DNA Methylation Profiles of Protease Nexin 1 (SERPINE2) Gene in Human Cell Lines

To investigated whether epigenetic mechanisms contribute to the variable expression of variable protease nexin1(PN-1) encoded by the SERPINE2 gene in different cell types.

Working with 5 human cell lines, we determined the CpG methylation status within two CpG islands in the SERPINE2 gene by bisulphate sequencing and the PN-1 mRNA level by Q-RT PCR.

A CpG island spanning the transcription initiation site showed little methylation in 3 of the cell lines and substantial methylation in 2 of the cell lines. A CpG island covering the translation starting site showed full methylation in all investigated cell lines. Methylation within the CpG island was not randomly distributed, but showed accumulation at specific sites. However, we were not able to distinguish any patterns which related the methylation frequency to the gene expression level. Inhibition of CpG methylation with 5-aza-2'-deoxycytidine led to a several fold increase in PN-1 mRNA levels, but based on the results on CpG methylation in the CpG island spanning the transcript, the effect is most likely indirect.

We have carefully mapped the CpG methylation pattern in two CpG islands in the 5' part of the SERPINE2 gene without finding any obvious inverse correlation between methylation frequency and expression level.