Caspase-3 Gene Activity
in Radiation-induced Apoptosis
TONG Xin, LUO Ying, DONG Yan and SUN Zhi-Xian
( Institute of Radiation Medicine, Academy of Military Medical Sciences,
Beijing 100850, China )
Abstract Previous experiments indicated
that caspase-3 was a mediator of ionizing radiation(IR)-induced apoptosis in
U937 cells. In present study, the caspase-3 activity in IR-induced apoptosis
was further measured by analyzing the Ac-DEVD-p-nitroanilide cleaving
activity, and results showed that caspase-3 activity increased in accordance to
the development of apoptosis, and reached peak at 6 h post-irradiation. However,
northern blot analysis showed that the expression of caspase-3 was not changed,
while Western blot found that the active P20 subunit concentration increased, and
from 3 h post-irradiation, active P17 subunit also increased. These findings
demonstrate that the increase of caspase-3 activity observed during IR-induced
apoptosis depends on the activation of inactive pre-caspase rather than the
change in gene expression.
Key Words Caspase-3; apoptosis; ionizing radiation
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