What is "transactivation"

n. 1 The activation of something by another entity that has a spatial relationship with it 2 (context genetics English) The activation of a gene by the presence of another at a different locus, especially following infection by a virus

In the context of gene regulation: transactivation is the increased rate of gene expression triggered either by biological processes or by artificial means, through the expression of an intermediate transactivator protein. In the context of receptor signaling, transactivation occurs when one or more receptors activate yet another; receptor transactivation may result from the crosstalk of signaling cascades.