title: Comprehensive search for X-ray-responsive elements and binding factors in the regulatory region of the GADD45a gene.
abstract: The growth arrest and DNA damage-inducible protein 45alpha (GADD45a) gene is responsive to a variety of DNA-damaging agents. It is known that induction of the GADD45a gene is regulated in a p53-dependent manner after ionizing irradiation. Our previous study showed that X-ray irradiation increased the transcription rate of the GADD45a gene much earlier than the maximum accumulation of stabilized p53 protein in human myeloblastic leukemia ML-1 cells. We hypothesized that some transcription factor(s) may cooperate with p53 in regulating the GADD45a gene early after the irradiation of ML-1 cells. This idea is supported by recent studies showing that the p53-dependent activation of several genes in human and mouse cells requires some additional transcription factors, such as Sp1, GKLF, Ets1, and IRF-1. To examine the possible involvement of cooperating factors in transcriptional regulation of the GADD45a gene by ionizing radiation, we comprehensively searched for the X-ray-inducible binding locus of the nuclear factor throughout the upstream region (-2244 bp/+89 bp) and the third intron (+1389 bp/+2488 bp) of the GADD45a gene by EMSA using 136 probes. The X-ray-responsive binding of nuclear factors was detected at eight loci. Oct, NF-kappaB, HNF, NF-AT, and KLF family transcription factors were identified by a competition assay. It is possible that some of these factors cooperate with p53 to mediate transcriptional regulation of the GADD45a gene after ionizing irradiation.
authors.affiliation: Life and Bioresourse, Graduate School of Science and Technology, Chiba University, Chiba, Japan.
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Daino
authors.forename: Sachiko
authors.initials: S
authors.lastname: Ichimura
authors.forename: Mitsuru
authors.initials: M
authors.lastname: Nenoi
mesh_terms: D001483:Base Sequence; D018797:Cell Cycle Proteins; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism; D004247:DNA / Q000528:radiation effects*; D004249:DNA Damage; D004307:Dose-Response Relationship, Radiation; D006801:Humans; D007438:Introns; D000090062:Kruppel-Like Factor 4; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009154:Mutation; D009687:Nuclear Proteins / Q000737:chemistry* / Q000235:genetics*; D011485:Protein Binding; D011839:Radiation, Ionizing; D012045:Regulatory Sequences, Nucleic Acid; D020218:Response Elements; D014158:Transcription, Genetic; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D014466:Ultraviolet Rays; D014965:X-Rays; D000097642:GADD45 Proteins
chemical_list: D018797:Cell Cycle Proteins; D004247:DNA; D000090062:Kruppel-Like Factor 4; D009687:Nuclear Proteins; D016159:Tumor Suppressor Protein p53; C439070:GADD45A protein, human; D000097642:GADD45 Proteins; C000715467:KLF4 protein, human; C000715468:Klf4 protein, mouse