Transcriptional regulation of the novobiocin biosynthetic gene cluster.
The aminocoumarin antibiotic novobiocin is a gyrase inhibitor formed by a Streptomyces strain. The biosynthetic gene cluster of novobiocin spans 23.4 kb and contains 20 coding sequences, among them the two regulatory genes novE and novG. We investigated the location of transcriptional promoters within this cluster by insertion of transcriptional terminator cassettes and RT-PCR analysis of the resulting mutants. The cluster was found to contain eight DNA regions with promoter activity. The regulatory protein NovG binds to a previously identified binding site within the promoter region located upstream of novH, but apparently not to any of the other seven promoters. Quantitative real-time PCR was used to compare the number of transcripts in a strain carrying an intact novobiocin cluster with strains carrying mutated clusters. Both in-frame deletion of the regulatory gene novG and insertion of a terminator cassette into the biosynthetic gene novH led to a strong reduction of the number of transcripts of the genes located between novH and novW. This suggested that these 16 biosynthetic genes form a single operon. Three internal promoters are located within this operon but appear to be of minor importance, if any, under our experimental conditions. Transcription of novG was found to depend on the presence of NovE, suggesting that the two regulatory genes, novE and novG, act in a cascade-like mechanism. The resistance gene gyrB(R), encoding an aminocoumarin-resistant gyrase B subunit, may initially be co-transcribed with the genes from novH to novW. However, when the gyrase inhibitor novobiocin accumulates in the cultures, gyrB(R) is transcribed from its own promoter. Previous work has suggested that this promoter is controlled by the superhelical density of chromosomal DNA.
Dangel
Volker
V
Pharmaceutical Biology, Pharmaceutical Institute, Eberhard-Karls-Universität Tübingen, Auf der Morgenstelle 8, 72076 Tübingen, Germany.
Härle
Johannes
J
Pharmaceutical Biology, Pharmaceutical Institute, Eberhard-Karls-Universität Tübingen, Auf der Morgenstelle 8, 72076 Tübingen, Germany.
Goerke
Christiane
C
Institute for Medical Microbiology and Hygiene, Universitätsklinikum Tübingen, Elfriede-Aulhorn-Strasse 6, 72076 Tübingen, Germany.
Wolz
Christiane
C
Institute for Medical Microbiology and Hygiene, Universitätsklinikum Tübingen, Elfriede-Aulhorn-Strasse 6, 72076 Tübingen, Germany.
Gust
Bertolt
B
Pharmaceutical Biology, Pharmaceutical Institute, Eberhard-Karls-Universität Tübingen, Auf der Morgenstelle 8, 72076 Tübingen, Germany.
Pernodet
Jean-Luc
JL
Univ. Paris-Sud 11, CNRS, UMR 8621, Institut de Génétique et Microbiologie, 91405 Orsay Cedex, France.
Heide
Lutz
L
Pharmaceutical Biology, Pharmaceutical Institute, Eberhard-Karls-Universität Tübingen, Auf der Morgenstelle 8, 72076 Tübingen, Germany.
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D027081:DNA Gyrase / Q000235:genetics / Q000378:metabolism; D004269:DNA, Bacterial / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D005822:Genetic Vectors; D008954:Models, Biological; D008969:Molecular Sequence Data; D005810:Multigene Family; D009675:Novobiocin / Q000096:biosynthesis* / Q000737:chemistry; D010957:Plasmids / Q000235:genetics; D011401:Promoter Regions, Genetic; D012329:RNA, Bacterial / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013302:Streptomyces / Q000235:genetics* / Q000378:metabolism*; D014158:Transcription, Genetic
D001426:Bacterial Proteins; D004269:DNA, Bacterial; D012329:RNA, Bacterial; D012333:RNA, Messenger; D009675:Novobiocin; D027081:DNA Gyrase