Cloning and characterization of the TATA-binding protein of the silkworm Bombyx mori

The TATA-binding protein is a general transcription factor required by all three eukaryotic nuclear RNA polymerases. In order to study the function of this protein in the transcription of tRNA genes in the silkworm Bombyx mori, we have cloned TBP cDNA from a silkworm cDNA library. As in most other eukaryotes, TBP in silkworms is encoded by a single copy gene and contains a highly conserved C-terminal domain that includes a basic region and two direct repeats. In the less conserved N-terminal domain, silkworm TBP exhibits characteristics such as a glutamine-rich stretch and three imperfect Pro-Met-Thr-like repeats that are also found in Drosophila and human TBP. Silkworm TBP expressed in Escherichia coli and purified to apparent homogeneity binds the TATA element of the wild-type adenovirus major late promoter with nanomolar affinity.