Nucleic Acids Research, Vol 26, Issue 19 4422-4425, Copyright © 1998 by Oxford University Press
DB Winter, PJ Gearhart and VA Bohr
DNA fragmentation during apoptosis is characterized by endonucleolytic
cleavage of chromosomal DNA into an oligonucleosomal ladder. To determine
if actively transcribed genes are more susceptible to cleavage during
apoptosis than non-transcribed genes, the rate of fragmentation of
differentially expressed genes was measured in B- lymphocyte hybridoma
cells. Five genes were studied based on their transcriptional activity
and/or nuclear localization, and mitochondrial DNA was assayed as a
negative control for apoptotic fragmentation. Apoptosis was induced in the
hybridoma cells by ultraviolet light, and DNA was prepared at multiple time
points after ultraviolet irradiation. Degradation into an oligonucleosomal
ladder appeared as early as 2 h after treatment, showing that fragmentation
is rapidly activated in hybridoma cells. The DNA was then digested with
restriction enzymes, separated by gel electrophoresis and hybridized with
the gene-specific probes for Southern blot analyses. Loss of gene-specific
signals was measured by quantitation of autoradiographs. The results show
all of the nuclear genes were degraded at the same rate regardless of their
transcriptional status or nuclear localization. The data suggest that once
the cell activates its destruction program, nuclear DNA is rapidly degraded
in a homogeneous manner.
ARTICLES
Homogeneous rate of degradation of nuclear DNA during apoptosis
Laboratory of Molecular Genetics, National Institute on Aging, National Institutes of Health, 5600 Nathan Shock Drive, Baltimore, MD 21224, USA.
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