Coordinated transcription of and genes is silenced by DNA methylation.

OBJECTIVE

To investigate the relationship between the transcription of , , and at the same locus and the regulation mechanism of .

METHODS

Publicly available database of Cancer Cell Line Encyclopedia (CCLE) was used in bioinformatic analyses. Methylation of CpG islands was detected by denaturing high performance liquid chromatography (DHPLC). Gene transcript levels were determined using quantitative real-time polymerase chain reaction (qRT-PCR) assays. An engineered -specific transcription factor and DNA methyltransferase were used to induce -specific DNA demethylation and methylation.

RESULTS

The expression level of was positively and significantly correlated with that of but not with that of in the CCLE database. This was confirmed in human cell lines and patient colon tissue samples. In addition, was significantly upregulated in colon cancer tissues. Transcription of and was observed only in cell lines in which the alleles were unmethylated and not in cell lines with fully methylated alleles. Notably, -specific methylation significantly decreased transcription of and in BGC823 and GES1 cells. In contrast, -specific demethylation re-activated transcription of and in H1299 cells (P<0.001). Alteration of expression was not induced by expression changes.

CONCLUSIONS

and are coordinately transcribed in human cells and regulated by the methylation status of the CpG islands around the transcription start site.