To qualify as a transcription factor, a protein must possess two qualities. 1) Ability to bind to DNA and 2) recruit RNA polymerase/alter transcription of a gene.

The most common GTFs are TFIIA, TFIIB, TFIID (see also TATA binding protein), TFIIE, TFIIF, and TFIIH. The preinitiation complex binds to promoter regions of DNA upstream to the gene that they regulate.

Commonly used techniques in the assessment of DNA binding of a transcription factor include EMSA and DNase I protection (footprinting) assay. Transcription factors are often purified and cloned based on their specific binding sequences.