Molecular cloning and characterization of the Saccharomyces cerevisiae SAB1 gene that suppresses a temperature-sensitive phenotype of the ARS-binding factor 1 mutant.

A high-copy number suppressor gene of the yeast temperature-sensitive lethal abf1 mutant was isolated and named SAB1 (suppressor of ABF1). Chromoblot hybridization and grid-filter hybridization analyses showed that the SAB1 gene was located on chromosome IV. Deletion analyses of the SAB1 plasmid revealed that the suppressor activity was contained in a 1.1 kb DNA region. The nucleotide sequence of the 1.1 kb DNA fragment was determined and turned out to be identical to that of the yeast phosphoribosylanthranilate isomerase gene (TRP1). A binding site for ARS-Binding Factor 1 was located in the coding sequence of the TRP1 gene, which has been known to be a part of the B domain of yeast autonomously replicating sequence 1 (ARS1). Our results suggest that ABF1 might be important for the transcription of the yeast TRP1 gene in addition to having important roles in the stimulation of replication at the ARS1 locus.