Requirement for integration of phorbol 12-myristate 13-acetate and calcium pathways is preserved in the transactivation domain of NFAT1.
The transcription factor NFAT integrates signals from both calcium- and phorbol ester-stimulated signaling pathways. The calcium signal activates the calmodulin (CaM)-dependent phosphatase calcineurin, which dephosphorylates the regulatory domain of NFAT and promotes its nuclear import, while the phorbol ester signal results in synthesis and activation of Fos and Jun, transcription factors that bind cooperatively with the NFAT DNA-binding domain in the nucleus to mediate the transcription of many target genes. Here we show that transactivation by a GAL4 fusion protein containing the strong acidic N-terminal transactivation domain (TAD) of NFAT1 also requires both calcium and phorbol ester stimulation. The calcium requirement can be mimicked by coexpression of activated versions of two CaM-dependent enzymes, calcineurin and CaM kinase IV. Our data indicate that a 144-amino acid segment of NFAT1, containing the N-terminal TAD but lacking the DNA-binding and Fos/Jun interaction domains, resembles the full-length protein in requiring a combined input from two separate signaling pathways for optimal function in cells.
García-Rodríguez
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C
Department of Pathology, Harvard Medical School, and the Center for Blood Research, Boston, MA 02115, USA.
Rao
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A
D019703:Calcineurin / Q000032:analysis; D002118:Calcium / Q000502:physiology*; D054734:Calcium-Calmodulin-Dependent Protein Kinase Type 4; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D016572:Cyclosporine / Q000494:pharmacology; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000502:physiology*; D006801:Humans; D019169:Jurkat Cells; D050778:NFATC Transcription Factors; D009687:Nuclear Proteins; D013329:Structure-Activity Relationship; D013601:T-Lymphocytes / Q000502:physiology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D014157:Transcription Factors / Q000737:chemistry / Q000502:physiology*; D015533:Transcriptional Activation
D004268:DNA-Binding Proteins; D050778:NFATC Transcription Factors; C494006:NFATC2 protein, human; D009687:Nuclear Proteins; D014157:Transcription Factors; D016572:Cyclosporine; C517683:CAMK4 protein, human; D054734:Calcium-Calmodulin-Dependent Protein Kinase Type 4; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D019703:Calcineurin; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium