Browsing by Subject "transcription factor"

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Open Access
A Wor1-Like Transcription Factor Is Essential for Virulence of Cryptococcus neoformans.
(Frontiers in Cellular and Infection Microbiology, 2018-01) Paes, Hugo Costa; Derengowski, Lorena da Silveira; Peconick, Luisa Defranco Ferreira; Albuquerque, Patrícia; Pappas, Georgios Joannis; Nicola, André Moraes; Silva, Fabiana Brandão Alves; Vallim, Marcelo Afonso; Alspaugh, J Andrew; Felipe, Maria Sueli Soares; Fernandes, Larissa
Gti1/Pac2 transcription factors occur exclusively in fungi and their roles vary according to species, including regulating morphological transition and virulence, mating and secondary metabolism. Many of these functions are important for fungal pathogenesis. We therefore hypothesized that one of the two proteins of this family in Cryptococcus neoformans, a major pathogen of humans, would also control virulence-associated cellular processes. Elimination of this protein in C. neoformans results in reduced polysaccharide capsule expression and defective cytokinesis and growth at 37°C. The mutant loses virulence in a mouse model of cryptococcal infection and retains only partial virulence in the Galleria mellonella alternative model at 30°C. We performed RNA-Seq experiments on the mutant and found abolished transcription of genes that, in combination, are known to account for all the observed phenotypes. The protein has been named Required for cytokinesis and virulence 1 (Rcv1).
Open Access
Perforin and IL-2 Upregulation Define Qualitative Differences among Highly Functional Virus-Specific Human CD8(+) T Cells
(2010) Ferrari, Guido
The prevailing paradigm of T lymphocyte control of viral replication is that the protective capacity of virus-specific CD8(+) T cells is directly proportional to the number of functions they can perform, with IL-2 production capacity considered critical. Having recently defined rapid perforin upregulation as a novel effector function of antigen-specific CD8(+) T cells, here we sought to determine whether new perforin production is a component of polyfunctional CD8(+) T cell responses that contributes to the control of several human viral infections: cytomegalovirus (CMV), Epstein-Barr virus (EBV), influenza (flu), and adenovirus (Ad). We stimulated normal human donor PBMC with synthetic peptides whose amino acid sequences correspond to defined CTL epitopes in the aforementioned viruses, and then used polychromatic flow cytometry to measure the functional capacity and the phenotype of the responding CD8(+) T cells. While EBV and flu-specific CD8(+) T cells rarely upregulate perforin, CMV-specific cells often do and Ad stimulates an exceptionally strong perforin response. The differential propensity of CD8(+) T cells to produce either IL-2 or perforin is in part related to levels of CD28 and the transcription factor T-bet, as CD8(+) T cells that rapidly upregulate perforin harbor high levels of T-bet and those producing IL-2 express high amounts of CD28. Thus, "polyfunctional'' profiling of antigen-specific CD8(+) T cells must not be limited to simply the number of functions the cell can perform, or one particular memory phenotype, but should actually define which combinations of memory markers and functions are relevant in each pathogenic context.
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Phosphorylation of Human Tristetraprolin in Response to Its Interaction with the CbI Interacting Protein CIN85
(2010) Kedar, Vishram P; Darby, Martyn K; Williams, Jason G; Blackshear, Perry J
Background: Tristetraprolin (TTP) is the prototype member of a family of CCCH tandem zinc finger proteins and is considered to be an anti-inflammatory protein in mammals. TTP plays a critical role in the decay of tumor necrosis factor alpha (TNF) mRNA, among others, by binding AU-rich RNA elements in the 3'-untranslated regions of this transcript and promoting its deadenylation and degradation. Methodology/Principal Findings: We used yeast two-hybrid analysis to identify potential protein binding partners for human TTP (hTTP). Various regions of hTTP recovered 31 proteins that fell into 12 categories based on sequence similarities. Among these, the interactions between hTTP and CIN85, cytoplasmic poly (A) binding protein (PABP), nucleolin and heat shock protein 70 were confirmed by co-immunoprecipitation experiments. CIN85 and hTTP co-localized in the cytoplasm of cells as determined by confocal microscopy. CIN85 contains three SH3 domains that specifically bind a unique proline-arginine motif (PXXXPR) found in several CIN85 effectors. We found that the SH3 domains of CIN85 bound to a PXXXPR motif located near the C-terminus of hTTP. Co-expression of CIN85 with hTTP resulted in the increased phosphorylation of hTTP at serine residues in positions 66 and 93, possibly due in part to the demonstrated association of mitogen-activated protein kinase kinase kinase 4 (MEKK4) to both proteins. The presence of CIN85 did not appear to alter hTTP's binding to RNA probes or its stimulated breakdown of TNF mRNA. Conclusions/Significance: These studies describe interactions between hTTP and nucleolin, cytoplasmic PABP, heat shock protein 70 and CIN85; these interactions were initially discovered by two-hybrid analysis, and confirmed by coimmunoprecipitation. We found that CIN85 binding to a C-terminal motif within hTTP led to the increased phosphorylation of hTTP, possibly through enhanced association with MEKK4. The functional consequences to each of the members of this putative complex remain to be determined.