Abstract
Here I review the properties of the mouse retroelement VL30-1, which apparently derived from retrotranspostions of a founder VL30 retrovirus that infected the mouse germline after the mouse-human speciation. The VL30-1 gene is transcribed as a long noncoding RNA (lncRNA) with an essential host function in an epigenetic transcription switch (ETS) that regulates transcription of multiple genes, including proto-oncogenes that control cell proliferation and oncogenesis. The ETS involves the tumor suppressor protein PSF that has a DNA-binding domain (DBD) and two RNA-binding domains (RBDs). The DBD binds to promoters that have a DBD-binding sequence and switches off transcription, and the RBDs bind lncRNAs that have a RBD-binding sequence, releasing PSF and switching on transcription. VL30-1 lncRNA has two RBD-binding sequences, apparently acquired by mutations during retrotranspositions of the founder retrovirus, which drive proto-oncogene transcription and oncogenesis via the ETS. VL30-1 lncRNA is a seminal example of the key role of endogenous retroviruses (ERVs) and their retroelements in the evolution of transcription regulatory systems.