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Cell cycle-dependent phosphorylation of human DNA polymerase alpha
H P Nasheuer1, A Moore, A F Wahl
1Department of Pathology, Stanford University School of Medicine, California 94305-5324.
The Journal of Biological Chemistry
|April 25, 1991
Summary
DNA polymerase alpha undergoes cell cycle-dependent phosphorylation, particularly in G2/M phase, affecting its DNA binding affinity. This suggests a role for mitotic phosphorylation in regulating DNA replication fork dynamics.
Area of Science:
- Molecular Biology
- Cell Biology
- Biochemistry
Background:
- DNA polymerase alpha is essential for chromosome replication.
- Its expression is constitutive throughout the cell cycle.
Purpose of the Study:
- To investigate the cell cycle-dependent phosphorylation of DNA polymerase alpha.
- To determine the kinases involved and the effect on DNA binding.
Main Methods:
- Cell cycle analysis
- In vitro kinase assays using p34cdc2
- Tryptic phosphopeptide mapping
- DNA binding assays
Main Results:
- DNA polymerase alpha catalytic subunit (p180) is phosphorylated throughout the cell cycle and hyperphosphorylated in G2/M phase.
- The p70 subunit is phosphorylated exclusively in G2/M phase.
- p34cdc2 kinase is involved in mitotic phosphorylation.
- Mitotic DNA polymerase alpha exhibits reduced affinity for single-stranded DNA.
Conclusions:
- Cell cycle-dependent phosphorylation, mediated by kinases like p34cdc2, regulates DNA polymerase alpha activity.
- Mitotic phosphorylation may modulate interactions with DNA and other proteins at the replication fork.