NIT-2, THE MAJOR POSITIVE-ACTING NITROGEN REGULATORY GENE OF NEUROSPORA-CRASSA, ENCODES A SEQUENCE-SPECIFIC DNA-BINDING PROTEIN

The nit-2 major nitrogen regulatory gene of Neurospora crassa turns on the expression of various unlinked structural genes that specify nitrogen-catabolic enzymes under nitrogen-limitation conditions. The nit-2 gene encodes a protein of 1036 amino acid residues with a single zinc finger and a downstream basic region that may make up a DNA-binding domain. The zinc-finger domain of the NIT2 protein was synthesized in two ways to examine its DNA-binding activity with gel-band-mobility shift and DNA-footprint experiments. The NIT2 protein binds to specific DNA recognition elements that are located upstream of nitrogen-regulated structural genes. Each recognition element contains at least two copies of a core sequence whose consensus is TATCTA.