Requirement of Ca2+ and CaMKII for Stat1 Ser-727 phosphorylation in response to IFN-gamma.
In response to IFN-gamma, the latent cytoplasmic protein signal transducers and activators of transcription 1 (Stat1) becomes phosphorylated on Y701, dimerizes, and accumulates in the nucleus to activate transcription of IFN-gamma-responsive genes. For maximal gene activation, S727 in the transcription activation domain of Stat1 also is inducibly phosphorylated by IFN-gamma. We previously purified a group of nuclear proteins that interact specifically with the Stat1 transcription activation domain. In this report, we identified one of them as the multifunctional Ca(2+)/calmodulin-dependent kinase (CaMK) II. We demonstrate that IFN-gamma mobilizes a Ca(2+) flux in cells and activates CaMKII. CaMKII can interact directly with Stat1 and phosphorylate Stat1 on S727 in vitro. Inhibition of Ca(2+) flux or CaMKII results in a lack of S727 phosphorylation and Stat1-dependent gene activation, suggesting in vivo phosphorylation of Stat1 S727 by CaMKII. Thus two different cellular signaling events, IFN-gamma receptor occupation and Ca(2+) flux, are required for Stat1 to achieve maximal transcriptional activation through regulation of phosphorylation.
Nair
Jayasree S
JS
Department of Pathology, Weill Medical College of Cornell University, 1300 York Avenue, New York, NY 10021, USA.
DaFonseca
Christopher J
CJ
Tjernberg
Agneta
A
Sun
Wei
W
Darnell
James E
JE
Chait
Brian T
BT
Zhang
J Jillian
JJ
D016475:3T3 Cells; D000818:Animals; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism / Q000502:physiology*; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000502:physiology*; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D019281:Dimerization; D005982:Glutathione Transferase / Q000378:metabolism; D006801:Humans; D007371:Interferon-gamma / Q000378:metabolism*; D051379:Mice; D010766:Phosphorylation; D011233:Precipitin Tests; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D050794:STAT1 Transcription Factor; D012694:Serine / Q000737:chemistry*; D013997:Time Factors; D015534:Trans-Activators / Q000378:metabolism*; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D014162:Transfection
D004268:DNA-Binding Proteins; D011993:Recombinant Fusion Proteins; D050794:STAT1 Transcription Factor; C494079:STAT1 protein, human; C494080:Stat1 protein, mouse; D015534:Trans-Activators; D012694:Serine; D007371:Interferon-gamma; D005982:Glutathione Transferase; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D002118:Calcium