Yeast TATA-box transcription factor gene.

Abstract

The first step in the transcription of most protein-encoding genes in eukaryotes is the binding of a transcription factor to the TATA-box promoter element. This TATA-box transcription factor was purified from extracts of the yeast Saccharomyces cerevisiae by using reconstitution of in vitro transcription reactions as an assay. The activity copurified with a protein whose sodium dodecyl sulfate/polyacrylamide gel mobility is 25 kDa. The sequence of the amino-terminal 21 residues of this protein was determined by sequential Edman degradation. A yeast genomic library was screened with mixed oligonucleotides encoding six residues of the protein sequence. The yeast TATA-box factor gene was cloned, and DNA sequencing revealed a 720-base-pair open reading frame encoding a 27,016-Da protein. The identity of the clone was confirmed by expressing the gene in Escherichia coli and detecting TATA-box factor DNA binding and transcriptional activities in extracts of the recombinant E. coli. The TATA-box factor gene was mapped to chromosome five of S. cerevisiae. RNA blot hybridization and nuclease S1 analysis indicated that the major TATA-box factor mRNA is 1.3 kilobases, including an unusually long 5' untranslated region of 188 +/- 5 nucleotides. Homology searches showed a region of distant similarity to the calcium-binding structures of calpains, a structure that has a conformation similar to the helix-turn-helix motif of DNA binding proteins.