activator \activator\ n.
   1. any agency bringing about activation; (Biol.) a molecule
      that increases the activity of an enzyme or a protein that
      increases the production of a gene product in DNA
      transcription.
      [WordNet 1.5]

	

	activator
    n 1: (biology) any agency bringing about activation; a molecule
         that increases the activity of an enzyme or a protein that
         increases the production of a gene product in DNA
         transcription [ant: inhibitor]