PrnA, a Zn2Cys6 activator with a unique DNA recognition mode, requires inducer for in vivo binding

The PrnA transcriptional activator of Aspergillus nidulans binds as a dimer to CCGG-N-CCGG inverted repeats and to CCGG-6/7N-CCGG direct repeats. The binding specificity of the PrnA Zn cluster differs from that of the Gal4p/Ppr1p/UaY/Put3p group of proteins. Chimeras with UaY, a protein that strictly recognizes a CGG-6N-CCG motif, show that the recognition of the direct repeats necessitates the PrnA dimerization and linker elements, but the recognition of the CCGG-N-CCGG inverted repeats depends crucially on the PrnA Zn binuclear cluster and/or on residues amino-terminal to it. Three high-affinity sites in two different promoters have been visualized by in vivo methylation protection. Proline induction is essential for in vivo binding to these three sites but, as shown previously, not for nuclear entry. Simultaneous repression by ammonium and glucose does not affect in vivo binding to these high-affinity sites. PrnA differs from the isofunctional Saccharomyces cerevisiæ protein Put3p, both in its unique binding specificity and in the requirement of induction for in vivo DNA binding.
Dennis Gómez was supported by a predoctoral scholarship from the French Ministère de l’Education Nationale, de l’Enseignement Supérieur et de la Recherche, a postdoctoral fellowship from ARC and European Union EUROFUNG contract no. BIO4-CT96-0535. Beatriz Cubero was supported by INRA and European Union contract BIO2CT930. Gianna Cecchetto was supported by CSSIC and Pedeciba Química. This work was supported by the CNRS, the Université Paris-Sud, the Institut Universitaire de France and European Union EUROFUNG contract (BIO4- CT96-0535).