Molecular properties and evolutionary origins of a parvovirus-derived myosin fusion gene in guinea pigs

Abstract

Sequences derived from parvoviruses (family Parvoviridae) are relatively common in animal genomes, but the functional significance of these endogenous parvoviral element (EPV) sequences remains unclear. In this study we use a combination of in silico and molecular biological approaches to investigate a fusion gene encoded by guinea pigs (genus Cavia) that is partially derived from an EPV. This gene, named enRep-Myo9, encodes a predicted polypeptide gene product comprising a partial myosin9 (Myo9)-like gene fused to a 3’ truncated, EPV- encoded replicase. We first examined the genomic and phylogenetic characteristics of the EPV locus that encodes the viral portions of enRep-Myo9. We show that this locus, named enRep, is specific to guinea pigs and derives from an ancient representative of the parvoviral genus Dependoparvovirus that integrated into the guinea pig germline 22-35 million years ago. Despite these ancient origins, however, the regions of enRep that are incorporated into the coding sequence of the enRep-Myo9 gene are conserved across multiple species in the family Caviidae (guinea pigs and cavies) consistent with purifying selection. Using molecular biological approaches, we further demonstrate that: (i) enRep-Myo9 mRNA is broadly transcribed in guinea pig cells; (ii) the cloned enRep-Myo9 transcript can express a protein of the expected size in guinea pig cells in vitro, and; (iii) the expressed protein localizes to the cytosol. Our findings demonstrate that, consistent with a functional role, the enRep-Myo9 fusion gene is evolutionarily conserved, broadly transcribed, and capable of expressing protein. Importance DNA from viruses has been ‘horizontally transferred’ to mammalian genomes during evolution, but the impact of this process on mammalian biology remains poorly understood. The findings of our study indicate that in guinea pigs a novel gene has evolved through fusion of host and virus genes.