Nonconventional initiation complex assembly by STAT and NF-kappaB transcription factors regulates nitric oxide synthase expression.
Bottom Line: NF-kappaB preceded ISGF3 at the Nos2 promoter and generated a transcriptional memory effect by depositing basal transcription factor TFIIH with the associated CDK7 kinase for serine 5 phosphorylation of the RNA polymerase II (pol II) carboxyterminal domain (CTD).Subsequent to TFIIH deposition by NF-kappaB, ISGF3 attracted the pol II enzyme and phosphorylation at CTD S5 occurred.Thus, STATs and NF-kappaB cooperate through pol II promoter recruitment and the phosphorylation of its CTD, respectively, as a prerequisite for productive elongation of iNOS mRNA.
Affiliation: Max F. Perutz Laboratories, Department of Genetics, Microbiology and Immunobiology, University of Vienna, Dr. Bohr-Gasse 9/4, A1030 Vienna, Austria.Show MeSH
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Mentions: As discussed above, the innate immune response to L. monocytogenes results initially from plasma membrane and endosomal pattern recognition during entry and from cytoplasmic sensing after cytoplasmic escape. The Nos2 gene is paradigmatic for a large group of genes coregulated by pattern recognition receptors and IFN-I (Doyle et al., 2002; Toshchakov et al., 2002). To test whether IFN-I synthesis was the only essential signal for Nos2 induction derived from the cytoplasmic signaling, the two recognition phases were separated by treating macrophages with heat-killed L. monocytogenes (hkL) and with IFN-β either separately or together. Heat-killed Listeria are confined to phagosomes and cannot stimulate the cytoplasmic signal required for IFN-I production. hkL and IFN-β alone were poor inducers of iNOS mRNA synthesis (Figure 1). By contrast, both signals together synergized to produce the full-blown iNOS synthesis seen with viable L. monocytogenes. This result suggests that cytoplasmic signaling can indeed be recapitulated by providing IFN-I. In addition, it provides a valuable experimental tool to separate effects of non-IFN-I and IFN-I signals on the Nos2 promoter and to study each independently from the other. In agreement with IFN-I synthesis preceding Nos2 transcription, the kinetics of mRNA synthesis after infection with viable L. monocytogenes were delayed compared to the simultaneous treatment with hkL and IFN-β.
Affiliation: Max F. Perutz Laboratories, Department of Genetics, Microbiology and Immunobiology, University of Vienna, Dr. Bohr-Gasse 9/4, A1030 Vienna, Austria.