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Published on: February 22, 2014
Systematic identification of mitotic phosphoproteins
P T Stukenberg1, K D Lustig, T J McGarry
1Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115, USA.
Current Biology : CB
|May 1, 1997
Summary
This study identified 20 mitotic phosphoproteins in Xenopus embryos, revealing that cyclin-dependent kinases (CDKs) directly phosphorylate many substrates, suggesting combinatorial regulation and chromatin stripping during cell division.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Cyclin-dependent kinases (CDKs) regulate cell division by phosphorylating key targets, but these substrates are often unknown.
- Understanding CDK substrates is crucial for deciphering cell cycle control mechanisms.
Purpose of the Study:
- To identify novel mitotic phosphoproteins in Xenopus embryos.
- To investigate the direct substrates of the mitotic CDK, cyclin B-Cdc2.
- To elucidate the regulatory roles of mitotic phosphorylation in cell cycle progression.
Main Methods:
- A screen was developed to detect protein phosphorylation in vitro using phosphoepitope antibody recognition or electrophoretic mobility shifts.
- Proteins were translated from cDNA plasmid pools.
- Xenopus embryos were used as the biological system.
Main Results:
- Twenty mitotically phosphorylated proteins were identified from Xenopus embryos.
- Fifteen of these proteins showed sequence similarity to known proteins.
- Fourteen of 16 tested substrates were directly phosphorylated by cyclin B-Cdc2 in vitro, indicating Cdc2 directly phosphorylates most mitotic phosphoproteins.
- A significant fraction of identified proteins were transcription factors, suggesting a role in chromatin regulation.
Conclusions:
- Cdc2 directly phosphorylates the majority of identified mitotic phosphoproteins.
- Mitotic phosphoprotein substrates are often multiply phosphorylated and may be targeted by multiple kinases, indicating combinatorial regulation.
- Mitotic phosphorylation of transcription factors suggests a mechanism for stripping gene expression-associated proteins from chromatin during cell division.
