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Query: EC:3.1.30.1 (S1 nuclease)
 3,660 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have cloned the early sporulation gene spo0F, which encodes an open reading frame of 124 codons. The putative Spo0F protein derived from this open reading frame, which has been shown to share homology with the Spo0A protein as well as several other regulatory proteins from Escherichia coli, Salmonella typhimurium, and Klebsiella pneumoniae, also shares homology with the E. coli EcoRI methyltransferase. We have shown by S1 nuclease mapping of in vivo transcripts that spo0F is regulated from dual promoters: RNA II was transcribed from an upstream promoter, and RNA I was initated 30 base pairs downstream from RNA II. The promoter sequences for RNA II, but not those for RNA I, conformed to the -10 region consensus sequence for sigma 43 promoters. RNA II was found in low amounts in exponentially growing cells but was not observed in stationary-phase cells, and the presence of RNA II was glucose insensitive. RNA I was found in low amounts in exponentially growing cells, increased three- to fivefold at the end of exponential growth, and remained at this higher level for at least 3 h into stationary phase. RNA I was repressed by glucose during exponential growth but not during stationary phase.
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PMID:Transcriptional regulation of the spo0F gene of Bacillus subtilis. 243 Sep 44

The prfB gene encodes peptide-chain-release factor 2 of Escherichia coli, which catalyzes translation termination at UGA and UAA codons. The gene, identified by sequencing, is located at the 62-min region of the E. coli chromosome. The prfB gene is followed by an open reading frame encoding a 57,603-Da protein. This downstream open reading frame was identified as herC, a gene defined by a suppressor mutation that restores replication of a ColE1 plasmid mutant. RNA blot hybridization and S1 nuclease protection analyses of in vivo transcripts showed that prfB and herC are cotranscribed into a 2800-base transcript in the counterclockwise direction with respect to the E. coli genetic map. Thus, we refer to the two genes as the prfB-herC operon. Data are presented that suggest that supK, a mutation in Salmonella typhimurium that suppresses UGA termination, is the structural gene for Salmonella release factor 2. Translation control within the prfB-herC operon and the relationship of these genes to a tRNA methyltransferase are discussed.
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PMID:Chromosomal location and structure of the operon encoding peptide-chain-release factor 2 of Escherichia coli. 245 75

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.
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PMID:Complex transcription of an operon encoding the SalI restriction-modification system of Streptomyces albus G. 831 78

Self-cloning experiments with a high-copy-number plasmid and Streptomyces griseus IFO13350 led to the cloning of a 11-kb DNA fragment that conferred yellow pigment production on the host. The cloned fragment contained a gene cluster for carotenoid biosynthesis, in which two polycistrons, crtE (encoding geranylgeranyl pyrophosphate synthase)-crtI (phytoene dehydrogenase)-crtB (phytoene synthase)-crtV (functionally unknown methyltransferase-like protein) and crtY (lycopene cyclase)-crtT (functionally unknown methyltransferase-like protein)-crtU (beta-carotene dehydrogenase), were present in a convergent way. Since strain IFO13350 produced no detectable amount of carotenoids, an increase in the copy number of the crt gene cluster led to production of carotenoids at a detectable level. Overexpression of the stress-responsive sigmaB-like protein CrtS from Streptomyces setonii also activated the cryptic crt genes in S. griseus and conferred pigmentation. A CrtS homologue (sigmaCrtS) in S. griseus, which was predicted by a computer-aided homology search, caused carotenogenesis to the same extent as CrtS of S. setonii, indicating that the two sigmaB-like proteins were functionally the same. Yellow pigment production by S. griseus containing crtS under the control of a strong promoter on a high-copy-number plasmid resulted from activation of transcription of the crt genes, because overexpression of sigmaCrtS in S. griseus led to transcriptional activation of the promoters in front of crtE and crtY. S1 nuclease mapping showed that crtS itself was transcribed at a low level under the laboratory conditions, which may account for undetectable production of carotenoids. The crt genes were suggested to locate very near one end of the linear chromosome, since they were completely deleted in mutant HH1 having large deletions at both ends. The gene organization of crt in S. griseus is similar to that in S. coelicolor A3(2) where the whole crt gene set is near one end of the chromosome.
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PMID:A sigmaB-like factor responsible for carotenoid biosynthesis in Streptomyces griseus. 1120 Feb 34

A widely distributed family of small regulators, called C proteins, controls a subset of restriction-modification systems. The C proteins studied to date activate transcription of their own genes and that of downstream endonuclease genes; this arrangement appears to delay endonuclease expression relative to that of the protective methyltransferase when the genes enter a new cell. C proteins bind to conserved sequences called C boxes. In the PvuII system, the C boxes have been reported to extend from -23 to +3 relative to the transcription start for the gene for the C protein, an unexpected starting position relative to a bound activator. This study suggests that transcript initiation within the C boxes represents initial, C-independent transcription of pvuIICR. The major C protein-dependent transcript appears to be a leaderless mRNA starting farther downstream, at the initiation codon for the pvuIIC gene. This conclusion is based on nuclease S1 transcript mapping and the effects of a series of nested deletions in the promoter region. Furthermore, replacing the region upstream of the pvuIIC initiation codon with a library of random oligonucleotides, followed by selection for C-dependent transcription, yielded clones having sequences that resemble -10 promoter hexamers. The -35 hexamer of this promoter would lie within the C boxes. However, the spacing between C boxes/-35 and the apparent -10 hexamer can be varied by +/-4 bp with little effect. This suggests that, like some other activator-dependent promoters, PpvuIICR may not require a -35 hexamer. Features of this transcription activation system suggest explanations for its broad host range.
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PMID:Nature of the promoter activated by C.PvuII, an unusual regulatory protein conserved among restriction-modification systems. 1562 20