Impact of SINEs and LINEs on the Mammalian Genome

H.   D.   Kass

Abstract

Several families of short and long interspersed DNA elements (SINEs and LINEs) inhabit mammalian genomes. Amplification of these elements (which can exceed one million copies) has occurred primarily by an RNA-mediated mechanism referred to as retroposition (or retrotransposition). When integrated into a gene, these elements may cause deleterious effects to the individual organism, as exemplified in various human disorders. Alternatively, several integration-recipient genes with altered function or expression are evolutionarily conserved within or among species. Experimental analyses further demonstrate effects of gene regulation by retroposed elements. Although most integrations apparently have no significant impact on the phenotype of various mammalian species, the accumulation of SINEs and LINEs provides a multitude of sites for homologous recombination and yields a considerable proportion of methylation sites in mammalian genomes. Specific and cumulative integrations may provide an integral component in the speciation process. This review examines the functional and regulatory impact of retroposon integrations on individual genes, the impact of accumulated integration events, and the evidence for the role of these elements in the evolution of species. Since these elements continue to integrate into mammalian genomes, it is important to further understand and evaluate their functional impact.

Keywords: SINEs, LINEs, Neurofibromatosis, Apert Syndrome, Alport Syndrome, Gyrate Atrophy of Choroid, Spastic, Canine Transmissible venereal tumor, Hemophilia