Sequence-specific DNA binding by NIT4, the pathway-specific regulatory protein that mediates nitrate induction in Neurospora.
The expression of the structural genes nit-3 and nit-6, which encode the nitrate assimilatory enzymes nitrate reductase and nitrite reductase, respectively, is highly regulated by the global-acting NIT2 regulatory protein. These structural genes are also controlled by nitrogen catabolite repression and by specific induction via nitrate. A pathway-specific regulatory protein, NIT4, appears to mediate nitrate induction of nit-3 and of nit-6. The NIT4 protein, composed of 1090 amino acids, contains a putative GAL4-like Cys-6 zinc cluster DNA-binding motif, which is joined by a short segment to a stretch of amino acids that appear to constitute a coiled-coil dimerization domain. Chemical crosslinking studies demonstrated that a truncated form of NIT4 forms homodimers. Mobility-shift and DNA-footprinting experiments have identified two NIT4-binding sites of significantly different strengths in the promoter region of the nit-3 gene. The stronger binding site contains a symmetrical octameric sequence, TCCGCGGA, whereas the weaker site has a related sequence. Sequences related to this palindromic element can be found upstream of the nit-6 gene.
Fu
Y H
YH
Department of Biochemistry, Ohio State University, Columbus 43210, USA.
Feng
B
B
Evans
S
S
Marzluf
G A
GA
D000595:Amino Acid Sequence; D001483:Base Sequence; D001665:Binding Sites; D004271:DNA, Fungal / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D003850:Deoxyribonuclease I / Q000378:metabolism; D005656:Fungal Proteins; D015870:Gene Expression / Q000235:genetics; D015966:Gene Expression Regulation, Fungal / Q000235:genetics; D008969:Molecular Sequence Data; D009491:Neurospora / Q000235:genetics / Q000378:metabolism*; D009566:Nitrates / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D017421:Sequence Analysis; D015534:Trans-Activators; D016335:Zinc Fingers / Q000235:genetics
D004271:DNA, Fungal; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D009566:Nitrates; D011993:Recombinant Fusion Proteins; D015534:Trans-Activators; C071240:NIT-4 protein, Neurospora crassa; D003850:Deoxyribonuclease I