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Chapter 43 : Interactions between Transposable Elements and the Host Genome
Category: Microbial Genetics and Molecular Biology
This chapter explores the issue of how eukaryotic transposable elements interact with their hosts, trying to disclose the benefits they can bring to the genome by analyzing the interactions at the molecular level in every step of the transposition process. The tendency of transposable elements to increase in copy number antagonizes the interest of the host genome to keep its genetic information free of the interference produced by new insertions. Due to this tradeoff, transposable elements and their hosts have developed mechanisms to control transposition, which is the most critical step in limiting their propensity to spread throughout the host genome. The same proteins would have evolved afterward to become major players in transcription regulation through alterations in chromatin structure. Another hint of how transposable elements could be subject to silencing and heterochromatization by the host genomes comes from studies of the organization of the pericentromeric regions of the chromosomes and the heterochromatic sex chromosomes. One of the more substantial contributions of this work is the conclusion that the phylogenetic distribution of elements in relation to their respective hosts can be explained without the necessity to assume horizontal transfer between species. Transposable elements, by virtue of the properties discussed here, have facilitated the shuffling and reorganization of the genome necessary for the magnitude of protein evolution observed when distant genomes such as yeast, worms, humans, and flies are compared.