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Identification of Cyclin-dependent Kinase 1 Specific Phosphorylation Sites by an In Vitro Kinase Assay
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Identification of Cyclin-dependent Kinase 1 Specific Phosphorylation Sites by an In Vitro Kinase Assay

Published on: May 3, 2018

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Cyclin A2/cyclin-dependent kinase 1-dependent phosphorylation of Top2a is required for S phase entry during retinal

Miaomiao Jin1, Jingyu Li1, Ruikun Hu1

  • 1Department of Clinical Laboratory Medicine of Shanghai Tenth People's Hospital, Tongji University School of Life Sciences and Technology, Shanghai 200092, China.

Journal of Genetics and Genomics = Yi Chuan Xue Bao
|April 9, 2021
PubMed

Insights

Cyclin-dependent kinase 1 (CDK1) is crucial for cell cycle regulation. Zebrafish studies reveal CDK1, with cyclin A2, controls S phase entry via Top2a, and with cyclin B1, regulates M phase progression.

Area of Science:

  • Developmental Biology
  • Cell Cycle Regulation
  • Molecular Genetics

Background:

  • Cyclin-dependent kinase 1 (CDK1) is vital for cell cycle control.
  • Mouse models are limited for studying CDK1's embryonic roles due to early lethality.
  • Zebrafish offer a valuable model for investigating CDK1 function in early development.

Purpose of the Study:

  • To elucidate the role of CDK1 in zebrafish embryonic development and cell cycle regulation.
  • To identify CDK1's interacting partners and downstream targets involved in cell cycle progression.
  • To understand the specific mechanisms by which CDK1 influences S phase and M phase entry.

Main Methods:

  • Generation and analysis of zebrafish cdk1 knockout embryos (cdk1-/-).
  • In silico analysis to predict CDK1 partners (cyclins) and targets (Top2a).
  • RNA interference (RNAi) to deplete cyclin A2 (ccna2) and cyclin B1 (ccnb1) in zebrafish.
  • Analysis of DNA replication (S phase) and cell division (M phase) markers.
  • Phosphorylation site analysis of Top2a and rescue experiments using a phosphomimetic mutant.

Main Results:

  • Zebrafish cdk1-/- embryos displayed microphthalmia and defects in S phase entry, M phase progression, and cell differentiation.
  • CDK1 interacts with cyclin A2 and cyclin B1; Top2a is a potential downstream target.
  • Depletion of cyclin A2 or Top2a impaired S phase entry; cyclin B1 depletion caused M phase arrest.
  • Phosphorylation of Top2a at S1213 was dependent on CDK1 and cyclin A2, but not cyclin B1.
  • Overexpression of a phosphomimetic Top2a mutant rescued S phase entry and microphthalmia in cdk1-/- and ccna2-/- embryos.

Conclusions:

  • CDK1, in complex with cyclin A2, regulates S phase entry partly via Top2a phosphorylation.
  • CDK1, in complex with cyclin B1, is essential for M phase progression.
  • These findings clarify CDK1's distinct roles in regulating different phases of the cell cycle during embryonic development.
Keywords:
Cdk1Cyclin A2Cyclin B1IKNMM phaseS phase entryTop2a

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