XRE

XRE is an acronym that can refer to several concepts across different fields. In computing, XRE commonly denotes the XUL Runtime Environment, a core component in Mozilla’s Gecko-based platforms such as XULRunner. The XRE is the runtime framework responsible for startup, embedding, and the basic lifecycle of Gecko-based applications. It provides the cross-platform code that initializes the engine, loads user profiles, and enables standalone apps to run Gecko without the full Firefox UI. The XRE binary is part of the runtime package and is seen in Mozilla-derived products as a startup process that boots the application and coordinates components.

In biology, XRE stands for Xenobiotic Response Element. These are DNA sequences found in the promoter regions of genes that respond to xenobiotic compounds, enabling transcriptional activation in response to environmental contaminants. The XRE is typically recognized by the aryl hydrocarbon receptor (AhR) complex, which partners with ARNT to induce expression of detoxification enzymes such as CYP1A1. The core motif often centers around the sequence 5'-GCGTG-3', with variations that affect binding affinity and regulatory strength.

Other uses exist in various domains, but the two above are among the most commonly encountered. As with many acronyms, the precise meaning of XRE depends on context—technical discussions about Mozilla software will refer to the runtime environment, while genetics texts will refer to the promoter element involved in xenobiotic response.