DNases and apoptosis

Here we review the different apoptotic DNases. From a functional point of v iew, DNases implicated in apoptosis may be classified into three groups: th e Ca2+/Mg2+ endonucleases, the Mg2+-endonucleases, and the cation-independe nt endonucleases. The first group includes DNase I which has no specificity for the linker region, DNase gamma which has some homology with DNase I, a nd other DNases which cleave DNA in the linker region. Both DNase I and DNa se gamma have been cloned. The other nucleases of this category have disper sed molecular weights. Their sequences are unknown and it is difficult to d etermine their role(s) in apoptosis. It seems that different pathways are p resent and that these nucleases may be activated either by caspases or seri ne proteases. The caspase 3 activated DNase (CAD, CPAN, or DFF40) belongs t o the Mg2+-dependent endonucleases. DNase II belongs to the third group of acid endonucleases or cation-independent DNases. We have shown the involvem ent of DNase II in lens cell differentiation. Recently, the molecular struc ture of two different enzymes has been elucidated, one of which has a signa l peptide and appears to be secreted. The other, called L-DNase II, is an i ntracellular protein having two enzymatic activities; in its native form, i t is an anti-protease, and after posttranslational modification, it becomes a nuclease.