Endogenous retroviruses (ERVs) constitute a significant part of vertebrate genomes. They originated from past retroviral infections and some of them retain transcriptional activity. The key mechanism avoiding uncontrolled ERV transcription is DNA methylation-mediated epigenetic silencing. Despite numerous studies describing the involvement of ERV activity in cellular processes, epigenetic regulation of ERVs is still poorly understood. We previously described a cervid endogenous retrovirus (CrERV) in the mule deer genome. This virus exhibits massive insertional polymorphism, suggesting recent activity. Here we employed NGS-based strategy to determine the methylation pattern of CrERV integrations in four mule deer. Besides the vast majority of methylated integrations, we identified a tiny fraction of demethylated proviral copies. These copies represent evolutionary older integrations located near gene promoters. In general, our work is a first attempt to characterize the epigenetic landscape of insertionally polymorphic ERV on a whole-genome scale and offers insight into its interactions with a host.
Keywords: DNA methylation; Endogenous retrovirus; Epigenetics; Mule deer; Retrovirus.
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