THE ASPERGILLUS PACC ZINC-FINGER TRANSCRIPTION FACTOR MEDIATES REGULATION OF BOTH ACID-EXPRESSED AND ALKALINE-EXPRESSED GENES BY AMBIENT PH

The pH regulation of gene expression in Aspergillus nidulans is mediated by pacC, whose 678 residue-derived protein contains three putative Cys(2)His(2) zinc fingers. Ten pacC(c) mutations mimicking growth at alkaline pH remove between 100 and 214 C-terminal residues, including a highly acidic region containing an acidic glutamine repeat. Nine pacC(+/-) mutations mimicking acidic growth conditions remove between 299 and 505 C-terminal residues, Deletion of the entire pacC coding region mimics acidity but leads additionally to poor growth and conidiation. A PacC fusion protein binds DNA with the core consensus GCCARG, At alkaline ambient pH, PacC activates transcription of alkaline-expressed genes (including pacC itself) and represses transcription of acid-expressed genes, pacC(c) mutations obviate the need for pH signal transduction.