title: Co-transcription of the celC gene cluster in Clostridium thermocellum.
abstract: Clostridium thermocellum, an anaerobic, thermophilic, and ethanogenic bacterium produces a large cellulase complex termed the cellulosome and many free glycosyl hydrolases. Most cellulase genes scatter around the genome. We mapped the transcripts of the six-gene cluster celC-glyR3-licA-orf4-manB-celT and determined their transcription initiation sites by primer extension. Northern blot showed that celC-glyR3-licA were co-transcribed into a polycistronic messenger with the transcription initiation site at -20 bp. Furthermore, RT-PCR mapping showed that manB and celT, two cellulosomal genes immediately downstream, were co-transcribed into a bicistronic messenger with the initiation site at -233 bp. In contrast, rf4 was transcribed alone with the two initiation sites at -130 and -138 bp, respectively. Finally, quantitative RT-PCR analysis showed that celC, glyR3, and licA were coordinately induced by growing on laminarin, a β-1,3 glucan. Gene expression peaked at the late exponential phase. Taking together with our previous report that GlyR3 binds to the celC promoter in the absence of laminaribiose, a β-1,3 glucose dimer, these results indicate that celC, glyR3, and licA form an operon repressible by GlyR3 and inducible by laminaribiose, signaling the availability of β-1,3 glucan. The celC operon is the first glycosyl hydrolase operon reported in this bacterium.
authors.affiliation: Department of Chemical Engineering, University of Rochester, Room 206 Gavett Hall, Rochester, NY 14627-0166, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Newcomb
authors.forename: Jonathan
authors.initials: J
authors.lastname: Millen
authors.forename: Chun-Yu
authors.initials: CY
authors.lastname: Chen
authors.forename: J H David
authors.initials: JH
authors.lastname: Wu
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D002480:Cellulase / Q000235:genetics / Q000378:metabolism; D048013:Acetivibrio thermocellus / Q000201:enzymology* / Q000235:genetics*; D004187:Disaccharides / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D005936:Glucans; D008359:Mannose-6-Phosphate Isomerase / Q000235:genetics; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000235:genetics; D005810:Multigene Family; D009699:N-Glycosyl Hydrolases / Q000378:metabolism; D009713:Nucleotidyltransferases / Q000235:genetics; D009876:Operon; D011134:Polysaccharides / Q000378:metabolism; D011401:Promoter Regions, Genetic; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014158:Transcription, Genetic; D001617:beta-Glucosidase / Q000235:genetics* / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D004187:Disaccharides; D005936:Glucans; D009097:Multienzyme Complexes; D011134:Polysaccharides; C014637:laminaribiose; C008247:laminaran; C093300:ManB protein, bacteria; D009713:Nucleotidyltransferases; C083712:celC protein, bacteria; D001617:beta-Glucosidase; D002480:Cellulase; D009699:N-Glycosyl Hydrolases; D008359:Mannose-6-Phosphate Isomerase