Functional characterization of DNase X, a novel endonuclease expressed in muscle cells

Biochemistry. 2000 Jun 27;39(25):7365-73. doi: 10.1021/bi000158w.


The activation of endonucleases resulting in the degradation of genomic DNA is one of the most characteristic changes in apoptosis. Here, we report the characterization of a novel endonuclease, termed DNase X due to its X-chromosomal localization. The active nuclease is a 35 kDa protein with 39% identity to DNase I. When incubated with isolated nuclei, recombinant DNase X was capable of triggering DNA degradation at internucleosomal sites. Similarly to DNase I, the nuclease activity of DNase X was dependent on Ca(2+) and Mg(2+) and inhibited by Zn(2+) ions or chelators of bivalent cations. Overexpression of DNase X caused internucleosomal DNA degradation and induction of cell death associated with increased caspase activation. Despite the presence of two potential caspase cleavage sites, DNase X was processed neither in vitro nor in vivo by different caspases. Interestingly, after initiation of apoptosis DNase X was translocated from the cytoplasm to the nuclear compartment and aggregated as a detergent-insoluble complex. Abundant expression of DNase X mRNA was detected in heart and skeletal muscle cells, suggesting that DNase X may be involved in apoptotic or other biological events in muscle tissues.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Apoptosis
  • Biological Transport
  • Cell Compartmentation
  • Cell Nucleus / enzymology
  • Deoxyribonucleases / metabolism*
  • Muscle, Skeletal / enzymology*
  • Myocardium / enzymology*
  • Recombinant Proteins / metabolism
  • Tumor Cells, Cultured


  • Recombinant Proteins
  • Deoxyribonucleases