Transposable Elements Play An Important Role in Genetic Expression and Evolution (IMAGE)
Caption
Chromatin loops are important for gene regulation because they define a gene's regulatory neighbor-hood, which contains the promoter and enhancer sequences responsible for determining its expression level. Remarkably, transposable elements (TEs) are responsible for creating around 1/3 of all loop boundaries in the human and mouse genomes, and contribute up to 75% of loops unique to either species. When a TE creates a human-specific or mouse-specific loop it can change a gene's regulatory neighborhood, leading to altered gene expression. The illustration shows a hypothetical region of the human and mouse genomes in which four enhancer sequences for the same target gene fall within a conserved loop. In this example, a TE-derived loop boundary in the human genome (orange bar) shrinks the regulatory neighborhood, preventing two of four enhancers from interacting with their target gene's promoter sequence. The net result is reduced gene expression in human relative to mouse. Looping variations such as these appear to be an important underlying cause of differential gene regulation across species and between different human cell types, suggesting that TE activity may play significant roles in evolution and disease.
Credit
Adam Diehl
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