Coactivator (genetics)
（重定向自Coactivator）
A coactivator is a protein that increases gene expression by binding to an activator (transcription factor) which contains a DNA binding domain. The coactivator is unable to bind DNA by itself.
The coactivator can enhance transcription initiation by stabilizing the formation of the RNA polymerase holoenzyme enabling faster clearance of the promoter. Coactivators may control many other substeps of transcription, including elongation, RNA splicing, and termination and degradation of the coactivator-activator complex.