Pavel Kovarik
Max F. Perutz Laboratories
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Featured researches published by Pavel Kovarik.
Oncogene | 2000
Thomas Decker; Pavel Kovarik
Tyrosine phosphorylation regulates the dimerization of STATs as an essential prerequisite for the establishment of a classical JAK-STAT signaling path. However, most vertebrate STATs contain a second phosphorylation site within their C-termini. The phosphorylated residue in this case is a serine contained within a P(M)SP motif, and in the majority of situations its mutation to alanine alters transcription factor activity. This review addresses recent advances in understanding the regulation of STAT serine phosphorylation, as well as the kinases and other signal transducers implied in this process. The biochemical and biological consequences of STAT serine phosphorylation are discussed.
Immunity | 2000
Marina Karaghiosoff; Hans Neubauer; Caroline Lassnig; Pavel Kovarik; Heike Schindler; Hanspeter Pircher; Barbara McCoy; Christian Bogdan; Thomas Decker; G. Brem; Klaus Pfeffer; Mathias Müller
To assess the role of the Janus kinase (Jak) family member Tyk2, we have generated Tyk2-/- mice. In contrast to other Jaks, where inactivation leads to a complete loss of the respective cytokine receptor signal, Tyk2-/- mice display reduced responses to IFNalpha/beta and IL-12 and a selective deficiency in Stat3 activation in these pathways. Unexpectedly, IFNgamma signaling is also impaired in Tyk2-/- mice. Tyk2-/- macrophages fail to produce nitric oxide upon lipopolysaccharide induction. Tyk2-/- mice are unable to clear vaccinia virus and show a reduced T cell response after LCMV challenge. These data imply a selective contribution of Tyk2 to the signals triggered by various biological stimuli and cytokine receptors.
Nature Immunology | 2003
Marina Karaghiosoff; Ralf Steinborn; Pavel Kovarik; Gernot Kriegshäuser; Manuela Baccarini; Birgit Donabauer; Ursula Reichart; Thomas Kolbe; Christian Bogdan; Tomas Leanderson; David E. Levy; Thomas Decker; Mathias Müller
Toll-like receptor-4 activation by lipopolysaccharide (LPS) induces the expression of interferon-β (IFN-β) in a MyD88-independent manner. Here we report that mice devoid of the JAK protein tyrosine kinase family member, Tyk2, were resistant to shock induced by high doses of LPS. Basal and LPS-induced expression of IFN-β and IFN-α4 mRNA in Tyk2-null macrophages were diminished. However, Tyk2-null mice showed normal systemic production of nitric oxide and proinflammatory cytokines and the in vivo response to tumor necrosis factor (TNF) was unperturbed. IFN-β–null but not STAT1-null mice were also resistant to high dose LPS treatment. Together, these data suggest that Tyk2 and IFN-β are essential effectors in LPS induced lethality.
The EMBO Journal | 1998
Pavel Kovarik; Dagmar Stoiber; Michael Novy; Thomas Decker
Complete activation of macrophages during immune responses results from stimulation with the activating cytokine interferon‐γ (IFN‐γ) and a second stimulus, usually a microbial product. Bacterial infection of macrophages, or treatment with bacterial lipopolysaccharide (LPS), resulted in rapid Stat1 phosphorylation on Ser727 (S727) independently of concomitant tyrosine phosphorylation. IFN‐γ also caused rapid phosphorylation of S727. In both situations, S727 phosphorylation was reduced by pre‐treatment of cells with the serine kinase inhibitor H7. When macrophages were treated sequentially or simultaneously with LPS and IFN‐γ, the pool of molecules phosphorylated on both Tyr701 (Y701) and S727 was strongly increased. Consistently, Stat1‐dependent transcription in response to IFN‐γ was significantly enhanced if the cells were pre‐treated with bacterial LPS. The relative amount of S727‐phosphorylated Stat1 in the non‐tyrosine phosphorylated fraction was considerably smaller than that in the tyrosine‐phosphorylated fraction. No evidence was found for an effect of S727 phosphorylation on the phosphorylation of Y701 by IFN‐γ. Thus, serine and tyrosine phosphorylation of Stat1 are caused independently of each other, but the serine kinase may recognize tyrosine‐phosphorylated Stat1 preferentially in the course of an IFN‐γ response. The data suggest Stat1 to be a convergence point for immunological stimuli in a macrophage proinflammatory response.
Journal of Clinical Investigation | 2002
Thomas Decker; Silvia Stockinger; Marina Karaghiosoff; Mathias Müller; Pavel Kovarik
Innate immune responses derive from the ability of cells to rapidly combat invading microorganisms without the requirement for an antigen-specific adaptation. These mechanisms have evolved to recognize common microbe-associated molecular patterns and to interfere with conserved replication and survival strategies that support the propagation of microbial invaders. Here, we consider the contributions of one cytokine family, the IFNs, to these innate defense mechanisms. IFNs were first recognized for their ability to impede viral replication, a function that is indeed critical for host survival in response to viral infection. In addition, IFN signaling is now known to play key roles in defending the host from bacteria and other pathogens and to help integrate early, innate responses with later events mediated by the adaptive immune system. The two recognized types of IFN exhibit distinct immunological properties (1). In humans and mice, type I IFNs include a number of IFN-α subtypes and a single species of IFN-β. (The immunological impact of another type I IFN, IFN-ω, is poorly understood and will not be considered here). While type I IFNs can be produced by all cells under appropriate conditions, a subpopulation of immature dendritic cells (DCs) that will be described in more detail below stands out for the extent of its contribution to overall IFN production during infections. IFN-γ is a type II IFN and serves not only to induce antiviral function, but also to activate macrophages, which strengthens innate responses to unicellular microorganisms (2). Unlike the type I IFNs, IFN-γ is produced by a limited number of cell types: activated NK cells, activated Th1 cells, and, in the presence of IL-12 and IL-18, activated DCs and macrophages. Expression of IFN-γ by Th1 cells provides an important link by which the adaptive immune response reinforces macrophage-based innate immunity.
The EMBO Journal | 2001
Pavel Kovarik; Monika Mangold; Katrin Ramsauer; Hamid Heidari; Ralf Steinborn; Angelika Zotter; David E. Levy; Mathias Müller; Thomas Decker
Complete activation of signal transducer and activator of transcription 1 (STAT1) requires phosphorylation at both Y701 and a conserved PMS727P sequence. S727 phosphorylation of STAT1 in interferon‐γ (IFN‐γ)‐treated mouse fibroblasts occurred without a need for p38 mitogen‐activated protein kinase (MAPK), extracellular signal‐regulated kinases 1 and 2 or c‐Jun kinases, and required both an intact SH2 domain and phosphorylation of Y701. In contrast, UV irradiation‐induced STAT1 phosphorylation on S727 required p38MAPK, but no SH2 domain– phosphotyrosine interactions. Mutation of S727 differentially affected IFN‐γ target genes, at the level of both basal and induced expression. Particularly strong effects were noted for the GBP1 and TAP1 genes. The PMS727P motif of STAT3 was phosphorylated by stimuli and signaling pathways different from those for STAT1 S727. Transfer of the STAT3 C‐terminus to STAT1 changed the stimulus and pathway specificity of STAT1 S727 phosphorylation to that of STAT3. Our data suggest that STAT C‐termini contribute to the specificity of cellular responses by linking individual STATs to different serine kinase pathways and through an intrinsically different requirement for serine phosphorylation at different target gene promoters.
Nucleic Acids Research | 2011
Andreas Gruber; Jörg Fallmann; Franz Kratochvill; Pavel Kovarik; Ivo L. Hofacker
AREsite is an online resource for the detailed investigation of AU-rich elements (ARE) in vertebrate mRNA 3′-untranslated regions (UTRs). AREs are one of the most prominent cis-acting regulatory elements found in 3′-UTRs of mRNAs. Various ARE-binding proteins that possess RNA stabilizing or destabilizing functions are recruited by sequence-specific motifs. Recent findings suggest an essential role of the structural mRNA context in which these sequence motifs are embedded. AREsite is the first database that allows to quantify the structuredness of ARE motif sites in terms of opening energies and accessibility probabilities. Moreover, we also provide a detailed phylogenetic analysis of ARE motifs and incorporate information about experimentally validated targets of the ARE-binding proteins TTP, HuR and Auf1. The database is publicly available at: http://rna.tbi.univie.ac.at/AREsite.
The EMBO Journal | 1999
Akinori Takaoka; Nobuyuki Tanaka; Yukiko Mitani; Tadaaki Miyazaki; Hodaka Fujii; Mitsuharu Sato; Pavel Kovarik; Thomas Decker; Joseph Schlessinger; Tadatsugu Taniguchi
Two distinct types of interferon, IFN‐α/β and IFN‐γ, commonly exhibit antiviral activities by transmitting signals to the interior of the cell via their homologous receptors. Receptor stimulation results in the activation of distinct combinations of Janus family protein tyrosine kinases (Jak PTKs); Jak1/Tyk2 and Jak1/Jak2 for IFN‐α/β and IFN‐γ, respectively. Jak PTK activation by these IFNs is commonly followed by tyrosine phosphorylation of the transcription factor Stat1 at Y701, which is essential for dimerization, translocation to the nucleus and DNA‐binding activity. To gain full transcriptional activity, Stat1 also requires serine phosphorylation at S727. In this paper we demonstrate that Pyk2, which belongs to another PTK family, is critical for the Jak‐mediated MAPK and Stat1 activation by IFN‐γ, but not IFN‐α. Pyk2 is selectively associated with Jak2 and activated by IFN‐γ. Overexpression of PKM, a dominant interfering form of Pyk2, in NIH 3T3 cells results in a strong inhibition of the IFN‐γ‐induced activation of Erk2, serine phosphorylation of Stat1 and Stat1‐dependent gene transcription. Finally, the antiviral action of IFN‐γ, but not IFN‐α, is severely impaired by PKM overexpression. Thus, the two types of IFN may utilize distinct Jak‐mediated Erk2, and possibly other MAPK activation pathways for their antiviral action.
Proceedings of the National Academy of Sciences of the United States of America | 2002
Katrin Ramsauer; Iwona Sadzak; Almudena Porras; Andreas Pilz; Angel R. Nebreda; Thomas Decker; Pavel Kovarik
The transcription factor signal transducer and activator of transcription 1 (STAT1) requires phosphorylation at both Tyr-701 and Ser-727 for full activation. IFN-γ induces phosphorylation of both residues, whereas stress signals like UV or lipopolysaccharide stimulate phosphorylation of Ser-727 only. Using p38α mitogen-activated protein kinase (MAPK)-deficient cells, we show that the stress-induced phosphorylation of Ser-727 requires p38α MAPK activity, whereas IFN-γ-stimulated Ser-727 phosphorylation occurs independently of the p38α pathway. Consistently, IFN-γ stimulated expression of the STAT1 target gene IRF1 to a similar extent in both wild-type and p38α-deficient cells. However, stress-induced activation of the p38 MAPK pathway considerably enhanced the IFN-γ-induced expression of both the endogenous IRF1 gene and a reporter driven by the IFN-γ-activated sequence element of the IRF1 promoter. This enhancement occurred independently of increased phosphorylation of Ser-727 by the p38 pathway. Taken together, these results demonstrate an interaction between IFN-γ signaling and the p38 pathway that leads to increased transcriptional activation by STAT1 independently of phosphorylation at Ser-727.
Immunity | 2013
Joanna Bancerek; Zachary C. Poss; Iris Steinparzer; Vitaly Sedlyarov; Thaddäus Pfaffenwimmer; Ivana Mikulic; Lars Dölken; Birgit Strobl; Mathias Müller; Dylan J. Taatjes; Pavel Kovarik
Summary Gene regulation by cytokine-activated transcription factors of the signal transducer and activator of transcription (STAT) family requires serine phosphorylation within the transactivation domain (TAD). STAT1 and STAT3 TAD phosphorylation occurs upon promoter binding by an unknown kinase. Here, we show that the cyclin-dependent kinase 8 (CDK8) module of the Mediator complex phosphorylated regulatory sites within the TADs of STAT1, STAT3, and STAT5, including S727 within the STAT1 TAD in the interferon (IFN) signaling pathway. We also observed a CDK8 requirement for IFN-γ-inducible antiviral responses. Microarray analyses revealed that CDK8-mediated STAT1 phosphorylation positively or negatively regulated over 40% of IFN-γ-responsive genes, and RNA polymerase II occupancy correlated with gene expression changes. This divergent regulation occurred despite similar CDK8 occupancy at both S727 phosphorylation-dependent and -independent genes. These data identify CDK8 as a key regulator of STAT1 and antiviral responses and suggest a general role for CDK8 in STAT-mediated transcription. As such, CDK8 represents a promising target for therapeutic manipulation of cytokine responses.