title: Complex transcription of an operon encoding the SalI restriction-modification system of Streptomyces albus G.
abstract: High-resolution S1 nuclease mapping of mRNA synthesised in vivo, in vitro run-off transcription with RNA polymerase from Streptomyces lividans and gene fusions were used to analyse the transcriptional organization of the SalI restriction-modification system of Streptomyces albus G. The salIR and salIM genes that encode the restriction endonuclease and its cognate methyltransferase constitute an operon which is mainly transcribed from sal-pR1, a promoter located immediately upstream of salIR, with two possible minor promoters further upstream. Another promoter, sal-pM, is within the 3' end of the salIR coding region, and allows expression of the modification gene in the absence of sal-pR1. The sal-pM promoter might be involved in the establishment of modification prior to restriction endonuclease activity. Sequences upstream of the apparent transcriptional start sites for sal-pR1 and sal-pM show similarity with the -10 region of typical vegetatively expressed eubacterial promoters, but appropriately centered -35 regions are absent.
authors.affiliation: Departamento de Biología Funcional, Universidad de Oviedo, Spain.
authors.forename: M A
authors.initials: MA
authors.lastname: Alvarez
authors.forename: K F
authors.initials: KF
authors.lastname: Chater
authors.forename: M R
authors.initials: MR
authors.lastname: Rodicio
mesh_terms: D001483:Base Sequence; D015280:DNA Restriction-Modification Enzymes / Q000235:genetics*; D015252:Deoxyribonucleases, Type II Site-Specific / Q000235:genetics*; D008969:Molecular Sequence Data; D009876:Operon; D011401:Promoter Regions, Genetic; D015265:Site-Specific DNA-Methyltransferase (Adenine-Specific) / Q000235:genetics*; D013302:Streptomyces / Q000235:genetics*; D014158:Transcription, Genetic
chemical_list: D015280:DNA Restriction-Modification Enzymes; C059634:DNA modification methylase SalGI; D015265:Site-Specific DNA-Methyltransferase (Adenine-Specific); D015252:Deoxyribonucleases, Type II Site-Specific; C029792:GTCGAC-specific type II deoxyribonucleases