Figure 1.

Models of how lncRNAs may function in the epigenetic control of gene expression, both activating and repressing transcription in cis and in trans. (A) Enhancer RNAs have been shown to play an RNA-mediated role in forming enhancer interactions resulting in long-range cis gene regulation by lncRNAs. (B) Activation by the JPX lncRNA as an example of a trans-acting lncRNA, which in this case facilitates Xist activation. (C) Xist as an example of an lncRNA that facilitates gene repression in cis across the majority of the X chromosome. (D) HOTAIR expression results in trans repression of HOX genes.