Cis-acting element

From Freepedia

Regulation has to be specific to particular genes. Regulatory systems, therefore, need to have something that is physically linked to a target gene as an address to tell the trans-acting factors that the gene they are linked to is something that should be regulated. These sequences, which can be in the DNA, the RNA or the protein are called cis-acting elements if their action depends on their being physically linked to the regulatory target.

All enhancers and promoters are cis-acting elements, as well as operators and promoters in bacteria.