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Molecular and Cellular Biology, April 1999, p. 2986-2997, Vol. 19, No. 4
Dana-Farber Cancer Institute, Harvard Medical
School, Boston, Massachusetts 021151;
BASF Bioresearch Corp., Worcester, Massachusetts
016052; and Department of Radiation
and Cellular Oncology, University of Chicago, Chicago, Illinois
606373
Received 29 July 1998/Returned for modification 18 September
1998/Accepted 15 December 1998
We report here that the Rad51 recombinase is cleaved in mammalian
cells during the induction of apoptosis by ionizing radiation (IR)
exposure. The results demonstrate that IR induces Rad51 cleavage by a
caspase-dependent mechanism. Further support for involvement of
caspases is provided by the finding that IR-induced proteolysis of
Rad51 is inhibited by Ac-DEVD-CHO. In vitro studies show that Rad51 is
cleaved by caspase 3 at a DVLD/N site. Stable expression of a Rad51
mutant in which the aspartic acid residues were mutated to alanines
(AVLA/N) confirmed that the DVLD/N site is responsible for the cleavage
of Rad51 in IR-induced apoptosis. The functional significance of Rad51
proteolysis is supported by the finding that, unlike intact Rad51, the
N- and C-terminal cleavage products fail to exhibit recombinase
activity. In cells, overexpression of the Rad51(D-A) mutant had no
effect on activation of caspase 3 but did abrogate in part the
apoptotic response to IR exposure. We conclude that proteolytic
inactivation of Rad51 by a caspase-mediated mechanism contributes
to the cell death response induced by DNA damage.
0270-7306/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Role for Caspase-Mediated Cleavage of Rad51 in
Induction of Apoptosis by DNA Damage
*
Corresponding author. Mailing address: Dana-Farber
Cancer Institute, Harvard Medical School, 44 Binney St., Boston,
MA 02115. Phone: (617) 632-3141. Fax: (617) 632-2934. E-mail:
donald_kufe{at}dfci.harvard.edu.
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