Endonuclease G: a (dG)n X (dC)n-specific DNase from higher eukaryotes.

Area of Science:

• Molecular Biology
• Enzymology
• Genetics

Background:

• DNA contains specific sequences known as (dG)n X (dC)n tracts.
• The function and enzymatic interactions with these tracts are not fully understood.
• Endonucleases are enzymes that play crucial roles in DNA metabolism and repair.

Purpose of the Study:

• To identify and characterize an enzyme that cleaves DNA at (dG)n X (dC)n tracts.
• To investigate the properties and potential biological role of this novel endonuclease.

Main Methods:

• Partial purification of endonuclease activity from immature chicken erythrocyte nuclei.
• Characterization of the enzyme's cleavage specificity and mechanism on supercoiled DNA.
• Assay of enzyme activity dependence on divalent cations (Mg2+ or Mn2+).

Main Results:

• A novel endonuclease G was purified, exhibiting selective cleavage at (dG)n X (dC)n tracts (n ≥ 9).
• The enzyme shows preferential nicking of the G-strand over the C-strand.
• Endonuclease G produces 5' phosphomonoester ends and requires Mg2+ or Mn2+ for activity.

Conclusions:

• Endonuclease G's wide distribution suggests a general biological role.
• The enzyme's activity on specific DNA sequences implies involvement in recombination processes.
• Potential link between endonuclease G, poly(dG) X poly(dC) tracts, and genetic instability.