量研学術機関リポジトリ「QST-Repository」は、国立研究開発法人 量子科学技術研究開発機構に所属する職員等が生み出した学術成果（学会誌発表論文、学会発表、研究開発報告書、特許等）を集積しインターネット上で広く公開するサービスです。 Welcome to QST-Repository where we accumulates and discloses the academic research results(Journal Publications, Conference presentation, Research and Development Report, Patent, etc.) of the members of National Institutes for Quantum and Radiological Science and Technology.
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Several stress-responsive genes, including p53-target genes, are induced by low-dose of ionizing radiation ranging from 0.02 to 0.5 Gy. We show here that 0.5 Gy of X-rays increase the transcription rate of the GADD45 gene, with maximum induction at 0.5 to 1 h after irradiation, much earlier than the maximum accumulation of stabilized p53 protein. It could be suggested that some transcription factors cooperate with p53 in regulating the GADD45 gene at an early time after low-dose irradiation. This idea is supported by the studies that showed GKLF and Sp1 are required for p53-dependent transcriptional activation of the p21WAF1/Cip1and BAX genes, respectively. To examine the possible involvement of cooperating transcription factors in regulation of the GADD45 gene after low-dose radiation, we attempted a comprehensive EMSA, in which 136 species of double-stranded DNA probes were used to identify X-ray-inducible factor-bindings to the upstream and the third intron regions of the gene after exposure to 0.5 Gy of X-rays in human myeloblastic leukemia ML-1 cells. Several X-ray-inducible DNA-protein complexes were observed. The factors related to forkhead transcription factors, POU domain transcription factors and kruppel-like factors were putatively identified by the competition assay. It is possible that these factors cooperate with p53 to mediate the transcriptional regulation of the GADD45 genes after low-dose irradiation.
Transcription factors binding to the cis-elements of GADD45 gene in ML-1cells after low-dose irradiation
