Sequence, expression and mutational analysis of BAF1, a transcriptional activator and ARS1-binding protein of the yeast Saccharomyces cerevisiae

Abstract

We report the cloning and sequence analysis of the yeast BAF1 gene which encodes an abundant protein previously shown to act as a transcription activator in the YPT1-TUB2 intergene region. As predicted from the DNA sequence, the highly hydrophilic BAf1 protein is 731 amino acids long and has a molecular mass of 81 748 daltons. The protein product of the cloned BAF1 gene produced in Escherichia coli is able to form specific complexes with DNA fragments containing the conserved element TCN7ACG. The protein binds also to the ABF1-binding site of the B-domain of ARS1, entertaining the possibility that BAF1 and ABF1 are identical proteins. Extensive deletion studies identified the N-terminal two thirds of the Baf1 protein to be required for specific DNA binding. Amino acid substitutions point to the N-terminal sequence CysX7HisX3HisX4CysX4Cys to form an atypical metal-binding 'finger' structure. Disruption of the BAF1 gene is lethal. The existence of five potential Baf1-protein binding sites in the 5' region of the gene suggests the involvement of the Baf1 protein in transcription regulation of its own gene.