SUMO motif on FOXP2 are required for its full SUMOylation capacity. Finally, our functional analysis using reporter gene assays showed that SUMOylation may modulate transcriptional activity of FOXP2 in regulating downstream target genes (DISC1, SRPX2, and MiR200c). Altogether, we provide the first evidence that FOXP2 is a substrate for SUMOylation and SUMOylation of FOXP2 plays a functional role in regulating its transcriptional activity.

Ubiquitin ligase Fbw7 restricts the replication of hepatitis C virus by targeting NS5B for ubiquitination and degradation

The nonstructural protein 5B (NS5B) of hepatitis C virus (HCV) is an RNA-dependent RNA polymerase (RdRp) and responsible for replicating the whole HCV genome with help of viral and cellular proteins. However, how cellular factors influence NS5B and, in turn, regulating HCV replication are still poorly defined. The well known tumor suppressor Fbw7, a component of E3 ubiquitin ligase SCF(Fbw7), targets oncoproteins or cellular regulatory proteins for ubiquitin-mediated degradation through a highly conserved binding site called a Cdc4 phosphodegron (CPD). But little is known about whether Fbw7 plays a role in regulation of viral proteins. In this study, we revealed that the conserved CPD is shared by NS5B of almost all genotype of HCV and our data demonstrated that NS5B is a bona fide substrate of Fbw7. Forced expression of Fbw7 promoted the ubiquination of NS5B and negatively regulated its turnover in the proteasome-dependent manner. We further revealed the interaction between NS5B and Fbw7, which resulted in the relocation of Fbw7 from nucleus to cytoplasm. During HCV replication, ectopic expression of Fbw7 could strongly down-regulate NS5B level and consequently inhibited the virus replication. When endogenous Fbw7 was knocked down, both NS5B protein abundance and HCV replication were remarkably up-regulated. The results provide more insights into the interplay of HCV and cellular factors and shed light on molecular mechanisms of HCV replication and pathogenesis.

Small ubiquitin-related modifier 2/3 interacts with p65 and stabilizes it in the cytoplasm in HBV-associated hepatocellular carcinoma

Background

SUMOylation, an important post-translational modification, associates with the development of hepatocellular carcinoma (HCC). p65, one of the most important subunits of NF-κB, is a key regulator in the development of HCC and has been reported to be SUMOylated by exogenous small ubiquitin-related modifier 3 (SUMO3) in HEK 293T cells. However, the relationship between p65 and SUMO2/3 in HCC remains unknown. This study was to investigate the interaction between p65 and SUMO2/3 and explore the potential roles involved in HCC.

Methods

The expressions of p65 and SUMO2/3 in the liver tissues were detected by using immunohistochemistry. We performed double-labeled immunofluorescence and co-immunoprecipitation assay to verify the interaction between p65 and SUMO2/3. The extraction of nuclear and cytoplasmic proteins was performed, and the subcellular localization of p65 was detected. The proliferation and migration of hepatoma cells were observed using MTT, colony formation, and transwell assays.

Results

We found a strong SUMO2/3-positive immunoreactivity in the cytoplasm in the non-tumor tissues of HCC. However, SUMO2/3 level was down regulated in the tumor tissues as compared with the adjacent non-tumor tissues. In accordance with this finding, p65 was up regulated in the adjacent non-tumor tissues and almost localized in the cytoplasm. There was a close correlation between SUMO2/3 and p65 expressions in the liver tissues (R = 0.800, p = 0.006). The interaction between p65 and SUMO2/3 was verified by co-immunoprecipitation and double-labeled immunofluorescent assays. TNF-α (10 ng/ml) treatment for 30 min not only up regulated the cytoplasmic conjugated SUMO2/3, but also enhanced SUMO2/3-p65 interaction. Furthermore, we found that SUMO2/3 up regulated the cytoplasmic p65 protein level in a dose-dependent manner, but not affected its mRNA level. The increase of p65 protein by SUMO2/3 was abolished by MG132 treatment, a reversible inhibitor of proteasome. Meanwhile, TNF-α-induced increase of SUMO2/3-conjugated p65 was along with the reduction of the ubiquitin-conjugated p65. The further study showed that SUMO2/3 over-expression decreased the proliferative ability of hepatoma cells, but did not affect the migration.

Conclusion

SUMO2/3-p65 interaction may be a novel mechanism involved in the transformation from chronic hepatitis B to HCC via stabilizing cytoplasmic p65, which might shed light on understanding the tumorigenesis and development.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1665-3) contains supplementary material, which is available to authorized users.

Aberrantly Expressed OTX Homeobox Genes Deregulate B-Cell Differentiation in Hodgkin Lymphoma

In Hodgkin lymphoma (HL) we recently reported that deregulated homeobox gene MSX1 mediates repression of the B-cell specific transcription factor ZHX2. In this study we investigated regulation of MSX1 in this B-cell malignancy. Accordingly, we analyzed expression and function of OTX homeobox genes which activate MSX1 transcription during embryonal development in the neural plate border region. Our data demonstrate that OTX1 and OTX2 are aberrantly expressed in both HL patients and cell lines. Moreover, both OTX loci are targeted by genomic gains in overexpressing cell lines. Comparative expression profiling and subsequent pathway modulations in HL cell lines indicated that aberrantly enhanced FGF2-signalling activates the expression of OTX2. Downstream analyses of OTX2 demonstrated transcriptional activation of genes encoding transcription factors MSX1, FOXC1 and ZHX1. Interestingly, examination of the physiological expression profile of ZHX1 in normal hematopoietic cells revealed elevated levels in T-cells and reduced expression in B-cells, indicating a discriminatory role in lymphopoiesis. Furthermore, two OTX-negative HL cell lines overexpressed ZHX1 in correlation with genomic amplification of its locus at chromosomal band 8q24, supporting the oncogenic potential of this gene in HL. Taken together, our data demonstrate that deregulated homeobox genes MSX1 and OTX2 respectively impact transcriptional inhibition of (B-cell specific) ZHX2 and activation of (T-cell specific) ZHX1. Thus, we show how reactivation of a specific embryonal gene regulatory network promotes disturbed B-cell differentiation in HL.

Severe acute respiratory syndrome coronavirus protein 6 mediates ubiquitin-dependent proteosomal degradation of N-Myc (and STAT) interactor

Severe acute respiratory syndrome coronavirus (SARS-CoV) encodes eight accessory proteins, the functions of which are not yet fully understood. SARS-CoV protein 6 (P6) is one of the previously studied accessory proteins that have been documented to enhance viral replication and suppress host interferon (IFN) signaling pathways. Through yeast two-hybrid screening, we identified eight potential cellular P6-interacting proteins from a human spleen cDNA library. For further investigation, we targeted the IFN signaling pathway-mediating protein, N-Myc (and STAT) interactor (Nmi). Its interaction with P6 was confirmed within cells. The results showed that P6 can promote the ubiquitin-dependent proteosomal degradation of Nmi. This study revealed a new mechanism of SARS-CoV P6 in limiting the IFN signaling to promote SARS-CoV survival in host cells.

VHL negatively regulates SARS coronavirus replication by modulating nsp16 ubiquitination and stability

Eukaryotic cellular and most viral RNAs carry a 5′-terminal cap structure, a 5′-5′ triphosphate linkage between the 5′ end of the RNA and a guanosine nucleotide (cap-0). SARS coronavirus (SARS-CoV) nonstructural protein nsp16 functions as a methyltransferase, to methylate mRNA cap-0 structure at the ribose 2′-O position of the first nucleotide to form cap-1 structures. However, whether there is interplay between nsp16 and host proteins was not yet clear. In this report, we identified several potential cellular nsp16-interacting proteins from a human thymus cDNA library by yeast two-hybrid screening. VHL, one of these proteins, was proven to interact with nsp16 both in vitro and in vivo. Further studies showed that VHL can inhibit SARS-CoV replication by regulating nsp16 ubiquitination and promoting its degradation. Our results have revealed the role of cellular VHL in the regulation of SARS-CoV replication.

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Several host proteins were identified to interact with SARS-CoV nsp16 by yeast two-hybrid screening.

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VHL was found to interact with SARS-CoV nsp16 and promotes nsp16 degradation.

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VHL involves in regulating nsp16 ubiquination and stability, and modulating SARS-CoV replication.

MiR-199a-3p promotes gastric cancer progression by targeting ZHX1

Accumulating evidence has indicated that microRNAs (miRNAs) act as critical epigenetic regulators in tumor carcinogenesis. Here, we report that miR-199a-3p was significantly upregulated in gastric cancer (GC) cell lines and tissues. Functional studies demonstrated that miR-199a-3p dramatically increased cell proliferation and suppressed cell apoptosis both in vitro and in vivo. Furthermore, the transcriptional regulator zinc fingers and homeoboxes 1 (ZHX1) was identified as one of the direct downstream targets of miR-199a-3p, miR-199a-3p bound to the ZHX1 3′ untranslated region (3′UTR) to regulate ZHX1 protein expression. In addition, the expression of miR-199a-3p was inversely associated with that of ZHX1 in GC cell lines. Overexpression of miR-199a-3p in SGC-7901 cells inhibited ZHX1 expression, while reduction in miR-199a-3p by inhibitors in NCI-N87 cells enhanced ZHX1 expression. Moreover, restoring ZHX1 expression in SGC-7901/miR-199a-3p cells inhibited the cell proliferation induced by miR-199a-3p. Taken together, these findings suggest that miR-199a-3p may function as a novel tumor promoter in GC and its oncogenic activity may involve the direct targeting and inhibition of ZHX1.

A non-SUMOylated tax protein is still functional for NF-κB pathway activation

Whether NF-κB promoter transactivation by the human T-cell leukemia virus type 1 (HTLV-1) Tax protein requires Tax SUMOylation is still a matter of debate. In this study, we revisited the role of Tax SUMOylation using a strategy based on the targeting of Ubc9, the unique E2 SUMO-conjugating enzyme. We show that either a catalytically inactive form of Ubc9 (Ubc9-C93S) or Ubc9 small interfering RNA (siRNA) dramatically reduces Tax conjugation to endogenous SUMO-1 or SUMO-2/3, demonstrating that as expected, Tax SUMOylation is under the control of the catalytic activity of Ubc9. We further report that a non-SUMOylated Tax protein produced in 293T cells is still able to activate either a transfected or an integrated NF-κB reporter promoter and to induce expression of an NF-κB-regulated endogenous gene. Importantly, blocking Ubc9 activity in T cells also results in the production of a non-SUMOylated Tax that is still fully functional for the activation of a NF-κB promoter. These results provide the definitive evidence that Tax SUMOylation is not required for NF-κB-driven gene induction.

IMPORTANCE

Human T-cell leukemia virus type 1 is able to transform CD4(+) T lymphocytes. The viral oncoprotein Tax plays a key role in this process by promoting cell proliferation and survival, mainly through permanent activation of the NF-κB pathway. Elucidating the molecular mechanisms involved in NF-κB pathway activation by Tax is therefore a key issue to understand HTLV-1-mediated transformation. Tax SUMOylation was initially proposed to be critical for Tax-induced NF-κB promoter activation, which was challenged by our later observation that a low-level-SUMOylated Tax mutant was still functional for activation of NF-κB promoters. To clarify the role of Tax SUMOylation, we set up a new approach based on the inhibition of the SUMOylation machinery in Tax-expressing cells. We show that blocking the SUMO-conjugating enzyme Ubc9 abolishes Tax SUMOylation and that a non-SUMOylated Tax still activates NF-κB promoters in either adherent cells or T cells.

Solution NMR structures of homeodomains from human proteins ALX4, ZHX1, and CASP8AP2 contribute to the structural coverage of the Human Cancer Protein Interaction Network

High-quality solution NMR structures of three homeodomains from human proteins ALX4, ZHX1 and CASP8AP2 were solved. These domains were chosen as targets of a biomedical theme project pursued by the Northeast Structural Genomics Consortium. This project focuses on increasing the structural coverage of human proteins associated with cancer.