DIRECT INVOLVEMENT OF THE Y-BOX BINDING-PROTEIN YB-1 IN GENOTOXIC STRESS-INDUCED ACTIVATION OF THE HUMAN MULTIDRUG-RESISTANCE-1 GENE

Citation
T. Ohga et al., DIRECT INVOLVEMENT OF THE Y-BOX BINDING-PROTEIN YB-1 IN GENOTOXIC STRESS-INDUCED ACTIVATION OF THE HUMAN MULTIDRUG-RESISTANCE-1 GENE, The Journal of biological chemistry, 273(11), 1998, pp. 5997-6000
Citations number
30
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Biology
ISSN journal
0021-9258
Volume
273
Issue
11
Year of publication
1998
Pages
5997 - 6000
Database
ISI
SICI code
0021-9258(1998)273:11<5997:DIOTYB>2.0.ZU;2-4
Abstract
The human multidrug resistance 1 (MDR1) gene encoding P-glycoprotein i s often overexpressed in various human tumors after chemotherapy. Duri ng treatment with various chemotherapeutic agents, the MDR1 gene is ac tivated at the transcriptional level and/or amplified, resulting in ov erexpression. 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 tr ansfection of antisense YB-1 expression constructs resulted in a decre ase of both YB-1 protein levels and DNA binding activity to the invert ed CCAAT box, as determined by Western blot and gel mobility shift ass ays. The limited expression and binding activity due to expression of antisense YB-1 constructs were also observed when cells were treated w ith UV. CAT activity of constructs containing the Y-box was enhanced a fter 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 contra st, 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 gen e activation in response to genotoxic stress.