Reporter assay using the beta-galactosidase (lacZ) gene. The lacZ gene is typically fused to the promoter of interest. Differential regulation of the promoter mediated by the TF is assessed by induction of the system and evaluation of lacZ expression. Bacteria expressing lacZ appear blue when grown on a X-gal medium. The assay is often performed using a plasmid borne construction on a lacZ(def) strain.

In DNA affinity purification, DNA from promoter regions thought to be bound by the protein is labelled (e.g. biotinylated) and bound to beads (or some type of matrix). The protein is then left to interact with DNA and eventually eluted. Bound protein will remain attached to beads. This can be detected through gel electophoresis. The protein can then be sequenced by mass-spectrometry. The techinque can be used to demonstrate binding of a purified protein, or to purify the binding protein from crude extract or a mix of proteins.

Electro-mobility shift-assays (or gel retardation assays) are a standard way of assessing TF-binding. A fragment of DNA of interest is amplified and labeled with a fluorophore. The fragment is left to incubate in a solution containing abundant TF and non-specific DNA (e.g. randomly cleaved DNA from salmon sperm, of all things) and then a gel is run with the incubated sample and a control (sample that has not been in contact with the TF). If the TF has bound the sample, the complex will migrate more slowly than unbound DNA through the gel, and this retarded band can be used as evidence of binding. The unspecific DNA ensures that the binding is specific to the fragment of interest and that any non-specific DNA-binding proteins left-over in the TF purification will bind there, instead of on the fragment of interest. EMSAs are typically carried out in a bunch of fragments, shown as multiple double (control+experiment) lanes in a wide picture. Certain additional controls are run in at least one of the fragments to ascertain specificity. In the most basic of these, specific competitor (the fragment of interest or a known positive control, unlabelled) is added to the reaction. This should sequester the TF and hence make the retardation band disappear, proving that the binding is indeed specific

Hydroxyl radical footprinting is almost identical to DNase footprinting, except that it uses hydroxyl radicals to digest non-protected DNA. While hydroxyl radicals yield much better resolution than DNases due to the considerable difference in their sizes, they are also harder and more time consuming to use, and thus this method is seen somewhat infrequently.