[Fundamental and applied aspects of research on the virus-like plasmids of the yeast Saccharomyces]. / Fundamental'nye i prikladnye aspekty izucheniia virusopodobnykh plazmid drozhzhei sakharomitsetov.

Six types of the antagonistic activity (AA) in Saccharomyces were distinguished and characterized. The K1, K2, K3 and K6 activities were associated with the presence of the two kinds of cytoplasmic killer virus-like particles (VLP)--cytoplasmic double-stranded RNAs (dsRNAs) consisting of the main (L) and minor (M) species. All four antagonistic groups contained the L dsRNAs of the same size. The size of the M dsRNAs are dependent on the origin of the host strain. The cytoplasmic inheritance of the K4 activity was observed among the strains which contained no dsRNAs. The AA of this type was not connected with the integrity of mitochondria, also. The K5 activity was under chromosomal control. The optimum and the limits of pH for detection of the AA were dependent on the type of activity. The natural route of extracellular infection by the killer VLPs was the penetration of the VLP into the early protoplast-like spore sprouts. The variability of the K2 activity was studied through mutagenesis of the marked genetic stocks. Twenty six chromosomal genes were involved in the control of this activity. Most of these genetic determinants differed from the chromosomal determinants of the K1 activity in their phenotypes or localization. Four phenotypically different mutational defects of the M-2 plasmid affected the manifestation of the K2 character. Epistatic and cumulative interactions between mutant chromosomal genes controlling the reproduction of the K2 plasmids were observed. Having compared the peculiarities of genetic control of the mutant phenotypes of the K1 and the K2 killers, we acquired the ability to propose a functional model of regulation of the killer virus-like plasmids reproduction. This model defines the interactions between hypothetical gene products and killer dsRNAs or their intermediates. The perspectives of selection of dsRNAs producers were studied. The methods for construction and maintaining the productive strains from the diploids homozygous for a chromosomal mutation increasing the copy number of both K2 killer plasmids were developed. These methods assisted in obtaining the producers suitable for large-scale cultivation.

[Chromosome polymorphism in the yeast Saccharomyces]. / Polimorfizm khromosome u drozhzhei Sakharomitsetov.

The variability of chromosomal band patterns was determined by pulse electrophoresis. The natural strains differed by the quantity and electrophoretic mobility of chromosomal DNA bands. The strains of independent genetic stocks originated from the XII race of Saccharomyces cerevisiae showed less significant difference in band patterns than the strains of different species of the Saccharomyces genus. The progeny of among strains with different karyotypes hybrid showed non-regular segregation of parental bands, the occurrence of new bands and the bands with altered mobility. Reverse crosses of hybrid progeny with strains of Peterhoff genetic stocks of S. cerevisiae led to decrease in chromosomal polymorphism. Homozygotization for ski5 allele and selection for increasing the copy number of killer plasmids was accompanied with repeated splash of polymorphism in 1-2 generations of intratetrad and intrafamily crossed hybrid progeny. Subsequent stabilization of electrophoretic karyotype took place, excluding the mendelian dimorphism of chromosome III, with was a stable trait of the last 6 generations of that progeny.

[Genetic strains of Hansenula polymorpha]. / Geneticheskie linii drozhzhei Hansenula polymorpha.

Six centromeric linkage groups and four non-centromeric fragments are revealed in the genetic stocks of Hansenula polymorpha which were obtained by intratetrad breeding in several generations of two genetically different parental strains progeny. Fourteen nuclear markers are mapped, including auxotrophic mutations, mating regulation loci, determinants of sporulation and heat tolerance. Complex origin of the haploid genome of these stocks leads to affinity interactions and to 14 per cent increase in DNA content in haploid stocks, as compared with the parental strains.

[Genetic control of the number of copies of type K2 killer plasmids in Saccharomyces cerevisiae]. / Geneticheskii kontrol' kopiinosti killernykh plazmid tipa K2 u Saccharomyces cerevisiae.

13 non-linked chromosomal mutations derepress the negative genetic control of copy number of K2 yeast killer plasmids and lead to 1.5-2-fold elevating of copy number of that type plasmids -L2A and M2 virus-like dsRNA. The content of both plasmids is increased 3-5-fold in cells with chromosomal ski5 mutation, as compared to the strains of wild type. Expression of ski5 allele is recessive. The dose effect of this allele is observed on haploid and diploid levels. Dominant ochre nonsense suppressors suppress the action of ski5 and the ski6 allele epistates that of ski5.

[A new type of antagonistic activity of Saccharomycetes yeasts and its mode of inheritance]. / Novyi tip antagonisticheskoi aktivnosti drozhzhei sakharomitsetov i kharakter ego nasledovaniia.

New type of killer activity of Saccharomyces cerevisiae was found. About 40% of this yeast strains tested formed growth inhibition zones on the lawn of the sensitive yeast Pachysolen tannophilus (Boldin et Adzet) BKM y-274. As shown by crossing these killers with non-killers and the tetrad analysis of hybrids obtained, 2 killer: 2 non-killer segregation took place, indicating the chromosomal mode of inheritance of the character. Mutants with weak expression of this killer activity were obtained after treating with 5-fluorouracil and cycloheximide.

[Killer systems of Saccharomyces cerevisiae yeasts]. / Killernye sistemy drozhzhei Saccharomyces cerevisiae.

The killer systems of Saccharomyces cerevisiae are a peculiar group of cytoplasmic symbionts of primitive eukaryotes. The genetic material of these symbionts is double-stranded RNA. Their basic properties are linearity of genome, its fragmentation, resulting in two separately replicating major and minor segments, and the ability to control the synthesis of secretory proteins--mycocins which can kill the taxonomically related strains. Secretion of mycocins also confers immunity to their action. The strains containing killer symbionts are toxigenic and resistant to their own toxins, while those with no killer double-stranded RNA are sensitive to mycocins. The killer systems of Saccharomyces cerevisiae possess some properties relevant to viruses and evidently are evolved during the evolution of infectious viruses. Occurrence of such systems in monocellular eucaryotic organisms is an example of genome complication in the course of putting together the virus-like components. The peculiarities of replication and expression of killer systems and their utilization for the construction of vector molecules are discussed.

[Transformation of the yeast Hansenula polymorpha by a hybrid plasmid containing the fragment of host DNA]. / Transformatsiia drozhzhei Hansenula polymorpha gibridnoi plazmidoi,soderzhashchei fragment khoziaiskoi DNK.

Spheroplasts of Hansenula polymorpha strain deficient in 2-isopropylmalate dehydrogenase have been shown to be transformed by the DNA of a hybrid plasmid pHRI, carrying the LEU2 gene from S. cerevisiae and 2.0 kilobase HindIII fragment of H. polymorpha genomic DNA. The frequency of transformants has reached 10(3) per 1 microgram of transforming DNA. Plasmid pHRI is maintained in transformants as an autonomous circular DNA molecule and is inherited by 1-2% fraction of cells from the population growing under the selective conditions. Transformation takes place under the same conditions that are required for spheroplast fusion. Thus, H. polymorpha becomes one more species of yeast susceptible to hybrid plasmid-mediated gene transfer in the process of DNA transformation.

[Interferon-inducing and antiviral activity of dsRNA of yeast origin]. / Interferonindutsiruiushchaia i protivovirusnaia aktivnost' dsRNK drozhzhevogo proiskhozhdeniia.

The paper describes derivation of double-stranded RNA from K plasmid of Sachcaromyces cerevisiae yeast by means of electrophoresis in agar gel and by differential salting out with 4 M lithium chloride. Studies in vitro and in vivo demonstrated a high interferon-inducing and antiviral activity of dsRNA preparations from the yeast plasmid.

[Nuclear mutants of Saccharomyces cerevisiae K2 yeasts with decreased killer activity]. / Iadernye mutanty drozhzhei Saccharomyces cerevisiae K2 s ponizhennoi ubivaiushchei aktivnost'iu.

Recessive mutations in two chromosomal unlinked genes kir1 and kir2 of Saccharomyces cerevisiae K2 result in weak killer activity or in complete loss of killer capacity. Kir1 is located on chromosome 7 and is linked to ade7 and ski6. The kir1 and kir2 mutants reveal no alteration of cell membrane. They normally excrete acid phosphatase and have a normal level of mating and sporulation. The analysis of the plasmid nucleic acid in two strains containing the mutant alleles kir1-12 and kir2-23 shows the increased content of L double-stranded DNA, the content of M double-stranded RNA being increased.

["Killer" plasmid mutants obtained by exposure to 5-fluorouracil]. / Issledovanie mutantov plazmidy "killer", poluchennykh pod vozdeistviem 5-ftoruratsila.

Weak killers were tolerated from a killer strain of type k2 of Saccharomyces cerevisiae by treatment with 5-fluorouracil. They segregated sensitive clones during vegetative growth with a frequency from 2 to 20 per cent (nonstable killers, Knst mutants). Alteration of killer activity in these mutants is the result of a mutation in the cytoplasmic killer determinant (KIL-k). The mutant form of this determinant, KIL-nst, partially suppresses the wild type determinant. K-nst have the same dsRNA composition as the wild type killer strain. In some mutants the decrease in M dsRNA amount is possible. The segregation of sensitive mitotic clones of these mutants is probably connected with secondary alterations of the KIL-nst determinant.

["Killer" plasmid in natural strains of Saccharomyces]. / Plazmida "killer" u prirodnykh shtammov Saccharomyces.

Double stranded RNA's of thirteen wine strains of Saccharomyces belonging to different species and exhibiting killing activity were studied. Two strains of Oxford genetic stocks were used for control. All these strains have four different spectra of killer activity and contain two double stranded RNAs, L and M. All strains regardless of the type of killer activity have the same electrophoretic mobility of L. The mobility of M varies in different strains but is not connected with the spectrum of killing activity. All strains can be cured by cycloheximide. Cured variants have no M. Certain cured strains contain small portions of double stranded RNAs with electrophoretical mobility faster than of M.

Virus-like particles in yeast: isolation and infectivity.

Virus-like particles containing electron dense cores are seen in thin sections of intact and degenerated cells of a thermosensitive (ts) strain of Candida tropicalis. A particulate fraction not present in wild-type cells has been isolated from the ts cells disrupted by pressure. The particles are 80-120 nm in diameter. Empty particles with a central cavity are observed. The method of infecting mating pairs of Saccharomyces cerevisiae by partially purified particles is described.

Double-stranded RNA of homothallic Saccharomycetes with different cytoplasmic determinants of antagonistic activity.

Double-stranded RNA of high molecular weight is found in the cytoplasm of the "killer" strain M-437-2. The RNA is homogeneous and contains no single strand poly(A) portions. The double-stranded RNA is associated with the cytoplasmic microsomes of strain M-437-2 and is contained in the fraction of the cell contents of this strain that was used to infect germinating spores of the sensitive S. cerevisiae 768(1)-15 with the cytoplasmic determinant [k]. The absence of this RNA in cells of the initial sensitive strain 768(1)-15, and its appearance in the "killer" derivative of this strain produced by infection with the determinant [k] by means of the above-mentioned fraction, indicate that the killer activity is due to the double-stranded RNA. The retention of the double-stranded RNA in the cytoplasm of derivatives of the newly-formed killer strain, containing the cytoplasmic determinants [k(ts)] and [n] suggests also that these determinants are a modification of determinant [k].

[Radiosensitive mutants of Escherichia coli with disrupted cell membrane permeability]. / Radiochuvstvitel'nye mutanty Escherichia coli s narushennoi pronitsaemost'iu kletochnoi obolochki

Membrane proteins and cell permeability of Escherichia coli B/r and different substrains of B/r containing mutations of loci uvrB, exrA, lon and suppressors of that mutations were studied. Membrane proteins were found to be modified only in E. coli B/r exrA. The content of 40 000--70 000 D polypeptides was increased and the content of 80 000--100 000 D polypeptides was decreased. Alteration of membrane proteins in E. coli B/r exrA was associated with the impaired permeability of cell membrane.

[Phenotypic characteristics of temperature-sensitive mutants of bacteriophage T4 in gene 19]. / Fenotipicheskaia kharakteristika temperaturochuvstvitel'nykh mutantov bakteriofaga T4 po genu 19

The order of three thermosensitive mutations in gene 19 is determined and compared with the character of defective structures observed in an electrone microscope study of the lysates obtained in non-permissive and semi-permissive conditions. The degree of defectiveness of core polymerization increases if the mutation is located near the beginning of the gene. In one the combinations among these mutants the interallelic complementation is found. The mechanism of complementation is discussed on the basis of the electrone microscopic pattern. The polymerization of core protein in vivo starts from the base plate.

[Dominant nonsense suppressors restricting the killer activity in Saccharomyces cerevisiae]. / Dominantnye nonsens-supressory, podavliaiushchie antagonisticheskuiu aktivnost' drozhzhei Saccharomyces cerevisiae

Dominant suppressors of the first type nonsense mutations, ade1-6, hisX, lys9-A21 and leu2-2, inhibit the killer activity in Peterhoff genetic stocks of Saccharomyces cerevisiae. Phenotypes CN (weak killer at 20 degrees, neutral at 32 degrees) and N (neutral at both temperatures) arising in the presence of the suppressors in killer strains are dominant toward S phenotype and toward K phenotype.