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The viral protein A238L inhibits cyclooxygenase-2 expression through a nuclear factor of activated T cell-dependent transactivation pathway.

Authors
  • Granja, Aitor G
  • Nogal, Maria L
  • Hurtado, Carolina
  • Vila, Virginia
  • Carrascosa, Angel L
  • Salas, María L
  • Fresno, Manuel
  • Revilla, Yolanda
Type
Published Article
Journal
The Journal of biological chemistry
Publication Date
Dec 17, 2004
Volume
279
Issue
51
Pages
53736–53746
Identifiers
PMID: 15471864
Source
Medline
License
Unknown

Abstract

Cyclooxygenase-2 is transiently induced upon cell activation or viral infections, resulting in inflammation and modulation of the immune response. Here we report that A238L, an African swine fever virus protein, efficiently inhibits cyclooxygenase-2 gene expression in Jurkat T cells and in virus-infected Vero cells. Transfection of Jurkat cells stably expressing A238L with cyclooxygenase-2 promoter-luciferase constructs containing 5'-terminal deletions or mutations in distal or proximal nuclear factor of activated T cell (NFAT) response elements revealed that these sequences are involved in the inhibition induced by A238L. Overexpression of a constitutively active version of the calcium-dependent phosphatase calcineurin or NFAT reversed the inhibition mediated by A238L on cyclooxygenase-2 promoter activation, whereas overexpression of p65 NFkappaB had no effect. A238L does not modify the nuclear localization of NFAT after phorbol 12-myristate 13-acetate/calcium ionophore stimulation. Moreover, we show that the mechanism by which the viral protein down-regulates cyclooxygenase-2 activity does not involve inhibition of the binding between NFAT and its specific DNA sequences into the cyclooxygenase-2 promoter. Strikingly, A238L dramatically inhibited the transactivation mediated by a GAL4-NFAT fusion protein containing the N-terminal transactivation domain of NFAT1. Taken together, these data indicate that A238L down-regulates cyclooxygenase-2 transcription through the NFAT response elements, being NFAT-dependent transactivation implicated in this down-regulation.

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