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Caspase-dependent conversion of Dicer ribonuclease into a death-promoting deoxyribonuclease

Akihisa Nakagawa1, Yong Shi, Eriko Kage-Nakadai

  • 1Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, CO 80309, USA.

Science (New York, N.Y.)
|March 13, 2010
PubMed

Insights

The study reveals that Dicer (DCR-1), an enzyme crucial for small RNA processing, also fragments DNA during apoptosis in C. elegans. Caspase-mediated cleavage converts DCR-1 into a deoxyribonuclease, conserving DNA degradation pathways.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Genetics

Background:

  • Chromosome fragmentation is a key event in apoptosis across species.
  • In mammals, caspases trigger this fragmentation by inhibiting nucleases.

Purpose of the Study:

  • To investigate the role of Caenorhabditis elegans Dicer (DCR-1) in apoptotic chromosome fragmentation.
  • To elucidate the mechanism of caspase-mediated DNA degradation during apoptosis.

Main Methods:

  • Gene inactivation of dcr-1 in C. elegans.
  • Analysis of apoptosis and chromosome fragmentation.
  • Biochemical assays to determine nuclease activity.

Main Results:

  • dcr-1 inactivation impaired apoptosis and blocked chromosome fragmentation.
  • The CED-3 caspase cleaved DCR-1, generating a C-terminal fragment with deoxyribonuclease activity.
  • This DCR-1 fragment induced 3' hydroxyl DNA breaks, promoting apoptosis.

Conclusions:

  • Caspase-mediated activation of DNA degradation is conserved in apoptosis.
  • DCR-1 plays a dual role: small RNA processing and chromosomal DNA fragmentation during apoptosis.
  • Protease-mediated conversion of DCR-1 from ribonuclease to deoxyribonuclease is a key regulatory step.

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