Arabidopsis thaliana contains two genes for TFIID

The general transcription initiation factor TFIID plays a primary part in the activation of eukaryotic genes transcribed by RNA polymerase II. Binding of TFIID to the TATA box initiates the assembly of other general transcription factors as well as RNA polymerase II at the promoter resulting in a preinitiation complex capable of accurate transcription initiation in vitro. Human TFIID has been shown to interact with various regulatory factors. The observation that stimulation of transcription by different trans-acting factors is mediated through distinct TATA elements led to the suggestion that different types of TFIID may exist in yeast, humans and plants. Here we report the cloning and characterization of two distinct TFIID complementary DNA clones from Arabidopsis thaliana. Furthermore, we have found that TFIID from Arabidopsis and other organisms shows homology to helix-loop-helix proteins.