title: Differential regulation of MAGE-A1 promoter activity by BORIS and Sp1, both interacting with the TATA binding protein.
abstract: BACKGROUND
  As cancer-testis MAGE-A antigens are targets for tumor immunotherapy, it is important to study the regulation of their expression in cancers. This regulation appears to be rather complex and at the moment controversial. Although it is generally accepted that MAGE-A expression is controlled by epigenetics, the exact mechanisms of that control remain poorly understood.
  
  
  METHODS
  We analyzed the interplay of another cancer-testis gene, BORIS, and the transcription factors Ets-1 and Sp1 in the regulation of MAGE-A1 gene expression performing luciferase assays, quantitative real-time PCR, sodium bisulfite sequencing, chromatin immunoprecipitation assays and pull down experiments.
  
  
  RESULTS
  We detected that ectopically expressed BORIS could activate and demethylate both endogenous and methylated reporter MAGE-A1 promoter in MCF-7 and micrometastatic BCM1 cancer cell lines. Overexpression of Ets-1 could not further upregulate the promoter activity mediated by BORIS. Surprisingly, in co-transfection experiments we observed that Sp1 partly repressed the BORIS-mediated stimulation, while addition of Ets-1 expression plasmid abrogated the Sp1 mediated repression of MAGE-A1 promoter. Both BORIS and Sp1 interacted with the TATA binding protein (hTBP) suggesting the possibility of a competitive mechanism of action between BORIS and Sp1.
  
  
  CONCLUSIONS
  Our findings show that BORIS and Sp1 have opposite effects on the regulation of MAGE-A1 gene expression. This differential regulation may be explained by direct protein-protein interaction of both factors or by interaction of MAGE-A1 promoter with BORIS alternatively spliced isoforms with different sequence specificity. We also show here that ectopic expression of BORIS can activate transcription from its own locus, inducing all its splice variants.
authors.affiliation: Department of Tumor Biology, University Medical Center Hamburg-Eppendorf, Martinistraße 52, Hamburg 20246, Germany. hschwarz@uke.uni-hamburg.de.
authors.forename: Heidi
authors.initials: H
authors.lastname: Schwarzenbach
authors.forename: Corinna
authors.initials: C
authors.lastname: Eichelser
authors.forename: Bettina
authors.initials: B
authors.lastname: Steinbach
authors.forename: Josefine
authors.initials: J
authors.lastname: Tadewaldt
authors.forename: Klaus
authors.initials: K
authors.lastname: Pantel
authors.forename: Victor
authors.initials: V
authors.lastname: Lobanenkov
authors.forename: Dmitri
authors.initials: D
authors.lastname: Loukinov
mesh_terms: D017398:Alternative Splicing; D045744:Cell Line, Tumor; D019175:DNA Methylation; D004268:DNA-Binding Proteins / Q000378:metabolism*; D015972:Gene Expression Regulation, Neoplastic; D055785:Gene Knockdown Techniques; D056426:Genetic Loci; D006657:Histones / Q000378:metabolism; D006801:Humans; D061986:MCF-7 Cells; D009363:Neoplasm Proteins / Q000235:genetics*; D010446:Peptide Fragments / Q000235:genetics*; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D050784:Proto-Oncogene Protein c-ets-1 / Q000378:metabolism; D034622:RNA Interference; D012333:RNA, Messenger / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics; D016329:Sp1 Transcription Factor / Q000378:metabolism*; D035181:TATA-Box Binding Protein / Q000378:metabolism*; D015533:Transcriptional Activation
chemical_list: C456540:CTCFL protein, human; D004268:DNA-Binding Proteins; D006657:Histones; C506530:MAGE-A1 protein (278-286), human; D009363:Neoplasm Proteins; D010446:Peptide Fragments; D050784:Proto-Oncogene Protein c-ets-1; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D016329:Sp1 Transcription Factor; D035181:TATA-Box Binding Protein