Transcription Profiling Demonstrates Epigenetic Control of Non-retroviral RNA Virus-Derived Elements in the Human Genome

• Seven H. sapiens endogenous bornavirus-like nucleoprotein elements are expressed as RNA in at least one tissue
• Expression of some hsEBLNs, for example, hsEBLN-1, is tissue-specific
• Expression from the hsEBLN-1 locus is epigenetically silenced in most tissues
• Integration of hsEBLN-1 in the genome affects the expression of a neighboring gene

SummaryEndogenous bornavirus-like nucleoprotein elements (EBLNs) are DNA sequences in vertebrate genomes formed by the retrotransposon-mediated integration of ancient bornavirus sequence. Thus, EBLNs evidence a mechanism of retrotransposon-mediated RNA-to-DNA information flow from environment to animals. Although EBLNs are non-transposable, they share some features with retrotransposons. Here, to test whether hosts control the expression of EBLNs similarly to retrotransposons, we profiled the transcription of all Homo sapiens EBLNs (hsEBLN-1 to hsEBLN-7). We could detect transcription of all hsEBLNs in at least one tissue. Among them, hsEBLN-1 is transcribed almost exclusively in the testis. In most tissues, expression from the hsEBLN-1 locus is silenced epigenetically. Finally, we showed the possibility that hsEBLN-1 integration at this locus affects the expression of a neighboring gene. Our results suggest that hosts regulate the expression of endogenous non-retroviral virus elements similarly to how they regulate the expression of retrotransposons, possibly contributing to new transcripts and regulatory complexity to the human genome.

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