Endogenized viral sequences in mammals
Nicholas F Parrish1 and Keizo Tomonaga2,3,4
1 Section of Surgical Sciences, Vanderbilt University Medical Center, Nashville, TN 37232, United States
2 Department of Viral Oncology, Institute for Virus Research, Kyoto University, Kyoto 606-8507, Japan
3 Department of Tumor Viruses, Graduate School of Medicine, Kyoto University, Kyoto 606-8507, Japan
4 Department of Mammalian Regulatory Network, Graduate School of Biostudies, Kyoto University, Kyoto 606-8507, Japan
Corresponding authors: Parrish, Nicholas F. () and Tomonaga, Keizo ()
Reverse-transcribed RNA molecules compose a significant portion of the human genome. Many of these RNA molecules were retrovirus genomes either infecting germline cells or having done so in a previous generation but retaining transcriptional activity. This mechanism itself accounts for a quarter of the genomic sequence information of mammals for which there is data. We understand relatively little about the causes and consequences of retroviral endogenization. This review highlights functions ascribed to sequences of viral origin endogenized into mammalian genomes and suggests some of the most pressing questions raised by these observations.