Chromatin Condensation Is Not Associated with Apoptosis*
- Michael J. Hendzel‡,
- Walter K. Nishioka§,
- Yves Raymond¶,
- C. David Allis‖,
- David P. Bazett-Jones‡ and
- John P. H. Th’ng**‡
- From the **Bloomfield Center for Research in Aging, Lady Davis Institute for Medical Research, Sir Mortimer B. Davis-Jewish General Hospital, McGill University, Montréal, Québec H3T 1E2, Canada, the ‡Departments of Anatomy and Medical Biochemistry, University of Calgary, Calgary, Alberta T2N 4N1, Canada,§Vical Inc., San Diego, California 92121, the¶Laboratoire de Recherche en Auto-Immunité, Centre Hospitalier de l’Université de Montréal, Montréal, Québec H2L 4M1, Canada, and the ‖Department of Biology, University of Rochester, Rochester, New York 14627
Abstract
Apoptosis plays an important role in the survival of an organism, and substantial work has been done to understand the signaling pathways that regulate this process. Characteristic changes in chromatin organization accompany apoptosis and are routinely used as markers for cell death. We have examined the organization of chromatin in apoptotic PC12 and HeLa cells by indirect immunofluorescence and electron spectroscopic imaging. Our results indicate that de novo chromatin condensation normally seen during mitosis does not occur when cells undergo apoptosis. Instead, the condensed chromatin typically observed results from aggregation of the heterochromatin. We present evidence that, early in apoptosis, there is a rapid degradation of the nuclease-hypersensitive euchromatin that contains hyperacetylated histones. This occurs coincident with the loss of nuclear integrity due to degradation of lamins and reorganization of intranuclear protein matrix. These events lead to collapse of the nucleus and aggregation of heterochromatin to produce the appearance of condensed apoptotic chromatin. This heterochromatin aggregate is then digested by nucleases to produce the oligonucleosomal DNA ladder that is a hallmark of late apoptosis. Unlike mitosis, we have not seen any evidence for the requirement of phosphorylated histones H1 and H3 to maintain the chromatin in the condensed state.
Footnotes
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↵* This work was supported by grants from the Jewish General Hospital and the Medical Research Council of Canada (to J. P. H. T) and from the Cancer Research Society, Inc. (to D. P. B.-J.).The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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↵‡ To whom correspondence should be addressed: Lady Davis Inst. for Medical Research, Sir Mortimer B. Davis-Jewish General Hospital, 3755 Côte Ste-Catherine Rd., Montréal, Québec H3T 1E2, Canada. E-mail: mdjt{at}musica.mcgill.ca.
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↵2 M. J. Hendzel and J. P. H. Th’ng, unpublished data.
- Abbreviations:
- PBS
-
phosphate-buffered saline
- DAPI
-
4,6-diamidino-2-phenylindole
- ESI
-
electron spectroscopic imaging
- MTT
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3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide
- NGF
-
nerve growth factor.
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- Received January 6, 1998.
- Revision received June 24, 1998.
- The American Society for Biochemistry and Molecular Biology, Inc.
