Comparative study of induction of endogenous DNA degradation in rat liver nuclei and intact thymocytes.
A common strongly ordered multi-step-pattern of endogenous DNA degradation was induced in rat liver nuclei and intact thymocytes, prepared in the presence of chelating agents and incubated in the presence of CaCl2 and/or MgCl2. It consisted of sequential generation of 0.3 Mbp, then 0.05 Mbp DNA fragments and finally of oligo- and mononucleosomal DNA. Oligonucleosomal DNA was generated when the genome had already been disintegrated into 0.05 Mbp DNA fragments. ZnCl2 completely inhibited advanced genome cleavage to oligo- and mononucleosomal DNA without affecting the initial generation of large DNA fragments. Therefore, the endonucleolytic activity which produce large DNA fragments is different from Ca2+/Mg2+ endonuclease. The similar pattern of DNA degradation was observed in thymocytes treated with dexamethasone and with the topoisomerase II inhibitor VM-26, the agents known to induce apoptosis. The effect of VM-26 strongly suggests the involvement of topoisomerase II in generation of large DNA fragments. Multi-level organization and regulation of the chromatin structure determine the stepwise process of genome degradation. Detachment of chromatin from the nuclear matrix attachment regions may be one of the possible mechanisms of switching off the genome function and triggering the multi-step process of endogenous chromatin degradation thus leading to cell death in terminal differentiation or stress-induced apoptosis.
Kokileva
L
L
Bulgarian Academy of Sciences, Institute of Molecular Biology, Sofia.
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D001482:Base Composition; D002122:Calcium Chloride / Q000494:pharmacology; D002413:Cations, Divalent; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism*; D002614:Chelating Agents / Q000494:pharmacology; D002712:Chlorides / Q000494:pharmacology; D004247:DNA / Q000378:metabolism*; D003907:Dexamethasone / Q000494:pharmacology; D008099:Liver / Q000648:ultrastructure*; D015636:Magnesium Chloride / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013713:Teniposide / Q000494:pharmacology; D013950:Thymus Gland / Q000187:drug effects / Q000378:metabolism*; D059005:Topoisomerase II Inhibitors; D017967:Zinc Compounds / Q000494:pharmacology
D002413:Cations, Divalent; D002614:Chelating Agents; D002712:Chlorides; D059005:Topoisomerase II Inhibitors; D017967:Zinc Compounds; D015636:Magnesium Chloride; D003907:Dexamethasone; C016837:zinc chloride; D004247:DNA; D013713:Teniposide; D002122:Calcium Chloride