Wheat endonuclease WEN1 dependent on S-adenosyl-L-methionine and sensitive to DNA methylation status

Area of Science:

• Biochemistry
• Molecular Biology
• Enzymology

Background:

• Wheat endonuclease WEN1 (27 kDa) is a Ca(2+)- and Mg(2+)-dependent enzyme isolated from coleoptiles.
• Endonucleases play crucial roles in DNA metabolism and repair, but their interaction with DNA methylation in higher eukaryotes is not fully understood.

Purpose of the Study:

• To characterize the enzymatic properties of wheat endonuclease WEN1.
• To investigate WEN1's substrate specificity, particularly its response to DNA methylation.
• To explore the enzyme's stability and modulation by specific compounds.

Main Methods:

• Isolation and purification of wheat endonuclease WEN1 from coleoptiles.
• Enzymatic activity assays using methylated and unmethylated lambda phage DNA.
• Determination of optimal pH, temperature stability, and effects of S-adenosyl-L-methionine (SAM) and its analogs on enzyme activity.

Main Results:

• WEN1 exhibited higher hydrolytic activity towards methylated DNA (dam(+), dcm(+)) compared to unmethylated DNA (dam(-), dcm(-)).
• The enzyme displayed two pH optima: 6.5-7.5 and 9.0-10.5 for double-stranded DNA hydrolysis.
• WEN1 demonstrated stability at 65°C and across a broad pH range.
• Enzyme activity was modulated by S-adenosyl-L-methionine, S-adenosyl-L-homocysteine, and S-isobutyladenosine.

Conclusions:

• Wheat endonuclease WEN1 is the first characterized higher eukaryote endonuclease capable of discriminating between DNA based on its methylation status.
• The enzyme's activity is modulated by S-adenosyl-L-methionine and its analogs, suggesting a potential role in epigenetic regulation or DNA repair pathways involving methylation.