Apoptotic nuclear morphological change without DNA fragmentation.
Apoptosis is characterized morphologically by condensation and fragmentation of nuclei and cells and biochemically by fragmentation of chromosomal DNA into nucleosomal units [1]. CAD, also known as CPAN or DFF-40, is a DNase that can be activated by caspases [2] [3] [4] [5] [6]. CAD is complexed with its inhibitor, ICAD, in growing, non-apoptotic cells [2] [7]. Caspases that are activated by apoptotic stimuli [8] cleave ICAD. CAD, thus released from ICAD, digests chromosomal DNA into nucleosomal units [2] [3]. Here, we examine whether nuclear morphological changes induced by apoptotic stimuli are caused by the degradation of chromosomal DNA. Human T-cell lymphoma Jurkat cells, as well as their transformants expressing caspase-resistant ICAD, were treated with staurosporine. The chromosomal DNA in Jurkat cells underwent fragmentation into nucleosomal units, which was preceded by large-scale chromatin fragmentation (50-200 kb). The chromosomal DNA in cells expressing caspase-resistant ICAD remained intact after treatment with staurosporine but their chromatin condensed as found in parental Jurkat cells. These results indicate that large-scale chromatin fragmentation and nucleosomal DNA fragmentation are caused by an ICAD-inhibitable DNase, most probably CAD, whereas chromatin condensation during apoptosis is controlled, at least in part, independently from the degradation of chromosomal DNA.
Sakahira
H
H
Department of Genetics, Core Research for Evolutional Science and Technology, Japan Science and Technology Corporation, 2-2 Yamada-oka, Suita, Osaka, 565-0871, Japan.
Enari
M
M
Ohsawa
Y
Y
Uchiyama
Y
Y
Nagata
S
S
D017209:Apoptosis; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D002843:Chromatin / Q000378:metabolism; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D053938:DNA Fragmentation; D006801:Humans; D019169:Jurkat Cells; D008854:Microscopy, Electron
D002843:Chromatin; D015853:Cysteine Proteinase Inhibitors