To understand how transposable elements shape genomes, where they are maintained over generations, it is vital to discover the mechanisms behind their targeted integration. Researchers from the Laboratoire Pathologie et Virologie Moléculaire (CNRS/Inserm/Université Paris Diderot), in collaboration with researchers from CEA3 and a laboratory at the University of Minnesota, have identified an interaction between two proteins that is essential for the integration of a transposable element into a specific area of the yeast genome. These results, published in the May 1, 2015 issue of Science, emphasize the role of these mobile DNA sequences in the evolution and adaptation of organisms, and their potential value for gene therapy. The article is titled “An RNA Polymerase III Subunit Determines Sites of Retrotransposon Integration.” Transposable elements are DNA sequences capable of moving within genomes. They represent a significant proportion of the genome and play an important role in its evolution. By integrating into the DNA, these transposable elements can contribute to genome plasticity and the emergence of new cellular functions. Conversely, they can also cause mutations that endanger cell survival. Their integration usually occurs in specific gene-poor regions, where such integration is least harmful. The mechanisms that make this targeted integration possible are still poorly understood. The authors of the current study focused on the Ty1 retrotransposon5 of the yeast Saccharomyces cerevisiae to examine how the integration site is determined. A retrotransposon is a particular type of transposable element, capable of replicating itself in a "copy and paste"-like method. It is thus able to multiply and invade a genome. This replication involves an RNA intermediate.
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