We have analyzed the DNA sequence requirements for the functioning of TATA elements by examining the transcriptional activities associated with 24 promoters, including representatives of each of the 21 point mutations in the consensus sequence from plants, TATATATA, in a HeLa in vitro system and in a chimeric in vitro system in which human TATA-binding protein (hTBP) was replaced by purified TBP of Arabidopsis (aTBP-1). Although the relative transcriptional activities varied among these promoters, both systems gave virtually identical results. Among the mutant TATA elements, those with the sequences TAGAGATA and GAGAGAGA had undetectable activity. The rest had activities that ranged from 7% to 130% of the activity associated with the consensus element. These results suggest the functional conservation of TBP between plants and animals.