Evolutionarily recent insertions of mobile elements and their contribution to human genome structure

Abstract

Mobile elements are DNA fragments able to self-replicate in the genome of a host organism. Typically, mobile elements account for approximately 40–50% of the mammalian genome. This review summarizes the evolutionarily recent insertions of mobile elements that have taken place after the divergence of human and chimpanzee ancestral lineages, i.e., later than about 6 MYA. The human-specific mobile elements are represented by relatively small copy numbers and fall into the four following groups: HERV-K (HML-2), L1, Alu, and SVA. The amount of human-specific HERV-K (HML-2), L1, Alu, and SVA is about 150, 1200, 5500, and 860 copies per genome, respectively. In addition, we have succeeded in describing a new family of human-specific mobile elements, which are only present in the human genome and absent in the DNA of other primates. The insertions of human-specific mobile elements can be considered to be important candidates for the role of molecular genetic agents of anthropogenesis, since each new insertion of such a mobile element supplies an acceptor genomic locus with a set of new functional sites of transcription factor binding that are able to significantly contribute to the function of adjacent genes. The known facts that demonstrate the effect of human-specific mobile elements on the expression of neighboring genes allow the total number of human genes controlled by them to be estimated as several hundred.