title: UV stimulation of nucleophosmin/B23 expression is an immediate-early gene response induced by damaged DNA.
abstract: Nucleophosmin/B23 (NPM/B23), a nucleolar protein, was rapidly up-regulated after UV irradiation (at 254 nm; 30 J/m(2)) in NIH 3T3 cells and HeLa/S3 cells. Levels of NPM/B23 mRNA peaked 45-60 min after UV treatment and returned to baseline by 12 h. Transcription inhibitor actinomycin D (5 microg/ml) prevented the UV-induced increase of NPM/B23 mRNA, suggesting that UV induction of NPM/B23 was mediated at the transcriptional level. Moreover, UV-induced NPM/B23 expression was super-induced by cycloheximide (20 microg/ml), which was characteristic of immediate-early gene response. The transcriptional activation of NPM/B23 by UV was also confirmed by NPM/B23 promoter activity assay. Thymine dinucleotide, mimicking the effects of UV-induced DNA damage, was able to trigger NPM/B23 expression in the absence of genomic DNA damage. UV-induced activation of NPM/B23 promoter could not be blocked by UV-inducible pathway inhibitors, such as those of growth factor tyrosine kinase, mitogen-activated protein kinase, AP-1, NF-kappaB, and DNA-dependent kinase. Our results indicate that UV stimulation of NPM/B23 expression may be mediated through a novel UV-inducible pathway and is an immediate-early gene response induced by damaged DNA. Induction of immediate-early gene is an initial step in the regulation of cellular and genomic responses to external stimuli. Our results thus provide important evidence for an involvement of NPM/B23 in the acute response of mammalian cells to environmental stress.
authors.affiliation: Graduate Institute of Pharmacology, National Yang Ming University, Taipei 112, Taiwan, Republic of China.
authors.forename: Ming H
authors.initials: MH
authors.lastname: Wu
authors.forename: Benjamin Y M
authors.initials: BY
authors.lastname: Yung
mesh_terms: D016475:3T3 Cells; D000818:Animals; D001483:Base Sequence; D004249:DNA Damage; D017931:DNA Primers; D005786:Gene Expression Regulation / Q000528:radiation effects*; D017781:Genes, Immediate-Early; D006367:HeLa Cells; D006801:Humans; D020935:MAP Kinase Signaling System; D051379:Mice; D009687:Nuclear Proteins / Q000235:genetics*; D000090243:Nucleophosmin; D011401:Promoter Regions, Genetic; D017978:Receptors, Growth Factor / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism; D014466:Ultraviolet Rays
chemical_list: D017931:DNA Primers; C000716967:NPM1 protein, human; C000715570:Npm1 protein, mouse; D009687:Nuclear Proteins; D017978:Receptors, Growth Factor; D014157:Transcription Factors; D000090243:Nucleophosmin