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DNA methylases separated through the HeLa cell cycle methodology show allosteric properties
FEBS Letters
|January 1, 1987
Summary
Two distinct DNA methylases (DNAmets) were identified, one in G1 and a major one in S phase. These enzymes protect plasmids from HpaII digestion, suggesting an allosteric nature of eukaryotic DNA methylation.
Area of Science:
- Molecular Biology
- Cell Biology
- Biochemistry
Background:
- DNA methylation is a crucial epigenetic mechanism regulating gene expression.
- The cell cycle-dependent activity of DNA methyltransferases (DNAmets) is not fully understood.
- Previous studies suggested the presence of multiple DNAmet forms.
Purpose of the Study:
- To investigate the cell cycle-specific activity of DNA methylases.
- To characterize the enzymatic properties of different DNAmet forms.
- To explore the potential allosteric regulation of eukaryotic DNA methylation.
Main Methods:
- Cell cycle synchronization and fractionation.
- Enzymatic assays using a modified pBR322 plasmid (H31) containing a human globin gene fragment.
- Kinetic analysis of DNA methylase activity under varying ionic strengths.
- Determination of Michaelis-Menten and Lineweaver-Burk plots.
Main Results:
- Two DNA methylases (DNAmets) were separated, with distinct activity peaks in G1 (minor) and S (major) phases.
- Both DNAmets protected the H31 plasmid from HpaII restriction enzyme digestion.
- Kinetic parameters (Km, ionic strength dependence) and plot types (sigmoidal vs. hyperbolical) differed between the two DNAmets.
Conclusions:
- Eukaryotic DNA methylation involves distinct enzymes with cell cycle-specific expression.
- The differential kinetic properties suggest the allosteric regulation of DNA methylase activity.
- This study provides the first evidence for an allosteric model of eukaryotic DNA methylation.