Gene/Protein Disease Symptom Drug Enzyme Compound
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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)

Five of the genes for the biosynthesis of isoleucine and valine form the ilvGMEDA operon of Escherichia coli K-12. Expression of the operon responds to changes in the availability of isoleucine, leucine, and valine (ILV). Addition of an excess of all three amino acids results in reduced expression of the operon, whereas limitation for one of the three amino acids causes an increase in expression. The operon is preceded by a leader-attenuator which clearly regulates the increased expression that occurs due to reduced aminoacylation of tRNA. To assess the factors that result in the reduced expression of this operon upon the addition of ILV, a series of plasmids were constructed in which the ilv regulatory region was fused to galK. In response to addition of the amino acids, expression of the galK gene fused to the leader-attenuator decreased five- to sevenfold, instead of the twofold observed for the chromosomal operon. A deletion analysis with these plasmids indicated that the ILV-specific decrease in expression required an intact leader-attenuator but not ilvGp2 or the DNA that precedes this promoter. This conclusion was supported by both S1 nuclease analysis of transcription initiation and determination of galK mRNA levels by RNA-RNA hybridization.
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PMID:Analysis of regulation of the ilvGMEDA operon by using leader-attenuator-galK gene fusions. 218 12

The ilvY gene of Escherichia coli is transcribed in a direction opposite to the ilvGMEDA operon, and the translational stop codons of the ilvA and ilvY genes are only 52 base pairs (bp) apart. We have employed galK transcriptional analyses, in vitro transcription assays, and S1 nuclease mapping to show that the converging transcripts of the ilvGMEDA operon and the ilvY gene overlap. The ilvGMEDA transcript terminates at two sites in the distal amino acid coding region of the ilvY gene: a rho-independent termination site 116 bp downstream of the ilvA translational stop codon, ilvA t, and a 62-bp-long rho-dependent termination site, ilvA t', beginning 70 bp beyond the ilvA t site. This tt' termination pattern at the distal end of the ilvGMEDA operon is similar to that of the trp operon of E. coli and the leu operon of Salmonella typhimurium. Termination of ilvY transcription occurs over a broad stretch of DNA several hundred base pairs downstream of the ilvY translational stop codon in the middle of the amino acid coding region of the ilvA gene. These experiments demonstrate that the converging transcripts from the ilvA and ilvY genes terminate in the coding region of the opposing gene.
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PMID:Overlapping transcription and termination of the convergent ilvA and ilvY genes of Escherichia coli. 264

The nucleotide sequence of the F plasmid transfer gene traH, which is involved in F-pilus assembly in Escherichia coli K-12, has been determined. From the sequence data, it would appear that traH encodes a 38,897-dalton precursor polypeptide which is processed to give a periplasmic protein. Furthermore, a new gene, trbF, has been located immediately upstream of traH and shown to be expressed by means of a translational fusion to lacZ. Using galK fusion and S1 nuclease protection studies, a weak traJ-dependent promoter, P trbF, has been mapped upstream and adjacent to trbF. Transcription of trbF and traH from P trbF may well serve to complement transcription from the major tra operon promoter PY located some 16 kb upstream of these genes.
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PMID:Nucleotide sequence of the F plasmid transfer gene, traH: identification of a new gene and a promoter within the transfer operon. 265 8

The pyrC gene of Salmonella typhimurium, encoding the third enzyme of pyrimidine nucleotide biosynthesis, dihydroorotase, has been cloned into the multicopy plasmid pBR322. The recombinant plasmid, pJRC1, promoted the synthesis of 20-30-fold elevated levels of dihydroorotase. The expression of pyrC was regulated to the same extent by pyrimidines whether present on the multicopy plasmid or in single copy on the chromosome. A comparison of the polypeptides encoded by pyrC-complementing and non-complementing plasmids showed the gene product to have a molecular mass of approximately 37 kDa. The nucleotide sequence of the gene and 400 base pairs upstream from the coding region was determined. An open-reading frame, encoding a protein with a calculated molecular mass of 38 500 Da, was deduced to be the coding region for pyrC. S1 nuclease mapping indicated that transcription of pyrC is initiated 40 base pairs upstream from the translational start. Subcloning of a 184-base-pair DNA fragment, which included 118 base pairs upstream from the transcriptional start, and the first eight codons of the pyrC structural gene, into a galK expression vector, established that the pyrC promoter and regulatory region are harbored on this fragment. The leader region does not show any features resembling the attenuators found in front of the coding regions of pyrB and pyrE; however, it contains a region of dyad symmetry, which may allow the leader transcript to form a stable hairpin. The possible significance of this putative hairpin formation in the regulation of pyrC expression is discussed.
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PMID:Cloning and structural characterization of the Salmonella typhimurium pyrC gene encoding dihydroorotase. 287 51

The fumarate reductase enzyme complex allows Escherichia coli to grow anaerobically with fumarate as a terminal electron acceptor for oxidative phosphorylation when the preferred compounds oxygen and nitrate are not available. We used the pKO promoter test vectors to identify a single promoter for the frdABCD genes which encode fumarate reductase. Expression of galactokinase from the frd promoter-galK operon fusion plasmid was repressed by oxygen and by nitrate and was induced by fumarate, indicating that frd gene expression is regulated at the transcriptional level by these terminal electron acceptors. S1 nuclease analysis, using a single-stranded DNA probe from the frd promoter region and mRNA isolated from a fumarate reductase-induced culture, revealed that the frd mRNA transcript initiates with an adenine residue 93 bases prior to the start of frdA translation. No promoters internal to the frd genes were revealed with the plasmid promoter screening system. S1 nuclease analysis revealed that the frd mRNA terminates in a uridine-rich region centered at 46 bases after the last codon of frdD. A stem and loop structure previously described as the growth rate-dependent attenuator for the linked ampC gene precedes the frd mRNA terminus. This result confirms the proposal that the stem and loop structure serves the dual role of a frd terminator anaerobically and an ampC attenuator aerobically. The four frd genes encoding the subunits of the fumarate reductase complex thus comprise an operon which is regulated at the transcriptional level in response to the cellular availability of the alternate electron acceptors oxygen, nitrate, and fumarate.
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PMID:Transcription of the Escherichia coli fumarate reductase genes (frdABCD) and their coordinate regulation by oxygen, nitrate, and fumarate. 299 70

Transcription in vitro of the regulatory region of the ilvGMEDA operon yields two attenuated RNAs initiated from the tandem promoters ilvGp1 and ilvGp2. Both S1 nuclease analysis and the fusion of ilvGp1 to galK indicate that transcription is not initiated in vivo from ilvGp1. However deletion of DNA sequences 150 to 100 bp upstream of ilvGp2 drastically reduces expression in vivo from ilvGp2. Both the distance separating ilvGp2 from the upstream DNA sequences and their relative orientation to each other on the DNA helix affect expression from ilvGp2. Deletion of DNA sequences approximately 400 bp upstream of ilvGp2 increases expression in vivo from this promoter. Analysis of products of transcription in vitro indicates that the effects observed in vivo are probably not due to DNA conformation or interactions of RNA polymerase.
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PMID:Effect of the deletion of upstream DNA sequences on expression from the ilvGp2 promoter of the ilvGMEDA operon of Escherichia coli K-12. 354 37

Two leftward Pc promoters for the repressor gene of bacteriophage Mu have been localized by fusions of the promoter region to the structural galK gene and by S1 nuclease mapping. Transcription initiated at the left-end-proximal promoter (Pc-1) starts 23 bp ahead of the c gene. The second promoter (Pc-2) is located 200 bp from the translation start codon of gene c. The RNA initiated from Pc-2 overlaps 35 bp with the rightward transcript from the early Mu promoter (Pe). The expression from Pe and both repressor promoters is positively regulated by the Escherichia coli HimD (Hip) protein, probably acting as a subunit of the integration host factor (IHF). Two overlapping sequences matching the consensus for the IHF binding site (ihf) are found between Pe and Pc-1.
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PMID:Regulation of Mu transposition. II. The escherichia coli HimD protein positively controls two repressor promoters and the early promoter of bacteriophage Mu. 609 26

The major leftward transcription of bacteriophage lambda is controlled by several terminators (t), including tL1, tL2, tL3, and others. The tL2 termination site, which was placed by Salstrom and Szybalski (Virology 88, 252-260, 1978) between lambda genes bet and ral, was found to consist of a cluster of four leftward terminators. As not to change the numbering of other leftward terminators, these were designated as tL2a, tL2b, tL2c, and tL2d. As determined by S1 nuclease mapping of the tL2-terminated in vitro transcripts, the normally pL-initiated major leftward lambda transcription should encounter termination points at 1653 bp (tL2a; between genes Ea10 and ral), 2089 bp (tL2b; between genes cIII and Ea10), 2441-2442 bp, and 2483 bp (tL2c and tL2d; both within gene gam) from the sL startpoint (= +1). All terminators were cloned in a pBR322-derived plasmid between the p'R promoter and the galK gene, and their in vivo termination efficiencies are 69% (tL2a), 53% (tL2b), and 38% (tL2c + tL2d), measured as reduction of galK expression in rho+galK- hosts at 30 degrees. The tL2a and tL2b), terminators depend little on the rho factor, whereas the efficiency of tL2c + tL2d decreases from 38 to only 14% in the rho- host. When shifted to 42 degrees, the termination efficiency of tL2b decreases from 53 to only 36%, while the other tL2 terminators are much less affected by increasing the temperature. The calculated joint efficiency of the entire tL2 cluster is 90%, which is in perfect agreement with the 90% termination efficiency reported by Salstrom and Szybalski (1978) for tL2. However, the natural location of tL2c and tL2d within the actively translated gam gene may interfere with their termination function. Under in vitro conditions, tL2c and tL2d are active only in the presence of rho factor, whereas tL2a and tL2b do not require rho. The structure of the tL2 terminators resembles that of some other known termination sites: a perfect (8 bp for tL2a and tL2b) or imperfect (8-9 bp) dyad symmetry and a T6 (tL2a), T5 (tL2b), T4 (tL2c) or TTATT sequence (tL2d) toward the 3' end of the mRNA-like DNA strand.
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PMID:The tL2 cluster of transcription termination sites between genes bet and ral of coliphage lambda. 622 May 15

Transcription during the lytic cycle of phage Mu occurs in three phases: early, middle, and late. Late transcription requires the Mu C protein and initiates at four promoters: Plys, PI, PP, and Pmom. Northern blot analysis of total RNA isolated 30 min after heat induction of Mu cts lysogens demonstrated that the full-length lys and P transcripts were approximately 7.6 and 6.3 kb long, respectively. The 3' ends of the lys and P transcripts were further localized by S1 nuclease mapping to intergenic regions between G and I and between U and U' in both the G(+) and G(-) orientations of the invertible G segment, respectively. As expected, when DNA fragments containing these termination regions were cloned into plasmids between Pgal and the galK gene, they showed efficient termination activity, even in a Rho-deficient background. Deletion analysis indicated that efficient termination required the presence of potential RNA stem-loop structures immediately preceding the RNA 3' ends. For the P transcript from phage with the G(-) orientation, full termination activity required both the region containing the stem-loop structure and upstream sequences. Taken together, these results suggest that the transcription termination sites of the lys and P transcripts are Rho-independent terminators.
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PMID:Identification and characterization of the terminators of the lys and P transcripts of bacteriophage Mu. 810 22