Analysis of signal transduction and nuclear denaturation in radiation-induced cell death

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The overall goal of the present project has been to analyze a mechanism of X-ray-induced apoptotic cell death in human T-cell leukemia cell line MOLT-4. Toward this goal, the purpose of the project were 1) to examine the involvement of p53 and/or SAPK/JNK, 2) to identify genes downstream of the p53 or SAPK/JNK, and to analyze the expressions of apoptosis-related genes by quantative RT-PCR methods, 3) to study a role of a new radiation-induced protein p41 in cell death.1) To examine the involvement of ceramide-SAPK/JNK pathway, the effect of acid sphingomyelinase inhibitor (D609) on X-ray-induced apoptotic cell death was studied. D609 suppressed X-ray-induced apoptotic cell death as well as phosphorylation of JNK.2) RT-PCR analysis of apoptosis-related genes revealed that the expression of c-myc gene was reduced following X-irradiation, but not in an X-ray-resistant variant cell line Rh-1a. The introduction of c-myc antisense oligonucleotides into MOLT-4 cells or the treatment of c-Myc inhibitor induced cell death.3) Specific antibodies for p41 and p42 have been generated. Western blot analysis showed that the activation of caspase-9, caspase-7, and caspas-3 ran paralleled with the generation of p41. Especially, caspase-7 among those was considered important in p41 generation.