Abstract
It is considered that induction of the GADD45 gene after X-ray irradiation is p53-dependent, requiring binding of p53 to the p53-recognition element in the third intron. However, it is not understood whether additional transcription factors (TFs) other than p53 are required for transcriptional regulation of the GADD45 gene after X-ray irradiation. We have previously revealed X-ray-inducible binding of factors at several loci in the regulatory region of the GADD45 gene in ML-1 cells. Among them, we focused on the locus, spanning -793 / -759 bp in the upstream region of the GADD45 gene, where binding of factors is induced after 0.5 Gy of X-rays irradiation. Although this locus is homologous to the consensus recognition sequences for TFs, GATA, Ikaros, and IRF, EMSA using competitor oligonucleotides revealed an association of none of these TFs. By introduction of point mutations into the probe, we revealed that this X-ray-inducible factor binds to the -775 bp / -759 bp region. [J Radiat Res 44:389 (2003)]
