scholarly journals Multiple Alternate Transcripts Direct the Biosynthesis of Microcystin, a Cyanobacterial

2002 ◽  
Vol 68 (2) ◽  
pp. 449-455 ◽  
Author(s):  
Melanie Kaebernick ◽  
Elke Dittmann ◽  
Thomas B�rner ◽  
Brett A. Neilan
Keyword(s):  
Gene Cluster ◽  
Polyketide Synthase ◽  
Bidirectional Promoter ◽  
Transcriptional Analysis ◽  
Transcription Start ◽  
Transcription Start Sites ◽  
Reverse Transcription Pcr ◽  
Peptide Synthetase ◽  
Rapid Amplification ◽  
Translational Start

ABSTRACT The mcyABCDEFGHIJ gene cluster of Microcystis aeruginosa encodes the mixed polyketide synthase/nonribosomal peptide synthetase (microcystin synthetase) which is responsible for biosynthesis of the potent liver toxin microcystin. The sequence and orientation of the mcy genes have previously been reported, but no transcriptional analysis had been performed prior to this study. The mcyABCDEFGHIJ genes are transcribed as two polycistronic operons, mcyABC and mcyDEFGHIJ, from a central bidirectional promoter between mcyA and mcyD. Two transcription start sites were detected for both mcyA and mcyD when cells were exposed to light intensities of 68 and 16 μmol of photons m−2 s−1. The start sites, located 206 and 254 bp upstream of the translational start for mcyD under high and low light conditions, respectively, indicate long untranslated leader regions. Putative transcription start sites were also identified for mcyE, mcyF, mcyG, mcyH, mcyI, and mcyJ but not for mcyB and mcyC. A combination of reverse transcription-PCR and rapid amplification of cDNA ends was employed throughout this work, which may have been one of the first transcriptional analyses of a large nonribosomal polyketide gene cluster.

scholarly journals Transcriptional Regulation of the Nitrile Hydratase Gene Cluster in Pseudomonas chlororaphis B23

2008 ◽  
Vol 190 (12) ◽  
pp. 4210-4217 ◽  
Author(s):  
Toshihide Sakashita ◽  
Yoshiteru Hashimoto ◽  
Ken-Ichi Oinuma ◽  
Michihiko Kobayashi
Keyword(s):  
Gene Cluster ◽  
Nitrile Hydratase ◽  
Transcriptional Regulator ◽  
Pseudomonas Chlororaphis ◽  
Reading Frame ◽  
Transcription Start Sites ◽  
Reverse Transcription Pcr ◽  
Enormous Amount ◽  
Extension Analysis ◽  
Arac Family

ABSTRACT An enormous amount of nitrile hydratase (NHase) is inducibly produced by Pseudomonas chlororaphis B23 after addition of methacrylamide as the sole nitrogen source to a medium. The expression pattern of the P. chlororaphis B23 NHase gene cluster in response to addition of methacrylamide to the medium was investigated. Recently, we reported that the NHase gene cluster comprises seven genes (oxdA, amiA, nhpA, nhpB, nhpC, nhpS, and acsA). Sequence analysis of the 1.5-kb region upstream of the oxdA gene revealed the presence of a 936-bp open reading frame (designated nhpR), which should encode a protein with a molecular mass of 35,098. The deduced amino acid sequence of the nhpR product showed similarity to the sequences of transcriptional regulators belonging to the XylS/AraC family. Although the transcription of the eight genes (nhpR, oxdA, amiA, nhpABC, nhpS, and acsA) in the NHase gene cluster was induced significantly in the P. chlororaphis B23 wild-type strain after addition of methacrylamide to the medium, transcription of these genes in the nhpR disruptant was not induced, demonstrating that nhpR codes for a positive transcriptional regulator in the NHase gene cluster. A reverse transcription-PCR experiment revealed that five genes (oxdA, amiA, nhpA, nhpB, and nhpC) are cotranscribed, as are two other genes (nhpS and acsA). The transcription start sites for nhpR, oxdA, nhpA, and nhpS were mapped by primer extension analysis, and putative −12 and −24 σ54-type promoter binding sites were identified. NhpR was found to be the first transcriptional regulator of NHase belonging to the XylS/AraC family.

Genomic organization of the 5′ end of human β-ENaC and preliminary characterization of its promoter

2002 ◽  
Vol 282 (5) ◽  
pp. F898-F909 ◽  
Author(s):  
Christie P. Thomas ◽  
Randy W. Loftus ◽  
Kang Z. Liu ◽  
Omar A. Itani
Keyword(s):  
Genomic Organization ◽  
Human Kidney ◽  
Β Subunit ◽  
Transcription Start ◽  
Transcription Start Sites ◽  
Nuclear Extracts ◽  
Flanking Region ◽  
Rapid Amplification ◽  
Flanking Regions

The mRNA for the β-subunit of the epithelial Na+ channel (β-ENaC) is regulated developmentally and, in some tissues, in response to corticosteroids. To understand the mechanisms of transcriptional regulation of the human β-ENaC gene, we characterized the 5′ end of the gene and its 5′-flanking regions. Adaptor-ligated human kidney and lung cDNA were amplified by 5′ rapid amplification of cDNA ends, and transcription start sites of two 5′ variant transcripts were determined by nuclease protection or primer extension assays. Cosmid clones that contain the 5′ end of the gene were isolated, and analysis of these clones indicated that alternate first exons ∼1.5 kb apart and ∼ 45 kb upstream of a common second exon formed the basis of these transcripts. Genomic fragments that included the proximal 5′-flanking region of either transcript were able to direct expression of a reporter gene in lung epithelia and to bind Sp1 in nuclear extracts, confirming the presence of separate promoters that regulate β-ENaC expression.

Analysis of mutations in the creA gene involved in carbon catabolite repression in Aspergillus nidulans

1996 ◽  
Vol 42 (9) ◽  
pp. 950-959 ◽  
Author(s):  
Robert A. Shroff ◽  
Robin A. Lockington ◽  
Joan M. Kelly
Keyword(s):  
Zinc Finger ◽  
Catabolite Repression ◽  
Carbon Catabolite Repression ◽  
Zinc Finger Protein ◽  
The Other ◽  
Transcriptional Analysis ◽  
Missense Mutations ◽  
Rapid Amplification ◽  
Translational Start ◽  
Carboxy Terminal

The molecular nature of a number of creA mutant alleles has been determined. Three alleles analysed are missense mutations in the DNA binding domain and predicted to reduce but not abolish binding. Of the other four alleles, two result from frameshifts: one has a nonsense mutation and the other has an inversion. All four alleles result in truncations of the protein after the zinc finger domain, such that the protein no longer contains at least the carboxy terminal 145 amino acids, so identifying a region required for repression. Transcriptional analysis of creA indicates that the transcript is autoregulated and analysis using 5′ rapid amplification of cDNA ends indicates that transcriptional start points exist in clusters over a region of 200 bp located up to 595 bp 5′ of the translational start point. The two major clusters have potential CREA-binding sites (SYGGRG) at appropriate positions to allow autoregulation. Autoregulation leads to the creA transcript being most abundant in carbon catabolite nonrepressing conditions, and this, together with the phenotypes of the mutant alleles, has led to the suggestion that CREA has effects under conditions generally not considered as carbon catabolite repressing, as well as in carbon catabolite repressing conditions.Key words: carbon catabolite repression, MIG1, CREA, zinc finger protein, transcriptional repressor.

scholarly journals Biosynthesis of a Complex Yersiniabactin-Like Natural Product via themicLocus in Phytopathogen Ralstonia solanacearum

2011 ◽  
Vol 77 (17) ◽  
pp. 6117-6124 ◽  
Author(s):  
Martin F. Kreutzer ◽  
Hirokazu Kage ◽  
Peter Gebhardt ◽  
Barbara Wackler ◽  
Hans P. Saluz ◽  
...  
Keyword(s):  
Natural Product ◽  
Gene Cluster ◽  
Ralstonia Solanacearum ◽  
Insertional Mutagenesis ◽  
Polyketide Synthase ◽  
Genome Mining ◽  
Content Type ◽  
A Genome ◽  
Iron Deficient ◽  
Peptide Synthetase

ABSTRACTA genome mining study in the plant pathogenic bacteriumRalstonia solanacearumGMI1000 unveiled a polyketide synthase/nonribosomal peptide synthetase gene cluster putatively involved in siderophore biosynthesis. Insertional mutagenesis confirmed the respective locus to be operational under iron-deficient conditions and spurred the isolation of the associated natural product. Bioinformatic analyses of the gene cluster facilitated the structural characterization of this compound, which was subsequently identified as the antimycoplasma agent micacocidin. The metal-chelating properties of micacocidin were evaluated in competition experiments, and the cellular uptake of gallium-micacocidin complexes was demonstrated inR. solanacearumGMI1000, indicating a possible siderophore role. Comparative genomics revealed a conservation of the micacocidin gene cluster in defined, but globally dispersed phylotypes ofR. solanacearum.

scholarly journals Nostophycin Biosynthesis Is Directed by a Hybrid Polyketide Synthase-Nonribosomal Peptide Synthetase in the Toxic Cyanobacterium Nostoc sp. Strain 152

2011 ◽  
Vol 77 (22) ◽  
pp. 8034-8040 ◽  
Author(s):  
David P. Fewer ◽  
Julia Österholm ◽  
Leo Rouhiainen ◽  
Jouni Jokela ◽  
Matti Wahlsten ◽  
...  
Keyword(s):  
Gene Cluster ◽  
Polyketide Synthase ◽  
Catalytic Domain ◽  
Phylogenetic Analyses ◽  
Biosynthetic Gene Cluster ◽  
Nonribosomal Peptide Synthetase ◽  
Open Reading Frames ◽  
Nonribosomal Peptide ◽  
Peptide Synthetase ◽  
Biochemical Analyses

ABSTRACTCyanobacteria are a rich source of natural products with interesting pharmaceutical properties. Here, we report the identification, sequencing, annotation, and biochemical analysis of the nostophycin (npn) biosynthetic gene cluster. Thenpngene cluster spans 45.1 kb and consists of three open reading frames encoding a polyketide synthase, a mixed polyketide nonribosomal peptide synthetase, and a nonribosomal peptide synthetase. The genetic architecture and catalytic domain organization of the proteins are colinear in arrangement, with the putative order of the biosynthetic assembly of the cyclic heptapeptide. NpnB contains an embedded monooxygenase domain linking nonribosomal peptide synthetase (NRPS) and polyketide synthase (PKS) catalytic domains and predicted here to hydroxylate the nostophycin during assembly. Expression of the adenylation domains and subsequent substrate specificity assays support the involvement of this cluster in nostophycin biosynthesis. Biochemical analyses suggest that the loading substrate of NpnA is likely to be a phenylpropanoic acid necessitating deletion of a carbon atom to explain the biosynthesis of nostophycin. Biosyntheses of nostophycin and microcystin resemble each other, but the phylogenetic analyses suggest that they are distantly related to one another.

scholarly journals Biosynthesis Gene Cluster and Oxazole Ring Formation Enzyme for Inthomycins in Streptomyces sp. Strain SYP-A7193

2020 ◽  
Vol 86 (20) ◽  
Author(s):  
Shao-Yang Hou ◽  
Meng-Yue Zhang ◽  
Hong-Da Wang ◽  
Yi-Xuan Zhang
Keyword(s):  
Gene Cluster ◽  
Genome Sequencing ◽  
Gene Disruption ◽  
Polyketide Synthase ◽  
Nonribosomal Peptide Synthetase ◽  
Ring Formation ◽  
Type I ◽  
Oxazole Ring ◽  
Peptide Synthetase ◽  
Biosynthesis Gene

ABSTRACT Inthomycins belong to a growing family of oxazole-containing polyketides and exhibit a broad spectrum of anti-oomycete and herbicidal activities. In this study, we purified inthomycins A and B from the metabolites of Streptomyces sp. strain SYP-A7193 and determined their chemical structures. Genome sequencing, comparative genomic analysis, and gene disruption of Streptomyces sp. SYP-A7193 showed that the inthomycin biosynthetic gene cluster (itm) belonged to the hybrid polyketide synthase (PKS)/nonribosomal peptide synthetase (NRPS) system. Functional domain comparison and disruption/complementation experiments of itm12 resulted in the complete loss of inthomycins A and B and the subsequent restoration of their production, confirming that itm12 encodes a discrete acyltransferase (AT), and hence, itm was considered to belong to the trans-AT type I PKS system. Moreover, the disruption/complementation experiments of itm15 also resulted in the loss and restoration of inthomycin A and B formation. Further gene cloning, expression, purification, and activity verification of itm15 revealed that Itm15 is a cyclodehydratase that catalyzes a straight-chain dehydration reaction to form an oxazole ring for the biosynthesis of inthomycins A and B. Thus, we discovered a novel enzyme that catalyzes oxazole ring formation and elucidated the complete biosynthetic pathway of inthomycins. IMPORTANCE Streptomyces species produce numerous secondary metabolites with diverse structures and pharmacological activities that are beneficial for human health and have several applications in agriculture. In this study, hybrid nonribosomal peptide synthetase/polyketide synthase metabolites inthomycins A and B were isolated from after fermenting Streptomyces sp. SYP-A7193. Genome sequencing, gene disruption, gene complementation, heterologous expression, and activity assay revealed that the biosynthesis gene assembly line of inthomycins A and B was a 95.3-kb trans-AT type I PKS system in the strain SYP-A7193. More importantly, Itm15, a cyclodehydratase, was identified to be an oxazole ring formation enzyme required for the biosynthesis of inthomycins A and B; it is significant to discover this catalyzation reaction in the PKS/NRPS system in the field of microbiology. Our findings could provide further insights into the diversity of trans-AT type I PKS systems and the mechanism of oxazole cyclization involved in the biosynthesis of natural products.

scholarly journals Characterization of a Gene Cluster Responsible for the Biosynthesis of Anticancer Agent FK228 in Chromobacterium violaceum No. 968

2007 ◽  
Vol 73 (11) ◽  
pp. 3460-3469 ◽  
Author(s):  
Yi-Qiang Cheng ◽  
Min Yang ◽  
Andrea M. Matter
Keyword(s):  
Gene Cluster ◽  
Genomic Dna ◽  
Polyketide Synthase ◽  
Anticancer Agent ◽  
Biosynthetic Gene Cluster ◽  
Nonribosomal Peptide Synthetase ◽  
Biosynthetic Gene ◽  
Biosynthetic Genes ◽  
Nonribosomal Peptide ◽  
Peptide Synthetase

ABSTRACT A gene cluster responsible for the biosynthesis of anticancer agent FK228 has been identified, cloned, and partially characterized in Chromobacterium violaceum no. 968. First, a genome-scanning approach was applied to identify three distinctive C. violaceum no. 968 genomic DNA clones that code for portions of nonribosomal peptide synthetase and polyketide synthase. Next, a gene replacement system developed originally for Pseudomonas aeruginosa was adapted to inactivate the genomic DNA-associated candidate natural product biosynthetic genes in vivo with high efficiency. Inactivation of a nonribosomal peptide synthetase-encoding gene completely abolished FK228 production in mutant strains. Subsequently, the entire FK228 biosynthetic gene cluster was cloned and sequenced. This gene cluster is predicted to encompass a 36.4-kb DNA region that includes 14 genes. The products of nine biosynthetic genes are proposed to constitute an unusual hybrid nonribosomal peptide synthetase-polyketide synthase-nonribosomal peptide synthetase assembly line including accessory activities for the biosynthesis of FK228. In particular, a putative flavin adenine dinucleotide-dependent pyridine nucleotide-disulfide oxidoreductase is proposed to catalyze disulfide bond formation between two sulfhydryl groups of cysteine residues as the final step in FK228 biosynthesis. Acquisition of the FK228 biosynthetic gene cluster and acclimation of an efficient genetic system should enable genetic engineering of the FK228 biosynthetic pathway in C. violaceum no. 968 for the generation of structural analogs as anticancer drug candidates.

scholarly journals Deletion of a regulatory gene within the cpk gene cluster reveals novel antibacterial activity in Streptomyces coelicolor A3(2)

Microbiology ◽  
2010 ◽  
Vol 156 (8) ◽  
pp. 2343-2353 ◽  
Author(s):  
Marco Gottelt ◽  
Stefan Kol ◽  
Juan Pablo Gomez-Escribano ◽  
Mervyn Bibb ◽  
Eriko Takano
Keyword(s):  
Antibacterial Activity ◽  
Gene Cluster ◽  
Polyketide Synthase ◽  
Streptomyces Coelicolor ◽  
Regulatory Gene ◽  
Feedback Mechanism ◽  
Biologically Active ◽  
Transcriptional Analysis ◽  
Type I ◽  
Negative Feedback Mechanism

Genome sequencing of Streptomyces coelicolor A3(2) revealed an uncharacterized type I polyketide synthase gene cluster (cpk). Here we describe the discovery of a novel antibacterial activity (abCPK) and a yellow-pigmented secondary metabolite (yCPK) after deleting a presumed pathway-specific regulatory gene (scbR2) that encodes a member of the γ-butyrolactone receptor family of proteins and which lies in the cpk gene cluster. Overproduction of yCPK and abCPK in a scbR2 deletion mutant, and the absence of the newly described compounds from cpk deletion mutants, suggest that they are products of the previously orphan cpk biosynthetic pathway in which abCPK is converted into the yellow pigment. Transcriptional analysis suggests that scbR2 may act in a negative feedback mechanism to eventually limit yCPK biosynthesis. The results described here represent a novel approach for the discovery of new, biologically active compounds.

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