title: Expression of AP-2 alpha in SV40 immortalized human lung fibroblasts is associated with a distinct pattern of cytosine methylation in the AP-2 alpha promoter.
abstract: Activator protein-2 alpha (AP-2 alpha) is a cell type-specific, developmentally regulated, transcription factor that has been implicated as a critical regulator of gene expression during vertebrate development and carcinogenesis. We found that AP-2 alpha was differentially expressed in the normal human lung fibroblast cell strains WI38, MRC-5 and their respective SV40-transformed cell counterparts WI38-VA, MRC-5VA. Since CpG methylation within genetic regulatory regions has been implicated as a mechanism of gene regulation, we investigated the CpG methylation status of the AP-2 alpha gene promoter in these cells. High resolution mapping of methylated cytosines revealed that differential expression of the AP-2 alpha gene in normal human lung fibroblasts and their SV40-transformed counterparts was associated with distinct patterns of cytosine methylation in the AP-2 alpha promoter just 5' to the transcription initiation site. Site-specific methylation was positively correlated with increased AP-2 alpha gene expression in both transformed cell lines investigated. Interestingly, one of the two major centers of hypermethylation in the transformed cells encompassed the cis-element for the AP-2 repressing transcription factor AP-2rep (KLF12). Finally, a sequence variation in human lung fibroblasts relative to the published sequence revealed a previously unidentified AP-2 binding site at position -528 with respect to the transcription initiation site that overlapped the AP-2rep site. Our results suggest that transcriptional activation of AP-2 alpha in the SV40-transformed cells is mediated, at least in part, by site-specific methylation of a negative regulatory cis-element in the AP-2 alpha promoter.
authors.affiliation: Free Radical and Radiation Biology Program, Department of Radiology, The University of Iowa, Iowa City, IA 52242, USA.
authors.forename: C H
authors.initials: CH
authors.lastname: Zhu
authors.forename: Y
authors.initials: Y
authors.lastname: Huang
authors.forename: M T
authors.initials: MT
authors.lastname: Broman
authors.forename: F E
authors.initials: FE
authors.lastname: Domann
mesh_terms: D001665:Binding Sites; D002460:Cell Line; D002461:Cell Line, Transformed; D018899:CpG Islands / Q000235:genetics*; D003596:Cytosine / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D005347:Fibroblasts; D005786:Gene Expression Regulation; D006801:Humans; D008745:Methylation; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000378:metabolism; D050656:Transcription Factor AP-2; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: D004268:DNA-Binding Proteins; D012333:RNA, Messenger; C493673:TFAP2A protein, human; D050656:Transcription Factor AP-2; D014157:Transcription Factors; D003596:Cytosine