Retrotransposon Hypomethylation in Melanoma and Expression of a Placenta-Specific Gene

Abstract

<div><p>In the human placenta, DNA hypomethylation permits the expression of retrotransposon-derived genes that are normally silenced by methylation in somatic tissues. We previously identified hypomethylation of a retrotransposon-derived transcript of the voltage-gated potassium channel gene <i>KCNH5</i> that is expressed only in human placenta. However, an RNA sequence from this placental-specific transcript has been reported in melanoma. This study examined the promoter methylation and expression of the retrotransposon-derived <i>KCNH5</i> transcript in 25 melanoma cell lines to determine whether the acquisition of ‘placental’ epigenetic marks is a feature of melanoma. Methylation and gene expression analysis revealed hypomethylation of this retrotransposon in melanoma cell lines, particularly in those samples that express the placental <i>KCNH5</i> transcript. Therefore we propose that hypomethylation of the placental-specific <i>KCNH5</i> promoter is frequently associated with <i>KCNH5</i> expression in melanoma cells. Our findings show that melanoma can develop hypomethylation of a retrotransposon-derived gene; a characteristic notably shared with the normal placenta.</p></div