Gene conversion and purifying selection of a placenta-specific ERV-V envelope gene during simian evolution

Area of Science:

• Evolutionary biology
• Genomics
• Virology

Background:

• Human endogenous retroviruses (HERVs) are ancient viral sequences integrated into the host genome.
• Most HERV genes are degraded, but some intact, ancient genes may confer host benefits.
• This study focuses on the evolutionary aspects of two tandem HERV-V envelope genes, ENVV1 and ENVV2.

Purpose of the Study:

• To investigate the evolutionary history and functional significance of the ENVV1 and ENVV2 genes.
• To determine the evolutionary timeline of ERV-V integration into the primate genome.
• To explore the potential beneficial role of these HERV genes in host biology.

Main Methods:

• Comparative genomics analysis across primate species.
• Phylogenetic analysis to trace gene presence and evolution.
• Assessment of transposon insertions and nucleotide substitutions.
• Analysis of gene expression patterns, specifically in placental tissues.

Main Results:

• The ENVV2 gene is intact in simian primates but absent in prosimians, indicating ERV-V integration post-simian/prosimian split.
• ENVV2 escaped transposon insertions, and purifying selection preserved its reading frame during primate evolution.
• ENVV1 appears involved in gene conversion of ENVV2, and both genes exhibit placenta-specific expression in humans and baboons.

Conclusions:

• ERV-V integration occurred after the divergence of simian and prosimian primates.
• Purifying selection and gene conversion have maintained functional ENVV1 and ENVV2 genes in most primate species.
• Placenta-specific expression suggests a beneficial role for these HERV envelope genes in host reproduction.