Regulation of branched-chain amino acid biosynthesis in Neurospora crassa: cloning and characterization of the leu-1 and ilv-3 genes.
The genes coding for the branched-chain amino acid biosynthetic enzymes comprise an integrated regulatory system. The expression of the several structural genes coding for enzymes of the isoleucine-valine and leucine pathways is controlled in parallel by the positive-acting regulatory gene, leu-3. The leu-1 and ilv-3 genes, coding for beta-isopropyl-malate dehydrogenase and aceto-hydroxyacid synthase, respectively, were cloned from a cosmid library. Restriction fragment length polymorphism analysis revealed that the two cloned fragments indeed mapped to the genomic locations of the leu-1 and ilv-3 genes, respectively. Northern blot analysis demonstrated that the leu-1 gene is transcribed to give an mRNA of approximately 1.5 kb, whereas the ilv-3 transcript size is 2.6 kb. The expression of both genes appears to be regulated at the transcriptional level. One leu-3 regulatory mutant was greatly deficient in both leu-1 and ilv-3 mRNAs, whereas another leu-3 allele showed an unusual antiparallel pattern of regulation.
Jarai
G
G
Department of Biochemistry, Ohio State University, Columbus 4321.
Yagmai
B
B
Fu
Y H
YH
Marzluf
G A
GA
D050539:3-Isopropylmalate Dehydrogenase; D000095:Acetolactate Synthase / Q000235:genetics*; D000429:Alcohol Oxidoreductases / Q000235:genetics*; D003001:Cloning, Molecular; D015966:Gene Expression Regulation, Fungal; D005800:Genes, Fungal; D009492:Neurospora crassa / Q000235:genetics*; D012150:Polymorphism, Restriction Fragment Length; D012331:RNA, Fungal / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics; D014158:Transcription, Genetic
D012331:RNA, Fungal; D012333:RNA, Messenger; D000429:Alcohol Oxidoreductases; D050539:3-Isopropylmalate Dehydrogenase; D000095:Acetolactate Synthase