Comparison of Cytomegalovirus-Specific Immune Cell Response to Proteins versus Peptides Using an IFN-γ ELISpot Assay after Hematopoietic Stem Cell Transplantation.

Cytomegalovirus (CMV) infection is a major cause of morbidity and mortality following hematopoietic stem cell transplantation (HSCT). Measuring CMV-specific cellular immunity may improve the risk stratification and management of patients. IFN-γ ELISpot assays, based on the stimulation of peripheral blood mononuclear cells with CMV pp65 and IE-1 proteins or peptides, have been validated in clinical settings. However, it remains unclear to which extend the T-cell response to synthetic peptides reflect that mediated by full-length proteins processed by antigen-presenting cells. We compared the stimulating ability of pp65 and IE-1 proteins and corresponding overlapping peptides in 16 HSCT recipients using a standardized IFN-γ ELISpot assay. Paired qualitative test results showed an overall 74.4% concordance. Discordant results were mainly due to low-response tests, with one exception. One patient with early CMV reactivation and graft-versus-host disease, sustained CMV DNAemia and high CD8+ counts showed successive negative protein-based ELISpot results but a high and sustained response to IE-1 peptides. Our results suggest that the response to exogenous proteins, which involves their uptake and processing by antigen-presenting cells, more closely reflects the physiological response to CMV infection, while the response to exogenous peptides may lead to artificial in vitro T-cell responses, especially in strongly immunosuppressed patients.

Standardized monitoring of cytomegalovirus-specific immunity can improve risk stratification of recurrent cytomegalovirus reactivation after hematopoietic stem cell transplantation.

Recurrence of cytomegalovirus reactivation remains a major cause of morbidity and mortality following allogeneic hematopoietic stem cell transplantation. Monitoring cytomegalovirus-specific cellular immunity using a standardized assay might improve the risk stratification of patients. A prospective multicenter study was conducted in 175 intermediate- and high-risk allogeneic hematopoietic stem cell transplant recipients under preemptive antiviral therapy. Cytomegalovirus-specific cellular immunity was measured using a standardized IFN-γ ELISpot assay (T-Track® CMV). Primary aim was to evaluate the suitability of measuring cytomegalovirus-specific immunity after end of treatment for a first cytomegalovirus reactivation to predict recurrent reactivation. 40/101 (39.6%) patients with a first cytomegalovirus reactivation experienced recurrent reactivations, mainly in the high-risk group (cytomegalovirus-seronegative donor/cytomegalovirus-seropositive recipient). The positive predictive value of T-Track® CMV (patients with a negative test after the first reactivation experienced at least one recurrent reactivation) was 84.2% in high-risk patients. Kaplan-Meier analysis revealed a higher probability of recurrent cytomegalovirus reactivation in high-risk patients with a negative test after the first reactivation (hazard ratio 2.73; p=0.007). Interestingly, a post-hoc analysis considering T-Track® CMV measurements at day 100 post-transplantation, a time point highly relevant for outpatient care, showed a positive predictive value of 90.0% in high-risk patients. Our results indicate that standardized cytomegalovirus-specific cellular immunity monitoring may allow improved risk stratification and management of recurrent cytomegalovirus reactivation after hematopoietic stem cell transplantation. This study was registered at www.clinicaltrials.gov as #NCT02156479.

An optimized IFN-γ ELISpot assay for the sensitive and standardized monitoring of CMV protein-reactive effector cells of cell-mediated immunity.

BACKGROUND: In healthy individuals, Cytomegalovirus (CMV) infection is efficiently controlled by CMV-specific cell-mediated immunity (CMI). Functional impairment of CMI in immunocompromized individuals however can lead to uncontrolled CMV replication and severe clinical complications. Close monitoring of CMV-specific CMI is therefore clinically relevant and might allow a reliable prognosis of CMV disease as well as assist personalized therapeutic decisions. METHODS: Objective of this work was the optimization and technical validation of an IFN-γ ELISpot assay for a standardized, sensitive and reliable quantification of CMV-reactive effector cells. T-activated® immunodominant CMV IE-1 and pp65 proteins were used as stimulants. All basic assay parameters and reagents were tested and optimized to establish a user-friendly protocol and maximize the signal-to-noise ratio of the ELISpot assay. RESULTS: Optimized and standardized ELISpot revealed low intra-assay, inter-assay and inter-operator variability (coefficient of variation CV below 22%) and CV inter-site was lower than 40%. Good assay linearity was obtained between 6 × 104 and 2 × 105 PBMC per well upon stimulation with T-activated® IE-1 (R2 = 0.97) and pp65 (R2 = 0.99) antigens. Remarkably, stimulation of peripheral blood mononuclear cells (PBMC) with T-activated® IE-1 and pp65 proteins resulted in the activation of a broad range of CMV-reactive effector cells, including CD3+CD4+ (Th), CD3+CD8+ (CTL), CD3-CD56+ (NK) and CD3+CD56+ (NKT-like) cells. Accordingly, the optimized IFN-γ ELISpot assay revealed very high sensitivity (97%) in a cohort of 45 healthy donors, of which 32 were CMV IgG-seropositive. CONCLUSION: The combined use of T-activated® IE-1 and pp65 proteins for the stimulation of PBMC with the optimized IFN-γ ELISpot assay represents a highly standardized, valuable tool to monitor the functionality of CMV-specific CMI with great sensitivity and reliability.

Assessing HDAC Function in the Regulation of Signal Transducer and Activator of Transcription 5 (STAT5) Activity Using Chromatin Immunoprecipitation (ChIP).

Transcriptional activation by STAT5 is repressed by deacetylase inhibitors. Investigating the role of deacetylases (HDACs) in STAT5-mediated transcription implies the analysis of molecular events taking place at the chromatin level. We describe here two alternative methods of chromatin immunoprecipitation that allow the characterization of chromatin modifications ensuing STAT5 activation and its inhibition by deacetylase inhibitors, in particular changes in histone acetylation, in histone occupancy, and in the association/dissociation of transcription factors and other chromatin-associated factors.

The Chemopreventive Phytochemical Moringin Isolated from Moringa oleifera Seeds Inhibits JAK/STAT Signaling.

Sulforaphane (SFN) and moringin (GMG-ITC) are edible isothiocyanates present as glucosinolate precursors in cruciferous vegetables and in the plant Moringa oleifera respectively, and recognized for their chemopreventive and medicinal properties. In contrast to the well-studied SFN, little is known about the molecular pathways targeted by GMG-ITC. We investigated the ability of GMG-ITC to inhibit essential signaling pathways that are frequently upregulated in cancer and immune disorders, such as JAK/STAT and NF-κB. We report for the first time that, similarly to SFN, GMG-ITC in the nanomolar range suppresses IL-3-induced expression of STAT5 target genes. GMG-ITC, like SFN, does not inhibit STAT5 phosphorylation, suggesting a downstream inhibitory event. Interestingly, treatment with GMG-ITC or SFN had a limited inhibitory effect on IFNα-induced STAT1 and STAT2 activity, indicating that both isothiocyanates differentially target JAK/STAT signaling pathways. Furthermore, we showed that GMG-ITC in the micromolar range is a more potent inhibitor of TNF-induced NF-κB activity than SFN. Finally, using a cellular system mimicking constitutive active STAT5-induced cell transformation, we demonstrated that SFN can reverse the survival and growth advantage mediated by oncogenic STAT5 and triggers cell death, therefore providing experimental evidence of a cancer chemopreventive activity of SFN. This work thus identified STAT5, and to a lesser extent STAT1/STAT2, as novel targets of moringin. It also contributes to a better understanding of the biological activities of the dietary isothiocyanates GMG-ITC and SFN and further supports their apparent beneficial role in the prevention of chronic illnesses such as cancer, inflammatory diseases and immune disorders.

Inhibition of interleukin-3- and interferon- α-induced JAK/STAT signaling by the synthetic α-X-2',3,4,4'-tetramethoxychalcones α-Br-TMC and α-CF3-TMC.

The JAK/STAT pathway is an essential mediator of cytokine signaling, often upregulated in human diseases and therefore recognized as a relevant therapeutic target. We previously identified the synthetic chalcone α-bromo-2',3,4,4'-tetramethoxychalcone (α-Br-TMC) as a novel JAK2/STAT5 inhibitor. We also found that treatment with α-Br-TMC resulted in a downward shift of STAT5 proteins in SDS-PAGE, suggesting a post-translational modification that might affect STAT5 function. In the present study, we show that a single cysteine within STAT5 is responsible for the α-Br-TMC-induced protein shift, and that this modification does not alter STAT5 transcriptional activity. We also compared the inhibitory activity of α-Br-TMC to that of another synthetic chalcone, α-trifluoromethyl-2',3,4,4'-tetramethoxychalcone (α-CF3-TMC). We found that, like α-Br-TMC, α-CF3-TMC inhibits JAK2 and STAT5 phosphorylation in response to interleukin-3, however without altering STAT5 mobility in SDS-PAGE. Moreover, we demonstrate that both α-Br-TMC and α-CF3-TMC inhibit interferon-α-induced activation of STAT1 and STAT2, by inhibiting their phosphorylation and the expression of downstream interferon-stimulated genes. Together with the previous finding that α-Br-TMC and α-CF3-TMC inhibit the response to inflammation by inducing Nrf2 and blocking NF-κB activities, our data suggest that synthetic chalcones might be useful as anti-inflammatory, anti-cancer and immunomodulatory agents in the treatment of human diseases.

Signal transducer and activator of transcription STAT5 is recruited to c-Myc super-enhancer.

BACKGROUND: c-Myc has been proposed as a putative target gene of signal transducer and activator of transcription 5 (STAT5). No functional STAT5 binding site has been identified so far within the c-Myc gene locus, therefore a direct transcriptional regulation by STAT5 remains uncertain. c-Myc super-enhancer, located 1.7 Mb downstream of the c-Myc gene locus, was recently reported as essential for the regulation of c-Myc gene expression by hematopoietic transcription factors and bromodomain and extra-terminal (BET) proteins and for leukemia maintenance. c-Myc super-enhancer is composed of five regulatory regions (E1-E5) which recruit transcription and chromatin-associated factors, mediating chromatin looping and interaction with the c-Myc promoter. RESULTS: We now show that STAT5 strongly binds to c-Myc super-enhancer regions E3 and E4, both in normal and transformed Ba/F3 cells. We also found that the BET protein bromodomain-containing protein 2 (BRD2), a co-factor of STAT5, co-localizes with STAT5 at E3/E4 in Ba/F3 cells transformed by the constitutively active STAT5-1*6 mutant, but not in non-transformed Ba/F3 cells. BRD2 binding at E3/E4 coincides with c-Myc transcriptional activation and is lost upon treatment with deacetylase and BET inhibitors, both of which inhibit STAT5 transcriptional activity and c-Myc gene expression. CONCLUSIONS: Our data suggest that constitutive STAT5 binding to c-Myc super-enhancer might contribute to BRD2 maintenance and thus allow sustained expression of c-Myc in Ba/F3 cells transformed by STAT5-1*6.

Revisited anti-inflammatory activity of matricine in vitro: Comparison with chamazulene.

The proazulene matricine (1) is present in chamomile flower heads and has been proven to exhibit strong in vivo anti-inflammatory activity. In contrast to other secondary metabolites in chamomile preparations like its degradation product chamazulene (2), no plausible targets have been found to explain this activity. Therefore we revisited 1 regarding its in vitro anti-inflammatory activity in cellular and molecular studies. Using ICAM-1 as a marker for NF-κB activation, it was shown that ICAM-1 protein expression induced by TNF-α and LPS, but not by IFN-γ, was remarkably inhibited by 1 in endothelial cells (HMEC-1). Inhibition was concentration-dependent in a micromolar range (10-75 µM) and did not involve cytotoxic effects. At 75 µM expression of the adhesion molecule ICAM-1 was down to 52.7 ± 3.3% and 20.4 ± 1.8% of control in TNF-α and LPS-stimulated HMEC-1, respectively. In contrast, 2 showed no activity. Quantitative RT-PCR experiments revealed that TNF-α-induced expression of the ICAM-1 gene was also reduced by 1 in a concentration-dependent manner, reaching 32.3 ± 6.2% of control at 100 µM matricine. Additional functional assays (NF-κB promotor activity and cytoplasm to nucleus translocation) confirmed the inhibitory effect of 1 on NF-κB signaling. Despite the fact that 1 lacks an α,ß-unsaturated carbonyl and is thus not able to act via a Michael reaction with electron rich SH groups of functional biological molecules, data gave strong evidence that 1 inhibits NF-κB transcriptional activity in endothelial cells by an hitherto unknown mechanism and this may contribute to its well-known anti-inflammatory activity in vivo.

Deacetylase inhibitors repress STAT5-mediated transcription by interfering with bromodomain and extra-terminal (BET) protein function.

Signal transducer and activator of transcription STAT5 is essential for the regulation of proliferation and survival genes. Its activity is tightly regulated through cytokine signaling and is often upregulated in cancer. We showed previously that the deacetylase inhibitor trichostatin A (TSA) inhibits STAT5-mediated transcription by preventing recruitment of the transcriptional machinery at a step following STAT5 binding to DNA. The mechanism and factors involved in this inhibition remain unknown. We now show that deacetylase inhibitors do not target STAT5 acetylation, as we initially hypothesized. Instead, they induce a rapid increase in global histone acetylation apparently resulting in the delocalization of the bromodomain and extra-terminal (BET) protein Brd2 and of the Brd2-associated factor TBP to hyperacetylated chromatin. Treatment with the BET inhibitor (+)-JQ1 inhibited expression of STAT5 target genes, supporting a role of BET proteins in the regulation of STAT5 activity. Accordingly, chromatin immunoprecipitation demonstrated that Brd2 is associated with the transcriptionally active STAT5 target gene Cis and is displaced upon TSA treatment. Our data therefore indicate that Brd2 is required for the proper recruitment of the transcriptional machinery at STAT5 target genes and that deacetylase inhibitors suppress STAT5-mediated transcription by interfering with Brd2 function.

Enhancing the anti-inflammatory activity of chalcones by tuning the Michael acceptor site.

Inflammatory signaling pathways orchestrate the cellular response to infection and injury. These pathways are known to be modulated by compounds that alkylate cysteinyl thiols. One class of phytochemicals with strong thiol alkylating activity is the chalcones. In this study we tested fourteen chalcone derivatives, α-X-substituted 2',3,4,4'-tetramethoxychalcones (α-X-TMCs, X = H, F, Cl, Br, I, CN, Me, p-NO2-C6H4, Ph, p-OMe-C6H4, NO2, CF3, COOEt, COOH), for their ability to modulate inflammatory responses, as monitored by their influence on heme oxygenase-1 (HO-1) activity, inducible nitric oxide synthase (iNOS) activity, and cytokine expression levels. We confirmed that the transcriptional activity of Nrf2 was activated by α-X-TMCs while for NF-κB it was inhibited. For most α-X-TMCs, anti-inflammatory activity was positively correlated with thiol alkylating activity, i.e. stronger electrophiles (X = CF3, Br and Cl) being more potent. Notably, this correlation did not hold true for the strongest electrophiles (X = CN and NO2) which were found to be ineffective as anti-inflammatory compounds. These results emphasize the idea that chemical fine-tuning of electrophilicity is needed to achieve and optimize desired therapeutic effects.

The natural chemopreventive agent sulforaphane inhibits STAT5 activity.

Signal transducer and activator of transcription STAT5 is an essential mediator of cytokine, growth factor and hormone signaling. While its activity is tightly regulated in normal cells, its constitutive activation directly contributes to oncogenesis and is associated to a number of hematological and solid tumor cancers. We previously showed that deacetylase inhibitors can inhibit STAT5 transcriptional activity. We now investigated whether the dietary chemopreventive agent sulforaphane, known for its activity as deacetylase inhibitor, might also inhibit STAT5 activity and thus could act as a chemopreventive agent in STAT5-associated cancers. We describe here sulforaphane (SFN) as a novel STAT5 inhibitor. We showed that SFN, like the deacetylase inhibitor trichostatin A (TSA), can inhibit expression of STAT5 target genes in the B cell line Ba/F3, as well as in its transformed counterpart Ba/F3-1*6 and in the human leukemic cell line K562 both of which express a constitutively active form of STAT5. Similarly to TSA, SFN does not alter STAT5 initial activation by phosphorylation or binding to the promoter of specific target genes, in favor of a downstream transcriptional inhibitory effect. Chromatin immunoprecipitation assays revealed that, in contrast to TSA however, SFN only partially impaired the recruitment of RNA polymerase II at STAT5 target genes and did not alter histone H3 and H4 acetylation, suggesting an inhibitory mechanism distinct from that of TSA. Altogether, our data revealed that the natural compound sulforaphane can inhibit STAT5 downstream activity, and as such represents an attractive cancer chemoprotective agent targeting the STAT5 signaling pathway.

The synthetic α-bromo-2',3,4,4'-tetramethoxychalcone (α-Br-TMC) inhibits the JAK/STAT signaling pathway.

Signal transducer and activator of transcription STAT5 and its upstream activating kinase JAK2 are essential mediators of cytokine signaling. Their activity is normally tightly regulated and transient. However, constitutive activation of STAT5 is found in numerous cancers and a driving force for malignant transformation. We describe here the identification of the synthetic chalcone α-Br-2',3,4,4'-tetramethoxychalcone (α-Br-TMC) as a novel JAK/STAT inhibitor. Using the non-transformed IL-3-dependent B cell line Ba/F3 and its oncogenic derivative Ba/F3-1*6 expressing constitutively activated STAT5, we show that α-Br-TMC targets the JAK/STAT pathway at multiple levels, inhibiting both JAK2 and STAT5 phosphorylation. Moreover, α-Br-TMC alters the mobility of STAT5A/B proteins in SDS-PAGE, indicating a change in their post-translational modification state. These alterations correlate with a decreased association of STAT5 and RNA polymerase II with STAT5 target genes in chromatin immunoprecipitation assays. Interestingly, expression of STAT5 target genes such as Cis and c-Myc was differentially regulated by α-Br-TMC in normal and cancer cells. While both genes were inhibited in IL-3-stimulated Ba/F3 cells, expression of the oncogene c-Myc was down-regulated and that of the tumor suppressor gene Cis was up-regulated in transformed Ba/F3-1*6 cells. The synthetic chalcone α-Br-TMC might therefore represent a promising novel anticancer agent for therapeutic intervention in STAT5-associated malignancies.

Polycystin-2 takes different routes to the somatic and ciliary plasma membrane.

Polycystin-2 (also called TRPP2), an integral membrane protein mutated in patients with cystic kidney disease, is located in the primary cilium where it is thought to transmit mechanical stimuli into the cell interior. After studying a series of polycystin-2 deletion mutants we identified two amino acids in loop 4 that were essential for the trafficking of polycystin-2 to the somatic (nonciliary) plasma membrane. However, polycystin-2 mutant proteins in which these two residues were replaced by alanine were still sorted into the cilium, thus indicating that the trafficking routes to the somatic and ciliary plasma membrane compartments are distinct. We also observed that the introduction of dominant-negative Sar1 mutant proteins and treatment of cells with brefeldin A prevented the transport into the ciliary plasma membrane compartment, whereas metabolic labeling experiments, light microscopical imaging, and high-resolution electron microscopy revealed that full-length polycystin-2 did not traverse the Golgi apparatus on its way to the cilium. These data argue that the transport of polycystin-2 to the ciliary and to the somatic plasma membrane compartments originates in a COPII-dependent fashion at the endoplasmic reticulum, that polycystin-2 reaches the cis side of the Golgi apparatus in either case, but that the trafficking to the somatic plasma membrane goes through the Golgi apparatus whereas transport vesicles to the cilium leave the Golgi apparatus at the cis compartment. Such an interpretation is supported by the finding that mycophenolic acid treatment resulted in the colocalization of polycystin-2 with GM130, a marker of the cis-Golgi apparatus. Remarkably, we also observed that wild-type Smoothened, an integral membrane protein involved in hedgehog signaling that under resting conditions resides in the somatic plasma membrane, passed through the Golgi apparatus, but the M2 mutant of Smoothened, which is constitutively located in the ciliary but not in the somatic plasma membrane, does not. Finally, a dominant-negative form of Rab8a, a BBSome-associated monomeric GTPase, prevented the delivery of polycystin-2 to the primary cilium whereas a dominant-negative form of Rab23 showed no inhibitory effect, which is consistent with the view that the ciliary trafficking of polycystin-2 is regulated by the BBSome.

The LIM-homeodomain transcription factor LMX1B regulates expression of NF-kappa B target genes.

LMX1B is a LIM-homeodomain transcription factor essential for development. Putative LMX1B target genes have been identified through mouse gene targeting studies, but their identity as direct LMX1B targets remains hypothetical. We describe here the first molecular characterization of LMX1B target gene regulation. Microarray analysis using a tetracycline-inducible LMX1B expression system in HeLa cells revealed that a subset of NF-kappaB target genes, including IL-6 and IL-8, are upregulated in LMX1B-expressing cells. Inhibition of NF-kappaB activity by short interfering RNA-mediated knock-down of p65 impairs, while activation of NF-kappaB activity by TNF-alpha synergizes induction of NF-kappaB target genes by LMX1B. Chromatin immunoprecipitation demonstrated that LMX1B binds to the proximal promoter of IL-6 and IL-8 in vivo, in the vicinity of the characterized kappaB site, and that LMX1B recruitment correlates with increased NF-kappaB DNA association. IL-6 promoter-reporter assays showed that the kappaB site and an adjacent putative LMX1B binding motif are both involved in LMX1B-mediated transcription. Expression of NF-kappaB target genes is affected in the kidney of Lmx1b(-/-) knock-out mice, thus supporting the biological relevance of our findings. Together, these data demonstrate for the first time that LMX1B directly regulates transcription of a subset of NF-kappaB target genes in cooperation with nuclear p50/p65 NF-kappaB.

In vivo identification of novel STAT5 target genes.

STAT5A and STAT5B proteins belong to the family of signal transducers and activators of transcription. They are encoded by two separate genes with 91% identity in their amino acid sequences. Despite their high degree of conservation, STAT5A and STAT5B exert non-redundant functions, resulting at least in part from differences in target gene activation. To better characterize the differential contribution of STAT5A and STAT5B in gene regulation, we performed single or double knockdown of STAT5A and STAT5B using small interfering RNA. Subsequent gene expression profiling and RT-qPCR analyses of IL-3-stimulated Ba/F3-beta cells led to the identification of putative novel STAT5 target genes. Chromatin immunoprecipitation assays analyzing the corresponding gene loci identified unusual STAT5 binding sites compared to conventional STAT5 responsive elements. Some of the STAT5 targets identified are upregulated in several human cancers, suggesting that they might represent potential oncogenes in STAT5-associated malignancies.

Role of transcription factors in podocytes.

Despite a wealth of information on structural proteins, comparatively little is known on the transcriptional regulation of podocyte structure and function. In this review we will highlight those transcription factors which, by gene inactivation or classical transgenic experiments, have been shown to be essential for podocytes or probably will turn out to be so. The tumor suppressor protein WT1 is not only indispensable for the initial stages of kidney development, but also very likely maintains the integrity of the fully differentiated podocyte. In the kidney, the LIM homeodomain transcription factor LMX1B is specifically synthesized in podocytes, and mutations in LMX1B lead to nail-patella syndrome and the associated nephropathy. Other transcription factors such as hypoxia-inducible factors and PAX2 are likely to play a role in podocytes, whereas the significance of others, e.g. of POD1 and CITED2, is more speculative at this point.

Interleukin-22 activates STAT3 and induces IL-10 by colon epithelial cells.

Human interleukin-22 (IL-22), a cytokine with structural homology to IL-10, is produced by activated T cells. The IL-22 receptor complex consists of a ligand-binding chain, the IL-22R1 and a signal-transducing chain, the IL-10R2. The aim of this study is to identify potential target cells and associated biological activity of IL-22 by identifying cell types that specifically express high levels of IL-22R1 as the expression of IL-10R2 is ubiquitous. Expression of IL-22R1 mRNA, as analyzed by real time quantitative polymerase chain reaction (PCR), was observed in human tumor cell lines of stromal or epithelial origin derived from liver, pancreas, colon and lung tissue. Furthermore, we examined the ability of IL-22 to activate the JAK-Signal Transducer and Activator of Transcription (STAT) pathway in epithelial cells of the colon. IL-22 induced the phosphorylation of STAT1 and STAT3 in Colo205, a colon epithelial cell line. Consequently, IL-22 upregulated mRNA for Suppressor of Cytokine Signaling 3 (SOCS3), a STAT3-responsive gene. Further analyses, by real time quantitative PCR, on a panel of chemokines and immune function related genes revealed that IL-22 induced expression of the acute phase proteins alpha-Antichymotrypsin and Serum Amyloid A, as well as IL-10 mRNA and protein production by Colo205. Induction of IL-10 by IL-22, in Colo205 cells, could be inhibited in the presence of a neutralizing antibody against IL-10R2. IL-22-mediated effects on the Colo205 cells were also inhibited in the presence of IL-22 binding protein (IL-22BP), a soluble receptor with structural similarity to IL-22R1. The high levels of expression of IL-22R1 observed in epithelial cells of the colon and the ability of IL-22 to upregulate production of acute phase proteins and IL-10 in Colo205 cells, suggest a functional role for IL-22 in intestinal inflammation.

DUB-3, a cytokine-inducible deubiquitinating enzyme that blocks proliferation.

Previous studies have identified the DUB family of cytokine-regulated murine deubiquitinating enzymes, which play a role in the control of cell proliferation and survival. Through data base analyses and cloning, we have identified a human cDNA (DUB-3) that shows significant homology to the known murine DUB family members. Northern blotting has shown expression of this gene in a number of tissues including brain, liver, and muscle, with two transcripts being apparent (1.6 and 1.7 kb). In addition, expression was observed in cell lines including those derived from a number of hematopoietic tumors such as the Burkitt's lymphoma cell line RAJI. We have also demonstrated that DUB-3, which was shown to be an active deubiquitinating enzyme, is induced in response to interleukin-4 and interleukin-6 stimulation. Finally, we have demonstrated that constitutive expression of DUB-3 blocks proliferation and can initiate apoptosis in both IL-3-dependent Ba/F3 cells and NIH3T3 fibroblasts. These findings suggest that human DUB-3, like the murine DUB family members, is transiently induced in response to cytokines and can, when constitutively expressed, block growth factor-dependent proliferation.

Chromatin acetylation and remodeling at the Cis promoter during STAT5-induced transcription.

The signal transducer and activator of transcription STAT5 plays a major role in cytokine-induced expression of genes involved in cell proliferation and survival. Although several STAT5 partners have been identified, the molecular events taking place at the promoter level upon STAT5 recruitment have not yet been characterized in great detail. Using chromatin immunoprecipitation and accessibility assays, we characterized histone acetylation and chromatin remodeling events occurring during transcriptional activation of the endogenous murine Cis gene, a STAT5 target gene, in response to IL-3. We found that STAT5 binding in vivo is associated with low histone H3 and H4 acetylation levels in the proximity of the STAT5 binding sites. STAT5 recruitment also results in chromatin reorganization over that promoter region. These events (STAT5 binding, histone acetylation and chromatin remodeling) are not sufficient for transcriptional activation, which requires a non-histone protein deacetylase. These data reveal novel implications of STAT5 in chromatin regulation during cytokine-induced transcription, thus contributing to a better understanding of the mechanism of transcriptional activation by STAT5.

L63, the Drosophila PFTAIRE, interacts with two novel proteins unrelated to cyclins.

L63 encodes a CDK-like protein homologous to the mammalian PFTAIRE. We showed previously that L63 provides a CDK-related function critical to development (Dev. Biol. 221 (2000) 23). We present here the first biochemical characterization of L63 kinase. In addition, we describe two novel Drosophila proteins, PIF-1 and PIF-2 (for PFTAIRE Interacting Factor-1 and -2), identified in a two-hybrid screen for their ability to interact with the amino-terminal region of L63. The full-length PIF-1 cDNA shows an unusual dicistronic organization. PIF-1A and PIF-1B (the L63 interactor) predicted proteins are expressed in vivo, and show a distinct expression profile during development. Interaction between L63 and PIF-1B was confirmed in vitro and in vivo. The role of this interaction remains to be demonstrated, but our data suggest that PIF-1B might serve as a regulator of L63.