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J N Hansen

Publications and source records attributed to J N Hansen.

At least 37 records · Page 2Linked to original sources
PubMed1988

Transcriptional analysis of Bacillus subtilis rRNA-tRNA operons. II. Unique properties of an operon containing a minor 5 S rRNA gene.

This is part of a series of two papers on gene regulation in Bacillus subtilis rRNA-tRNA operons that contain large clusters of tRNA genes. The preceding paper (Vold, B.S., Okamoto, K., Murphy, B.J., and Green, C.J. (1988) J. Biol. Chem. 263, 14480-14484) investigates the rrnB operon containing 21 tRNA genes, and this paper investigates a B. subtilis rRNA-tRNA operon containing 16 tRNA genes and a minor 5 S rRNA. Hybridization studies suggest this minor 5 S rRNA occurs as a single copy in the B. subtilis 168 genome. S1 nuclease mapping indicates that this minor 5 S rRNA gene has its own promoter. No promoters have been found immediately 5' to any of the major 5 S rRNA species in B. subtilis rRNA operons. S1 mapping of the spacer region between the 23 S and minor 5 S rRNA revealed that the maturation of the 23 S rRNA in this operon may arise from an unusual processing mechanism. S1 nuclease mapping experiments suggest the existence of a promoter element immediately upstream of the last gene, for tRNA(Leu CAA), in the operon. A precursor leucine tRNA resulting from transcription of this last tRNA gene was observed in Northern hybridizations, and the amounts of this precursor increased during sporulation. A single terminator-like element is located just upstream of this last tRNA gene; however, S1 nuclease mapping experiments suggest that some read-through transcription occurs. Thus, all 16 tRNA genes are under control of the upstream 16 S rRNA promoters and the minor 5 S rRNA promoter. However, the last tRNA gene is primarily under the control of its own unique promoter.

Bacillus subtilis↗
PubMed1988

Structure and expression of a gene encoding the precursor of subtilin, a small protein antibiotic.

A gene has been cloned from Bacillus subtilis ATCC 6633 that encodes a 56-residue peptide precursor for the 32-residue peptide antibiotic, subtilin. The precursor contains serines, threonines, and cysteines at positions that permit them to undergo a series of dehydration and cross-linking steps to give the mature antibiotic peptide which contains the unusual amino acids lanthionine, beta-methyllanthionine, D-alanine, dehydroalanine, and dehydrobutyrine. The precursor peptide contains a leader region that has an unusual hydropathic character for an exported protein. The subtilin gene is expressed from a monocistronic transcriptional unit as identified by S1 mapping of the gene transcript. The (-35) region of the promoter is not typical of Bacillus subtilis vegetatively-expressed genes. The subtilin transcript was present in very low amounts during exponential growth, but in large amounts during stationary phase; at which time mature subtilin peptide and antibiotic activity were also observed. The subtilin transcript contains a cleavage-sensitive region that overlaps the ribosome binding site. The primary transcript has an unusually long half-life of about 45 min. These observations confirm that subtilin is derived from a small protein that is synthesized on ribosomes.

Amino Acid Sequence↗
PubMed1988

Modern evolution of a single-copy gene: the immunoglobulin C kappa locus in wild mice.

The immunoglobulin kappa light-chain constant region gene (C kappa) has been cloned and sequenced from five wild mouse species. Analysis of these data has permitted an assessment of single-copy gene evolution during a limited time period as defined by the genus Mus. Sequence conservation was found to be as high (or higher) in the 5' and enhancer regions as in the coding region. The pattern of substitutions throughout these genes suggests that parallel evolution has occurred frequently and that substitutions at replacement sites have not decreased significantly, owing to saturation during this period of approximately 10 Myr. Phylogenetic relationships have been determined among these wild species as well as among members of the genus Rattus.

Animals↗
PubMed1987

Severe secondary postpartum haemorrhage after caesarean section.

Between January 1982 and April 1985 13 patients with severe secondary postpartum haemorrhage after caesarean section were seen at King Edward VIII Hospital, Durban. The bleeding occurred in the second, third and fourth weeks after delivery, but there were no maternal deaths. Eight of these patients were treated by total abdominal hysterectomy and 1 by revision of the uterine wound and ligation of the bleeding uterine vessels. The last 4 patients, seen in 1985, were treated by selective transcatheter embolisation with Gelfoam pledgets. This method was successful in 3 patients and failed in 1. It is suggested that the latter method has a place in the treatment of these patients.

Cesarean Section↗
PubMed1987

Modification of membrane sulfhydryl groups in bacteriostatic action of nitrite.

The mechanism by which nitrite inhibits outgrowing spores of Bacillus cereus T was examined by using techniques developed earlier for nitrite analogs. The morphological stage of inhibition, cooperativity effects, effect of pH on inhibition, kinetics of protection against iodoacetate incorporation into membrane sulfhydryl groups, and protection against the bacteriocidal effect of carboxymethylation by iodoacetate indicate that nitrite acts as a membrane-directed sulfhydryl agent. The mechanism by which nitrite modifies the chemical reactivity of the sulfhydryl group could be either direct covalent modification or inactivation through communication with another modified membrane component. Profiles of pH effects suggest that the active agent is the protonated form of nitrite. The nitrite concentrations which modify membrane sulfhydryl activity coincide with those which have a bacteriostatic effect. These results are consistent with membrane sulfhydryl modification as a component of the mechanism of nitrite-induced bacteriostasis in this aerobic sporeformer.

Bacillus cereus↗
PubMed1984

Identification and characterization of some bacterial membrane sulfhydryl groups which are targets of bacteriostatic and antibiotic action.

Covalent modification of sulfhydryl groups which become sensitive toward sulfhydryl agents during germination of Bacillus cereus spores exerts a profound bacteriostatic effect, resulting in outgrowth inhibition. The modified spore components are membrane species of 13,000, 28,000, and 29,000 daltons. Detergent disruption of the membrane inactivated the sulfhydryl groups. A highly sigmoid inhibition curve (n = 11.8) with diamide suggested the participation of closely neighboring sulfhydryl groups. Substate and substrate analogs of the lactose and dicarboxylic acid permeases protected the sulfhydryl groups against modification. Nisin, a 34-residue peptide antibiotic, inhibited spore outgrowth and sulfhydryl modification at a concentration of about 0.1 microM. Since these sulfhydryl groups have been implicated as involved with the bacteriostatic action of nitrite, substances directed toward them may be a useful new class of bacteriostatic agents and antibiotics.

Anti-Bacterial Agents↗
PubMed1984

Two large clusters with thirty-seven transfer RNA genes adjacent to ribosomal RNA gene sets in Bacillus subtilis. Sequence and organization of trrnD and trrnE gene clusters.

Sequences of two large tRNA gene clusters (trrnD and trrnE) in Bacillus subtilis 168 revealed 16 and 21 tRNA genes, respectively, as identified by anticodon assignments. Each cluster contains upstream flanking 23 and 5 S rRNA sequences. The 23-5 S intergenic space in trrnE corresponds exactly to the analogous space in trrnB, which was previously sequenced (Wawrousek, E.F., and Hansen, J.N. (1983) J.Biol. Chem. 258, 291-298). The 5 S rRNA genes in trrnB and trrnE are B. subtilis major species; but trrnD possesses a minor species (Raue, H.A., and Planta, R. J. (1977) Mol. Gen. Genet. 156, 185-193) gene with a putative promoter that may allow differential expression with respect to the upstream rRNA gene set. Most of the tRNA genes are probably expressed as large transcriptional units, except for a LeuTTG tRNA in the trrnD cluster that appears to constitute its own operon with putative promoter and terminator sequences. Although all the amino acids are represented among the tRNA anticodons, there are few repeats of amino acid types within clusters; trrnD with 16 tRNA genes has anticodons corresponding to 15 amino acids. About two-thirds of the tRNA genes encode a 3'-terminal-CCA, and these are intermingled with those that do not, with no apparent pattern.

Anticodon↗
PubMed1984

Effect of purine and pyrimidine limitations on RNA synthesis in Bacillus subtilis.

The effects of varying the intracellular levels of GTP or UTP on the rate of RNA synthesis in Bacillus subtilis were studied. The levels of these nucleotides were manipulated by pyrimidine limitation in a pyr auxotroph, by purine limitation in a pur auxotroph, or by the addition of decoyinine , which specifically inhibits GMP synthesis. Decreased levels of UTP and GTP were accompanied by dramatically decreased synthesis and accumulation of stable RNAs (tRNA and rRNA), but mRNA synthesis was less affected. However, sporulation was initiated only when the intracellular level of GTP decreased.

Bacillus subtilis↗
PubMed1983

Structure and organization of a cluster of sic tRNA genes in the space between tandem ribosomal RNA gene sets in Bacillus subtilis.

Hybridization of Southern blots of EcoRI digests of total Bacillus subtilis DNA with ribosomal RNA and transfer RNA probes provides evidence of highly clustered tRNA and rRNA genes, with several tRNA clusters being located in spaces which span between tandem ribosomal RNA gene sets. Clones containing these tRNA clusters were isolated from a Charon 4A library. One of them, denoted trrnB, was partially sequenced. A cluster of six tRNA genes was found, with anticodon assignments of Asn, Thr, Gly, Arg, Pro, Ala. This cluster is closely flanked on both sides by ribosomal RNA gene sets, which were identified by sequencing upward through the 5 S rRNA gene, across a space, and into the 23 S rRNA gene, and also sequencing downward into the 16 S rRNA gene. The tRNA gene cluster appears to be organized into at least two transcriptional units separated by an attenuator region. These transcriptional units may be components of the flanking ribosomal RNA operons. The putative promoter region of the downstream 16 S rRNA is organized differently from Escherichia coli; it is smaller and seems less complex. This gene organization provides insight into possible mechanisms for coordinate and differential control of transfer and ribosomal RNA gene expression.

Anticodon↗
PubMed1983

Lactoferrin and transferrin fragments react with nitrite to form an inhibitor of Bacillus cereus spore outgrowth.

Tryptone is a pancreatic digest of casein which contains a heterogeneous mixture of substances that react with nitrite when heated in the presence of sodium thioglycolate to form a bacteriostatic agent which inhibits outgrowth of Bacillus cereus T spores. The substances which are precursors to the bacteriostatic agent can be fractionated on the basis of molecular size and charge and have properties which indicate that they are fragments of lactoferrin, an iron-binding glycoprotein. The bacteriostatic agent could also be formed directly from purified lactoferrin after it had been subjected to proteolysis. Transferrin, an analogous iron-binding protein found in animal serum, also showed these same properties. This system may be a useful model for studies of the mechanism and site of nitrite bacteriostatic action.

Bacillus cereus↗
PubMed1982

The sequence of a mouse embryonic beta-globin gene. Evolution of the gene and its signal region.

We have determined the nucleotide sequence of an embryonic beta-globin gene of the Balb/c mouse. It possesses structural features typical of known expressed beta-globins, including 5'-untranslated region, potential capping site, initiation and terminator codons, poly(A) addition signal, splicing signals, and intervening sequences. There is a striking 15-base homology between the putative RNA polymerase binding site of this gene and the corresponding region of a human embryonic beta-gene which may be important in the control of expression during embryonic development. The sequence of the gene predicts the sequence of the entire y2 protein, which has not previously been available. As expected from evolutionary considerations, it is more homologous to human embryonic beta-globin than to mouse adult beta-globin.

Animals↗
PubMed1981

Bacterial spore components which enhance the bacteriostatic effectiveness of S-nitrosothiol.

Spore components exuded into the medium during outgrowth of Bacillus cereus T enhanced the bacteriostatic effectiveness of S-nitrosomercaptoethanol, an inhibitor which prevents outgrowth at low concentrations and germination at higher concentrations. The enhancement effect was slight with respect to outgrowth, but dramatic with respect to germination, in that the inhibitory effectiveness of nitrosothiols toward germination inhibition was enhanced by as much as 33-fold when nitrosothiols was in the presence of the exuded spore component. Exudate activity was freely dialyzable and was not measurably affected by a broad-spectrum protease (proteinase K), by autoclaving at 121 degrees C, or by freezing and thawing. Sephadex G-25 chromatography of the exudate indicated that two active species were present, a major component with a molecular weight of less than 1,000 and a minor component with a molecular weight of more than 5,000.

Bacillus cereus↗
PubMed1981

Inhibition of Bacillus cereus spore outgrowth by covalent modification of a sulfhydryl group by nitrosothiol and iodoacetate.

Nitrosothiols with the general structure RSN==O were studied as a model system of bacteriostatic action toward outgrowing bacterial spores. With a Taft plot analysis, the influence of the structure of the R group on the inhibitory effectiveness of a series of nitrosothiols showed that effectiveness as an inhibitor of Bacillus cereus T outgrowth correlated with the electron withdrawal of R, but that size, shape, charge, hydrophobicity, and transportability had little influence. This was interpreted to mean that nitrosothiols do not traverse the membrane to act. The Taft plot together with competition data between nitrosothiol and iodoacetate indicated that the mode of nitrosothiol action is the covalent modification of a sulfhydryl group, probably to form RSN(OH)--SX, where --SX is derived from a sensitive spore sulfhydryl group. Cooperativity effects indicated that outgrowth inhibition is accompanied by a conformational change occurring upon sulfhydryl group modification, which is communicated among at least three to five subunits. Uptake of label during spore germination indicated that most of the sulfhydryl groups which can be modified are associated with the inhibitory event. These data suggest that this sulfhydryl group may be sufficiently unique that inhibitors designed to interfere specifically with it could have value as bacteriostatic agents.

Bacillus cereus↗
PubMed1980

Mouse globin system: a functional and evolutionary analysis.

Structural and functional analysis of the mouse alpha-globin and beta-globin genes reveals that the globin genes are encoded in discontinous bits of coding information and that each gene locus is much more complex than was originally supposed. Each seems to consist of an array of several authentic genes as well as several apparently inactive pseudogenes. Comparison of the sequences of some of these genes to one another indicates that chromosomal DNA is a dynamic structure. Flanking and intervening sequences change in two ways: quickly, by duplication and extensive insertions and deletions, and slowly, by point mutation. Active coding sequences are usually limited to the slower mode of evolution. In addition to identifying fast and slow modes of evolution, it has also been possible to test the function of several signals that surround these genes and to identify those that appear to play a role in gene expression.

Animals↗