Shadow enhancers: Frequently asked questions about distributed cis ‐regulatory information and enhancer redundancy

摘要

This paper, in the form of a frequently asked questions page (FAQ), addresses outstanding questions about “shadow enhancers”, quasi‐redundant cis ‐regulatory elements, and their proposed roles in transcriptional control. Questions include: What exactly are shadow enhancers? How many genes have shadow/redundant/distributed enhancers? How redundant are these elements? What is the function of distributed enhancers? How modular are enhancers? Is it useful to study a single enhancer in isolation? In addition, a revised definition of “shadow enhancers” is proposed, and possible mechanisms of shadow enhancer function and evolution are discussed. The term “shadow enhancer” was coined rather recently and this article not only gives a revised definition of this term but also discusses possible mechanisms of shadow enhancer function and evolution.