An artificial transcription factor is an example of a chimeral protein, designed to target and modulate gene transcription. They are generally composed of a DNA-binding domain (specific to a certain sequence) coupled to a modulatory domain (which acts upon other transcription factors) in order to alter the expression of a particular gene. It is also possible to downregulate expression of a gene by targeting the 5' untranslated region with a DNA-binding domain that lacks a regulatory domain; this will reduce transcription simply by blocking RNA polymerase progression along the DNA template.