An insertion of Escherichia coli transposable element IS1K into the site immediately before tetracycline-resistance determinant of Bacillus subtilis chromosomal DNA fragment in cloning in E. coli

In cloning in Escherichia coli C600 of a 4.5-kbp HindIII DNA fragment with the tetracycline-resistance determinant (tetBS908) from Bacillus subtilis GSY908 chromosome using a plasmid vector, a 5.2-kbp HindIII DNA fragment was also isolated at a ratio of 2 to 89. The two independently obtained 5.2-kbp fragments were an insertion derivative of the 4.5-kbp fragment and carried E. coli transposable element ISlK, which was inserted at the same site immediately before tetBS908 in the same direction. For the ISlK insertions, the 8-bp sequence CAAATTTT was used as a target, this having no similarity to any published sequences.

A limited number of Bacillus subtilis strains carry a tetracycline-resistance determinant at a site close to the origin of replication

Several strains of Bacillus subtilis, e.g., 168 derivatives and R, were found to carry a single copy of a tetracycline-resistance (TcR) determinant (named tetBS908) at a site close to the origin of replication on the chromosome. This gene is highly homologous (80% identical) to the TcR determinant of plasmids widely dispersed among aerobic spore-forming bacilli. B. subtilis RM125 (168 strain) transformants which carry a varying number of tetBS908 sequences in a tandem array on the chromosome were constructed and examined for their TcR level. A nearly proportional relationship between the TcR level and copy number of tetBS908 existed.

A new defective phage containing a randomly selected 8 kilobase-pairs fragment of host chromosomal DNA inducible in a strain of Bacillus natto

A new defective phage, designated PBND8, was induced in Bacillus natto strain IAM1207 with bleomycin and mitomycin C. PBND8 particles contained a randomly selected 8 kilobase-pairs (kbp) fragment of the host chromosomal DNA. Electron microscopy showed that PBND8 has a small head with a complex tail structure like PBSX, a defective phage of Bacillus subtilis 168. The PBND8 head, however, is clearly smaller than that of PBSX which contains 13-kbp fragments of the host chromosomal DNA. SDS-polyacrylamide gel electrophoretic analysis revealed that the structural proteins of PBND8 are distinct from those of PBSX and PBSY (PBSZ) of B. subtilis W23. PBND8 exhibited a bacteriocin-like killing activity to the other Bacillus cells.

[Antitumor effect of a novel antitumor compound, NC-190, in the double grafted tumor system]

The antitumor effect of NC-190, N-beta-dimethylaminoethyl-9-carboxy-5-hydroxy-10-methoxybenzo [alpha] phenazine-6-carboxamide sodium salt, with a new experimental mouse model was studied. Intratumoral administration of NC-190 strongly inhibited the growth of Meth-A solid tumors in male BALB/c mice and led to a complete tumor regression and also resistance to the reinoculated tumor. Subsequently, the anti-metastatic effect of NC-190 was examined in the double grafted tumor system, in which mice first received simultaneous intradermal inoculations of Meth-A in both right (10(6) cells) and left (2 X 10(5) cells) flanks and were then injected with 25 micrograms of NC-190 in the right tumor on days 3, 4 and 5. NC-190 inhibited the growth of not only the right but also the left, non-treated tumor. Immunized spleen cells were taken from mice which had been cured by the intratumoral administration of NC-190. Adoptive transfer of NC-190 immunized spleen cells caused a complete regression of Meth-A tumors. The effector cell activity was lost only after treatment with anti-Lyt-2 antibody. These results suggest that intratumoral administration of NC-190 might induce Lyt-2 positive cytotoxic cells in the spleen and the left, non-treated tumor. In BALB/c nude mice, NC-190 inhibited slightly the growth of the right tumor but did not that of the left tumor. Therefore, the antitumor activity of NC-190 in the double grafted tumor system was judged as associated with a sequential immune mechanism in which T cells may play an important role. TILs (tumor infiltrating lymphocytes) obtained from the left and right sides tumors treated with NC-190 were examined by Winn assay for their antitumor activity against Meth-A sarcoma in BALB/c mice. TILs obtained from neither sides inhibited the growth of admixed Meth-A cells. Different from immunopotentiators such PSK or IL-1, NC-190 enhanced neither concomitant immunity nor sinecomitant immunity.

The basidiomycete Lentinus edodes linear mitochondrial DNA plasmid contains a segment exhibiting a high autonomously replicating sequence activity in Saccharomyces cerevisiae

A linear DNA plasmid, designated pLLE1, has been isolated from a mitochondrial fraction of a strain of Lentinus edodes. pLLE1(11.0 kbp) was sensitive to the 3'----5'-acting exonuclease III and resistant to the 5'----3'-acting lambda exonuclease. It showed no homology with mitochondrial and nuclear genomic DNAs of plasmidless strain as well as the pLLE1-harboring host strain of L. edodes. The 1434-bp fragment (sequences) capable of autonomous replication in the yeast Saccharomyces cerevisiae (ARSs) was cloned from pLLE1 DNA with YIp32 (pBR322 containing yeast LEU2 DNA), which displayed a high ARS activity. The cloned 1434-bp fragment was shown to lie near to the end of pLLE1 DNA (nucleotides about 800-2200) and contained three consecutive ARS consensus sequences (A/T)TTTAT(A/G)TTT(A/T) of S. cerevisiae and dispersive eight ARS consensus-like sequences. The subcloned 366-bp fragment containing the three ARSs retained original ARS activity of the 1434-bp fragment.

The presence of the region on pBR322 that encodes resistance to tetracycline is responsible for high levels of plasmid DNA knotting in Escherichia coli DNA topoisomerase I deletion mutant

Plasmid pBR322 DNA isolated from Escherichia coli DNA topoisomerase I deletion mutant DM800 is estimated to contain about 10% of the knotted forms (Shishido et al., 1987). These knotted DNA species were shown to have the same primary structure as usual, unknotted pBR322 DNA. Analysis of the knotting level of deletion, insertion and sequence-rearranged derivatives of pBR322 in DM800 showed that the presence of the region on pBR322 encoding resistance to tetracycline (tet) is required for high levels of plasmid knotting. When the entire tet region is present in a native orientation, the level of knotting is highest. Inactivating the tet promoter is manifested by a middle level of knotting. For deletion derivatives lacking various portions of the tet region, the level of knotting ranges from lowest to high depending on the site and length of the tet gene remaining. Inverting the orientation of tet region on the pBR322 genome results in a middle level of knotting. Deleting the ampicillin-resistance (bla)gene outside of its second promoter does not affect the level of knotting, if the entire tet gene remains. A possible mechanism of regulation of plasmid knotting is discussed.

Two linear plasmid-like DNA elements simultaneously maintained in Pleurotus ostreatus

Two linear plasmid-like DNA elements, designated pLP01 and pLP02, have been isolated from a strain of Pleurotus ostreatus, an edible basidiomycete. pLP01 (10.0 kb) and pLP02 (9.4 kb) were found in mitochondrial preparations of the fungus and appear to have 5' ends blocked by association of a protein. Proteinase K cleavability of the 5'-terminal protein of pLP01 was higher than that of pLP02, indicating that the terminal proteins of both plasmid-like elements are distinct from one another. pLP01 and pLP02 were estimated to be present to the extent of 1-2 copies each per mitochondrial genome equivalent. The two plasmid-like elements had no homology between them and also were not homologous with the mitochondrial and nuclear genomic DNAs of the fungus.

Nucleotide sequence homology of the tetracycline-resistance determinant naturally maintained in Bacillus subtilis Marburg 168 chromosome and the tetracycline-resistance gene of B. subtilis plasmid pNS1981

The nucleotide sequence (1579 bp) of tetracycline-resistance determinant and flanking regions of the cloned 5.1 kb DNA fragment from Bacillus subtilis GSY908 chromosome (Sakaguchi, R. and Shishido, K. (1988) Biochim. Biophys. Acta 949, 49-57) were determined and compared with those of the B. subtilis tetracycline-resistance plasmid pNS1981. The tetracycline-resistance structural (tet) genes of the B. subtilis GSY908 chromosome (tetBS908) and pNS1981 (tetpNS1981) were found to be highly homologous (80% identical). Both tet genes were composed of 1374 bp and 458 amino-acid residues initiating from a GTG codon preceded by a ribosome-binding site (RBS-2). Upstream from tetBS908 there exists a short open reading frame (20 amino acids) initiating from a ATG codon preceded by its own RBS (RBS-1). This leader sequence was also highly homologous to that of tetpNS1981 except for a deletion of one bp between the RBS-1 and the ATG codon.

Alpha-factor-directed synthesis of Bacillus stearothermophilus alpha-amylase in Saccharomyces cerevisiae

Promoter and leader sequence of Bacillus stearothermophilus alpha-amylase gene were removed and the gene was joined in-frame to sequences encoding the leader region of Saccharomyces cerevisiae mating pheromone alpha-factor on plasmid p69A (a hybrid of pBR322 and S. cerevisiae 2-microns plasmid). S. cerevisiae cells were transformed with plasmids containing the hybrid genes, obtaining yeast transformants which exhibit a significant extra-cellular amylolytic activity in solid medium, but not in liquid medium. Levels of alpha-amylase activity in solid medium were found to depend on the mode of fusion of the alpha-amylase gene to the alpha-factor leader region.

Reevaluation of analytical procedures on quantitation of urinary protein in rats

In this study, the original method (Lowry method) of Lowry et al. (1951), its modified method (Lowry-TCA method) with protein precipitation by trichloroacetic acid (TCA) and the new method (BCA method) with bicinchoninic acid reaction, were reexamined as to whether these three methods were applicable to urinary protein quantitation of rats. Because of the presence of the urinary interfering substances, the quantitations in the Lowry- and BCA methods were found to be overestimated more than 3 times as large as in the Lowry-TCA method. When the urine sample was dialyzed against water and determined by the Lowry- and BCA methods, more than 24 hours were found to be needed in order to completely exclude the interfering substances from the urine. From these findings, the Lowry-TCA method is recommended for quantitation of urinary protein in rats.

Molecular cloning of a tetracycline-resistance determinant from Bacillus subtilis chromosomal DNA and its expression in Escherichia coli and B. subtilis

Bacillus subtilis GSY908 DNA fragments (5.1 and 4.4 kilobase pairs (kb)) containing a tetracycline-resistance determinant were cloned in Escherichia coli using a shuttle plasmid vector pLS353. Restriction endonucelase analysis showed that the 4.4 kb fragment is a spontaneous deletion derivative of the 5.1 kb fragment. E. coli tetracycline-resistance transformants carrying pLS353 with the 5.1 kb fragment (named pTBS1) and that with 4.4 kb fragment (pTBS1.1) could grow at tetracycline concentrations up to 80 and 50 micrograms per ml, respectively. B. subtilis MI112 and RM125 were transformed by pTBS1, resulting in isolation of transformants of MI112 maintaining pTBS1 and RM125 maintaining either pTBS1 or pTBS1.1. Maximum tetracycline concentrations permitting growth of plasmidless MI112 and MI112 with pTBS1 were 4 and 10 micrograms per ml, respectively, while those of plasmidless RM125, RM125 with pTBS1 and RM125 with pTBS1.1 were 7, 50 and 80 micrograms per ml, respectively. It was interesting to note that the tetracycline-resistance level in E. coli conferred by the 5.1 kb fragment is higher than that conferred by the 4.4 kb fragment, but in B. subtilis the 4.4 kb fragment, in contrast, confers a higher level of tetracycline resistance. The level of tetracycline resistance in B. subtilis conferred by the cloned determinant clearly depends on the host strain. The tetracycline resistance conferred by the cloned determinant was associated with decreased accumulation of the drug into the cells. However, it was constitutive in E. coli, but inducible in B. subtilis. The cloned tetracycline-resistance determinant was detected specifically on the chromosome of B. subtilis Marburg 168 derivatives.

Clinical study of sudden deafness with special reference to onset

In a comparative study, patients with sudden deafness were classified into four groups according to type of onset. The results showed that those who noticed deafness occurring when awakening had a better prognosis than others, particularly those who found themselves already suffering from deafness on awakening. These findings suggest that among patients who have deafness on awaking, the disorder may not be sudden deafness in sensu strictu.

Increased production of a knotted form of plasmid pBR322 DNA in Escherichia coli DNA topoisomerase mutants

Plasmid pBR322 prepared from Escherichia coli strains carrying deletion of the DNA topoisomerase I gene (delta topA) with a compensatory mutation of the DNA gyrase gene (gyrA or gyrB) and from their TopA+ transductants was analyzed by agarose gel electrophoresis followed by electron microscopy, and compared with that from isogenic wild-type strains. It was found that about 1% of the plasmid DNA molecules was a knotted species in the topA+ gyr+ strains W3110 and DM4100, while strains DM750 (delta topA gyrA224), DM800 (delta topA gyrB225), SD275 (topA+ gyrA224) and SD108 (topA+ gyrB225) produced six to ten times as much knotted DNA as the topA+ gyr+ controls. The results suggest that the increased production of knotted pBR322 DNA is closely related to mutations of the gyrase genes.

Purification of S1 nuclease to homogeneity and its chemical, physical and catalytic properties

An S1 nuclease preparation was used to purify the enzyme to homogeneity. The enzyme had an isoelectric point of 4.2, and a high content of hydrophobic amino acids, especially tyrosine. It exhibited low 3'-ribonucleotidase activity. Circular dichroism analysis suggested that the contents of alpha-helix, beta-structure and random coil are 25%, 31% and 44%, respectively. The enzyme contained about 3 g atoms Zn/mol and the removal of Zn from the enzyme by addition of EDTA resulted in disruption of its secondary structure with resultant inactivation. From Con A-Sepharose chromatography, we suggest that the enzyme is a high-mannose glycoprotein. After treatment with endo-beta-N-acetylglucosaminidase H under moderate conditions, a small part of the enzyme was converted to a form lacking the sugar side chain. This form of the enzyme was as thermostable as the parent enzyme, suggesting that the sugar side chain may not be involved in thermostability of the enzyme.

An infrequent generation of catenated network of pBR322 in Escherichia coli

It was demonstrated that Escherichia coli infrequently generates the catenated network of pBR322. This complex pBR322 form was detected when DNA molecules could hardly enter the agarose gel during electrophoresis and was found to comprise monomers and dimers of the plasmid.

Cloning of Lentinus edodes mitochondrial DNA fragment capable of autonomous replication in Saccharomyces cerevisiae

Mitochondrial (mt) DNA of the higher basidiomycetes Lentinus edodes with a molecular weight of about 69 kb was partially digested with Sau3AI, cloned with plasmid YIp32 (a hybrid of pBR322 and the yeast leu2 gene) and analyzed for sequences capable of autonomous replication (ARSs) in the eukaryote Saccharomyces cerevisiae. One recombinant plasmid was isolated which contained 3.2 kb fragment of the mtDNA with ARS activity. This plasmid (named pSK52) exhibited a high-frequency yeast transformation and was found to be maintained within the cell as an extrachromosomal element. The stability and copy number properties of pSK52 were similar to those of the recombinant plasmid of YIp32 and S. cerevisiae mt-ARS constructed as a reference. Subcloning experiments were carried out to assess the localization of ARS on the above 3.2 kb fragment, revealing that the fragment contains at least two ARSs.

Studies on binding of toromycin, an antitumor antibiotic, to DNA

Toromycin, an antitumor, bactericidal and antiviral compound, was found to bind to DNA in such a way as to interfere with the dissociation of double helix at an elevated temperature. The antibiotic did not introduce strand scission into DNA. Single-strand-specific nuclease S1-susceptibility of negatively supercoiled DNA was not influenced by its binding. The antibiotic was shown to bind to both of the alternating purine-pyrimidine copolymers, poly(dG-dC):poly(dG-dC) and poly(dA-dT):poly(dA-dT). The unique C-glycoside molecule of toromycin interacted with single-stranded DNA, but was found to have no affinity for RNA.