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Identification of deoxyribonuclease II as an endonuclease involved in apoptosis

M A Barry1, A Eastman

  • 1Department of Pharmacology and Toxicology, Dartmouth Medical School, Hanover, New Hampshire 03755-3835.

Archives of Biochemistry and Biophysics
|January 1, 1993
PubMed

Insights

This study reveals that an acidic endonuclease, identified as deoxyribonuclease II (DNase II), mediates internucleosomal DNA digestion during apoptosis. This finding challenges the long-held belief that only Ca2+/Mg2+-dependent endonucleases are involved in programmed cell death.

Area of Science:

  • Molecular Biology
  • Biochemistry
  • Cell Biology

Background:

  • Apoptosis, or programmed cell death, involves internucleosomal DNA digestion.
  • This DNA digestion is mediated by endogenous endonucleases.
  • The Ca2+/Mg2+-dependent endonuclease has been considered the primary enzyme responsible for this process.

Purpose of the Study:

  • To investigate the role of endonucleases in apoptosis.
  • To identify the specific endonuclease responsible for DNA fragmentation during apoptosis.
  • To challenge the established understanding of endonuclease involvement in programmed cell death.

Main Methods:

  • Purification of endonucleases from Chinese hamster ovary cells.
  • Assaying endonuclease activity at different pH levels.
  • Activating endonucleases in intact cells using a proton ionophore.
  • Comparing the properties of the identified acidic endonuclease with bovine deoxyribonuclease II (DNase II).
  • Inducing DNA digestion in isolated nuclei using acidic endonuclease or DNase II.

Main Results:

  • A significant amount of endonuclease activity was found to be active below pH 7.
  • This acidic endonuclease, activated by intracellular acidification, induced internucleosomal DNA digestion characteristic of apoptosis.
  • The acidic endonuclease was identified as deoxyribonuclease II (DNase II) based on inhibitor sensitivity, purification, and antibody recognition.
  • DNase II induced internucleosomal DNA digestion in isolated nuclei at acidic pH.

Conclusions:

  • Deoxyribonuclease II (DNase II) can mediate internucleosomal DNA digestion during apoptosis.
  • Intracellular acidification activates DNase II, leading to DNA fragmentation.
  • The findings question the exclusive role of Ca2+/Mg2+-dependent endonucleases in apoptosis, suggesting DNase II is also a key player.

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