Scientists have discovered in the pig genome a family of unique short repeats that have evolutionary similarities to similar repeats in primates.
Scientists from Jilin University (Changchun, China) and the Academy of Agricultural Sciences (Heilongjiang, China) took part in the project in collaboration with Firefly BioWorks Corporation (USA).
After analyzing the structure and origin of PRE-1 (porcine repeat element, literally - "pig repeating element"), they came to the conclusion that the closest relatives of primates on the former supercontinent Laurasia could be pigs. The research preprint was published on the bioRxiv server on August 31, 2015.
The studied CDP (short dispersed repeat) PRE-1 is located in the intergenic region, approximately 686 ~ 985 base pairs before the start of the gene encoding the insulin growth factor binding protein (IGFBP7). The repeated PRE-1 sequence of 299 base pairs was compared with 40 different primate Alu repeats, and significant similarities were found both in the sequences themselves and in the pattern of the distribution of their repeats across chromosomes.
The predicted secondary structure of the RNA repeats PRE-1 folded into a model similar to the Alu-repeats. Finally, the common origin of PRE-1 and Alu from the so-called 7SL RNA (signal recognition RNA) suggested their evolutionary similarity and attributed pigs to the family, which mainly includes primates.
Previously, to build phylogenetic trees, scientists relied only on the similarities and differences of genes, ignoring the fact that during the course of evolution the entire genome underwent changes, including those elements that do not encode proteins or RNA and whose meaning is still largely unclear to scientists.
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This study, based on an integrated approach to the analysis of intergenic elements, provides, according to the authors, "very convincing" facts from which evolutionary conclusions can be drawn. In particular, according to these results, the estimated time of divergence of species shifts from 65 to 80-100 million years ago.
