Leptin receptor isoform 219.1: an example of protein evolution by LINE-1-mediated human-specific retrotransposition of a coding SVA element.

Phylogenetically new insertions of repetitive sequences may contribute to genome evolution by altering the function of preexisting proteins. One example is the SVA sequence, which forms the C-terminal coding exon of the human leptin receptor isoform 219.1. Here, we report that the SVA insertion into the LEPR locus has occurred after divergence of humans and chimpanzees. The SVA element was inserted into a Hal-1/LINE element present in all monkeys and apes tested. Structural features point toward an integration event that was mediated by the L1 protein machinery acting in trans. Thus, our findings add evidence to the hypothesis that retrotransposition events are a driving force in genomic evolution and that the presence or absence of specific retroelements are one distinguishing feature that separates humans from chimpanzees.