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J Maniloff

Publications and source records attributed to J Maniloff.

At least 37 records · Page 2Linked to original sources
PubMed1987

Mapping of mycoplasma virus DNA replication origins and termini.

A pulse-labeling protocol has been used to study DNA replication and map replication origins and termini in mycoplasma viruses L2 and L2ins1. The L2 genome is circular, double-stranded DNA of 11.63 kilobase pairs (kb), and the 14.89-kb L2ins1 genome is L2 DNA containing a 3.26-kb insertion. The data show that DNA replication is bidirectional from two origins in L2 and three origins in L2ins1. The extra origin in L2ins1 arises from the fact that one of the L2 origins is in one of the sequences that have been shown to be duplicated and transposed in the generation of L2ins1 from L2.

Acholeplasma laidlawii↗
PubMed1987

Endonuclease from Acholeplasma laidlawii strain JA1 associated with in vivo restriction of DNA containing 5-methylcytosine.

Transfection of Acholeplasma laidlawii strain JA1 with viral DNAs that have been sequence-specifically methylated in vitro has led us to previously postulate that JA1 cells contain an enzyme which cleaves only DNA containing 5-methylcytosine, regardless of the nucleotide sequence containing that base. In this paper we show that an endonuclease activity is present in extracts from JA1 cells but not in extracts from a restriction-deficient variant of JA1. The partially purified enzyme cleaves not only DNA containing 5-methylcytosine, but also DNA containing no methylated bases. We discuss why this endonuclease activity may not have the same in vitro specificity as would be expected from in vivo experiments.

5-Methylcytosine↗
PubMed1987

Characterization of monoclonal IgG cryoglobulins: fine-structural and morphological analysis.

The morphology of the amorphous, gelatinous, and crystalline varieties of monoclonal IgG cryoglobulins was analyzed by light and transmission and scanning electron microscopy. Each cryoglobulin had a characteristic fine structure that correlated with its gross morphology. Transmission electron microscopy showed that the amorphous precipitates were random and disorganized molecular clumps. In contrast, cryogels were thin-walled, well-organized, and hydrated strawlike clusters, whereas cryocrystals formed tightly compacted, highly structured molecular clusters. Crystals that formed in blood produced rouleaux, and analysis by scanning electron microscopy indicated that the crystals could form thick-walled, branching, macromolecular nets that could physically trap cells. The morphological properties provided visual impressions by which cryoglobulins could cause clinical disease secondary to vascular occlusion produced by self-associated IgG cryoglobulin molecules.

Cryoglobulins↗
PubMed1986

Chromosome analysis by two-dimensional fingerprinting.

A two-dimensional fingerprinting technique has been developed that allows large, cell genome-size DNA's to be analyzed by restriction endonuclease cleavage and separation of DNA fragments by agarose gel electrophoresis. Equations have been derived to determine the genome size and number of cleavage sites from analysis of the distribution of fragment lengths. Genome sizes of Escherichia coli strain JM101 and two strains of the mycoplasma Acholeplasma laidlawii measured by this method are in agreement with published values. Other uses of two-dimensional fingerprinting for studies of prokaryotic and eukaryotic genome structure and organization are described.

Acholeplasma laidlawii↗
PubMed1986

Mycoplasma restriction: identification of a new type of restriction specificity for DNA containing 5-methylcytosine.

Mycoplasma bacteriophage L51 single-stranded DNA and L2 double-stranded DNA are host cell modified and restricted when they transfect Acholeplasma laidlawii JA1 and K2 cells. The L51 genome has a single restriction endonuclease MboI site (recognition sequence GATC), which contains 5-methylcytosine when the DNA is isolated from L51 phage grown in K2 cells but is unmethylated when the DNA is from phage grown in JA1 cells. This GATC sequence is nonessential, since an L51 mutant in which the MboI site was deleted was still viable. DNA from this deletion mutant phage was not restricted during transfection of either strain K2 or JA1. Therefore, strain K2 restricts DNA containing the sequence GATC, and strain JA1 restricts DNA containing the sequence GAT 5-methylcytosine. We conclude that K2 cells have a restriction system specific for DNA containing the sequence GATC and protect their DNA by methylating cytosine in this sequence. In contrast, JA1 cells (which contain no methylated DNA bases) have a newly discovered type of restriction-modification system. From results of studies of the restriction of specifically methylated DNAs, we conclude that JA1 cells restrict DNA containing 5-methylcytosine, regardless of the nucleotide sequence containing 5-methylcytosine. This is the first report of a DNA restriction activity specific for a single (methylated) base. Modification in this system is the absence of cytosine methylating activity. A restriction-deficient variant of strain JA1, which retains the JA1 modification phenotype, was isolated, indicating that JA1 cells have a gene product with restriction specificity for DNA containing 5-methylcytosine.

5-Methylcytosine↗
PubMed1986

Isolation of mycoplasma virus L2 insertion variants and miniviruses.

We isolated two spontaneous variants of mycoplasma virus L2. Both variants, designated L2ins1 and L2ins2, contained a 3.1-kilobase-pair (kbp) insertion in the 11.8-kbp wild-type L2 genome. The insert DNA was shown to be derived from two noncontiguous regions of the L2 genome, and L2ins1 and L2ins2 differed only in the location of the 3.1-kbp insertion. We also isolated L2 miniviruses from serial passages of L2, L2ins1, and L2ins2 viruses. Miniviruses contained circular DNA molecules of 3.1 kbp or multimers of 3.1 kbp. Minivirus 3.1-kbp DNAs had the same sequences as the 3.1-kbp insert DNAs found in L2ins1 and L2ins2 viruses. Miniviruses were not infectious and interfered with the growth of L2, L2ins1, and L2ins2 viruses; hence, L2 miniviruses appeared to be defective interfering particles.

Acholeplasma laidlawii↗
PubMed1985

Transfection of REP- mycoplasmas with viral single-stranded DNA.

Double-stranded DNA from mycoplasma virus L2 can transfect Acholeplasma laidlawii cells in the presence of polyethylene glycol (T. L. Sladek and J. Maniloff, J. Bacteriol. 155:734-741, 1983). We report here that both single-stranded DNA and double-stranded replicative form DNA, from the single-stranded DNA mycoplasma virus L51, are also infectious in this system. For both DNAs transfection frequencies were in the range of 10(-8) transfectants per DNA molecule and 10(-3) transfectants per CFU. An unexpected finding was that both DNAs could transfect A. laidlawii strain REP-, a variant which is a nonpermissive host for single-stranded DNA mycoplasma viruses due to a block in viral DNA replication (Nowak et al., J. Bacteriol. 127:832-836, 1976). The number of viruses produced by transfected REP- cells was comparable to the number produced by both transfected and infected wild-type cells. Therefore, transfected L51 DNAs are able to bypass the replication block in REP- cells that occurs when these cells are infected by L51 virions.

Acholeplasma laidlawii↗
PubMed1985

Identification of an enveloped phage, mycoplasma virus L172, that contains a 14-kilobase single-stranded DNA genome.

We have found that mycoplasma virus L172 is an enveloped globular virion containing circular, single-stranded DNA of 14.0 kilobases. L172 has been reported by other workers to have a double-stranded DNA genome of 13 to 17 kilobase pairs and has been classified as a plasmavirus, a group for which mycoplasma virus L2 is the type member. Mycoplasma viruses L172 and L2 differ in genome size and structure, DNA base composition, and protein composition, and they have no detectable DNA homology. As the only reported enveloped virion containing single-stranded DNA, L172 represents a new group of viruses.

Acholeplasma laidlawii↗
PubMed1985

Heterogeneous progeny viruses are produced by a budding enveloped phage.

Infection of Acholeplasma laidlawii cells by the temperate enveloped mycoplasma virus L2 results in production of three morphological forms of progeny L2 virus: L2-I, L2-II, and L2-III. These morphological forms can be separated by velocity sedimentation and agarose gel electrophoresis. The latter technique was used to size the quasi-spherical particles: L2-I is 74 nm, L2-II is 88 nm, and L2-III is 132 nm in diameter. The protein composition of the three L2 forms is the same, although there are differences in protein stoichiometric ratios. L2-I, L2-II, and L2-III have the same 11.8 kilobase pair superhelical DNA genome. However, UV inactivation studies and restriction frequency measurements indicate that L2-I and L2-III each contain 1 genome copy, while L2-II contains 2-3 genome copies.

Acholeplasma laidlawii↗
PubMed1984

Effect of novobiocin on mycoplasma virus L2 replication.

L2 is a temperate mycoplasma virus containing 11.8 kilobase pairs of negatively superhelical double-stranded DNA. We observed L2 DNA with less superhelicity in novobiocin-treated cells than that in untreated cells. However, although no change in viral DNA superhelicity could be found in novobiocin-treated novobiocin-resistant cells, L2 production decreased in these novobiocin-treated cells.

Acholeplasma laidlawii↗
PubMed1983

Integration and lysogeny by an enveloped mycoplasma virus.

The 11.8 kilobase pair (7.8 X 10(6) mol. wt.) genome of mycoplasma virus L2 in lysogenic Acholeplasma laidlawii cells was examined. For this study, DNAs were analysed by agarose gel electrophoresis and viral DNA sequences identified by DNA-DNA hybridization. L2 DNA was found to be integrated into the lysogenic host cell chromosome at a unique site in both viral and cellular DNA. The viral DNA site was roughly mapped and the approximate time of integration during the L2 non-cytocidal infectious cycle was determined.

Acholeplasma laidlawii↗
PubMed1983

Polyethylene glycol-dependent transfection of Acholeplasma laidlawii with mycoplasma virus L2 DNA.

Phenol-extracted DNA from mycoplasma virus L2 was able to transfect Acholeplasma laidlawii in the presence of polyethylene glycol. Transfection was sensitive to DNase and was most efficient with 36% (wt/vol) polyethylene glycol 8000 and cells in logarithmic growth. Virus production by the transfected cells was similar to that of the cells infected by intact virus. L2 DNA transfected A. laidlawii with a single-hit dose-response curve, reaching saturation at high DNA concentrations. Optimum transfection frequencies were about 10(-7) transfectants per L2 DNA molecule and 10(-4) transfectants per CFU. When DNA was present in saturating amounts, the number of transfectants increased linearly with the number of CFU present in the transfection mixture, suggesting that DNA uptake does not occur by a mechanism involving cell fusion. The cleavage of the superhelical mycoplasma virus L2 genome with restriction endonucleases that cleave the DNA molecule once reduced the transfection frequency. Host cell modification and restriction of transfecting L2 DNA were similar to those for infecting L2 virions.

Acholeplasma laidlawii↗
PubMed1982

Cytosine methylation of the sequence GATC in a mycoplasma.

Mycoplasma virus L2 is subject to host-specific restriction and modification in Acholeplasma laidlawii strains JA1 and K2. We have examined the DNAs from both host cells and viruses propagated on these strains with respect to susceptibility to cleavage by restriction endonucleases and for DNA base modifications. We show that, in strain K2 and L2 virus grown on K2 cells, cytosine in the sequence GATC is methylated to 5-methylcytosine and, although strain K2 and L2 viruses grown on K2 contain N6-methyladenine in their DNA, adenine in the sequence GATC is not methylated. In contrast to K2, strain JA1 and L2 virus grown on JA1 cells contain no detectable methylated bases. It is not known which of the methylated bases in K2 is the basis for the K2 restriction-modification system operative on L2 virus.

5-Methylcytosine↗
PubMed1982

Adsorption of the tailed mycoplasma virus L3 to cell membranes.

The adsorption properties of the tailed bacteriophage L3 to Acholeplasma laidlawii cells were studied. Adsorption followed a biphasic curve. Reversibility and virus heterogeneity were not sufficient to explain the break in the adsorption curve. Binding studies showed that each colony-forming unit could bind about 350 virions. The electrostatic nature of L3 adsorption was indicated by the effect of cations, pH, and temperature on the adsorption rate constant. L3 adsorption appeared to have a requirement for Ca2+, which could not be replaced by the mono- and divalent cations examined. Ethylene glycol-bis(beta-aminoethyl ether)-N,N-tetraacetic acid inhibition of adsorption was totally reversed by added Ca2+. The effects of EDTA, proteases, and lectins on absorption indicated that membrane proteins are the L3 receptors. The model for L3 adsorption is a multivalent one involving lateral diffusion of adsorbed virions and receptor proteins.

Acholeplasma laidlawii↗
PubMed1982

Replication of mycoplasma virus L51. VII. Effect of chloramphenicol on the synthesis of DNA replicative intermediates.

Chloramphenicol affects several steps in the DNA replication of mycoplasma virus L51, a noncytocidal, naked, bullet-shaped virion containing circular single-stranded (SS) DNA of 1.5 X 10(6) daltons (4.5 kilobases). In the presence of chloramphenicol, adsorption was normal and parental SS DNA was converted to double-stranded replicative forms (RF), but subsequent RF leads to RF replication was inhibited. Chloramphenicol added late in infection, when most viral nascent DNA is in progeny SS molecules, inhibited SS synthesis, but nascent RF molecules were formed. However, a chase experiment showed that these RF molecules could not be converted to SS DNA. Therefore, viral RF molecules made in the presence of chloramphenicol are not functional as SS DNA precursors.

Acholeplasma laidlawii↗
PubMed1981

Cytoskeletal elements in mycoplasmas and other prokaryotes.

This paper reviews the relationship of mycoplasmas to eubacteria, the question of whether mycoplasmas and eubacteria have a cytoskeleton, and whether the unique ultrastructural features of certain mycoplasmas function as a mitotic-like apparatus. Although cytochalasins have inhibitory effects on some mycoplasmas and eubacteria, there are no data indicating that eubacteria have an actin-like protein or other cytoskeletal element. However, the situation for the mycoplasmas remain confusing. While mycoplasma may not contain actin, the data do suggest the presence of other cytoskeletal elements.

Bacteria↗