title: Alternative sigma factor over-expression enables heterologous expression of a type II polyketide biosynthetic pathway in Escherichia coli.
abstract: BACKGROUND
  Heterologous expression of bacterial biosynthetic gene clusters is currently an indispensable tool for characterizing biosynthetic pathways. Development of an effective, general heterologous expression system that can be applied to bioprospecting from metagenomic DNA will enable the discovery of a wealth of new natural products.
  
  
  METHODS
  We have developed a new Escherichia coli-based heterologous expression system for polyketide biosynthetic gene clusters. We have demonstrated the over-expression of the alternative sigma factor σ(54) directly and positively regulates heterologous expression of the oxytetracycline biosynthetic gene cluster in E. coli. Bioinformatics analysis indicates that σ(54) promoters are present in nearly 70% of polyketide and non-ribosomal peptide biosynthetic pathways.
  
  
  CONCLUSIONS
  We have demonstrated a new mechanism for heterologous expression of the oxytetracycline polyketide biosynthetic pathway, where high-level pleiotropic sigma factors from the heterologous host directly and positively regulate transcription of the non-native biosynthetic gene cluster. Our bioinformatics analysis is consistent with the hypothesis that heterologous expression mediated by the alternative sigma factor σ(54) may be a viable method for the production of additional polyketide products.
authors.affiliation: Department of Chemistry, University of Ottawa, Ottawa, Ontario, Canada.
authors.forename: David Cole
authors.initials: DC
authors.lastname: Stevens
authors.forename: Kyle R
authors.initials: KR
authors.lastname: Conway
authors.forename: Nelson
authors.initials: N
authors.lastname: Pearce
authors.forename: Luis Roberto
authors.initials: LR
authors.lastname: Villegas-Peñaranda
authors.forename: Anthony G
authors.initials: AG
authors.lastname: Garza
authors.forename: Christopher N
authors.initials: CN
authors.lastname: Boddy
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001483:Base Sequence; D052160:Benzothiazoles; D053898:Biosynthetic Pathways; D003959:Diamines; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D008969:Molecular Sequence Data; D009930:Organic Chemicals / Q000378:metabolism; D010118:Oxytetracycline / Q000096:biosynthesis / Q000737:chemistry / Q000494:pharmacology; D010455:Peptides / Q000378:metabolism; D061065:Polyketides / Q000737:chemistry / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000235:genetics; D011804:Quinolines; D051877:RNA Polymerase Sigma 54 / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic / Q000187:drug effects
chemical_list: D000900:Anti-Bacterial Agents; D052160:Benzothiazoles; D003959:Diamines; D029968:Escherichia coli Proteins; D009930:Organic Chemicals; D010455:Peptides; D061065:Polyketides; D011804:Quinolines; C497751:rpoN protein, E coli; C098022:SYBR Green I; D051877:RNA Polymerase Sigma 54; D010118:Oxytetracycline