Keeping active endogenous retroviral-like elements in check: the epigenetic perspective.

Endogenous retrovirus-like elements, or ERVs, are an abundant component of all eukaryotic genomes. Their transcriptional and retrotranspositional activities have great potential for deleterious effects on gene expression. Consequences of such activity may include germline mutagenesis and cancerous transformation. As a result, mammalian genomes have evolved means of counteracting ERV transcription and mobilization. In this review, we discuss epigenetic mechanisms of ERV and LTR retrotransposon control during mouse development, focusing on involvement of DNA methylation, histone modifications, small RNAs and their interaction with one another. We also address relevance of research performed in the mouse system to human and challenges associated with studying repetitive families. (Part of a multi-author review).