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Mol. Cell. Biol., 04 1997, 2020-2029, Vol 17, No. 4
SE Morgan, C Lovly, TK Pandita, Y Shiloh and MB Kastan
The ATM protein has been implicated in pathways controlling cell cycle
checkpoints, radiosensitivity, genetic instability, and aging. Expression
of ATM fragments containing a leucine zipper motif in a human tumor cell
line abrogated the S-phase checkpoint after ionizing irradiation and
enhanced radiosensitivity and chromosomal breakage. These fragments did not
abrogate irradiation-induced G1 or G2 checkpoints, suggesting that cell
cycle checkpoint defects alone cannot account for chromosomal instability
in ataxia telangiectasia (AT) cells. Expression of the carboxy-terminal
portion of ATM, which contains the PI-3 kinase domain, complemented
radiosensitivity and the S-phase checkpoint and reduced chromosomal
breakage after irradiation in AT cells. These observations suggest that ATM
function is dependent on interactions with itself or other proteins through
the leucine zipper region and that the PI-3 kinase domain contains much of
the significant activity of ATM.
Copyright © 1997, American Society for Microbiology
Fragments of ATM which have dominant-negative or complementing activity
The Johns Hopkins Oncology Center, Baltimore, Maryland 21205, USA.
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