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Background Hemangioblastomas express erythropoietin and the patients often present with polycythemia. Methods Serum erythropoietin was measured using a commercial immunoassay, a functional erythropoietin assay and iso-electric focusing. Results Despite the polycythemia, serum erythropoietin remained low, while a functional erythropoietin-assay showed a 4–5 higher activity in serum compared to the immunoassay. Iso-electric focusing of serum erythropoietin indicated overrepresentation of highly sialylated erythropoietin isoforms produced by the tumor. As a result, altered affinity of the monoclonal antibody used in the immunoassay for the hypersialylated isoforms was suggested. Conclusion Analysis of erythropoietin isoforms may be helpful in distinguishing the ectopic erythropoietin isoforms from normally glycosylated erythropoietin. [ABSTRACT FROM AUTHOR]

Presents a study on the mechanism of the human interleukin-5 (IL-5) antagonist E13Q. Role of IL-5 in the activation of eosinophils, a cell type associated with several allergic diseases; Measurement of E13Q binding and activity; In vitro binding of E13Q to the IL-5R α subunit.

Using a fusion protein of the human interleukin-5-receptor α chain (hIL5R α) and the human IgG C γ 3 chain (hIL5R α-h γ 3), we have developed a solid-phase assay for high-flux screening of a collection of synthetic compounds. We report on the identification of isothiazolone derivatives as potent inhibitors of binding of interleukin-5 (IL5) to the hIL5R α, as measured in a solid-phase assay (soluble hIL5R α or hIL5R α-h γ 3) or on COS-1 cells expressing the hIL5R α on the cell membrane. The binding of hIL4 and human granulocyte macrophage colony-stimulating factor (hGM-CSF) to their respective receptors is not inhibited by the isothiazolones in similar assay systems. Scatchard analysis revealed that these compounds caused a decrease in affinity of the IL5R α for IL5. The inhibition of binding IL5 to its receptor by the isothiazolone derivatives is abrogated by free-sulfhydryl-containing compounds such as dithiothreitol, indicating that the isothiazolones react with the sulfhydryl group of free cysteine residues in the hIL5R α. Mutation of Cys66 led to a receptor which still binds hIL5, but which was insensitive to the inhibition by isothiazolones. Mutation of Cys249 and Cys296 to serine resulted in complete loss of IL-5-binding activity. The use of radio-labeled isothiazolone confirmed that Cys66, present in the first domain of the receptor, is the target for covalent modification leading to a decrease in affinity. [ABSTRACT FROM AUTHOR]

Describes the nucleotide sequence of the 26-kDa cDNA in human fibroblasts and part of the corresponding genomic clone. Observation that the 26-kDa protein gene and the so-called interferon-β gene are identical; Indication that the 26-kDa protein does not show statistically significant sequence homology with any known interferon species.

The Ca2+-permeable Transient Receptor Potential channel vanilloid subfamily member 4 (TRPV4) is involved in a broad range of physiological processes, including the regulation of systemic osmotic pressure, bone resorption, vascular tone, and bladder function. Mutations in the TRPV4 gene are the cause of a spectrum of inherited diseases (or TRPV4-pathies), which include skeletal dysplasias, arthropathies, and neuropathies. There is little understanding of the pathophysiological mechanisms underlying these variable disease phenotypes, but it has been hypothesized that disease-causing mutations affect interaction with regulatory proteins. Here, we performed a mammalian protein–protein interaction trap (MAPPIT) screen to identify proteins that interact with the cytosolic N terminus of human TRPV4, a region containing the majority of disease-causing mutations. We discovered the zinc-finger domain-containing protein ZC4H2 as a TRPV4-interacting protein. In heterologous expression experiments, we found that ZC4H2 increases both the basal activity of human TRPV4 as well as Ca2+ responses evoked by ligands or hypotonic cell swelling. Using total internal reflection fluorescence (TIRF) microscopy, we further showed that ZC4H2 accelerates TRPV4 turnover at the plasma membrane. Overall, these data demonstrate that ZC4H2 is a positive modulator of TRPV4, and suggest a link between TRPV4 and ZC4H2-associated rare disorders, which have several neuromuscular symptoms in common with TRPV4-pathies. [ABSTRACT FROM AUTHOR]

Recent approval of chimeric antigen receptor (CAR) T cell therapy by the European Medicines Agency (EMA)/Federal and Drug Administration (FDA) and the remarkable results of CAR T clinical trials illustrate the curative potential of this therapy. While CARs against a multitude of different antigens are being developed and tested (pre)clinically, there is still a need for optimization. The use of single-chain variable fragments (scFvs) as targeting moieties hampers the quick generation of functional CARs and could potentially limit the efficacy. Instead, nanobodies may largely circumvent these difficulties. We used an available nanobody library generated after immunization of llamas against Cluster of Differentiation (CD) 20 through DNA vaccination or against the ectodomain of CD33 using soluble protein. The nanobody specific sequences were amplified by PCR and cloned by Gibson Assembly into a retroviral vector containing two different second-generation CAR constructs. After transduction in T cells, we observed high cell membrane nanoCAR expression in all cases. Following stimulation of nanoCAR-expressing T cells with antigen-positive cell lines, robust T cell activation, cytokine production and tumor cell lysis both in vitro and in vivo was observed. The use of nanobody technology in combination with PCR and Gibson Assembly allows for the rapid and effective generation of compact CARs. [ABSTRACT FROM AUTHOR]

Background: Eosinophils develop from bone marrow (BM) progenitors, and interleukin–5 (IL–5) and eotaxin may act in expansion and mobilisation of BM eosinophils in asthma. Methods: We have examined phenotypic changes as CD34+ cells develop to the eosinophil lineage in vitro, and have evaluated BM eosinophils from asthmatic and control subjects for expression of the eotaxin receptor, CCR3. Results: Acquisition of receptors for IL–5 and CCR3 was an early event in eosinophil development. There were increased CD34+ cells, and mature and immature CCR3+ eosinophils in BM from asthmatics. Conclusion: These data suggest that IL–5 may act early in eosinophil development, and that eotaxin has the capacity to mobilise a BM eosinophil pool in asthma. [ABSTRACT FROM AUTHOR]

Protein-protein interaction (PPI) studies have dramatically expanded our knowledge about cellular behaviour and development in different conditions. A multitude of high-throughput PPI techniques have been developed to achieve proteome-scale coverage for PPI studies, including the microarray based Mammalian Protein-Protein Interaction Trap (MAPPIT) system. Because such high-throughput techniques typically report thousands of interactions, managing and analysing the large amounts of acquired data is a challenge. We have therefore built the MAPPIT cell microArray Protein Protein Interaction-Data management & Analysis Tool (MAPPI-DAT) as an automated data management and analysis tool for MAPPIT cell microarray experiments. MAPPI-DAT stores the experimental data and metadata in a systematic and structured way, automates data analysis and interpretation, and enables the meta-analysis of MAPPIT cell microarray data across all stored experiments. [ABSTRACT FROM AUTHOR]

DSCAM and DSCAML1 are immunoglobulin and cell adhesion‐type receptors serving important neurodevelopmental functions including control of axon growth, branching, neurite self‐avoidance, and neuronal cell death. The signal transduction mechanisms or effectors of DSCAM receptors, however, remain poorly characterized. We used a human ORFeome library to perform a high‐throughput screen in mammalian cells and identified novel cytoplasmic signaling effector candidates including the Down syndrome kinase Dyrk1a, STAT3, USP21, and SH2D2A. Unexpectedly, we also found that the intracellular domains (ICDs) of DSCAM and DSCAML1 specifically and directly interact with IPO5, a nuclear import protein of the importin beta family, via a conserved nuclear localization signal. The DSCAM ICD is released by γ‐secretase‐dependent cleavage, and both the DSCAM and DSCAML1 ICDs efficiently translocate to the nucleus. Furthermore, RNA sequencing confirms that expression of the DSCAM as well as the DSCAML1 ICDs alone can profoundly alter the expression of genes associated with neuronal differentiation and apoptosis, as well as synapse formation and function. Gain‐of‐function experiments using primary cortical neurons show that increasing the levels of either the DSCAM or the DSCAML1 ICD leads to an impairment of neurite growth. Strikingly, increased expression of either full‐length DSCAM or the DSCAM ICD, but not the DSCAML1 ICD, significantly decreases synapse numbers in primary hippocampal neurons. Taken together, we identified a novel membrane‐to‐nucleus signaling mechanism by which DSCAM receptors can alter the expression of regulators of neuronal differentiation and synapse formation and function. Considering that chromosomal duplications lead to increased DSCAM expression in trisomy 21, our findings may help uncover novel mechanisms contributing to intellectual disability in Down syndrome. Synopsis: A novel membrane‐to‐nucleus signaling mechanism of DSCAMs affects the expression of neuronal target genes. Nuclear enrichment of the cleaved intracellular domain of DSCAM (DSCAM‐ICD) in developing neurons can lead to an impairment of neurite growth and strong decrease of synapse numbers. The DYRK family kinases DYRK1A and DYRK1B, the SH2‐domain adaptor SH2D2A, the Ubiquitin specific peptidase USP21, and the transcription factor STAT3 are novel cytoplasmic binding partners of DSCAM and DSCAML1.The ICDs of DSCAM and DSCAML1 interact with the importin beta IPO5 via a conserved nuclear localization signal.γ‐secretase mediated intra‐membrane cleavage of DSCAM results in the release of the DSCAM ICD and both the DSCAM and DSCAML1 ICDs efficiently translocate to the nucleus.In the nucleus, the DSCAM ICD alters the transcription of several genes involved in neuronal differentiation and synapse formation. A novel membrane‐to‐nucleus signaling mechanism of the cell adhesion receptors DSCAM and DSCAML1 affects the expression of neuronal target genes causing reduced neurite growth and decreased synapse formation. [ABSTRACT FROM AUTHOR]

Background: Neuronal Ca2+ dyshomeostasis and hyperactivity play a central role in Alzheimer's disease pathology and progression. Amyloid-beta together with non-genetic risk-factors of Alzheimer's disease contributes to increased Ca2+ influx and aberrant neuronal activity, which accelerates neurodegeneration in a feed-forward fashion. As such, identifying new targets and drugs to modulate excessive Ca2+ signalling and neuronal hyperactivity, without overly suppressing them, has promising therapeutic potential. Methods: Here we show, using biochemical, electrophysiological, imaging, and behavioural tools, that pharmacological modulation of Rap1 signalling by inhibiting its interaction with Pde6δ normalises disease associated Ca2+ aberrations and neuronal activity, conferring neuroprotection in models of Alzheimer's disease. Results: The newly identified inhibitors of the Rap1-Pde6δ interaction counteract AD phenotypes, by reconfiguring Rap1 signalling underlying synaptic efficacy, Ca2+ influx, and neuronal repolarisation, without adverse effects in-cellulo or in-vivo. Thus, modulation of Rap1 by Pde6δ accommodates key mechanisms underlying neuronal activity, and therefore represents a promising new drug target for early or late intervention in neurodegenerative disorders. Conclusion: Targeting the Pde6δ-Rap1 interaction has promising therapeutic potential for disorders characterised by neuronal hyperactivity, such as Alzheimer's disease. [ABSTRACT FROM AUTHOR]

Summary Loss of ER Ca 2+ homeostasis triggers endoplasmic reticulum (ER) stress and drives ER-PM contact sites formation in order to refill ER-luminal Ca 2+ . Recent studies suggest that the ER stress sensor and mediator of the unfolded protein response (UPR) PERK regulates intracellular Ca 2+ fluxes, but the mechanisms remain elusive. Here, using proximity-dependent biotin identification (BioID), we identified the actin-binding protein Filamin A (FLNA) as a key PERK interactor. Cells lacking PERK accumulate F-actin at the cell edges and display reduced ER-PM contacts. Following ER-Ca 2+ store depletion, the PERK-FLNA interaction drives the expansion of ER-PM juxtapositions by regulating F-actin-assisted relocation of the ER-associated tethering proteins Stromal Interaction Molecule 1 (STIM1) and Extended Synaptotagmin-1 (E-Syt1) to the PM. Cytosolic Ca 2+ elevation elicits rapid and UPR-independent PERK dimerization, which enforces PERK-FLNA-mediated ER-PM juxtapositions. Collectively, our data unravel an unprecedented role of PERK in the regulation of ER-PM appositions through the modulation of the actin cytoskeleton. [ABSTRACT FROM AUTHOR]

β 2-adrenergic receptor ( β 2-AR) agonists are widely applied in the clinic for treatment of respiratory disease. Although their therapeutic effect mainly results from their spasmolytic activity, β -agonists have also been attributed with anti-inflammatory properties. We studied the effect of β -agonist cotreatment on TNF- α -induced activation of inflammatory signalling in astrocytes, focusing on Nuclear Factor- κ B (NF- κ B), a master regulator of inflammatory gene expression. Unexpectedly, we observed that, unlike other anti-inflammatory drugs, β -agonists did not inhibit the activity of NF- κ B. Instead, β -agonist cotreatment enhanced TNF- α -induced expression of a subset of prototypical NF- κ B target genes. The most pronounced effect was apparent for Interleukin-6 (IL-6) and the CXC chemokines CXCL2 and CXCL3. We established that cooperativity between NF- κ B and β 2-AR-induced transcriptional regulators is at the basis of the synergy. Our current research aims at further defining the molecular players regulating IL-6 transcription using a novel approach combining DNA affinity purification and mass spectrometry. Importantly, the β 2-agonist-induced potentiation of inflammatory responses was also recapitulated in vivo , in rats treated intracerebroventricularly with a combination of TNF- α and clenbuterol. Gene expression changes were furthermore reflected in a redistribution of the leukocyte subsets present in the brain. More specifically, a skewing of the T-cell population towards a double-negative phenotype, and a shift towards neutrophilic expansion in the myeloid subset were apparent. Although functional characterization of the infiltrating leukocytes remains to be done, these results suggest β -agonists can catalyze inflammatory reactions in vivo and warrant further study into their mode of action. [ABSTRACT FROM AUTHOR]

The activating JAK2-V617F mutation is found in many patients suffering from Myeloproliferative neoplasms such as Polycythemia Vera and Essential Thrombocythemia. JAK2-V617F mutation confers cytokine hypersensitivity, constitutive activation of the JAK-STAT pathway, and cytokine-independent growth. We demonstrate uncontrolled membrane binding of the multi-site docking protein Gab1 in JAK2-V617F expressing cells. We elaborated the molecular mechanism and regulation of Gab1-membrane recruitment. In line with the regulatory function of Gab1 on STAT-independent signalling we show that PI3K signalling regulates MAPK activation in JAK2-V617F-positive cells. This cross-regulation of the MAPK pathway by PI3K affects JAK2-V617F-specific target gene induction, erythroid colony formation, and regulates proliferation of JAK2-V617F-positive patient cells in a synergistically manner. In summary, our study demands to consider cross-talk mechanisms as potential new targets. This may increase the specificity for intervention approaches compared to the interference in very upstream signalling elements such as receptor kinases or receptor-associated kinases. [ABSTRACT FROM AUTHOR]

Objectives: One of the hallmarks of severe pneumonia and associated acute lung injury is neutrophil recruitment to the lung. Leptin is thought to be up-regulated in the lung following injury and to exert diverse effects on leukocytes, influencing both chemotaxis and survival. We hypothesized that pulmonary leptin contributes directly to the development of pulmonary neutrophilia during pneumonia and acute lung injury.Design: Controlled human and murine in vivo and ex vivo experimental studies.Setting: Research laboratory of a university hospital.Subjects: Healthy human volunteers and subjects hospitalized with bacterial and H1N1 pneumonia. C57Bl/6 and db/db mice were also used.Interventions: Lung samples from patients and mice with either bacterial or H1N1 pneumonia and associated acute lung injury were immunostained for leptin. Human bronchoalveolar lavage samples obtained after lipopolysaccharide-induced lung injury were assayed for leptin. C57Bl/6 mice were examined after oropharyngeal aspiration of recombinant leptin alone or in combination with Escherichia coli- or Klebsiella pneumoniae-induced pneumonia. Leptin-resistant (db/db) mice were also examined using the E. coli model. Bronchoalveolar lavage neutrophilia and cytokine levels were measured. Leptin-induced chemotaxis was examined in human blood- and murine marrow-derived neutrophils in vitro.Measurements and Main Results: Injured human and murine lung tissue showed leptin induction compared to normal lung, as did human bronchoalveolar lavage following lipopolysaccharide instillation. Bronchoalveolar lavage neutrophilia in uninjured and infected mice was increased and lung bacterial load decreased by airway leptin administration, whereas bronchoalveolar lavage neutrophilia in infected leptin-resistant mice was decreased. In sterile lung injury by lipopolysaccharide, leptin also appeared to decrease airspace neutrophil apoptosis. Both human and murine neutrophils migrated toward leptin in vitro, and this required intact signaling through the Janus Kinase 2/phosphatidylinositol-4,5-bisphosphate 3-kinase pathway.Conclusions: We demonstrate that pulmonary leptin is induced in injured human and murine lungs and that this cytokine is effective in driving alveolar airspace neutrophilia. This action appears to be caused by direct effects of leptin on neutrophils. [ABSTRACT FROM AUTHOR]

Systemic toxicity currently prevents full clinical application of type I interferons (IFNs) for the treatment of cancers and viral infections. Although the use of IFNs fused to antibodies resulted in a 10-fold increased activity towards targeted cells, off-target side effects experienced by the patients are expected to remain a major obstacle. We present a novel strategy to engineer IFNα with high in vitro and in vivo activity towards cells expressing a specific surface marker while having an up to 1000-fold reduced activity towards non-relevant cells. The concept lies in the use of immunocytokines based on IFN mutants with strongly reduced binding affinity for the IFN receptor. Such a targeted IFN recovers almost maximally its antiviral activity uniquely on the targeted cells and acts to selected cell populations in mice with targeting efficiencies up to 3 orders of magnitude. This novel concept holds promise to revitalize the clinical potential of IFNα and other cytokines. [ABSTRACT FROM AUTHOR]

An abstract of the article "Peroxiredoxin-controlled G-CSF signalling at the endoplasmic reticulum"early endosome interface," by Karishma Palande and colleagues is presented.

Cytokines, such as interferons, erythropoietin, leptin and most interleukins, signal through type 1 cytokine receptors and activate the canonical JAK-STAT pathway. Aberrant cytokine signalling underlies numerous pathologies and adequate, temporary receptor activation is therefore under tight control. Negative-feedback mechanisms are very well studied, but cellular sensitivity also depends on the number of receptors exposed at the cell surface. This is determined by the equilibrium between receptor synthesis and transport to the plasma membrane, internalisation and recycling, degradation and ectodomain shedding, but the molecular basis of how cells establish steady state receptor levels is poorly understood. Here, we report that ring finger protein 41 (RNF41, also known as E3 ubiquitin-protein ligase Nrdp1) interacts with JAK2-associated cytokine receptor complexes and modulates their cell surface exposure and signalling. Moreover, ectopic expression of RNF41 affected turnover of leptin, leukaemia inhibitory factor and interleukin-6 receptor in a dual way: it blocked intracellular cathepsin-L-dependent receptor cleavage and concomitantly enhanced receptor shedding by metalloproteases of the ADAM family. Receptor degradation and shedding are thus interconnected phenomena with a single protein, RNF41, determining the balance. [ABSTRACT FROM AUTHOR]

Background: Stromal fibroblasts participate in the development of a permissive environment for tumor growth, yet molecular pathways to therapeutically target fibroblasts are poorly defined. CD248, also known as endosialin or tumor endothelial marker 1 (TEM1), is a transmembrane glycoprotein expressed on activated fibroblasts. We recently showed that the cytoplasmic domain of CD248 is important in facilitating an inflammatory response in a mouse model of arthritis. Others have reported that CD248 gene inactivation in mice results in dampened tumor growth. We hypothesized that the conserved cytoplasmic domain of CD248 is important in regulating tumor growth.Methods: Mice lacking the cytoplasmic domain of CD248 (CD248CyD/CyD) were generated and evaluated in tumor models, comparing the findings with wild-type mice (CD248WT/WT).Results: As compared to the response in CD248WT/WT mice, growth of T241 fibrosarcomas and Lewis lung carcinomas was significantly reduced in CD248CyD/CyD mice. Tumor size was similar to that seen with CD248-deficient mice. Conditioned media from CD248CyD/CyD fibroblasts were less effective at supporting T241 fibrosarcoma cell survival. In addition to our previous observation of reduced release of activated matrix metalloproteinase (MMP)-9, CD248CyD/CyD fibroblasts also had impaired PDGF-BB-induced migration and expressed higher transcripts of tumor suppressor factors, transgelin (SM22α), Hes and Hey1.Conclusions: The multiple pathways regulated by the cytoplasmic domain of CD248 highlight its potential as a therapeutic target to treat cancer. [ABSTRACT FROM AUTHOR]

Toll-like receptors (TLRs) are crucial components of innate immunity, ensuring efficient responses against invading pathogens. After ligand binding, TLR signaling is initiated by recruitment of adaptor molecules, a step mediated by homotypic Toll-IL-1 receptor (TIR) domain interactions. Four TIR-containing TLR adaptor molecules are described, all of which are susceptible to modification and strict regulation. For example, caspase-1 is reported to cleave the TLR adaptor Mal at position D198, an event that is indispensible for Mal function. In this report, we use the mammalian two-hybrid technique MAPPIT to study the implications of Mal cleavage. We show that a Mal mutant, which mimics caspase-1 cleavage and a caspase-1-uncleavable MalD198A mutant, are abrogated in their bridging function and lose the ability to activate NF-κ B. A MalD198E mutant is still fully functional, suggesting that caspase-1 cleavage of Mal is not necessary for Mal-mediated signaling. D198 of Mal is conserved in MyD88 and TLR4 TIR domains and the negatively charged amino acid at this position is crucial for the interactions and function of Mal, MyD88 and TLR4 TIR. Our data suggest an inhibitory, rather than an activating role for caspase-1 in Mal regulation, and show that the caspase-1 cleavage site in Mal is part of a TIR-domain interaction site. [ABSTRACT FROM AUTHOR]

An abstract of the article "Definition of the Interacting Interfaces of Apobec3G and HIV-1 Vif Using MAPPIT Mutagenesis Analysis," by Delphine Lavens, Frank Peelman, José Van der Heyden, Isabel Uyttendaele, Dominiek Catteeuw, Bertrand Van Schouwbroeck, Julia Kurth, Sabine Hallenberger, Reginald Clayton and Jan Tavernier is presented.

The cellular bromodomain protein Brd4 is a major interacting partner of the papillomavirus (PV) E2 protein. Interaction of E2 with Brd4 contributes to viral episome maintenance. The E2-Brd4 interaction also plays an important role in repressing viral oncogene expression from the integrated viral genome in human PV (HPV)-positive cancer cells. However, the underlying mechanism is not clearly understood. In host cells, Brd4 recruits positive transcription elongation factor b (P-TEFb) to stimulate RNA polymerase II phosphorylation during cellular and viral gene expression. P-TEFb associates with the C terminus of Brd4, which largely overlaps with the E2 binding site on Brd4. In this study, we demonstrate that E2 binding to Brd4 inhibits the interaction of endogenous Brd4 and P-TEFb. P-TEFb is essential for viral oncogene E6/E7 transcription in both HeLa and CaSki cells that contain integrated HPV genomes. E2 binding to Brd4 abrogates the recruitment of P-TEFb to the integrated viral chromatin template, leading to inactivation of P-TEFb and repression of the viral oncogene E6/E7. Furthermore, dissociation of the Brd4-P-TEFb complex from the integrated viral chromatin template using a Brd4 bromodomain dominant-negative inhibitor also hampers HPV E6/E7 oncogene expression. Our data support that Brd4 recruitment of P-TEFb to the viral chromatin template is essential for viral oncogene expression. Abrogation of the interaction between P-TEFb and Brd4 thus provides a mechanism for E2-mediated repression of the viral oncogenes from the integrated viral genomes in cancer cells. [ABSTRACT FROM AUTHOR]

Hypothalamic leptin receptor signalling plays a central role in weight regulation by controlling fat storage and energy expenditure. In addition, leptin also has direct effects on peripheral cell types involved in regulation of diverse body functions including immune response, bone formation and reproduction. Previous studies have demonstrated the important role of SOCS3 (suppressor of cytokine signalling 3) in leptin physiology. Here, we show that CIS (cytokine-inducible SH2 protein) and SOCS2 can also interact with the leptin receptor. Using MAPPIT (mammalian protein-protein interaction trap), a cytokine receptor-based two-hybrid method operating in intact cells, we show specific binding of CIS with the conserved Y985 and Y1077 motifs in the cytosolic domain of the leptin receptor. SOCS2 only interacts with the Y1077 motif, but with higher binding affinity and can interfere with CIS and STAT5a prey recruitment at this site. Furthermore, although SOCS2 does not associate with Y985 of the leptin receptor, we find that SOCS2 can block interaction of CIS with this position. This unexpected interference can be explained by the direct binding of SOCS2 on the CIS SOCS box, whereby elongin B/C recruitment is crucial to suppress CIS activity. [ABSTRACT FROM AUTHOR]