Methylation of a CpG island within the uroplakin Ib promoter: a possible mechanism for loss of uroplakin Ib expression in bladder carcinoma.
Uroplakin Ib is a structural protein on the surface of urothelial cells. Expression of uroplakin Ib mRNA is reduced or absent in many transitional cell carcinomas (TCCs) but molecular mechanisms underlying loss of expression remain to be determined. Analysis of the uroplakin Ib promoter identified a weak CpG island spanning the proximal promoter, exon 1, and the beginning of intron 1. This study examined the hypothesis that methylation of this CpG island regulates uroplakin Ib expression. Uroplakin Ib mRNA levels were determined by reverse transcription polymerase chain reaction and CpG methylation was assessed by bisulfite modification of DNA, PCR, and sequencing. A correlation was demonstrated in 15 TCC lines between uroplakin Ib mRNA expression and lack of CpG methylation. In support of a regulatory role for methylation, incubating uroplakin Ib-negative lines with 5-aza-2'-deoxycytidine reactivated uroplakin Ib mRNA expression. A trend between uroplakin Ib mRNA expression and CpG methylation was also observed in normal urothelium and bladder carcinomas. In particular, loss of uroplakin Ib expression correlated with methylation of a putative Sp1/NFkappaB binding motif. The data are consistent with the hypothesis that methylation of specific sites within the uroplakin Ib promoter may be an important factor in the loss of uroplakin Ib expression in TCCs.
Varga
Andrea E
AE
Department of Surgery, The University of Adelaide, The Queen Elizabeth Hospital, Woodville, South Australia, Australia.
Leonardos
Lefta
L
Jackson
Paul
P
Marreiros
Alexandra
A
Cowled
Prue A
PA
D001374:Azacitidine / Q000031:analogs & derivatives* / Q000494:pharmacology; D001483:Base Sequence; D018899:CpG Islands; D019175:DNA Methylation; D015254:DNA Modification Methylases / Q000037:antagonists & inhibitors; D000077209:Decitabine; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008562:Membrane Glycoproteins / Q000235:genetics*; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014407:Tumor Cells, Cultured; D001749:Urinary Bladder Neoplasms / Q000235:genetics*; D060169:Uroplakin Ib; D019459:Urothelium / Q000378:metabolism / Q000473:pathology
D004791:Enzyme Inhibitors; D008562:Membrane Glycoproteins; C086452:UPK1B protein, human; D060169:Uroplakin Ib; D000077209:Decitabine; D015254:DNA Modification Methylases; D001374:Azacitidine