« Transactivation is an increased rate of gene expression triggered either by endogenous cellular or viral proteins - transactivators. These protein factors act in trans (i.e., intermolecularly).
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Transactivation is also a technique used in molecular biology to control gene expression by stimulating transcription. During transactivation, the transactivator gene and special promoter regions of DNA are inserted into the genome at areas of interest. The transactivator gene expresses a transcription factor that binds to specific promoter region of DNA. By binding to the promoter region of a gene, the transcription factor causes that gene to be expressed. The expression of one transactivator gene can activate multiple genes, as long as they have the specific promoter region attached. Because the expression of the transactivator gene can be controlled, transactivation can be used to turn genes on and off. »

Transactivation, From Wikipedia, the free encyclopedia.