Human Endogenous Retroviruses as Biomedicine Markers

Abstract

Human endogenous retroviruses (HERVs) were formed via ancient integration of exogenous retroviruses into the human genome and are considered to be viral "fossils". The human genome is embedded with a considerable amount of HERVs, witnessing the long-term evolutionary history of the viruses and the host. Most HERVs have lost coding capability during selection but still function in terms of HERV-mediated regulation of host gene expression. In this review, we summarize the roles of HERV activation in response to viral infections and diseases, and emphasize the potential use of HERVs as biomedicine markers in the early diagnosis of diseases such as cancer, which provides a new perspective for the clinical application of HERVs.

Keywords: Biomedicine marker; Cancer; Disease; Human endogenous retrovirus (HERVs); Viral infection.

Fig. 1

A A brief sketch map of endogenous retrovirus. An intact ERV includes gag, pro, pol, env genes and two long terminal repeats. B Current phylogeny of representative HERV clade. HERVs are divided into three groups, Class I (Gamma-like), Class II (Beta-like), Class III (Spuma-like). The classification of HERVs was constructed based on the article Classification and characterization of human endogenous retroviruses; mosaic forms are common (Vargiu et al. 2016). Reference POL proteins also come from this paper. Phylogenetic tree was constructed by using IQ-TREE 2, with ultrafast bootstrap 1000 (Hoang et al. ; Minh et al. 2020). Asterisk indicates HERV-W belongs to Class I using pol gene to construct phylogenetic tree, but belongs to Class II (D-type-related retrovirus) if using ENV protein motif to construct phylogenetic tree (Lin et al. ; Henzy and Johnson 2013).