1,720,973 research outputs found
HTLV-1 and HTLV-2 Tax, HBZ and APH-2 interaction with host factors: their involvement in cellular pathways regulation.
No full textBackground: HTLV-1 and HTLV-2 encode several genes which play a pivotal role in viral replication and proliferation of infected cells. Among them, Tax and the antisense strand genes HBZ and APH-2 are the most investigated. HBZ is directly involved in HTLV-1 infection and persistence. Tax-1 and HBZ expression causes an opposite effect on NF-ĸB activation and exerts a central role in transforming and immortalizing T lymphocytes. Unlike HBZ, APH-2 binds Tax-2, but both repress Tax LTR transactivation interacting with CREB. In previous study, we have compared the effect of Tax-1 and Tax-2 interaction with cellular factors that act on NF-ĸB and IFN-I cell signaling pathways regulation. Based on the differences between HBZ and APH-2 interaction with Tax-1 and Tax-2 proteins, we aimed to investigate whether HBZ and APH-2 differ in the interactions with cellular factors, and how these interactions modulate cellular pathways regulation.
Methods: The study is based on cell culture models transiently transfected with vectors expressing viral proteins. Protein interactions were demonstrated by complexes immunoprecipitations performed using Dynabeads® Protein G with specific antibodies and western blot analyses. NF-ĸB promoter activation was quantified by luciferase reporter assay in co-transfected HEK293T cells. Tax, HBZ, APH-2 and host factors intracellular distribution was analyzed by confocal microscopy.
Results: In our comparative studies, we observed that APH-2 shares with HBZ the ability to suppress the Tax-mediated NF-ĸB activation. Both proteins form complexes with p65. APH-2, like HBZ, inhibits the p65-induced NF-ĸB activation. Consistent with the differences in binding properties, we observed, by confocal microscopy, a different intracellular redistribution of APH-2 compared to HBZ when Tax proteins are expressed. Moreover, by immunoprecipitation and intracellular co-localization analyses, we have identified cellular factors involved in cell signaling pathways that form complexes with APH-2 when Tax-2 is expressed.
Conclusions: These results contribute to understand the different involvement of the antisense proteins in the regulation of the NF-κB pathway. Our results demonstrate that APH-2, unlike HBZ, is present in Tax-2 complexes in the cytoplasm and interacts with factors that crosstalk between cellular pathways affecting cell growth and survival
Human T-cell leukemia virus HBZ and APH-2 antisense proteins interaction with host factors and their involvement in NF-Kb activation
No full textHuman T-cell leukemia viruses type 1 and 2 (HTLV-1 and 2) are genetically related
retroviruses that differ in terms of clinical impact. HTLV-1 is the causative agent of adult
T-cell leukemia (ATL), whereas HTLV-2 is sporadically associated with neurological
disorders. HTLV genome encodes a regulatory protein Tax, which transactivates viral and
host genes and induces cell transformation. An additional key factor involved in viral
pathogenesis is the unique regulatory protein expressed by the minus strand of HTLV-1 and 2,
namely HBZ (HTLV-1 b-Zip factor) and APH-2 (HTLV-2 antisense protein). APH-2 and
HBZ share the ability to suppress Tax-dependent viral transcription, although not to a similar
extent. We have previously demonstrated that Tax proteins form complexes with several host
factors deregulating the NF-κB pathway. In the present study, we aimed to investigate HBZ
and APH-2 interactions with cellular and viral factors and their involvement in the NF-kB
activation. We observed that both APH-2 and HBZ proteins, form complexes with p65. In
transactivation assays they inhibit the p65-induced NF-kB activation, even in the presence of
Tax that is known to induce a persistent activation of NF-kB. Immunoprecipitation analyses
showed that, compared to HBZ, only APH-2 is able to interact with Tax. Confocal
microscopy observations confirm a different cellular distribution of the viral proteins: HBZ
has a prevalently punctuate nuclear distribution, whereas APH-2 is distributed both in the
nucleus and cytoplasm. By immunoprecipitation analyses, we found that the cellular factor
TNF receptor associated factor 3 (TRAF3), involved in the alternative NF-κB cell signaling
pathway, forms complexes with APH-2. Further studies will be performed to investigate the
molecular mechanism by which HBZ and APH-2 antisense viral proteins cellular interactions
modulate the alternative NF-κB cell signaling pathway
CRISPR/Cas9 as a tool for the study of the interactions between viruses and host
No full textCRISPR/Cas9 in virolog
The human T-cell leukemia virus -2 (HTLV-2) antisense protein APH-2 interacts with p65 and inhibits NF-ĸB Tax-2 activation.
No full textHuman T-cell leukemia virus types 1 and 2 (HTLV-1 and 2) are genetically related retroviruses that cause persistent infections in vivo. HTLV-1 is the causative agent of adult T-cell leukemia (ATL) and myelopathy/tropical spastic paraparesis, while HTLV-2 is not associated with ATL-like disorders. HTLV genome codes for a transactivator protein, Tax, which is crucial for enhancing viral expression and driving cell transformation. The promoter located in the 3’ LTR in both HTLV-1 and 2 drives the transcription of antisense RNAs coding for regulatory proteins named HBZ (HTLV-1 b-Zip factor) for HTLV-1 and APH-2 (antisense protein of HTLV-2) for HTLV-2. Both proteins contain basic residues required for nuclear localization, but differ in their N- and C- terminus. They negatively regulate HTLV transcription, inhibiting Tax-dependent LTR activation, although not in a similar extent. HBZ does not bind Tax-1, whereas APH-2 binds to Tax-2. We therefore aim to investigate the presence of APH-2 in complexes that recruit Tax-2 and the effect of APH-2 expression on NF-ĸB activation. We found that APH-2 interacts with p65, as well as with Tax-2 and Tax-1, indicating that protein structural differences between APH-2 and HBZ are responsible for Tax proteins interaction. We performed promoter activated luciferase assays showing that when co-expressed with p65 or Tax-2, increased amounts of APH-2 inhibited the mediated p65 and Tax-2 NF-ĸB activation. Immunofluorescence analyses indicated that APH-2, unlike HBZ, localized in both nucleus and cytoplasm. Altogether, our results demonstrate that APH-2 shares with HBZ the affinity with p65 and the inhibition of p65 induced NF-ĸB activation and highlight the difference between APH-2 and HBZ in the selectivity for the interaction that may explain their diversity in cellular localization. The different role of these proteins in altering cellular pathways will be further investigated. This study is funded by AIRC-Cariverona
RNA-binding proteins RBM20 and PTBP1 regulate the alternative splicing of FHOD3
No full textRegulation of alternative splicing events is an essential step required for the expression of functional cytoskeleton and sarcomere proteins in cardiomyocytes. About 3% of idiopathic dilated cardiomyopathy cases present mutations in the RNA binding protein RBM20, a tissue specific regulator of alternative splicing. Transcripts expressed preferentially in skeletal and cardiac muscle, including TTN, CAMK2D, LDB3, LMO7, PDLIM3, RTN4, and RYR2, are RBM20-dependent splice variants. In the present study, we investigated the RBM20 involvement in post-transcriptional regulation of splicing variants expressed by Formin homology 2 domain containing 3 (FHOD3) gene. FHOD3 is a sarcomeric protein highly expressed in the cardiac tissue and required for the assembly of the contractile apparatus. Recently, FHOD3 mutations have been found associated with heart diseases. We identified novel FHOD3 splicing variants differentially expressed in human tissues and provided evidences that FHOD3 transcripts are specific RBM20 and PTBP1 targets. Furthermore, we demonstrated that the expression of RBM20 and PTBP1 promoted the alternative shift, from inclusion to exclusion, of selected FHOD3 exons. These results indicate that RBM20 and PTBP1 play a role in the actin filament functional organization mediated by FHOD3 isoforms and suggest their possible involvement in heart diseases
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
HTLV Tax, HBZ and APH-2 regulatory protein interaction with host cell factors: implications for NF-κB pathway deregulation and tumorigenesis.
Full text linkHuman T-cell leukemia virus type 1 (HTLV-1) is a retrovirus that infects approximately 20 million people worldwide and 5% of them develop adult T-cell leukemia (ATL), a fatal T-cell malignancy with a poor prognosis. The HTLV-1 genome encodes two proteins that play a pivotal role in the oncogenic process, the regulatory protein Tax and the accessory protein HBZ. The expression of HTLV-1 oncoprotein Tax plays a key role in CD4+ T-cell transformation, interacting with host factors and deregulating several cell pathways implicated in the regulation of cell cycle and cell survival. Among them, Tax activates contitutively the NF-κB pathway, which play a primary role in inflammation, immunity, cell proliferation, apoptosis and cancer. HTLV-1 basic zipper protein (HBZ), encoded by the antisense viral genome strand, is essential for viral persistence and promotion of T-cell proliferation, acting in concert with Tax and contributing to ATL development. The purpose of my PhD research is to expand the knowledge of the molecular mechanism of NF-κB pathway deregulation mediated by the interactions of Tax and HBZ regulatory proteins with selected host factors. We studied the effect of Tax-1 and HBZ on NF-κB promoter activation by comparative analyses with the homologous regulatory proteins expressed by the genetically related HTLV type 2, which is not associated with ATL disease. We focused the experimental analyses on two relevant aspects of the NF-κB deregulation: the interactions of Tax and the antisense proteins with key factors of the NF-κB pathway mediating p65 activation, and their role on the alternative NF-κB pathway modulation. Our data demonstrated for the first time that HBZ and APH-2 differ in the inhibitory mechanism of Tax-dependent NF-κB activation. By confocal microscopy, we observed that APH-2, unlike HBZ, was recruited in Tax-2-cytoplasmic structures containing the NF-κB factors that are essential for the activation of the pathway, the adaptor protein TAB2 and the NF-κB modulator NEMO. The formation of these complexes results in the impairment of p65 transcription factor translocation into the nucleus. The analyses of these complexes showed that TRAF3, a key factor of the alternative NF-κB pathway, interacts with Tax and APH-2. Applying the CRISPR/Cas9 system, we generated a cell model that allowed us to define the contribution of TRAF3 in the inhibition of NF-κB. The results obtained revealed for the first time that the absence of TRAF3 dramatically reduced the Tax-1 transactivating activity of NF-κB. In conclusion, the results of my PhD thesis identify a new cellular factor essential for the action of HTLV Tax protein in the deregulation of cellular pathways and support the hypothesis that the different molecular mechanism of HBZ and APH-2 in the NF-κB inhibition may reflect divergent effects on HTLV-infected cells survival and probably on leukemogenesis induced by HTLV
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