An Evolutionarily Young Polar Bear (Ursus maritimus) Endogenous Retrovirus Identified from Next Generation Sequence...

Area of Science:

• Genomics
• Virology
• Evolutionary Biology

Background:

• Endogenous retroviruses (ERVs) are remnants of ancient retroviral infections integrated into host genomes.
• Porcine Endogenous Retroviruses (PERVs) are well-characterized ERVs found in pigs.

Purpose of the Study:

• To identify and characterize novel endogenous retroviruses in polar bear (Ursus maritimus) genomes.
• To investigate the evolutionary history and origin of UrsusERV.

Main Methods:

• Transcriptome analysis of polar bear tissues.
• Genome sequencing and analysis of polar bear, brown bear, and black bear.
• Polymerase Chain Reaction (PCR) for sequence identification.
• Phylogenetic analysis of retroviral protein sequences.

Main Results:

• Discovery of four proviral copies and 15 long terminal repeats (LTRs) of a new ERV, named UrsusERV, in polar bears.
• Identification of UrsusERV in brown and black bears, but not in other bear species, suggesting lineage specificity.
• Evidence of at least two UrsusERV variants and recent genomic invasions.
• Age estimation suggests UrsusERV is only a few million years old, with the youngest provirus potentially encoding functional proteins.
• Phylogenetic analysis places UrsusERV within a clade of pig, gibbon, and koala retroviruses.

Conclusions:

• UrsusERV represents one of the youngest ERVs identified in mammals.
• Its lineage specificity and young age suggest a recent cross-species transmission from an unknown reservoir.
• The potential for functional protein expression in the youngest provirus warrants further investigation.