Identification of a novel conserved motif in the STAT family that is required for tyrosine phosphorylation.
The rapid transcriptional activation of cellular genes by either type 1 interferons (IFNalpha/beta) or type 2 interferon (IFNgamma) is responsible for many of the pleiotropic effects of these cytokines, including their antiviral, antigrowth, and immunomodulatory activities. Interferon-stimulated gene expression is mediated by transcription factors termed Stats, which upon being tyrosine-phosphorylated, translocate to the nucleus and bind enhancers of interferon-activated genes. We have recently characterized a new Jurkat cell variant, named H123, where IFNalpha stimulates programmed cell death. H123 clones that are resistant to the apoptotic actions of IFNalpha have been selected. One of these clones (Clone 8) is defective in its responses to IFNalpha with regard to activation of genes that require tyrosine phosphorylation of Stat2. Stimulation of Clone 8 cells with IFNalpha induces normal tyrosine phosphorylation of Stat1 and Stat3. Sequencing of Stat2 RNA reveals a substitution of proline 630 located within the Src homology 2 domain of Stat2 to leucine (P630L). Pro-630 and its adjacent amino acids are conserved in all Stat family members but are absent in other proteins that contain Src homology 2 domains. Expression of Stat2 P630L in cells inhibits IFNalpha-stimulated gene expression. These results not only define a critical motif in Stat2 required for its transcriptional activity, but they also provide evidence that resistance to type one IFNs can be mediated by mutations in Stat2 as well as those previously described for Stat1.
Gamero
Ana M
AM
Department of Immunology, Lerner Research Institute, The Cleveland Clinic Foundation, 9500 Euclid Avenue, Cleveland, OH 44195, USA.
Sakamoto
Shuji
S
Montenegro
Javier
J
Larner
Andrew C
AC
D021581:Active Transport, Cell Nucleus; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D017209:Apoptosis; D001483:Base Sequence; D015153:Blotting, Western; D017124:Conserved Sequence; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004591:Electrophoresis, Polyacrylamide Gel; D005434:Flow Cytometry; D005786:Gene Expression Regulation; D006801:Humans; D016898:Interferon-alpha / Q000378:metabolism; D016899:Interferon-beta / Q000378:metabolism; D007371:Interferon-gamma / Q000378:metabolism; D019169:Jurkat Cells; D007930:Leucine / Q000737:chemistry; D008156:Luciferases / Q000378:metabolism; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D010766:Phosphorylation; D011233:Precipitin Tests; D011392:Proline / Q000737:chemistry; D017434:Protein Structure, Tertiary; D012313:RNA / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012260:Ribonucleases / Q000737:chemistry; D050794:STAT1 Transcription Factor; D050795:STAT2 Transcription Factor; D050796:STAT3 Transcription Factor; D017386:Sequence Homology, Amino Acid; D015534:Trans-Activators / Q000378:metabolism*; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D014162:Transfection; D014443:Tyrosine / Q000737:chemistry* / Q000378:metabolism
D004268:DNA-Binding Proteins; D016898:Interferon-alpha; D050794:STAT1 Transcription Factor; C494079:STAT1 protein, human; D050795:STAT2 Transcription Factor; C494084:STAT2 protein, human; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; D015534:Trans-Activators; D014443:Tyrosine; D012313:RNA; D016899:Interferon-beta; D007371:Interferon-gamma; D011392:Proline; D008156:Luciferases; D012260:Ribonucleases; D007930:Leucine