title: Direct involvement of the Y-box binding protein YB-1 in genotoxic stress-induced activation of the human multidrug resistance 1 gene.
abstract: The human multidrug resistance 1 (MDR1) gene encoding P-glycoprotein is often overexpressed in various human tumors after chemotherapy. During treatment with various chemotherapeutic agents, the MDR1 gene is activated at the transcriptional level and/or amplified, resulting in overexpression. Our previous studies demonstrated that an inverted CCAAT box (Y-box) might be a critical cis-regulatory element regulating UV or drug-induced MDR1 gene expression. We have now established various cell lines from human head and neck cancer KB cells which were stably transfected with the chloramphenicol acetyltransferase (CAT) reporter gene driven by various MDR1 promoter deletion constructs. Transient transfection of antisense YB-1 expression constructs resulted in a decrease of both YB-1 protein levels and DNA binding activity to the inverted CCAAT box, as determined by Western blot and gel mobility shift assays. The limited expression and binding activity due to expression of antisense YB-1 constructs were also observed when cells were treated with UV. CAT activity of constructs containing the Y-box was enhanced after treatment with UV irradiation as well as genotoxic agents such as cisplatin and etoposide. Moreover, this activation was reduced by 50-80% by transfection of antisense YB-1 expression constructs. In contrast, transfection of antisense YB-1 expression constructs had no effect on CAT activity driven by MDR1 promoter constructs not containing the Y-box. These data indicate that YB-1 is directly involved in MDR1 gene activation in response to genotoxic stress.
authors.affiliation: Department of Biochemistry, Kyushu University, School of Medicine, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-82, Japan. ohga@biochem1.med.kyushu-u.ac.jp
authors.forename: T
authors.initials: T
authors.lastname: Ohga
authors.forename: T
authors.initials: T
authors.lastname: Uchiumi
authors.forename: Y
authors.initials: Y
authors.lastname: Makino
authors.forename: K
authors.initials: K
authors.lastname: Koike
authors.forename: M
authors.initials: M
authors.lastname: Wada
authors.forename: M
authors.initials: M
authors.lastname: Kuwano
authors.forename: K
authors.initials: K
authors.lastname: Kohno
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000096:biosynthesis*; D022762:CCAAT-Enhancer-Binding Proteins; D016373:DNA, Antisense; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D015972:Gene Expression Regulation, Neoplastic; D019450:Genes, MDR / Q000528:radiation effects*; D006258:Head and Neck Neoplasms / Q000235:genetics*; D006801:Humans; D051839:NFI Transcription Factors; D009363:Neoplasm Proteins / Q000096:biosynthesis*; D009687:Nuclear Proteins; D011485:Protein Binding; D014157:Transcription Factors; D015533:Transcriptional Activation; D014407:Tumor Cells, Cultured; D014466:Ultraviolet Rays; D051840:Y-Box-Binding Protein 1
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D022762:CCAAT-Enhancer-Binding Proteins; D016373:DNA, Antisense; D004268:DNA-Binding Proteins; D051839:NFI Transcription Factors; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D014157:Transcription Factors; D051840:Y-Box-Binding Protein 1; C070856:YBX1 protein, human