TY - JOUR T1 - Ancient Exaptation of a CORE-SINE Retroposon into a Highly Conserved Mammalian Neuronal Enhancer of the Proopiomelanocortin Gene A1 - Santangelo, Andrea M A1 - de Souza, Flávio S. J A1 - Franchini, Lucía F A1 - Bumaschny, Viviana F A1 - Low, Malcolm J A1 - Rubinstein, Marcelo Y1 - 2007/10/05 N2 -
One of the most striking observations derived from the genomic era is the overwhelming contribution of transposed elements to mammalian genomes. For example, 45% of the human genome is derived from mobile element fragments. Although historically viewed as “junk DNA,” transposed elements could also contribute to novel advantageous functional elements in their host genomes, a process called exaptation. Functionally proven examples of exaptation derived from ancient retroposition events are rare. Using an in silico paleogenomic strategy, we unraveled the evolutionary origin of nPE2, a neuronal enhancer of the proopiomelancortin gene that participates in the production of hypothalamic peptides involved in feeding behavior and stress-induced analgesia. We demonstrate that nPE2 originated from the exaptation of a SINE retroposon in the lineage leading to mammals and remained under purifying selection for the last 170 million years. The difficulty in detecting nPE2 origin as an exapted retroposon illustrates the underestimation of this phenomenon and encourages the finding of the many thousands of retroposon-derived functional elements still hidden within the genomes. Their discovery will contribute to a better understanding of the dynamics of gene evolution and, at a larger scale, the origin of macroevolutionary novelties that lead to the appearance of new species, orders, or classes.