title: [XBP-1 enhances the transcriptional activity of estrogen receptor alpha].
abstract: The estrogen receptor (ERalpha) is a member of a large superfamily of nuclear receptors that regulates the transcription of estrogen-responsive genes. Several recent studies have demonstrated that human X-box binding protein 1 (XBP-1) mRNA expression is associated with ERalpha status in breast tumors. More recently, two forms of XBP-1 were identified due to their unique splicing. The two splicing variants of XBP-1 were designated XBP-1S and XBP-1U, respectively. In this study, the coding sequences of XBP-1S and XBP-1U were cloned respectively into the expression vector pcDNA3 harboring FLAG epitope, generating the recombinant plasmids pcDNA3-FLAG-XBP-1S and pcDNA3-FLAG-XBP-1U. Western blot analysis showed that both XBP-1S and XBP-1U were expressed in mammalian cells. To determine the effects of XBP-1S and XBP-1U on the transcriptional activity of ERalpha, MDA-MB-231 breast cancer cells were cotransfected with the expression vectors for ERalpha and either pcDNA3-FLAG-XBP-1S or pcDNA3-FLAG-XBP-1U. The results indicated that XBP-1S and XBP-1U enhanced ERalpha-mediated transcriptional activities in a hormone-independent manner. GST pull-down assay showed that both XBP-1S and XBP-1U interacted with ERalpha. These data suggest that XBP-1S and XBP-1U may play an important role in breast cancer growth and progression through ERalpha signaling.
authors.affiliation: Beijing Institute of Biotechnology, Beijing 100850, China.
authors.forename: Li-Hua
authors.initials: LH
authors.lastname: Ding
authors.forename: Qi-Nong
authors.initials: QN
authors.lastname: Ye
authors.forename: Jian-Hua
authors.initials: JH
authors.lastname: Zhu
authors.forename: Jing-Hua
authors.initials: JH
authors.lastname: Yan
authors.forename: Hong-Jun
authors.initials: HJ
authors.lastname: Zhong
authors.forename: Zong-Hua
authors.initials: ZH
authors.lastname: Wang
authors.forename: Cui-Fen
authors.initials: CF
authors.lastname: Huang
mesh_terms: D017398:Alternative Splicing; D015153:Blotting, Western; D002460:Cell Line; D045744:Cell Line, Tumor; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D047628:Estrogen Receptor alpha; D005982:Glutathione Transferase / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008156:Luciferases / Q000235:genetics / Q000378:metabolism; D010957:Plasmids / Q000235:genetics; D011485:Protein Binding; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D011960:Receptors, Estrogen / Q000235:genetics / Q000378:metabolism*; D000071701:Regulatory Factor X Transcription Factors; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014162:Transfection; D015854:Up-Regulation; D000071717:X-Box Binding Protein 1
chemical_list: D004268:DNA-Binding Proteins; D047628:Estrogen Receptor alpha; D020033:Protein Isoforms; D011960:Receptors, Estrogen; D000071701:Regulatory Factor X Transcription Factors; D014157:Transcription Factors; D000071717:X-Box Binding Protein 1; C000605543:XBP1 protein, human; D008156:Luciferases; D005982:Glutathione Transferase