Strain-Specific Epigenetic Regulation of Endogenous Retroviruses: The Role of Trans-Acting Modifiers

• Published in: Viruses Vol. 12; no. 8; p. 810
• Main Authors: Elmer, Jessica L., Ferguson-Smith, Anne C.
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 27.07.2020; MDPI
• Subjects: Animals; Coevolution; Deoxyribonucleic acid; DNA; DNA methylation; Embryos; Endogenous Retroviruses - genetics; Epigenesis, Genetic; epigenetic regulation; Epigenetics; ERVs; Gene expression; Gene Expression Regulation; Genera; Genomes; Heredity; histone code; Humans; Inbreeding; inheritance (genetics); KRAB zinc finger proteins; Kruppel-Like Transcription Factors - genetics; metastable epialleles; Mice; Mice, Inbred Strains; modifiers; Mutation; Promoter Regions, Genetic; Proteins; Retroviridae; Retroviridae Infections; Review; Stem cells; strain-specific; Trans-Activators - genetics; Transgenes; zinc finger motif; Zinc finger proteins; strain-specific; KRAB zinc finger proteins; metastable epialleles; ERVs; modifiers; epigenetic regulation; transgenes
• ISSN: 1999-4915; 1999-4915
• DOI: 10.3390/v12080810

Approximately 10 percent of the mouse genome consists of endogenous retroviruses (ERVs), relics of ancient retroviral infections that are classified based on their relatedness to exogenous retroviral genera. Because of the ability of ERVs to retrotranspose, as well as their cis-acting regulatory potential due to functional elements located within the elements, mammalian ERVs are generally subject to epigenetic silencing by DNA methylation and repressive histone modifications. The mobilisation and expansion of ERV elements is strain-specific, leading to ERVs being highly polymorphic between inbred mouse strains, hinting at the possibility of the strain-specific regulation of ERVs. In this review, we describe the existing evidence of mouse strain-specific epigenetic control of ERVs and discuss the implications of differential ERV regulation on epigenetic inheritance models. We consider Krüppel-associated box domain (KRAB) zinc finger proteins as likely candidates for strain-specific ERV modifiers, drawing on insights gained from the study of the strain-specific behaviour of transgenes. We conclude by considering the coevolution of KRAB zinc finger proteins and actively transposing ERV elements, and highlight the importance of cross-strain studies in elucidating the mechanisms and consequences of strain-specific ERV regulation.