Instability of bacteriophage lambda initiator O and P proteins in DNA replication

Lambda dv plasmids having an amber mutation in an initiator gene, O or P, were constructed from mutant lambda phages by recombinant DNA techniques and several properties of such derivatives were investigated. These plasmids are perpetuated in suppressor-plus (amber-permissive) cells, but not in non-suppressor cells. The plasmid copy number in the suppressor-plus cells was low as compared to that of the plasmid without the amber mutation. In cells carrying a thermosensitive suppressor 2, raising the temperature is expected to block new production of amber proteins, but should not affect conservation of the protein made prior to heating. It was observed, however, that replication of the plasmids carrying an amber mutation in the O or P gene was abolished soon after raising the temperature, suggesting that neither of the initiator proteins can continue functioning unless replenished. Pulse-chase experiments demonstrated that O protein decays with a half-life of 8 min. Several lines of evidence suggest that this degradation occurs independently of the protein function. On the other hand, P protein was not degraded under the same experimental conditions. These observations are discussed in connection with functional instability of the initiator molecules. It appears that they do not work catalytically.

Cloning and structural analyses of hepatitis B virus DNAs, subtype adr

Entire genomes of hepatitis B virus (subtype adr) have been cloned. The nucleotide sequence data were compared with other sequences of HBV genome including: adw [Valenzuela et al. (1981) in Animal Virus Genetics. Fields et al. eds. Academic Press, Inc., NY. pp. 57-70], ayw [Galibert et al. (1979) Nature, 281, 646-650], and adyw [Pasek et al. (1979) Nature 282, 575-579]. Four open coding frames for polypeptides larger than 6,000 dalton were found to be conserved and were highly compressed by overlapping with each other in one strand (L-strand). Sites of initiation of the S gene and termination of the P gene were not conserved. No conserved coding frame was found on the opposite strand (S strand). Amino acid sequences of six surface antigen (HBsAg) peptides, including subtypes adr, adw, and ayw, are deduced from the DNA sequences, and the substitution of amino acid residues which are consistent with the change of subtypes are demonstrated.

Role of nine repeating sequences of the mini-F genome for expression of F-specific incompatibility phenotype and copy number control

An autonomously replicating 2,248-base-pair DNA segment of the mini-F plasmid carries nine 19-base-pair repeating sequences. Five of the repeats are arranged in one direction and form the right cluster, whereas the remaining four repeats are arranged in the opposite direction and form the left cluster (Murotsu et al., Gene 15:257-271, 1981). Each cluster, cloned separately into the multicopy plasmid vector pBR322, exhibited a strong F-specific incompatibility phenotype (FIP). These clusters were thought to be responsible for the expression of IncB and IncC phenotypes, causing a switchoff function on mini-F replication. Mini-F DNA fragments containing two, three, or more than four repeats were inserted into pBR322. Cells carrying these recombinant plasmids exhibited, respectively, no, intermediate, and strong FIP intensity. Cloning of five repeats into pSC101, whose copy number is about 6 in contrast to 20 for pBR322, resulted in an FIP of intermediate intensity. Thus, the intensity of FIP reflects the dosage of repeats in a cell. The five repeats in the right cluster were eliminated from the mini-F derivative without impairing its autonomous-replicating ability (Bergquist et al., J. Bacteriol. 147:888-889, 1981; Kline and Palchavdhuri, Plasmid 4:281-289). Such deletion, however, caused a sixfold elevation of the copy number. When the eliminated cluster of repeats was reinserted in the derivative, the copy number was lowered to the original value, viz., 1 to 2. The position and orientation of this insertion was not important in the copy number control. Thus, the repeats are also related to copy number control. A model to account for the role of the repeating sequences in the control of copy number and FIP is discussed.

Expression of hepatitis B surface antigen gene in yeast

The DNA sequence coding for hepatitis B virus surface antigen (HBsAg) was placed under control of the repressible acid phosphatase promoter of the yeast Saccharomyces cerevisiae in a plasmid capable of autonomous replication in both yeast and Escherichia coli. Yeast transformed by this plasmid synthesized up to 5 X 10(5) molecules per cell of immunologically active HBsAg polypeptide in phosphate-free medium. The HBsAg polypeptides produced in the yeast cells were assembled into 20- to 22-nm spherical or oval particles and were immunogenic.

Formation of oligomeric structures from plasmid DNA carrying cos lambda that is packaged into bacteriophage lambda heads

Plasmids that carry cos lambda, the region necessary for lambda phage packaging and that are as small as four kilobases in size can be packaged into lambda phage heads in head-to-tail tandem oligomeric structures. Multimeric oligomers as large as undecamers have been detected. Oligomer formation depends upon the products of red and gam of lambda, and the general recombination occurs between different plasmids that share homologous DNA regions. The packaging efficiency of plasmids depends on its copy number in cells and its genome size. Upon injection into a cell, the DNA establishes itself as a plasmid in a tandem structure. When such a plasmid in a high oligomeric structure is used as the source of packaging DNA, the packaging efficiency of the plasmids is elevated. The oligomers are stable in recA cells, whereas they drift toward lower oligomers in recA+ cells.

Replication of lambda dv plasmid in vitro promoted by purified lambda O and P proteins

An in vitro system for replication of lambda dv plasmid DNA has been constructed. This system consists of an ammonium sulfate fraction from Escherichia coli extract, exogenously added purified lambda O and P proteins, and lambda dv DNA in closed circular form. More than 85% of the added template DNA replicated semiconservatively. In the same system, another plasmid, pBR322, also replicated, but less efficiently than lambda dv. Furthermore, its replication was independent of O and P proteins. Inhibitors of DNA gyrase entirely blocked the replication activity, whereas rifampicin, an inhibitor of RNA polymerase, showed a significant effect only when added prior to initiation of the DNA replication. DNA replication was initiated from a region near to or within the four direct repeats in lambda origin (lambda ori) and proceeded bidirectionally, as examined by DNA chain elongation termination with dideoxy CTP. A cloned DNA carrying a 350-base-pair region including the initiation site also initiated replication, dependent on O and P proteins, and its initiation occurred at the same position as with native lambda dv DNA. An A + T-rich structure neighboring the repeats was found to be essential for lambda DNA replication. Regions corresponding to ice and oop were not required for O,P-dependent initiation.

Identification of sequences necessary for packaging DNA into lambda phage heads

Several species of DNA molecules are packaged into lambda phage heads if they carry the region around the cohesive end site of lambda phage (cos lambda). The minimal functional sequence around cos lambda needed for packaging was examined by cloning in pBR322. The results showed that the minimal region contained 85 bp around cos lambda; 45 bp of the left arm of lambda phage and 40 bp of the right arm. A 75-bp region located to the right of the minimal region seems to enhance packaging. A 223-bp fragment containing these regions can be used as a portable element for plasmid DNA packaging into lambda phage heads. Plasmid ppBest 322, a derivative of pBR322 carrying this portable packager and both amp and tet genes, was constructed. This plasmid is useful for cloning of large DNA fragments.

Bacteriophage lambda initiators: preparation from a strain that overproduces the O and P proteins

A recombinant plasmid was constructed which carries bacteriophage lambda initiator genes O and P under control of tandemly arranged PL and PR promoters. These promoters were repressed by a thermosensitive repressor, cI857, at low temperature, but became active when the culture was incubated at 42 degrees C. Upon elevation of the temperature, the O and P proteins were overproduced to the extent that they constituted several per cent of the total E. coli cellular proteins. Both the O and P proteins have been purified to apparent homogeneity, and were shown to consist of 298 and 233 amino acid residues, respectively. The amino acid composition and the terminal partial amino acid sequence of each protein were determined. Through these analyses, the locations of the O and P genes in the known lambda DNA sequence were determined. The termination codon for the O gene overlaps with the initiation codon for the P gene. The purified O protein binds specifically to the replication origin of lambda (lambda ori) in accordance with our previous observations. The purified P protein inhibits an ATPase activity of dnaB protein.

Detection and mapping of six miniF-encoded proteins by cloning analysis of dissected miniF segments

Various DNA subfragments were derived from miniF DNA by complete or partial PstI cleavage, and cloned in the plasmid vectors pBR322 or lambda dv1. The recombinant plasmids obtained were introduced into an Escherichia coli minicell-producing strain, and the plasmid-coded proteins were radiolabeled and analyzed by gel electrophoresis. Six miniF-encoded proteins, larger than 11 000 daltons, were detected and their coding regions were mapped on the F plasmid genome. Three of them were assigned by taking into account the known nucleotide sequences (Murotsu et al. 1981; K. Yoshioka, personal communication). The coding directions of some proteins were determined by inserting the lac promotor into one of the recombinant plasmids and analyzing the increase in production of the proteins. The coding direction of the five proteins analyzed so far was uniform. Comparison of these results with a functional map of miniF suggested possible roles of the proteins.

Acute effects of ethanol and acetaldehyde on plasma phosphate level

Oral administration of ethanol in a dose of 65 mmol kg-1 produced marked change of plasma phosphate level in rabbits. Hypophosphataemia was observed for the first 2 h after administration followed by significant increase of plasma phosphate at 5 h. Hypophosphataemia did not appear when ethanol was given to the rabbits pretreated with pyrazole. When animals were injected with disulfiram in advance, the duration of hyperphosphataemia due to ethanol was prolonged. Administration of acetaldehyde at a dose of 1.5 mmol kg-1 produced hyperphosphataemia. In this study, plasma phosphate was not associated with change in calcium level. These results suggest that the hypophosphataemia observed was related to the metabolic process of ethanol utilizing alcohol dehydrogenase, and that acetaldehyde, a metabolite of ethanol, might induce the hyperphosphataemia in the animals.

Changes in ambulatory activities and muscle relaxation in rats after repeated doses of diazepam

Changes in rat ambulatory activity and muscle tone after diazepam treatments (2.5, 5, 10, and 20 mg/kg orally) were compared under single and repeated (for 2, 4, 7, and 14 days) administration schedules. Ambulatory activity in the open field test was enhanced by a single dose of 2.5 mg/kg and reduced by 20 mg/kg. However, after all repeated treatment schedules, diazepam resulted in dose-dependent elevations of activity. Even with a treatment period of only 2 days, 20 mg/kg diazepam produced a marked increase in ambulation, which became more conspicuous with increases in the treatment periods. Acutely administered diazepam produced a dose-dependent reduction in muscle tone, but tolerance was noted to this effect during repeated administrations. Thus, time- and dose-dependent increases in ambulation during repeated treatments with diazepam can be partially explained by time-dependent tolerance development to its muscle relaxant effects. The enhancement in ambulation after short-term repetitive dosings of benzodiazepines can be used as a simple indicator for detecting their disinhibitory potentials.

Nine unique repeating sequences in a region essential for replication and incompatibility of the mini-F plasmid

The nucleotide sequence of a 2248 bp portion of the plasmid mini-F has been determined. This region includes the replication origin and all of the plasmid-coded information required for replication. The same region is also capable of expressing incompatibility. A striking feature of the sequence is the presence of nine 19-bp repeating units. Four of these repeats, all arranged in one direction, comprise a cluster, and the remaining five, all arranged in the opposite direction, comprise another cluster. These clusters are separated by a region of about 850 bp that encodes a hypothetical 29-kd polypeptide. This region has sequences highly homologous to those found in the origin regions of the Escherichia coli (Sugimoto et al., 1979; Meijer et al., 1979) and Salmonella typhimurium (Zyskind and Smith, 1980) genomes.

Replication control and switch-off function as observed with a mini-F factor plasmid

Mini-F is a fragment of the F plasmid, consisting of 9,000 base pairs, which carries all of the genes and sites required for replicon maintenance and control. Its copy number is one to two per chromosome. This plasmid is joined to ColE1, whose copy number is 16 to 20. Under normal circumstances the composite plasmid replication exhibited ColE1 characteristics, maintaining a high copy number. However, when ColE1 replication was inhibited by deoxyribonucleic acid polymerase I inactivation, its replication exhibited mini-F characteristics, maintaining a low copy number. These observations are in complete agreement with those of Timmis et al. (Proc. Natl. Acad. Sci. U.S.A. 71:4556-4560, 1974), who examined the behavior of a recombinant plasmid formed between pSC101 and ColE1. The transition from high to low copy number allowed us to examine the control system acting in cells carrying plasmids exhibiting intermediate copy numbers. The initiation of the mini-F replication system as represented by deoxyribonucleic acid synthesis of the composite plasmid was completely blocked when there were multiple copies of mini-F in a cell. It was not restored until the copy number was lowered to one to two, after which replication was first detected. ppF, a mini-F replicon packaged in a phage lambda head behaved similarly: its replication was completely shut off when the resident mini-F genome copy number was high and was inhibited partially when the resident mini-F genome copy number was low. These experiments clearly demonstrate that there is a switch-off mechanism acting on deoxyribonucleic acid synthesis (initiation) in a cell carrying mini-F, and its intensity is related to the plasmid copy number. This result supports the "inhibitor dilution model" proposed by Pritchard et al. (Symp. Soc. Gen. Microbiol. 19:263-297, 1969). The nature of the hypothetical inhibitor is discussed.

Structure of the baboon endogenous virus genome: cloning of circular virus DNA in bacteriophage lambda

Linear, small and large circular forms of unintegrated viral DNAs were detected in Hirt supernatant fraction of human cultured cells infected with baboon endogenous virus M7. The circular M7 DNAs were cloned in bacteriophage lambda, Charon 28. Seventeen independent clones were isolated and analyzed by restriction endonuclease mapping. Nine clones were carrying a viral sequence of 8.6 kilobase pairs (kb) with two tandem repeats of 0.6 kb, which correspond to the large circular form of the unintegrated M7 DNA. Eight other clones had the viral insert of 8.0 kb, i. e., the small circular form, and were deleted one of the repeated sequences. The repeated sequences correspond to the long terminal repeats of 0.6 kb, located at both ends of the linear M7 DNA of 8.6 kb. One of the recombinants of the large circular M7 DNA had an inversion of 2.5 kb. One end of the inverted sequence was near the terminus of the long terminal repeats and the other in the gag gene region. The inversion seems to be occurred by integration of a viral DNA within itself during early periods of infection. The mechanism of the processes leading to integration is discussed from the structure of these unintegrated M7 DNAs as the precursors.

Purified bacteriophage lambda O protein binds to four repeating sequences at the lambda replication origin

The bacteriophage lambda O protein is needed for initiation of lambda DNA replication. Several lines of evidence suggest that initiation requires that this protein interacts with a specific sequence called ori (for origin) in lambda DNA. We have purified this protein to near homogeneity and studied the protection against nuclease cleavage of the origin DNA sequences. Our data demonstrate that the O protein binds within an interval of about 95 base pairs (bp), which contains four tandemly arranged 19bp repeating sequences, ATCCCTCAAAACGA (G)GG GAT(A). At a low concentration of O protein, the inner two repeats are primarily covered, while binding to the outer two repeats requires a high concentration of O protein. From the molecular size of O protein (32,000 daltons), and the internal symmetry in each 19bp repeat, we inferred that the O protein may bind in dimeric form, and that the 95bp region may be filled only when four such dimers have bound. This interaction is discussed in connection with the "activation" of the ori by O protein leading to initiation of DNA synthesis.

Purification of bacteriophage lambda O protein that specifically binds to the origin of replication

By means of a nitrocellulose filter binding assay, DNA binding activities among proteins fractionated from extracts of Escherichia coli carrying lambda dv have been surveyed. An activity was found that binds specifically to a fragment of 164 base pairs that specifies the lambda replication origin (lambda ori). This activity was not detected in an extract of cells not carrying the lambda dv plasmid. The activity was detected in extracts of cells carrying a hybrid plasmid in which the entire lambda O gene had been cloned and placed under the control of the lac promoter. Deletion of a 60 base pair segment in the 'amino-terminal region' of the O gene abolished this activity, indicating that the lambda ori binding protein is coded for by the lambda O gene. The ori-specific binding protein was purified by five fractionation steps. The most purified preparation consists of a major polypepide that migrates with a molecular weight of 32,000 in SDS-polyacrylamide gel electrophoresis. Binding of O protein to ori occurs in the absence of other protein aceous components.

Role of an autorepression system in the control of lambda dv plasmid copy number and incompatibility

The lambda dv plasmid genome is composed of two regions: (1) the autorepressor region which consists of promoter-operator (pRoR) and autorepressor (tof) and (2) the origin region which consists of the origin of replication (ori) and two initiator genes (O and P) (Matsubara 1976). Replication of this plasmid is directly connected with transcription from pRoR. Using lambda dvs having various mutations in pRoR, the transcription ability was examined in detail in connection with the control mechanism of replication. The transcription ability of the autorepressor region is controlled by the binding affinity of the tof protein and pRoR. Thus, at steady-state, lambda dvs carrying a highly-constitutive ('strong') pRoR produced the autorepressor at high levels, whereas those carrying a low-constitutive ('weak') pRoR produced the autorepressor at low levels. This relationship did not change even when a fragment of lambda dv genome covering the autorepressor region was cloned into the plasmids pBR322 and pSC138, which could be maintained in a fixed amount within a cell. It was also shown that the autorepressor level at steady-state is a function of copy number of the DNA carrying the region for autorepression. These observations fit the autorepression model of Sompayrac and Maaløe (1973), which predicts that a decreased level of autorepressor activates pRoR and initiates transcription which leads to the production of tof protein until a new steady-state is established. By the same token, if the affinity of autorepressor and pRoR is decreased, pRoR remains active until a higher level of autorepressor is produced. Transcription of the autorepressor region directly affects the level of transcription of the origin region which is located distal to the promoter. Thus, the ability to replicate is connected with an ability to produce autorepressor. The lambda dv plasmids with 'strong' or 'weak' pRoR were maintained at a high or low copy number, respectively. The phenomenon of incompatibility of lambda dv was also examined using pBR322 and pSC138 plasmids carrying the cloned autorepressor region of lambda dv. The chimeric plasmids with 'strong' pRoR exhibited strong incompatibility with lambda dv, whereas those with 'weak' pRoR showed weak incompatibility. This indicates that interaction of the autorepressor and pRoR is related to the incompatibility of lambda dv plasmids.

A new method for detecting diatoms in human organs

A new method for diatom detection is described. It includes an ultrasonic irradiation procedure with the use of a tissue solubilizer. The method is easy to carry out and is less time-consuming than previous techniques.

[The comparative study of renogram both in case of dehydration and hydration (author's transl)]

In order to study the merit or demerit of the dehydration or hydration as the preparation of renographic examination, the following 25 cases--11 cases of uterine cancer, 2 cases of breast cancer, a case of esophageal cancer, pharyngeal cancer, maxillary cancer, salivary gland tumor, leiomyosarcoma of uterus and others are examined by renography using 131I-hippurate. Renogram is performed in case of patient's dehydration and followed in case of patient's hydration with 600 ml of water intake. Renographic findings such as Tmax, T1/2, HB/HA and step-like pattern are studied as a parameter. Following 600 ml water intake, Tmax is significantly shortened and the step-like pattern is disappeared. This study is strongly suggested that patient's hydration is significantly necessary in the performance of renogram as the preparatory procedure.

[Clinical evaluation of 67Ga-citrate scintigraphy with reference to tumor detectability (author's transl)]

The clinical usefulness of 67Ga-citrate whole body scanning is evaluated in 178 cases of the various diseases in a period of 1976-1978. The cases are 59 cases of thoracic lesions, 41 cases of head and neck lesions, 35 cases of abdominal, bone, and soft tissue lesions, and 43 cases of benign and malignant lymphoma. The clinical results and detectability of various known lesions are shown in tables 1, 2, 3 and 4. The detectability of unknown lesions of malignant lymphoma is shown in table 5. The study demonstrates the particular clinical values of 67Ga-citrate scan in detectability of unknown lesions to be in cases of malignant lymphoma.

The pharmacology of 20681-S and 20682-S, 6-oxo-N-cyclopropylmethylmorphinans, as narcotic antagonist analgesics

It has been demonstrated that L-3hydroxy-6-oxo-N-cyclopropylmethylmorphinan methansulfonate (20681-S) and L-3,14-dihydroxy-6-oxo-N-cyclopropylmethylmorphinan methansulfonate (20682-S), have antinociceptive and narcotic antagonistic properties. In the rodent antinociceptive test, the action of 20681-S was more potent and of longer duration than that of morphine and of cyclazocine after subcutaneous or oral administration. The antinociceptive effect of 20682-S ranked between that of morphine and that of pentazocine in the mouse acetic acid-writhing test. Both compounds possessed potent narcotic antagonistic activities, 20682-S being more active than naloxone and oxilorphan and 20681-S being equipotent with cyclazocine. The latent side effects (respiratory depression and fall in blood pressure) and the acute toxicity of 20681-S and 20682-S, were less than those of reference narcotic antagonists or of narcotic antagonist analgesics.

Construction and some properties of packageable plasmid F

A derivative of plasmid F which is packageable in lambda phage coat was constructed using techniques of in vitro recombination. This plasmid is composed of three DNA fragments generated by restriction enzyme EcoRI: a miniF fragment (fragment f5 of F'lac) which is able to replicate autonomously, a DNA fragment from Staphylococcus plasmid that carries the beta-lactamase gene, and a portion of guaA (B) transducing lambda phage DNA carrying lambda cohesive ends (cos site) along with almost all the late genes but devoid of all those genes and sites that are needed for replication, regulation, and recombination. The hybrid plasmid has a molecular weight of 2.7 x 10(7) daltons, about 84% size of lambda phage genome, and can be packaged in lambda coat when helper phage replicates in the plasmid-carrier cell. The packaged plasmid and the helper lambda phage particles are separated by CsCl density gradient centrifugation. The replication characteristics of the recombinant plasmid are all those of F including the copy number, incompatibility, and curing with acidine orange. The packaged plasmid is injected into an F- cell and establishes a plasmid state with normal efficiency. In F+ or Hfr cells, the resident F factor hinders this process.

Vascular anatomy of the inner ear of the guinea pig--a sem study of the corrosion cast--

This paper shows a casting method of the vascular system of the inner ear of the guinea pig with the use of fluid resin injected intravascularly and the observation of those specimens by means of the scanning electron microscopy. First, fluid resin was injected into the blood vessels of a live or just sacrificed guinea pig. After taking the temporal bone out of the animal, it was decalcified and macerated completely. Then, a cast of the inner ear vessels was taken and observed with a scanning electron microscope. A pair of photos differing in teh view angle by seven degrees were taken simultaneously, and observed with a stereoviewer. This technique brought photographs of well magnified three-dimensional construction of the inner ear blood vessels.