title: Three genes hrdB, hrdD and hrdT of Streptomyces griseus IMRU 3570, encoding sigma factor-like proteins, are differentially expressed under specific nutritional conditions.
abstract: Three genes (hrd) homologous to the rpoD gene of Escherichia coli, that encode sigma factor-like proteins, have been cloned from DNA of the candicidin-producing strain Streptomyces griseus IMRU 3570. They are located in different regions of the chromosome. Sequence analysis showed that the first one is analogous to the hrdB gene of S. coelicolor. The second showed high similarity to the hrdD gene of S. coelicolor and S. aureofaciens and is linked, as in S. coelicolor, to a N-acetyltransferase-encoding gene (nat) distantly related to the pat and bar genes that encode resistance to bialafos. The third showed no close homology with other known hrd genes from actinomycetes and has been named hrdT. Functional domains in the three S. griseus Hrd proteins are highly conserved in relation to those of the sigma 70 protein family. Northern analysis showed that hrdB is expressed as a 1.9-kb transcript during active growth in phosphate-rich medium, but it is less efficiently transcribed under sporulation conditions (phosphate-starved) or after a heat-shock treatment. Two other shorter transcripts of 1.2 and 0.7 kb were also detected with the same probe. The hrdD gene is transcribed as a single 1.1-kb transcript under sporulation conditions following nutritional shiftdown and, to a lower extent, during growth conditions in phosphate-rich medium. The hrdT gene is weakly transcribed (1.5-kb RNA) under all conditions tested. The hrd-encoded sigma factors probably recognize actinomycetes promoters (SEP type) with E. coli-like consensus sequences.
authors.affiliation: Department of Ecology, Genetics and Microbiology, Faculty of Biology, University of León, Spain.
authors.forename: A T
authors.initials: AT
authors.lastname: Marcos
authors.forename: S
authors.initials: S
authors.lastname: Gutiérrez
authors.forename: B
authors.initials: B
authors.lastname: Díez
authors.forename: F J
authors.initials: FJ
authors.lastname: Fernández
authors.forename: J A
authors.initials: JA
authors.lastname: Oguiza
authors.forename: J F
authors.initials: JF
authors.lastname: Martín
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics; D001483:Base Sequence; D002174:Candicidin / Q000378:metabolism; D003470:Culture Media / Q000494:pharmacology; D012321:DNA-Directed RNA Polymerases / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics*; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D006358:Hot Temperature; D008969:Molecular Sequence Data; D009693:Nucleic Acid Hybridization; D016366:Open Reading Frames; D010710:Phosphates / Q000494:pharmacology; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D012808:Sigma Factor / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics*; D013045:Species Specificity; D013302:Streptomyces / Q000235:genetics; D013305:Streptomyces griseus / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: D001426:Bacterial Proteins; D003470:Culture Media; D010710:Phosphates; D012808:Sigma Factor; D002174:Candicidin; C081775:RNA polymerase sigma 70; D012321:DNA-Directed RNA Polymerases