Enhancer (genetics)

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Enhancers are small regions of DNA that help turn genes on more strongly. They work by binding proteins called transcription factors (activators). When an enhancer is active, it makes it more likely that a gene will be copied into RNA, starting the process of making a protein.

Key ideas about enhancers
- They are cis-regulatory elements: they affect genes on the same chromosome and often sit far away from the gene they control.
- Distance and direction don’t limit them: an enhancer can be located thousands or even hundreds of thousands of bases away from the gene, upstream or downstream, or even inside another gene.
- They work by looping DNA: through the 3D folding of the genome, the enhancer comes into contact with the gene’s promoter and helps recruit the machinery (like RNA polymerase II) that starts transcription.
- They often produce enhancer RNAs: active enhancers can be transcribed into short, non-coding RNAs, and the level of these RNAs often matches how much the target gene is expressed.
- They can be located in many places: enhancers can be in noncoding regions, introns, or even near or within other genes, and they can act on genes on other chromosomes in some cases.
- They’re not the only regulators: silencers are DNA elements that repress gene expression by binding repressor proteins. Enhancers and silencers can be close together but act with different transcription factors.

How enhancers are identified and studied
- Thousands of enhancers exist in the human genome, and only a subset are active in a given cell type.
- Modern techniques map open or accessible DNA regions to find potential enhancers (for example, methods that identify open chromatin).
- Researchers test enhancer activity by linking DNA fragments to a reporter gene to see where and when they drive expression.
- Large-scale methods can test thousands of candidate enhancers at once to understand their function.

Enhancers in development and evolution
- Enhancers control when and where genes are turned on during development, shaping body plans and organ formation.
- Some genes have multiple enhancers (including “shadow enhancers”) that work together to ensure reliable expression under different conditions.
- Changes in enhancer sequences or activity can lead to differences between species or even help explain certain traits within a species.

Artificial and synthetic enhancers
- Scientists are learning to design synthetic enhancers that steer gene expression to particular cell types.
- Since 2022, artificial intelligence has helped predict and create new enhancers, and researchers have started using them in living organisms to study and potentially treat diseases.

In short, enhancers are versatile DNA regions that, by binding specific proteins, boost the activity of target genes in specific cells and at certain times—an essential part of how genes are turned on during development, health, and disease.