title: Both the basal transcriptional activity of the GADD45A gene and its enhancement after ionizing irradiation are mediated by AP-1 element.
abstract: The growth arrest and DNA damage-inducible gene 45A (GADD45A) is involved in the DNA repair, maintenance of genomic stability, cell cycle control and apoptosis, and thus plays an important role in cellular response to DNA damage. The GADD45A gene is responsive to a variety of DNA-damaging agents, including ionizing radiation (IR), methyl methanesulfonate (MMS), and ultraviolet (UV) radiation. It is generally thought that induction of the GADD45A gene after IR exposure is principally p53-dependent, requiring binding of the p53 protein to the p53-recognition sequence in the third intron. However, the involvement of factors other than p53 in transcriptional regulation of the GADD45A gene after IR exposure has not been elucidated. In the present study, we show that the 5'-flanking region containing two OCT sites and a CCAAT box, as well as p53 and AP-1 sites in the third intron, are required for the basal transcriptional activity of the reporter gene. In addition, AP-1 recognition element was shown to be involved in the transcriptional enhancement of the GADD45A gene after X-ray irradiation. Electrophoretic mobility shift analysis (EMSA) and Chromatin immunoprecipitation (ChIP) assay revealed that JunD binds to the third intron of the GADD45A gene. These observations suggest that AP-1 complexes containing JunD, in addition to p53, play an important role not only in transcriptional enhancement by IR but also in basal expression of the GADD45A gene via binding to the AP-1 site in the third intron.
authors.affiliation: Radiation Hazards Research Group, National Institute of Radiological Sciences, 9-1, Anagawa-4-chome, Inage-ku, Chiba 263-8555, 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; D001665:Binding Sites; D015153:Blotting, Western; D018797:Cell Cycle Proteins / Q000235:genetics*; D045744:Cell Line, Tumor; D017931:DNA Primers; D006801:Humans; D007438:Introns; D009687:Nuclear Proteins / Q000235:genetics*; D011839:Radiation, Ionizing; D018808:Transcription Factor AP-1 / Q000378:metabolism / Q000502:physiology*; D014158:Transcription, Genetic / Q000235:genetics*; D000097642:GADD45 Proteins
chemical_list: D018797:Cell Cycle Proteins; D017931:DNA Primers; D009687:Nuclear Proteins; D018808:Transcription Factor AP-1; C439070:GADD45A protein, human; D000097642:GADD45 Proteins