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Updated: May 7, 2026

Identification of Cyclin-dependent Kinase 1 Specific Phosphorylation Sites by an In Vitro Kinase Assay
Published on: May 3, 2018
CDK8 as the STAT1 serine 727 kinase?
Julia Staab1, Christoph Herrmann-Lingen, Thomas Meyer
1Department of Psychosomatic Medicine and Psychotherapy; University of Göttingen; Göttingen, Germany.
Cyclin-dependent kinase 8 (CDK8) phosphorylates STAT1 serine 727 upon interferon-gamma (IFNγ) stimulation. This CDK8 module links STAT1 serine phosphorylation to gene transcription.
Area of Science:
- Molecular Biology
- Cell Signaling
- Gene Regulation
Background:
- Cytokine signaling involves JAK kinases phosphorylating STAT proteins on tyrosine residues.
- Regulation of STAT proteins by serine kinases remains less understood.
- STAT1 serine phosphorylation is crucial for transcriptional activity.
Purpose of the Study:
- To investigate the role of serine kinases in STAT1 signaling.
- To identify the specific kinase responsible for STAT1 serine phosphorylation.
- To elucidate the functional consequences of STAT1 serine phosphorylation.
Main Methods:
- Cellular stimulation with interferon-gamma (IFNγ).
- Chromatin immunoprecipitation assays.
- Western blotting to detect STAT1 phosphorylation.
- Analysis of the Mediator complex component CDK8.
Main Results:
- Interferon-gamma (IFNγ) stimulation activates the chromatin-associated cyclin-dependent kinase 8 (CDK8).
- CDK8 directly phosphorylates serine residue 727 in the STAT1 transactivation domain.
- The CDK8 module of the Mediator complex is essential for STAT1-mediated gene transcription.
Conclusions:
- CDK8 is a key STAT1-specific serine kinase.
- STAT1 serine 727 phosphorylation by CDK8 is a critical step in IFNγ signaling.
- The CDK8-Mediator complex links STAT1 activation to gene-specific transcriptional outcomes.
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