Human-specific endogenous retroviruses

Abstract

This review focuses on a small family of human-specific genomic repetitive elements, presented by 134 members that shaped ∼330 kb of the human DNA. Although modest in terms of its copy number, this group appeared to modify the human genome activity by endogenizing ∼50 functional copies of viral genes that may have important implications in the immune response, cancer progression, and antiretroviral host defense. A total of 134 potential promoters and enhancers have been added to the human DNA, about 50% of them in the close gene vicinity and 22% in gene introns. For 60 such human-specific promoters, their activity was confirmed by in vivo assays, with the transcriptional level varying ∼1000-fold from hardly detectable to as high as ∼3% of β-actin transcript level. New polyadenylation signals have been provided to four human RNAs, and a number of potential antisense regulators of known human genes appeared due to human-specific retroviral insertional activity. This information is given here in the context of other major genomic changes underlining differences between human and chimpanzee DNAs. Finally, a comprehensive database, is available for download, of human-specific and polymorphic endogenous retroviruses is presented, which encompasses the data on their genomic localization, primary structure, encoded viral genes, human gene neighborhood, transcriptional activity, and methylation status. ©2007 with author. Published by TheScientificWorld.