A constitutively nuclear form of NFATx shows efficient transactivation activity and induces differentiation of CD4(+)CD8(+) T cells.
The Ca(2+) signal facilitates nuclear translocation of NFAT through the dephosphorylation of clustered serine residues in the calcium regulatory domain by the Ca(2+)/calmodulin-dependent phosphatase calcineurin. The conformation of dephosphorylated NFAT exposes the nuclear localization signal for translocation into the nucleus and masks the nuclear export sequence to keep the protein in the nucleus. It has been reported that deletion of some serine-rich motifs masking the nuclear localization signal results in the translocation of NFAT into the nucleus, but that the nuclear export sequence located at the N terminus also needs to be deleted for NFATx (NFAT4/NFATc3) to exert efficient transactivation function. Here, we report that deletion of the critical serine-rich motifs of NFATx leads to a conformation that efficiently exposes the nuclear localization signal and that has stronger transcription activity compared with the fully activated wild-type protein in the presence of the nuclear export sequence. This also suggests that the regulation of the transactivation domain by phosphorylation observed in NFAT1 may not contribute significantly to the transcription activity of NFATx. The expression of this constitutively nuclear form of NFATx in the CD4(+)CD8(+) T cell line facilitates differentiation into the CD4 single-positive stage upon stimulation with phorbol ester. Our data suggest that NFATx is involved in the regulation of co-receptor expression during differentiation into the CD4 single-positive stage.
Amasaki
Yoshiharu
Y
Department of Molecular and Developmental Biology, Institute of Medical Science, University of Tokyo, Japan.
Adachi
Satoko
S
Ishida
Yukisato
Y
Iwata
Makoto
M
Arai
Naoko
N
Arai
Ken-ichi
K
Miyatake
Shoichiro
S
D000595:Amino Acid Sequence; D000818:Animals; D015496:CD4-Positive T-Lymphocytes / Q000166:cytology*; D018414:CD8-Positive T-Lymphocytes / Q000166:cytology*; D019556:COS Cells; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology*; D002467:Cell Nucleus / Q000378:metabolism*; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D006801:Humans; D019169:Jurkat Cells; D008969:Molecular Sequence Data; D050778:NFATC Transcription Factors; D009687:Nuclear Proteins; D017386:Sequence Homology, Amino Acid; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014157:Transcription Factors / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D015533:Transcriptional Activation / Q000502:physiology*
D004268:DNA-Binding Proteins; D050778:NFATC Transcription Factors; C494006:NFATC2 protein, human; C494008:NFATC3 protein, human; D009687:Nuclear Proteins; D014157:Transcription Factors; D004247:DNA; D013755:Tetradecanoylphorbol Acetate