[Calcium and magnesium ion-dependent endonuclease 37 kDa is activated during colchicine-induced apoptosis in HL-60 cells].

With the aim of revealing endonuclease(s), activating in apoptotic cells, a nuclease activity of nuclear protein extract from human leukemic HL-60 cells treated with colchicine was studied. After a 30 h incubation with colchicine, a specific DNA fragmentation--a multiple of 200 base pair subunits--was clearly observed that was an evidence for the endonuclease activation. After 48 h almost the whole DNA was fragmented. At the same time histones appeared the major proteins of nuclear extract. Using the method for detection of nuclease activity in a gel, protein 37 kDa was identified as a Ca2+, Mg(2+)-dependent endonuclease. The maximum increase in nuclease activity occurred after a 24 h incubation with colchicine. A low activity of this protein was also found in control cells. These data suggest that in apoptotic cells activation of constantly expressed nucleases may occur, rather than a new synthesis of apoptotic nucleases.