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Enhancers are stretches of DNA that regulate where and when a gene is expressed. While the sequences of enhancers can vary among species, their function is highly conserved across hundreds of millions of years of evolution. For example, a recent study found that an enhancer from the sponge Amphimedon queenslandica can drive transcription in specific cell types in mice and zebrafish. While enhancers in the more complex organisms didn’t match the sequence of the sponge enhancer, the regions contained different arrangements of shared transcription factor binding motifs. The same was also true in the human region that most closely matched the sponge enhancer.
Enhancers mediate gene expression by recruiting transcription factors (TFs) that subsequently recruit additional machinery to initiate transcription. Enhancers often act across great distances in the genome—up to about 1 million base pairs, as is the case for the developmental patterning gene Shh—and ...
