Ra. Gottlieb et al., THE ACID DEOXYRIBONUCLEASE OF NEUTROPHILS - A POSSIBLE PARTICIPANT INAPOPTOSIS-ASSOCIATED GENOME DESTRUCTION, Blood, 86(6), 1995, pp. 2414-2418
Human neutrophils are terminally differentiated cells that spontaneous
ly undergo apoptosis in tissue culture. Apoptosis in these cells can b
e delayed by culture in the presence of granulocyte colony-stimulating
factor or other inflammatory mediators. Neutrophils were found to con
tain an acid endonuclease that appeared to be responsible for the inte
rnucleosomal DNA cleavage that accompanies apoptosis. As measured by a
plasmid nicking assay, this endonuclease had a molecular weight (M(r)
) of 35,000, a pH optimum of 5.5, and a threshold for activity of pH 6
.6 to 6.8, It was weakly inhibited by divalent cations (Ca2+, Mg2+, an
d Zn2+) and more strongly inhibited by aurintricarboxylic acid and N-b
romosuccinimide. DNA from neutrophils treated with nigericin in buffer
s of defined pH displayed nucleosomal ladders whose prominence varied
with pH in a manner that paralleled the pH dependence of the plasmid c
leavage assays, consistent with internucleosomal DNA cleavage by the a
cid endonuclease. We have previously shown that neutrophils undergo ac
idification to a pH value as low as 6.0 during apoptosis; we suggest t
hat this endonuclease may be responsible for the DNA cleavage seen in
apoptotic neutrophils. (C) 1995 by The American Society of Hematology.