cys-3, the Positive-Acting Sulfur Regulatory Gene ofNeurospora crassa, Encodes a Protein with a Putative Leucine Zipper DNA-Binding Element

Abstract

The sulfur-regulatory circuit of Neurospora crassa consists of a set of unlinked structural genes which encode sulfur-catabolic enzymes and two major regulatory genes which govern their expression. The positive-acting cys-3 regulatory gene is required to turn on the expression of the sulfur-related enzymes, whereas the other regulatory gene, scon, acts in a negative fashion to repress the synthesis of the same set of enzymes. Expression of the cys-3 regulatory gene was found to be controlled by scon and by sulfur availability. The nucleotide sequence of the cys-3 gene was determined and can be translated to yield a protein of molecular weight 25,892 which displays significant homology with the oncogene protein Fos, yeast GCN4 protein, and sea urchin histone H1. Moreover, the putative cys-3 protein has a well-defined leucine zipper element plus an adjacent charged region which together may make up a DNA-binding site. A cys-3 mutant and a cys-3 temperature-sensitive mutant lead to substitutions of glutamine for basic amino acids within the charged region and thus may alter DNA-binding properties of the cys-3 protein.

The DNA-binding domain of the Cys-3 regulatory protein of Neurospora crassa is bipartite

“…Neurospora transformants arise by the stable integration of plasmid DNAs, nearly always at ectopic sites. The transformation procedure has been described in detail previously (Fu et al, 1989;Kanaan & Marzluf, 1991).…”

“…Furthermore, a truncated CYS3 protein corresponding to just the bzip region was found to mediate dimer formation and to possess DNA-binding activity. A CYS3 mutant protein with a pure methionine zipper showed significant, although reduced, function in vivo and in vitro.Cys-3, the major sulfur regulatory gene of Neurospora crassa, controls the expression of a set of unlinked structural genes which encode sulfur catabolic enzymes (Fu et al, 1989;…”

“…Cys-3, the major sulfur regulatory gene of Neurospora crassa, controls the expression of a set of unlinked structural genes which encode sulfur catabolic enzymes (Fu et al, 1989;…”

“…that is required for expression of the sulfur-related enzymes, presumably by binding DNA element(s) upstream of each structural gene (Fu et al, 1990;Paietta et al, 1987). DNA footprinting and mobility shift analysis showed that an Escherichia coli expressed CYS3 protein binds specifically to 5'-upstream DNA sequences of cys-14 (sulfate permease gene) and the cys-3 gene itself (Fu et al, 1989). Cys-3 encodes a protein of 236 amino acid residues which shows considerable 0006-2960/92/0431-3197S03.00/0 © 1992 American Chemical Society Leucine zipper of the CYS3 protein, comprised of amino acids residues from Arg-89 to Gly-164.…”

Nucleotide sequence, messenger RNA stability, and DNA recognition elements of CYS-14, the structural gene for sulfate permease II in Neurospora crassa

“…A major positive-acting control genes, cys-3, encodes a regulatory protein which is required to activate the structural genes of the circuit (Marzluf & Metzenberg, 1968; Paietta et al, 1987). The CYS3 protein possesses a leucine zipper and an adjacent basic region, which together constitute a DNA binding domain (Fu et al, 1989;Fu & Marzluf, 1990). A distinct negative-acting control gene appears to prevent cys-3 expression when cellular levels of sulfur are high (Burton & Metzenberg, 1972).…”