Action of apoptotic endonuclease DNase γ on naked DNA and chromatin substrates

The internucleosomal cleavage of genomic DNA is a biochemical hallmark of apoptosis. DNase γ, a Mg2+/Ca2+-dependent endonuclease, has been suggested to be one of the apoptotic endonucleases, but its biochemical characteristic has not been fully elucidated. Here, using recombinant DNase γ, we showed that DNase γ is a Mg2+/Ca2+-dependent single-stranded DNA nickase and has a high activity at low ionic strength. Under higher ionic strength, such as physiological buffer conditions, the endonuclease activity of DNase γ is restricted, but its activity is enhanced in the presence of linker histone H1, which explains DNA cleavage at linker regions of apoptotic nuclei.