Tumor necrosis factor (TNF) is a pleiotropic cytokine expressed <

Tumor necrosis factor (TNF) is a pleiotropic cytokine expressed BAY 73-4506 cost by various types of lymphoid and myeloid cells, including T cells, B cells, NK cells, monocytes, macrophages, DCs, and mast cells (reviewed in [1, 2]). TNF is involved in development, homeostasis, and activation of the immune system [3-8]. Physiological functions mediated by TNF depend on the cellular sources and the molecular form of this cytokine [9-11]. In particular, TNF produced by macrophages and T cells plays different roles in immune and inflammatory reactions [9, 10]. TNF is the primary response

gene in macrophages where it has a permissive chromatin conformation [12, 13]. Even without stimulation, the proximal TNF promoter and transcription start site (TSS) have an open chromatin configuration in primary monocytes and macrophages and in the majority of tested myelomonocytic cell lines[14-22]. Various T-cell subsets produce different amounts of TNF in correlation with their pathophysiological

potential [23]. Earlier studies [24] as well as recent advances in high-throughput analysis of DNaseI chromatin accessibility indicate that the proximal part of the TNF promoter in T cells is open (Supporting Information Fig. 1); however, in contrast to macrophages, the TSS of TNF in T cells acquires Ibrutinib open chromatin conformation only after activation or polarization under Th1 or Th17 (where Th is T helper) conditions. TNF gene expression in T cells is regulated by the NFAT and AP-1 families of transcription

factors; in particular, activation of the proximal TNF promoter region involves functional interactions with the transcription factors NFATc2 and c-Jun [25-31]. Numerous reports also supported the involvement of the NF-κB family members in transcriptional regulation of the TNF gene in macrophages, in spite of the lack of canonical high-affinity NF-κB binding sites within the proximal TNF promoter [32-39]. However, specific role of NF-κB family members in regulation of the TNF gene is still being debated ([1, 2] and Discussion section). In murine T cells, members of the NF-κB family were shown to bind to the distal Bcl-w part of the TNF promoter [40] and to the enhancer element immediately downstream of the TNF gene (3′-TNF enhancer) [24], but the functional significance of these interactions is not clear. Here, we demonstrate the difference in chromatin structure around TNF TSS between T cells and macrophages. We further show that active forms of c-Jun and NFATc2 transcription factors are involved in chromatin remodeling occurring at the TNF TSS in activated Th cells and in T cells polarized under Th1 and Th17 conditions. c-Jun alone appears to be sufficient for the maintenance of such open chromatin conformation at the TNF TSS. Thus, our data uncover additional level of TNF expression control occurring through chromatin remodeling.

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