The role of CpG methylation in cell type-specific expression of the aquaporin-5 gene.
Aquaporin-5 (AQP5) is expressed in a cell type-specific manner. Here, we show that the AQP5 gene is regulated by CpG methylation. The AQP5 promoter containing a putative CpG island was highly methylated in NIH-3T3 or freshly isolated alveolar epithelial cells, correlating with the repression of this gene in these cells. In contrast, the AQP5 promoter was hypo-methylated in MLE-12 or cultured alveolar epithelial cells, which express high levels of AQP5. Repression of AQP5 transcription in NIH-3T3 cells could be relieved with 5-azacytidine, and in vitro methylation of the AQP5 promoter resulted in inhibition of transcription of the reporter gene in MLE-12 cells. Chromatin immunoprecipitation assays showed that endogenous Sp1 bound to the hypo-methylated, but not highly methylated, AQP5 promoter region. These results demonstrate that the hypo-methylated state of the AQP5 promoter leading to increased Sp1 binding may play a role in regulation of cell type-specific expression of the AQP5 gene.
Nomura
Johji
J
Department of Chemico-Pharmacological Sciences, Graduate School of Pharmaceutical Sciences, Kumamoto University, 5-1 Oe-honmachi, Kumamoto 862-0973, Japan.
Hisatsune
Akinori
A
Miyata
Takeshi
T
Isohama
Yoichiro
Y
D000818:Animals; D051402:Aquaporin 5 / Q000235:genetics* / Q000378:metabolism; D001374:Azacitidine / Q000494:pharmacology; D001483:Base Sequence; D015153:Blotting, Western; D002461:Cell Line, Transformed; D002478:Cells, Cultured; D018899:CpG Islands / Q000235:genetics*; D019175:DNA Methylation; D004305:Dose-Response Relationship, Drug; D020869:Gene Expression Profiling; D008156:Luciferases / Q000235:genetics / Q000378:metabolism; D008297:Male; D051379:Mice; D008969:Molecular Sequence Data; D041681:NIH 3T3 Cells; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016329:Sp1 Transcription Factor / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects; D014162:Transfection
D051402:Aquaporin 5; D011993:Recombinant Fusion Proteins; D016329:Sp1 Transcription Factor; D008156:Luciferases; D001374:Azacitidine