Molecular Genetic Analysis of the Yeast Komagataea (Williopsis) pratensisStrains Isolated from the Caucasian and Tien Shan Soils

The analysis of sixteen Komagataea (Williopsis) pratensisisolates from Caucasian and Tien Shan soils by the PCR, blot hybridization, and isoenzyme electrophoresis techniques showed that fifteen of them do belong to the species K. pratensis. The isolates from the two geographic areas differed in some physiological characteristics and in the PCR product profiles obtained with the microsatellite primers (CAC)₅and (GACA)₄.     

A new family of polymorphic metallothionein-encoding genes MTH1 (CUP1) and MTH2 in Saccharomyces cerevisiae.

By pulsed-field gel electrophoresis of chromosomal DNA and hybridization with a cloned MTH1 (CUP1) gene, we determined the locations of metallothionein-encoding gene sequences on chromosomes in monosporic cultures of 76 natural strains of Saccharomyces cerevisiae. Most of the strains (68) exhibited a previously known location for the MTH sequence on chromosome (chr.) VIII. Seven strains (resistant or sensitive to Cu2+) showed a MTH sequence in a new locus, MTH2, on chr. XVI. One strain carried an MTH locus on both chromosomes VIII and XVI. Restriction fragment and Southern blot analyses showed that the two MTH loci were very closely related. The strains displayed heterogeneity in the size and structure of their MTH2 locus. The length of the repeat unit of MTH2 varied: a 1.9-kb or 1.7-kb unit was found, instead of the 2.0-kb unit of the MTH1 locus. The most resistant strain (resistant to 1.2 mM CuSO4) contained a 0.9-kb repeat unit in addition to those of 1.9 kb and 1.7 kb. All three sensitive (to over 0.3 mM CuSO4) strains with an mth2 locus had a repeat unit of 1.9 kb or 1.7 kb, suggesting the presence of at least two copies of the MTH2 gene, with one always being in the junction area outside of the repeat unit. A monogenic tetrad segregation of 2:2 was usually found in crosses of resistant MTH2 and sensitive mth2 strains. Hybrids between strains with different MTH loci in all combinations showed low ascospore viability, suggesting that the complete lack of an MTH locus may lead to the death of segregants on YPD medium. The MTH1 and MTH2 loci were exchangeable. Strains with a high level of Cu2+ resistance were also resistant to Cd2+. However, these two properties did not cosegregate in heterozygotic hybrids.     

The Chromosome End in Yeast: Its Mosaic Nature and Influence on Recombinational Dynamics

Yeast chromosome ends are composed of several different repeated elements. Among six clones of chromosome ends from two strains of Saccharomyces cerevisiae, at least seven different repeated sequence families were found. These included the previously identified Y'' and X elements. Some families are highly variable in copy number and location between strains of S. cerevisiae, while other elements appear constant in copy number and location. Three repeated sequence elements are specific to S. cerevisiae and are not found in its evolutionarily close relative, Saccharomyces paradoxus. Two other repeated sequences are found in both S. cerevisiae and S. paradoxus. None of those described here is found (by low stringency DNA hybridization) in the next closest species, Saccharomyces bayanus. The loosely characterized X element is now more precisely defined. X is a composite of at least four small (ca. 45-140 bp) sequences found at some, but not all, ends. There is also a potential ``core'''' X element of approximately 560 bp which may be found at all ends. Distal to X, only one of six clones had (TG(1-3))(n) telomere sequence at the junction between X and Y''. The presence of these internal (TG(1-3))(n) sequences correlates with the ability of a single Y'' to expand into a tandem array of Y''s by unequal sister chromatid exchange. The presence of shared repeated elements proximal to the X region can override the strong preference of Y''s to recombine ectopically with other Y''s of the same size class. The chromosome ends in yeast are evolutionarily dynamic in terms of subtelomeric repeat structure and variability.     

Characterization and transferability of microsatellite markers of the cultivated peanut (<Emphasis Type="Italic">Arachis hypogaea</Emphasis>)

Background  

The genus Arachis includes Arachis hypogaea (cultivated peanut) and wild species that are used in peanut breeding or as forage. Molecular markers have been employed in several studies of this genus, but microsatellite markers have only been used in few investigations. Microsatellites are very informative and are useful to assess genetic variability, analyze mating systems and in genetic mapping. The objectives of this study were to develop A. hypogaea microsatellite loci and to evaluate the transferability of these markers to other Arachis species.     

In vitro and in vivo conditional sensitization of hepatocellular carcinoma cells to TNF-induced apoptosis by Taxol

High mortality among hepatocellular carcinoma (HCC) patients reflects both late diagnosis and low curability, due to pharmacoresistance. Taxol (TAX) is toxic for many human HCC-derived cell lines, yet its clinical efficacy on HCCs is poor. Combining TAX with other drugs appears a promising possibility to overcome such refractoriness. We analyzed whether combining tumor necrosis factor (TNF) with TAX would improve their toxicity. Human HCC-derived cell lines were treated with TAX or TNF, alone or combined. Apoptosis was assessed by morphology and flow-cytometry. Several pro- and anti-apoptotic molecules were evaluated by western blotting and/or enzymatic assay. After a 24 hour treatment, TNF was ineffective and TAX modestly cytotoxic, whereas HCC cells were conditionally sensitized to TNF by TAX. Indeed some relevant parameters were shifted to a prodeath setting: TNF-receptor 1 was increased, SOCS3, c-FLIP and pSTAT3 were markedly downregulated. These observations provide a significant clue to critically improve the drug susceptibility of HCC cells by combining 2 agents, TAX and TNF. The sequential application of TAX at a low dosage followed by TNF for only a short time triggered a strong apoptotic response. Of interest, prior TAX administration could also sensitize to TNF-induced apoptosis in the Yoshida AH-130 hepatoma transplanted in mice. Therefore, scrutinizing the possibility to develop similar combination drug regimens in suitable preclinical models seems highly advisable.     

Novel approach to abuse the hyperactive K-Ras pathway for adenoviral gene therapy of colorectal cancer

BackgroundFunctional activation of oncogenic K-Ras signaling pathway plays an important role in the early events of colorectal carcinogenesis (CRC). K-Ras proto-oncogene is involved in 35–40% of CRC cases. Mutations in the Ras gene trigger the transduction of proliferative and anti-apoptotic signals, even in the absence of extra cellular stimuli. The objective of the current study was to use a gene-targeting approach to kill human CRC cells selectively harboring mutated K-Ras.ResultsA recombinant adenovirus that carries a lethal gene, PUMA, under the control of a Ras responsive promoter (Ad-Py4-SV40-PUMA) was used selectively to target CRC cells (HCT116, SW480, DLD1 and RIE-Ras) that possess a hyperactive Ras pathway while using HT29 and RIE cells as a control that harbors wild type Ras and exhibit very low Ras activity. Control vector, without the Ras responsive promoter elements was used to assess the specificity of our “gene therapy” approach. Both adenoviral vectors were assed in vitro and in xenograft model in vivo. Ad-Py4-SV40-PUMA showed high potency to induce ~ 50% apoptosis in vitro, to abolish completely tumor formation by infecting cells with the Ad-Py4-SV40-PUMA prior xenografting them in nude mice and high ability to suppress by ~ 35% tumor progression in vivo in already established tumors.ConclusionsSelective targeting of CRC cells with the activated Ras pathway may be a novel and effective therapy in CRC. The high potency of this adenoviral vector may help to overcome an undetectable micro metastasis that is the major hurdle in challenging with CRC.     

Molecular genetic and physiological differentiation of <Emphasis Type="Italic">Kluyveromyces lactis</Emphasis> and <Emphasis Type="Italic">Kluyveromyces marxianus</Emphasis>: Analysis of strains from the all-Russian collection of microorganisms (VKM)

Molecular genetic identification of 52 Kluyveromyces strains from VKM, mainly of dairy origin, was carried out. Restriction analysis of 5.8S-ITS rDNA fragments was used to differentiate between Kl. lactis var. lactis, Kl. lactis var. drosophilarum (European population of “krassilnikovii”), and Kl. marxianus. Kl. lactis was shown to differ from Kl. marxianus in its ability to assimilate α-glucosides: maltose, melezitose, and α-methyl-glucoside.