DNA Methylation Plays Regulatory Role in DNA Metabolism, Study Reveals

Strategic Insights -

In a recent study, investigators from South Korea have reported that methylation of DNA plays a regulatory role in DNA metabolism. The researchers found that the Escherichia coli DNA adenine methyltransferase methylates the N6 positions of adenines in the sequence 5'-GATC-3', which exists in the fully methylated state during most of the cell cycle. However, just after DNA replication, the GATC sites transiently become hemimethylated, a condition that is indispensable for various cellular processes.

Key Takeaways:

  • The Escherichia coli DNA adenine methyltransferase methylates the N6 positions of adenines in the sequence 5'-GATC-3', which exists in the fully methylated state during most of the cell cycle.
  • Just after DNA replication, the GATC sites transiently become hemimethylated, a condition that is indispensable for various cellular processes, such as negative modulation of replication initiation at oriC by SeqA.
  • The researchers used NMR spectroscopy to characterize the solution structure of a dodecamer DNA duplex that contained a fully methylated GATC site and the dynamics of the unmethylated, hemimethylated, and fully methylated GATC duplexes.
  • Only the hemimethylated GATC duplex displays a unique major groove conformation, which is optimized for entrance into the cleft structure of SeqA.
  • The apparent equilibrium constants for base-pair opening of the three differentially methylated GATC duplexes revealed that N6-methylation of the adenine residue affects the thermodynamics and kinetics of its own and neighboring base pairs.
  • The researchers concluded that the two G.C base pairs of the hemimethylated GATC duplex displayed a faster base-pair opening rate and required less energy for the base-pair opening reaction than did those of the fully methylated one.

Statistics:

  • The researchers used NMR spectroscopy to characterize the solution structure of a dodecamer DNA duplex.
  • The apparent equilibrium constants for base-pair opening of the three differentially methylated GATC duplexes were determined using proton exchange catalyzed by TRIS.
  • The two G.C base pairs of the hemimethylated GATC duplex displayed a faster base-pair opening rate (2546 ms) compared to the fully methylated GATC duplex (3054 ms).
  • The two G.C base pairs of the hemimethylated GATC duplex required less energy (10.25 kJ/mol) for the base-pair opening reaction compared to the fully methylated GATC duplex (12.57 kJ/mol).

Sources:

  • J. Bang et al., "Structural and Dynamics Study of DNA Dodecamer Duplexes That Contain Un-, Hemi-, or Fully Methylated GATC Sites," Journal of the American Chemical Society, 2008; 130(52): 17688-17696.
  • Biotech Week, "DNA Methylation Plays Regulatory Role in DNA Metabolism, Study Reveals," 2009, NewsRx.com.