TRIM3 facilitates estrogen signaling and modulates breast cancer cell progression.

BACKGROUND: Breast cancer is the most common cancer in women worldwide. More than 70% of breast cancers are estrogen receptor (ER) alpha positive. Compared with ER alpha-negative breast cancer, which is more aggressive and has a shorter survival time, ER alpha-positive breast cancer could benefit from endocrine therapy. Selective estrogen receptor modulators, such as tamoxifen, are widely used in endocrine therapy. Approximately half of ER alpha-positive breast cancer patients will eventually develop endocrine resistance, making it a major clinical challenge in therapy. Thus, decoding the throughput of estrogen signaling, including the control of ER alpha expression and stability, is critical for the improvement of breast cancer therapeutics. METHODS: TRIM3 and ER alpha protein expression levels were measured by western blotting, while the mRNA levels of ER alpha target genes were measured by RT-PCR. A CCK-8 assay was used to measure cell viability. RNA sequencing data were analyzed by Ingenuity Pathway Analysis. Identification of ER alpha signaling activity was accomplished with luciferase assays, RT-PCR and western blotting. Protein stability assays and ubiquitin assays were used to detect ER alpha protein degradation. Ubiquitin-based immunoprecipitation assays were used to detect the specific ubiquitination modification on the ER alpha protein. RESULTS: In our current study, we found that TRIM3, an E3 ligase, can promote ER alpha signaling activity and breast cancer progression. TRIM3 depletion inhibits breast cancer cell proliferation and migration, while unbiased RNA sequencing data indicated that TRIM3 is required for the activity of estrogen signaling on the -genome-wide scale. The immunoprecipitation assays indicated that TRIM3 associates with ER alpha and promotes its stability, possibly by inducing K63-linked polyubiquitination of ER alpha. In conclusion, our data implicate a nongenomic mechanism by which TRIM3 stabilizes the ER alpha protein to control ER alpha target gene expression linked to breast cancer progression. CONCLUSION: Our study provides a novel posttranslational mechanism in estrogen signaling. Modulation of TRIM3 expression or function could be an interesting approach for breast cancer treatment. Video abstract.

ZNF213 negatively controls triple negative breast cancer progression via Hippo/YAP signaling.

Breast cancer is one of the most commonly diagnosed malignancies worldwide, while the triple negative breast cancer (TNBC) is the most aggressive and virulent subtype in breast cancers. Compared with luminal type breast cancers, which could be well controlled by endocrine treatment, TNBC is worse in prognosis and lack of effective targeted therapy. Thus, it would be interesting and meaningful to identify novel therapeutic targets for TNBC treatments. Recent genomic data showed the activation of Hippo/YAP signaling in TNBC, indicating its critical roles in TNBC carcinogenesis and cancer progression. Hippo/YAP signaling could subject to several kinds of protein modifications, including ubiquitination and phosphorylation. Quite a few studies have demonstrated these modifications, which controlled YAP protein stability and turnover, played critical role in Hippo signaling activation In our current study, we identified ZNF213 as a negative modifier for Hippo/YAP axis. ZNF213 depletion promoted TNBC cell migration and invasion, which could be rescued by further YAP silencing. ZNF213 knocking down facilitated YAP protein stability and Hippo target gene expression, including CTGF and CYR61. Further mechanism studies demonstrated that ZNF213 associated with YAP and facilitated YAP K48-linked poly-ubiquitination at several YAP lysine sites (K252, K254, K321 and K497). Besides, the clinical data showed that ZNF213 negatively correlated with YAP protein level and Hippo target gene expression in TNBC samples. ZNF213 expression correlated with good prognosis in TNBC patients. Our data provided novel insights in YAP proteolytic regulation and TNBC progression.

Regulatory innate lymphoid cells suppress innate immunity and reduce renal ischemia/reperfusion injury.

Innate lymphoid cells are a recently recognized group of immune cells with critical roles in tissue homeostasis and inflammation. Regulatory innate lymphoid cells are a newly identified subset of innate lymphoid cells, which play a suppressive role in the innate immune response, favoring the resolution of intestinal inflammation. However, the expression and role of regulatory innate lymphoid cells in kidney has not been reported. Here, we show that regulatory innate lymphoid cells are present in both human and mouse kidney, express similar surface markers and form a similar proportion of total kidney innate lymphoid cells. Regulatory innate lymphoid cells from kidney were expanded in vitro with a combination of IL-2, IL-7 and transforming growth factor-ß. These cells exhibited immunosuppressive effects on innate immune cells via secretion of IL-10 and transforming growth factor-ß. Moreover, treatment with IL-2/IL-2 antibody complexes (IL-2C) promoted expansion of regulatory innate lymphoid cells in vivo, and prevent renal ischemia/reperfusion injury in Rag-/- mice that lack adaptive immune cells including Tregs. Depletion of regulatory innate lymphoid cells with anti-CD25 antibody abolished the beneficial effects of IL-2C in the Rag-/- mice. Adoptive transfer of ex vivo expanded regulatory innate lymphoid cells improved renal function and attenuated histologic damage when given before or after induction of ischemia/reperfusion injury in association with reduction of neutrophil infiltration and induction of reparative M2 macrophages in kidney. Thus, our study shows that regulatory innate lymphoid cells suppress innate renal inflammation and ischemia/reperfusion injury.

The three members of the Vav family proteins form complexes that concur to foam cell formation and atherosclerosis.

During foam cell formation and atherosclerosis development, the scavenger receptor CD36 plays critical roles in lipid uptake and triggering of atherogenicity via the activation of Vav molecules. The Vav family includes three highly conserved members known as Vav1, Vav2, and Vav3. As Vav1 and Vav3 were found to exert function in atherosclerosis development, it remains thus to decipher whether Vav2 also plays a role in the development of atherosclerosis. In this study we found that Vav2 deficiency in RAW264.7 macrophages significantly diminished oxidized LDL uptake and CD36 signaling, demonstrating that each Vav protein family member was required for foam cell formation. Genetic disruption of Vav2 in ApoE-deficient C57BL/6 mice significantly inhibited the severity of atherosclerosis. Strikingly, we further found that the genetic deletion of each member of the Vav protein family by CRISPR/Cas9 resulted in a similar alteration of transcriptomic profiles of macrophages. The three members of the Vav proteins were found to form complexes, and genetic ablation of each single Vav molecule was sufficient to prevent endocytosis of CD36. The functional interdependence of the three Vav family members in foam cell formation was due to their indispensable roles in transcriptomic programing, lipid uptake, and activation of the JNK kinase in macrophages.

A Biomass-Derived Carbon-Based Electrocatalyst for Efficient N2 Fixation to NH3 under Ambient Conditions.

Currently, NH3 production primarily depends on the Haber-Bosch process, which operates at elevated temperatures and pressures and leads to serious CO2 emissions. Electrocatalytic N2 reduction offers an environmentally benign approach for the sustainable synthesis of NH3 under ambient conditions. This work reports the development of biomass-derived amorphous oxygen-doped carbon nanosheet (O-CN) using tannin as the precursor. As a metal-free electrocatalyst for N2 -to-NH3 conversion, such O-CN shows high catalytic performances, achieving a large NH3 yield of 20.15 µg h-1 mg-1 cat. and a high Faradic efficiency of 4.97 % at -0.6 V vs. reversible hydrogen electrode (RHE) in 0.1 m HCl at ambient conditions. Remarkably, it also exhibits high electrochemical selectivity and durability.

Potentiating Tissue-Resident Type 2 Innate Lymphoid Cells by IL-33 to Prevent Renal Ischemia-Reperfusion Injury.

The IL-33-type 2 innate lymphoid cell (ILC2) axis has an important role in tissue homeostasis, inflammation, and wound healing. However, the relative importance of this innate immune pathway for immunotherapy against inflammation and tissue damage remains unclear. Here, we show that treatment with recombinant mouse IL-33 prevented renal structural and functional injury and reduced mortality in mice subjected to ischemia-reperfusion injury (IRI). Compared with control-treated IRI mice, IL-33-treated IRI mice had increased levels of IL-4 and IL-13 in serum and kidney and more ILC2, regulatory T cells (Tregs), and anti-inflammatory (M2) macrophages. Depletion of ILC2, but not Tregs, substantially abolished the protective effect of IL-33 on renal IRI. Adoptive transfer of ex vivo-expanded ILC2 prevented renal injury in mice subjected to IRI. This protective effect associated with induction of M2 macrophages in kidney and required ILC2 production of amphiregulin. Treatment of mice with IL-33 or ILC2 after IRI was also renoprotective. Furthermore, in a humanized mouse model of renal IRI, treatment with human IL-33 or transfer of ex vivo-expanded human ILC2 ameliorated renal IRI. This study has uncovered a major protective role of the IL-33-ILC2 axis in renal IRI that could be potentiated as a therapeutic strategy.

IL-25 Elicits Innate Lymphoid Cells and Multipotent Progenitor Type 2 Cells That Reduce Renal Ischemic/Reperfusion Injury.

IL-25 is an important immune regulator that can promote Th2 immune response-dependent immunity, inflammation, and tissue repair in asthma, intestinal infection, and autoimmune diseases. In this study, we examined the effects of IL-25 in renal ischemic/reperfusion injury (IRI). Treating IRI mice with IL-25 significantly improved renal function and reduced renal injury. Furthermore, IL-25 treatment increased the levels of IL-4, IL-5, and IL-13 in serum and kidney and promoted induction of alternatively activated (M2) macrophages in kidney. Notably, IL-25 treatment also increased the frequency of type 2 innate lymphoid cells (ILC2s) and multipotent progenitor type 2 (MPP(type2)) cells in kidney. IL-25-responsive ILC2 and MPP(type2) cells produced greater amounts of Th2 cytokines that associated with the induction of M2 macrophages and suppression of classically activated (M1) macrophages in vitro. Finally, adoptive transfer of ILC2s or MPP(type2) cells not only reduced renal functional and histologic injury in IRI mice but also induced M2 macrophages in kidney. In conclusion, our data identify a mechanism whereby IL-25-elicited ILC2 and MPP(type2) cells regulate macrophage phenotype in kidney and prevent renal IRI.

Type 2 innate lymphoid cells are protective against hepatic ischaemia/reperfusion injury.

Background and Aims: Although type 2 innate lymphoid cells (ILC2s) were originally found to be liver-resident lymphocytes, the role and importance of ILC2 in liver injury remains poorly understood. In the current study, we sought to determine whether ILC2 is an important regulator of hepatic ischaemia/reperfusion injury (IRI). Methods: ILC2-deficient mice (ICOS-T or NSG) and genetically modified ILC2s were used to investigate the role of ILC2s in murine hepatic IRI. Interactions between ILC2s and eosinophils or macrophages were studied in coculture. The role of human ILC2s was assessed in an immunocompromised mouse model of hepatic IRI. Results: Administration of IL-33 prevented hepatic IRI in association with reduction of neutrophil infiltration and inflammatory mediators in the liver. IL-33-treated mice had elevated numbers of ILC2s, eosinophils, and regulatory T cells. Eosinophils, but not regulatory T cells, were required for IL-33-mediated hepatoprotection in IRI mice. Depletion of ILC2s substantially abolished the protective effect of IL-33 in hepatic IRI, indicating that ILC2s play critical roles in IL-33-mediated liver protection. Adoptive transfer of ex vivo-expanded ILC2s improved liver function and attenuated histologic damage in mice subjected to IRI. Mechanistic studies combining genetic and adoptive transfer approaches identified a protective role of ILC2s through promoting IL-13-dependent induction of anti-inflammatory macrophages and IL-5-dependent elevation of eosinophils in IRI. Furthermore, in vivo expansion of human ILC2s by IL-33 or transfer of ex vivo-expanded human ILC2s ameliorated hepatic IRI in an immunocompromised mouse model of hepatic IRI. Conclusions: This study provides insight into the mechanisms of ILC2-mediated liver protection that could serve as therapeutic targets to treat acute liver injury. Impact and Implications: We report that type 2 innate lymphoid cells (ILC2s) are important regulators in a mouse model of liver ischaemia/reperfusion injury (IRI). Through manipulation of macrophage and eosinophil phenotypes, ILC2s mitigate liver inflammation and injury during liver IRI. We propose that ILC2s have the potential to serve as a therapeutic tool for protecting against acute liver injury and lay the foundation for translation of ILC2 therapy to human liver disease.

RBCK1 regulates the progression of ER-positive breast cancer through the HIF1α signaling.

Breast cancer is the most common malignancy in women on a global scale. It can generally be divided into four main categories, of which estrogen receptor ER-positive breast cancer accounts for most breast cancer cases. RBCK1 protein is an E3 ubiquitin ligase containing the UBL, NZF, and RBR domains. It is well known to exhibit abnormal expression in breast tumors, making it a valuable diagnostic marker and drug target. Additionally, studies have confirmed that in breast cancer, about 25 to 40% of tumors appear as visible hypoxic regions, while in hypoxia, tumor cells can activate the hypoxia-inducing factor HIF1 pathway and widely activate the expression of downstream genes. Previous studies have confirmed that in the hypoxic environment of tumors, HIF1α promotes the remodeling of extracellular matrix, induces the recruitment of tumor-associated macrophages (TAM) and immunosuppression of allogeneic tumors, thereby influencing tumor recurrence and metastasis. This research aims to identify RBCK1 as an important regulator of HIF1α signaling pathway. Targeted therapy with RBCK1 could be a promising treatment strategy for ER-positive breast cancer.

UHRF1 modulates breast cancer cell growth via estrogen signaling.

The ubiquitination process, which involves that binding of an ubiquitin protein to certain substrates, regulates several human biological processes and human cancers. Several studies report that the abnormal expression of quite a few E3 ubiquitin ligases could play critical role in carcinogenic process and cancer progression. In our current study, we identify UHRF1 (Ubiquitin Like with PHD And Ring Finger Domain 1) is an important regulator for breast cancer growth. UHRF1 depletion significantly decreases breast cancer growth in vitro and in vivo. Clinical data analysis reveals that UHRF1 is dramatically elevated in breast cancer, compared to normal breast tissue. UHRF1 correlates with poor survival in luminal type of breast cancer patients, but not in ER-negative groups. The molecular biological studies show that UHRF1 localizes in the nuclear and interact with ERα via its SRA domain, which subsequently inhibits K48-linked ubiquitination of ERα and enhances ERα stability. Our study provides a novel function of UHRF1 in regulation estrogen signaling in breast cancer and a promising target for breast cancer therapeutics.

Regulation of P53 signaling in breast cancer by the E3 ubiquitin ligase RNF187.

The tumor suppressor P53 plays critical role in preventing cancer. P53 is rarely mutated and remains functional in luminal-type breast cancer(1). According to current knowledge, wild-type P53 function is tightly controlled by posttranslational modifications, such as ubiquitination. Several ubiquitin ligases have been shown to regulate P53 ubiquitination and protein stability. Here, we report that RNF187, a RING family ubiquitin ligase, facilitates breast cancer growth and inhibits apoptosis by modulating P53 signaling. RNF187 expression was elevated in breast cancer and correlated with breast cancer survival only in the P53 wild-type groups. Bioinformatic analysis showed that the expression of RNF187 was negatively correlated with the expression of P53 target genes, such as IGFBP3 and FAS, in breast cancer. RNF187 depletion inhibited breast cancer growth and facilitated cell death. RNA sequencing analysis indicated that RNF187 could be an important modulator of P53 signaling. Further experiments showed that RNF187 interacts with P53 and promotes its degradation by facilitating its polyubiquitination in breast cancer cells. Interestingly, the in vitro ubiquitin assay showed that RNF187 can directly ubiquitinate P53 in a manner independent of MDM2. These findings reveal a novel direct P53 regulator and a potential therapeutic target for breast cancer.

ZNF213 Facilitates ER Alpha Signaling in Breast Cancer Cells.

BACKGROUND: Breast cancer is the most common women malignancy worldwide, while estrogen receptor alpha positive type accounts for two third of all breast cancers. Although ER alpha positive breast cancer could be effectively controlled by endocrine therapy, more than half of the cases could develop endocrine resistance, making it an important clinical issue in breast cancer treatment. Thus, decoding the detailed mechanism, which controls ER alpha signaling activation and ER alpha protein stability, is of great importance for the improvement of breast cancer therapy. Several zinc finger proteins were shown to mediate the ubiquitination process and modulate protein stability. Thus, we further explore the function of Zinc finger protein 213 on ER alpha protein stability and tamoxifen resistance. METHODS: CCK8 and Edu assay was used to measure cell proliferation. RNA sequence was performed by Ingenuity pathway analysis. The ER alpha signaling activities were measured with luciferase assay, real-time quantitative PCR, and western blotting. Protein stability assay and ubiquitin assay were used to determine ER alpha protein degradation and ubiquitination. The immuno-precipitation was utilized to determine ER alpha and ZNF213 interaction. The ubiquitin-based immuno-precipitation assay was sued to detect specific ubiquitination manner on ER alpha. RESULTS: We identified ZNF213 as a novel zinc finger protein, which modulated ER alpha protein. ZNF213 expression correlated with poor outcome in endocrine treated patients. ZNF213 depletion inhibited ER alpha signaling and proliferation in breast cancer cells. Further mechanistic studies showed ZNF213 located in cytosol and nuclear, which modulated ER alpha stability via inhibiting ER alpha K48-linked ubiquitination. CONCLUSIONS: Our study reveals an interesting post-translational mechanism between ER alpha and ZNF213 in breast cancer. Targeting ZNF213 could be an appealing strategy for ER alpha positive breast cancer.

The E3 Ubiquitin Ligase HOIP inhibits Cancer Cell Apoptosis via modulating PTEN stability.

Chemotherapy is widely used in a variety of solid tumors, such as lung cancer, gastric cancer and breast cancer. The genotoxic drugs, such as cisplatin, suppress cancer progression either by inhibition cell proliferation or facilitating apoptosis. However, the chemotherapy resistance remains an urgent challenge in cancer therapy, especially in advanced stages. Several studies showed that the activation of pro-survival pathways, such as PI3K-AKT, participated in mediating chemotherapy resistance. The insights into the molecular mechanisms for underlying chemotherapy resistance are of great importance to improve cancer patient survival in advanced stages. The HOIP protein belongs to the RING family E3 ubiquitin ligases and modulates several atypical ubiquitination processes in cellular signaling. Previous studies showed that HOIP might be an important effector in modulating cancer cell death under genotoxic drugs. Here, we report that HOIP associates with PTEN and facilitates PTEN degradation in cancer cells. Depletion of HOIP causes cell cycle arrest and apoptosis, which effects could be rescued by PTEN silencing. Besides, the survival data from public available database show that HOIP expression correlates with poor survival in several types of chemotherapy-treated cancer patients. In conclusion, our study establishes a novel mechanism by which HOIP modulates PTEN stability and facilitates chemotherapy resistance in malignancies.

The deubiquitinating enzyme USP1 modulates ERα and modulates breast cancer progression.

Breast cancer is one of the most common malignancies worldwide, while the luminal types (ERα positive) accounts for two third of all breast cancer cases. Although ERα positive breast cancer could be effective controlled by endocrine therapy, most of the patients will develop endocrine resistance, which becomes a headache clinical issue for breast cancer field. Endocrine resistance could be caused by multiple pathway disorders, the dys-regulation of ERα signaling might be a critical factor, which makes it urgent and important to reveal the potential molecular mechanism of ERα signaling. In our current study, we identified a new deubiquitination enzyme USP1 through screening the whole DUB (Deubiquitinases) siRNA library. The expression of USP1 is elevated in human breast cancer compared with normal mammary tissues. Importantly, USP1 expression levels are specially correlated with poor survival in ERα positive patients. USP1 depletion inhibited breast cancer cell progression and ERα signaling activity. Immuno-precipitation assays indicate that USP1 associates with ERα and promotes its stability possibly via inhibiting ERα K48-linked poly-ubiquitination. In conclusion, our data implicate a non-genomic mechanism by USP1 via stabilizing ERα protein controls ERα target gene expression linked to breast cancer progression.

IL-10 producing type 2 innate lymphoid cells prolong islet allograft survival.

Type 2 innate lymphoid cells (ILC2s) are a subset of ILCs with critical roles in immunoregulation. However, the possible role of ILC2s as immunotherapy against allograft rejection remains unclear. Here, we show that IL-33 significantly prolonged islet allograft survival. IL-33-treated mice had elevated numbers of ILC2s and regulatory T cells (Tregs). Depletion of Tregs partially abolished the protective effect of IL-33 on allograft survival, and additional ILC2 depletion in Treg-depleted DEREG mice completely abolished the protective effects of IL-33, indicating that ILC2s play critical roles in IL-33-mediated islet graft protection. Two subsets of ILC2s were identified in islet allografts of IL-33-treated mice: IL-10 producing ILC2s (ILC210 ) and non-IL-10 producing ILC2s (non-ILC10 ). Intravenous transfer of ILC210 cells, but not non-ILC10 , prolonged islet allograft survival in an IL-10-dependent manner. Locally transferred ILC210 cells led to long-term islet graft survival, suggesting that ILC210 cells are required within the allograft for maximal suppressive effect and graft protection. This study has uncovered a major protective role of ILC210 in islet transplantation which could be potentiated as a therapeutic strategy.

Defect-rich fluorographene nanosheets for artificial N2 fixation under ambient conditions.

NH3, synthesized by the Haber-Bosch process, is essential for fertilisers in order to feed the world's growing population, however, it causes massive energy consumption and generates large amounts of greenhouse gases. Electrochemical N2 reduction reaction (NRR) at ambient conditions is highly desirable for energy-efficient and sustainable NH3 production but this requires an efficient catalyst. In this work, we report a defect-rich fluorographene nanosheet synthesised via fluorination of graphene for NRR electrocatalysis. Such an electrocatalyst shows an NH3 formation rate of 9.3 µg h-1 mgcat.-1 and a faradaic efficiency of 4.2% at -0.7 V vs. reversible hydrogen electrode in 0.1 M Na2SO4. Density functional theory calculations reveal that the fluorination of graphene induces defects, which not only provide reaction sites for NRR but effectively activate N2 molecules.

HTLV-1 Tax upregulates early growth response protein 1 through nuclear factor-κB signaling.

Human T cell leukemia virus type 1 (HTLV-1) is a complex retrovirus that causes adult T cell leukemia (ATL) in susceptible individuals. The HTLV-1-encoded oncoprotein Tax induces persistent activation of the nuclear factor-κB (NF-κB) pathway. Early growth response protein 1 (EGR1) is overexpressed in HTLV-1-infected T cell lines and ATL cells. Here, we showed that both Tax expression and HTLV-1 infection promoted EGR1 overexpression. Loss of the NF-κB binding site in the EGR1 promotor or inhibition of NF-κB activation reduced Tax-induced EGR1 upregulation. Tax mutants unable to activate NF-κB induced only slight EGR1 upregulation as compared with wild-type Tax, confirming NF-κB pathway involvement in EGR1 regulation. Tax also directly interacted with the EGR1 protein and increased endogenous EGR1 stability. Elevated EGR1 in turn promoted p65 nuclear translocation and increased NF-κB activation. These results demonstrate a positive feedback loop between EGR1 expression and NF-κB activation in HTLV-1-infected and Tax-expressing cells. Both NF-κB activation and Tax-induced EGR1 stability upregulated EGR1, which in turn enhanced constitutive NF-κB activation and facilitated ATL progression in HTLV-1-infected cells. These findings suggest EGR1 may be an effective anti-ATL therapeutic target.

Bcl-3 suppresses Tax-induced NF-κB activation through p65 nuclear translocation blockage in HTLV-1-infected cells.

Human T cell leukemia virus type 1 (HTLV-1) Tax-induced persistent activation of the NF-κB pathway is perceived as the primary cause of adult T cell leukemia (ATL), an aggressive leukemia caused by HTLV-1. Although elevated oncoprotein Bcl-3 levels are found in many HTLV-1-infected T cell lines and ATL cells, the role of Bcl-3 in the malignant progression caused by HTLV-1 retrovirus remains poorly understood. We confirmed, in the present study, that the Tax-induced NF-κB activation involves the regulation of Bcl-3. Both knockdown and overexpression of Bcl-3 inhibit the Tax-induced NF-κB activation. Similarly, excessive Bcl-3 inhibits the NF-κB/DNA binding activity and significantly decreases Tax-induced p65 nuclear translocation. The present results demonstrate the pleiotropic roles of Bcl-3 in Tax-induced NF-κB activation and indicate that a balance in the aberrant Bcl-3 expression may be established to play an important role in the maintenance of proliferation and inhibition of apoptosis in HTLV-1-infected and ATL cells.

Tax is involved in up-regulation of HMGB1 expression levels by interaction with C/EBP.

The high mobility group box 1 (HMGB1) protein is a multifunctional cytokine-like molecule that plays an important role in the pathogenesis of tumors. In this study, real-time polymerase chain reactions and Western blot assays indicated that HMGB1 transcriptional activity and protein level are increased in Tax+-T cells (TaxP). To clarify the mechanisms, a series of HMGB1 deletion reporter plasmids (pHLuc1 to pHLuc6) were transfected into Tax--T cells (TaxN, Jurkat) and Tax+-T cells (TaxP). We found that promoter activity in Tax+-T cells to be higher than that in Tax--T cells, indicating a significant increase in pHLuc6. Bay11-7082 (NF-κB inhibitor) treatment did not block the enhancing effect. Chromatin immunoprecipitation assays revealed that Tax was retained on a HMGB1 promoter fragment encompassing -1163 to -975. Bioinformatics analysis showed six characteristic cis-elements for CdxA, AP-1, AML-1a, USF, v-Myb, and C/EBP in the fragment in question. Mutation of cis- elements for C/EBP reduced significant HMGB1 promoter activity induced by Tax. These findings indicate that Tax enhances the expression of HMGB1 gene at the transcriptional level, possibly by interacting with C/EBP.

The pyrimidine analog FNC inhibits cell proliferation and viral protein synthesis in HTLV­1­infected cells.

Human T­cell leukemia virus type 1 (HTLV­1), the first retrovirus to be identified, is the etiological agent of an aggressive clonal malignancy of mature CD4+ T lymphocytes known as adult T­cell leukemia (ATL). The prognosis of ATL patients remains poor despite the availability of a number of clinical chemotherapy drugs. In addition, HTLV­1­infected and ATL cells possess an intrinsic resistance to anticancer drugs. 2'­Deoxy­2'­ß­fluoro­4'­azidocytidine (FNC) is a novel pyrimidine analog that is efficiently phosphorylated by cellular kinases and is a substrate for RNA and DNA polymerases. In the present study, the antiviral potential of FNC was investigated in HTLV­1­infected cell lines. Following FNC treatment, the HTLV­1­infected cells underwent G1 or S phase cell cycle arrest. FNC was also observed to reduce cell growth of the HTLV­1­infected cell lines in a dose­dependent manner. Notably, FNC was found to efficiently inhibit the expression of the viral proteins, Tax and p19Gag, in a dose­ and time­dependent manner. Treatment with FNC and the protein biosynthesis inhibitor, cycloheximide (CHX), accelerated the inhibition of viral protein synthesis in the HTLV­1­infected cells. Collectively, these results demonstrated the efficient antiretroviral effect of FNC in HTLV­1­infected cells and indicate that FNC may be utilized as a valuable therapy in HTLV­1­infected patients and those with ATL.