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Mol. Cell. Biol., Apr 1997, 2066-2075, Vol 17, No. 4
ES Masuda, J Liu, R Imamura, SI Imai, KI Arai and N Arai
The nuclear factor of activated T cells (NFAT) regulates cytokine gene
expression in T cells through cis-acting elements located in the promoters
of several cytokine genes. NFATx1, which is preferentially expressed in the
thymus and peripheral blood leukocytes, is one of four members of the NFAT
family of transcription factors. We have performed domain analysis of
NFATx1 by examining the effects of deletion mutations. We found that NFATx1
DNA binding activity and interaction with AP-1 polypeptides were dependent
on its central Rel similarity region and that transcriptional activation
was reduced by deletions of either its N-terminal domain or its C-terminal
domain, suggesting the presence of intrinsic transcriptional activation
motifs in both regions. We also identified a potent inhibitory sequence
within its N- terminal domain. We show that the inactivation of the
inhibition was dependent on the activity of calcineurin, a
calcium-calmodulin- dependent phosphatase. We also show that calcineurin
associated with the N-terminal domain of NFATx1 at multiple docking sites
and caused a reduction of size, indicative of dephosphorylation, in NFATx1.
We have mapped the inhibitory activity to less than 60 residues, containing
motifs that are conserved in all NFAT proteins. Finally, we demonstrate
that deletion in NFATx1 of the mapped 60 residues leads to its nuclear
translocation independent of calcium signaling. Our results support the
model proposing that the N-terminal domain confers calcium-signaling
dependence on NFATx1 transactivation activity by regulating its
intracellular localization through a protein module that associates with
calcineurin and is a target of its phosphatase activity.
Copyright © 1997, American Society for Microbiology
Control of NFATx1 nuclear translocation by a calcineurin-regulated inhibitory domain
Department of Cell Signaling, DNAX Research Institute of Molecular and Cellular Biology, Palo Alto, California 94304, USA.
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