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Articles by A Ghosh
Total Records ( 3 ) for A Ghosh
  Z. A Cooper , A Ghosh , A Gupta , T Maity , I. J Benjamin , S. N Vogel , J. D Hasday and I. S. Singh

We previously showed that exposure to febrile-range temperatures (FRT, 39.5–40°C) reduces LPS-induced TNF- expression, in part through the direct interaction of heat shock factor-1 (HSF1) with the TNF- gene promoter. However, it is not known whether exposure to FRT also modifies more proximal LPS-induced signaling events. Using HSF1-null mice, we confirmed that HSF1 is required for FRT-induced repression of TNF- in vitro by LPS-stimulated bone marrow-derived macrophages and in vivo in mice challenged intratracheally with LPS. Exposing LPS-stimulated RAW 264.7 mouse macrophages to FRT reduced TNF- expression while increasing IL-1β expression despite the two genes sharing a common myeloid differentiation protein-88 (MyD88)-dependent pathway. Global activation of the three LPS-induced signaling intermediates that lead to cytokine gene expression, ERK and p38 MAPKs and NF-B, was not affected by exposing RAW 264.7 cells to FRT as assessed by ERK and p38 phosphorylation and NF-B in vitro DNA-binding activity and activation of a NF-B-dependent synthetic promoter. However, chromatin immunoprecipitation (ChIP) analysis demonstrated that exposure to FRT reduced LPS-induced recruitment of NF-B p65 to the TNF- promoter while simultaneously increasing its recruitment to the IL-1β promoter. These data suggest that FRT exerts its effects on cytokine gene expression in a gene-specific manner through distal effects on promoter activation rather than proximal receptor activation and signal transduction.

  D Rajagopal , R. W Maul , A Ghosh , T Chakraborty , A. A Khamlichi , R Sen and P. J. Gearhart

Repetitive DNA sequences in the immunoglobulin switch µ region form RNA-containing secondary structures and undergo hypermutation by activation-induced deaminase (AID). To examine how DNA structure affects transcription and hypermutation, we mapped the position of RNA polymerase II molecules and mutations across a 5-kb region spanning the intronic enhancer to the constant µ gene. For RNA polymerase II, the distribution was determined by nuclear run-on and chromatin immunoprecipitation assays in B cells from uracil-DNA glycosylase (UNG)–deficient mice stimulated ex vivo. RNA polymerases were found at a high density in DNA flanking both sides of a 1-kb repetitive sequence that forms the core of the switch region. The pileup of polymerases was similar in unstimulated and stimulated cells from Ung–/– and Aid–/–Ung–/– mice but was absent in cells from mice with a deletion of the switch region. For mutations, DNA was sequenced from Ung–/– B cells stimulated in vivo. Surprisingly, mutations of A nucleotides, which are incorporated by DNA polymerase , decreased 10-fold before the repetitive sequence, suggesting that the polymerase was less active in this region. We propose that altered DNA structure in the switch region pauses RNA polymerase II and limits access of DNA polymerase during hypermutation.

  O Penack , O. M Smith , A Cunningham Bussel , X Liu , U Rao , N Yim , I. K Na , A. M Holland , A Ghosh , S. X Lu , R. R Jenq , C Liu , G. F Murphy , K Brandl and M. R.M. van den Brink

Nucleotide-binding oligomerization domain 2 (NOD2) polymorphisms are independent risk factors for Crohn's disease and graft-versus-host disease (GVHD). In Crohn's disease, the proinflammatory state resulting from NOD2 mutations have been associated with a loss of antibacterial function of enterocytes such as paneth cells. NOD2 has not been studied in experimental allogeneic bone marrow transplantation (allo-BMT). Using chimeric recipients with NOD2–/– hematopoietic cells, we demonstrate that NOD2 deficiency in host hematopoietic cells exacerbates GVHD. We found that proliferation and activation of donor T cells was enhanced in NOD-deficient allo-BMT recipients, suggesting that NOD2 plays a role in the regulation of host antigen-presenting cells (APCs). Next, we used bone marrow chimeras in an experimental colitis model and observed again that NOD2 deficiency in the hematopoietic cells results in increased intestinal inflammation. We conclude that NOD2 regulates the development of GVHD through its inhibitory effect on host APC function.

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