MUTATIONAL ANALYSIS OF AREA, A TRANSCRIPTIONAL ACTIVATOR MEDIATING NITROGEN METABOLITE REPRESSION IN ASPERGILLUS-NIDULANS AND A MEMBER OF THE STREETWISE GATA FAMILY OF TRANSCRIPTION FACTORS

The transcriptional activator AREA is a member of the GA TA family of transcription factors and mediates nitrogen metabolite repression in t he fungus Aspergillus nidulans. The nutritional versatility of A. nidu lans and its amenability to classical and reverse genetic manipulation s make the AREA DNA binding domain (DBD) a useful model for analyzing GATA family DBDs, particularly as structures of two AREA-DNA complexes have been determined. The Ias extant mutant forms of the AREA DBD sur veyed here constitute one of the highest totals of eukaryotic transcri ption factor DBD mutants, are discussed in light of the roles of indiv idual residues, and are compared to corresponding mutant sequence chan ges in other fungal GATA factor DBDs. Other topics include delineation of the DBD using both homology and mutational truncation, use of fram eshift reversion to detect regions of tolerance to mutational change, the finding that duplication of the DBD can apparently enhance AREA fu nction, and use of the AREA system to analyze a vertebrate GATA factor DBD. Some major points to emerge from work on the AREA DBD are (i) to lerance to sequence change (with retention of function) is surprisingl y great, (ii) mutational changes in a transcription factor can have wi dely differing even opposing, effects on expression of different struc tural genes so that monitoring expression of one or even several struc tural genes can be insufficient and possibly misleading, and (iii) a m utational change altering local hydrophobic packing and DNA binding ta rget specificity can markedly influence the behavior of mutational cha nges elsewhere in the DBD.