PARTICIPATION OF ABF-1 PROTEIN IN EXPRESSION OF THE SACCHAROMYCES-CEREVISIAE CAR1 GENE

DNA fragments previously shown to be required for expression of the CAR1 (arginase) gene in Saccharomyces cerevisiae and to support transcriptional activation of a reporter gene in a heterologous expression vector were shown to bind purified regulatory protein ABF-1. Two ABF-1 sites were identified in the CAR1 upstream region, one to which ABF-1 protein bound with high affinity and a second to which it bound much less avidly. The higher-affinity ABF-1 binding site upstream of CAR1 was an effective competitor of the HMRE, ARS1 B domain, and COR2-GFI binding sequences for protein binding. Point mutations in the CAR1 high-affinity ABF-1 binding site resulted in a 12-fold loss of transcriptional activation of a reporter gene compared with the wild-type CAR1 DNA fragment. These data are consistent with the suggestion that ABF-1 protein is one of the transcription factors involved in expression of the CAR1 gene.