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Updated: Apr 19, 2026
Identification of Cyclin-dependent Kinase 1 Specific Phosphorylation Sites by an In Vitro Kinase Assay
Published on: May 3, 2018
Cdk1-mediated phosphorylation of human ATF7 at Thr-51 and Thr-53 promotes cell-cycle progression into M phase
Hitomi Hasegawa1, Kenichi Ishibashi1, Shoichi Kubota1
1Department of Molecular Cell Biology, Graduate School of Pharmaceutical Sciences, Chiba University, Chiba, Japan.
Abstract:
Activating transcription factor 2 (ATF2) and its homolog ATF7 are phosphorylated at Thr-69/Thr-71 and at Thr-51/Thr-53, respectively, by stress-activated MAPKs regulating their transcriptional functions in G1 and S phases. However, little is known about the role of ATF2 and ATF7 in G2/M phase. Here, we show that Cdk1-cyclin B1 phosphorylates ATF2 at Thr-69/Thr-71 and ATF7 at Thr-51/Thr-53 from early prophase to anaphase in the absence of any stress stimulation. Knockdown of ATF2 or ATF7 decreases the rate of cell proliferation and the number of cells in M-phase. In particular, the knockdown of ATF7 severely inhibits cell proliferation and G2/M progression. The inducible expression of a mitotically nonphosphorylatable version of ATF7 inhibits G2/M progression despite the presence of endogenous ATF7. We also show that mitotic phosphorylation of ATF7 promotes the activation of Aurora kinases, which are key enzymes for early mitotic events. These results suggest that the Cdk1-mediated phosphorylation of ATF7 facilitates G2/M progression, at least in part, by enabling Aurora signaling.
Insights
Activating transcription factor 2 (ATF2) and ATF7 are phosphorylated during mitosis by Cdk1-cyclin B1, promoting cell division. Mitotic phosphorylation of ATF7 is crucial for G2/M progression and Aurora kinase activation.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Activating transcription factor 2 (ATF2) and ATF7 regulate gene transcription in G1 and S phases via stress-activated MAPK phosphorylation.
- The role of ATF2 and ATF7 in the G2/M phase of the cell cycle remains largely uncharacterized.
Purpose of the Study:
- To investigate the function of ATF2 and ATF7 during the G2/M phase.
- To elucidate the regulatory mechanisms of ATF2 and ATF7 phosphorylation in mitosis.
Main Methods:
- Western blotting to detect phosphorylation.
- Cell proliferation assays.
- Mitotic progression analysis using knockdown and inducible expression systems.
- Kinase activity assays.
Main Results:
- Cdk1-cyclin B1 phosphorylates ATF2 and ATF7 at specific threonine residues during early mitosis (prophase to anaphase) without stress.
- Knockdown of ATF2 or ATF7 impairs cell proliferation and M-phase progression, with ATF7 knockdown having a severe effect.
- A non-phosphorylatable ATF7 mutant inhibits G2/M progression.
- Mitotic phosphorylation of ATF7 activates Aurora kinases, essential for mitosis.
Conclusions:
- Cdk1-mediated phosphorylation of ATF7 plays a critical role in facilitating G2/M progression.
- Mitotic phosphorylation of ATF7 contributes to cell cycle progression by activating Aurora signaling pathways.
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