Supercoiling-dependent sequence specificity of mammalian DNA methyltransferase

Area of Science:

• Biochemistry
• Molecular Biology
• Epigenetics

Background:

• Mammalian DNA methyltransferases (DNA MeTases) are crucial enzymes for epigenetic regulation.
• Understanding the sequence specificity of DNA MeTase is vital for comprehending gene regulation and disease.
• DNA methylation patterns are influenced by DNA structure and protein interactions.

Purpose of the Study:

• To investigate the effect of DNA supercoiling on the sequence specificity of mammalian DNA methyltransferase (DNA MeTase).
• To explore the potential role of DNA secondary structures and protein binding in regulating in vivo DNA methylation site selection.
• To assess the utility of DNA MeTase as a probe for supercoiling-induced DNA structural transitions.

Main Methods:

• In vitro assays measuring DNA methyltransferase activity on supercoiled DNA substrates.
• Analysis of DNA MeTase activity on DNA in alternative secondary structures, including Z-form DNA.
• Comparative studies of DNA MeTase sequence preference under varying supercoiling conditions.

Main Results:

• Negative supercoiling of substrate DNA significantly alters the in vitro sequence specificity of mammalian DNA MeTase.
• DNA MeTase exhibits no activity on DNA substrates adopting the left-handed Z-form.
• These findings indicate that DNA conformation plays a critical role in DNA MeTase activity.

Conclusions:

• In vivo DNA methylation site selection by DNA MeTase may be regulated by DNA supercoiling-induced conformational changes or protein binding.
• The structural sensitivity of DNA MeTase suggests its potential application as a tool to identify sequences undergoing supercoiling-dependent structural transitions.