title: CpG methylation of the PAI-1 gene 5'-flanking region is inversely correlated with PAI-1 mRNA levels in human cell lines.
abstract: The physiological and pathophysiological functions of PAI-1 are related to its expression by specific cell types in normal and diseased tissues. We analysed the contribution of DNA methylation to the variation in PAI-1 mRNA levels in five cell lines. We found varying frequencies of methylation of 25 CpGs in the -805/+152 region of the PAI-1 gene in Bowes, MCF-7 and U937 cells, while little or no methylation was detected in Hep2 and HT- 1080 cells. The methylation frequency was inversely correlated with PAI-1 mRNA level within its 20-fold range in Bowes, MCF-7, U937,and Hep2 cells, while the lack of methylation in both Hep2 and HT-1080 cells suggested another mechanism behind the 150-fold higher level in HT- 1080 cells than in Hep2 cells. However, all cell lines exhibited a high frequency of methylation of 10 CpGs in a CpG island at about--1800. Treatment with 5-aza-2'-deoxycytidine led up to circa a 40-fold increase in the PAI-1 mRNA level and a strong decrease in the frequency of methylation in the -805/+152 region in Bowes, MCF-7 and U937. The histone deacetylase inhibitor trichostatin A induced a several fold increase of the PAI-I mRNA level in cells with a high methylation frequency of the -805/+152 region. As compared with matched normal tissue, three samples of oral squamous cell carcinomas displayed decreased frequencies of methylation of the PAI-1 5' flanking region and increased levels of PAI-1 mRNA. These results for the first time implicate DNA methylation and histone acetylation in regulation of the PAI-1 gene, and indicate that without proper CpG islands in 5'-flanking region,trancription may be regulated by methylation of less dense CpGs in the 5'-flanking region rather than methylation of upstream CpG island.
authors.affiliation: Department of Molecular Biology, University of Aarhus, Aarhus C, Denmark. shg@mb.au.dk
authors.forename: Shan
authors.initials: S
authors.lastname: Gao
authors.forename: Sune
authors.initials: S
authors.lastname: Skeldal
authors.forename: Annelise
authors.initials: A
authors.lastname: Krogdahl
authors.forename: Jens Ahm
authors.initials: JA
authors.lastname: Sørensen
authors.forename: Peter A
authors.initials: PA
authors.lastname: Andreasen
mesh_terms: D024506:5' Flanking Region / Q000235:genetics; D001374:Azacitidine / Q000031:analogs & derivatives / Q000494:pharmacology; D002294:Carcinoma, Squamous Cell / Q000235:genetics / Q000378:metabolism*; D018899:CpG Islands; D004247:DNA / Q000378:metabolism*; D019175:DNA Methylation / Q000187:drug effects; D015254:DNA Modification Methylases / Q000037:antagonists & inhibitors; D000077209:Decitabine; D004305:Dose-Response Relationship, Drug; D015972:Gene Expression Regulation, Neoplastic; D020868:Gene Silencing; D056572:Histone Deacetylase Inhibitors; D006801:Humans; D006877:Hydroxamic Acids / Q000494:pharmacology; D009062:Mouth Neoplasms / Q000235:genetics / Q000378:metabolism*; D017395:Plasminogen Activator Inhibitor 1 / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism*; D017422:Sequence Analysis, DNA; D013997:Time Factors; D020298:U937 Cells / Q000378:metabolism
chemical_list: D056572:Histone Deacetylase Inhibitors; D006877:Hydroxamic Acids; D017395:Plasminogen Activator Inhibitor 1; D012333:RNA, Messenger; C012589:trichostatin A; D000077209:Decitabine; D004247:DNA; D015254:DNA Modification Methylases; D001374:Azacitidine