title: Transcription factors Sp1 and Sp3 regulate expression of human ABCG2 gene and chemoresistance phenotype.
abstract: ABCG2 is a member of the ATP binding cassette (ABC) transmembrane proteins that plays an important role in stem cell biology and drug resistance of cancer cells. In this study, we investigated how expression of human ABCG2 gene is regulated in lung cancer A549 cells. Binding of Sp1 and Sp3 transcription factors to the ABCG2 promoter in vitro and in vivo was elucidated by electrophoretic mobility shift assay and chromatin immunoprecipitation assay. The ABCG2 promoter activity was impaired when Sp1 sites were mutated but was enhanced by overexpression of Sp1 or Sp3 proteins. Knockdown of Sp1 or Sp3 expression by short interfering RNA significantly decreased the expression of ABCG2 mRNA and protein, resulting in attenuated formation of the side population in A549 cells. In addition, Sp1 inhibition in vivo by mithramycin A suppressed the percentage of the side population fraction and sphere forming activities of A549 cells. Moreover, inhibiting Sp1- or Sp3-dependent ABCG2 expression caused chemosensitization to the anticancer drug cisplatin. Collectively, our results demonstrate that Sp1 and Sp3 transcription factors are the primary determinants for activating basal transcription of the ABCG2 gene and play an important role in maintaining the side population phenotype of lung cancer cells.
authors.affiliation: Department of Environmental Medical Biology, Institute of Tropical Medicine, and Brain Korea 21 Project for Medical Science, Yonsei University College of Medicine, Seoul, 120-752, Korea.
authors.forename: Wook-Jin
authors.initials: WJ
authors.lastname: Yang
authors.forename: Min-Ji
authors.initials: MJ
authors.lastname: Song
authors.forename: Eun Young
authors.initials: EY
authors.lastname: Park
authors.forename: Jong-Joo
authors.initials: JJ
authors.lastname: Lee
authors.forename: Joo-Hong
authors.initials: JH
authors.lastname: Park
authors.forename: Keunhee
authors.initials: K
authors.lastname: Park
authors.forename: Jong Hoon
authors.initials: JH
authors.lastname: Park
authors.forename: Hyoung-Pyo
authors.initials: HP
authors.lastname: Kim
mesh_terms: D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters / Q000235:genetics* / Q000378:metabolism*; D001665:Binding Sites; D002460:Cell Line; D002945:Cisplatin / Q000494:pharmacology; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D024202:Electrophoretic Mobility Shift Assay; D015972:Gene Expression Regulation, Neoplastic; D055785:Gene Knockdown Techniques; D006801:Humans; D008175:Lung Neoplasms / Q000235:genetics* / Q000473:pathology; D009363:Neoplasm Proteins / Q000235:genetics* / Q000378:metabolism*; D008926:Plicamycin / Q000031:analogs & derivatives / Q000494:pharmacology; D011401:Promoter Regions, Genetic; D058985:Side-Population Cells / Q000502:physiology; D016329:Sp1 Transcription Factor / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D051705:Sp3 Transcription Factor / Q000235:genetics / Q000378:metabolism*
chemical_list: C116614:ABCG2 protein, human; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters; D009363:Neoplasm Proteins; D016329:Sp1 Transcription Factor; D051705:Sp3 Transcription Factor; C066851:mithramycin A; D008926:Plicamycin; D002945:Cisplatin