Activators combine with a gene sequence to up-regulate gene expression. A catabolite gene activator protein (im), also called catabolite gene activator, is a cAMP dependent RNA polymerase that up-regulates gene expression by binding the polymerase at or near the DNA to be transcribed (families). In developmental biology or embryology, activators are substances that stimulate the development of a particular embryonic structure (inductor and organizer).
In biochemistry, an activator is a substance that combines with an enzyme to increase its catalytic activity.
In microbiology, autoinducers are signaling molecules in bacterial quorum sensing that regulate mRNA production for specific genes in response to population density. Autoinducer molecules, which include certain peptides and compounds known as homoserine lactones, can interact with specific repressor or enhancer sequences in DNA. The presence or absence of the autoinducer controls the production of mRNA, and therefore regulates gene expression into protein.
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