Biological effects of carbon ion beams with various LETs on budding yeast Saccharomyces cerevisiae.

It has been established that irradiation with higher linear energy transfer (LET) increases lethality and mutagenicity more than that with lower LET. However, the characteristics specific to carbon ion beam have not yet been elucidated. Yeast cells were irradiated with carbon ions with an LET of 13 or 50keV/μm, and cell survival and mutation frequency were analyzed.

Fundamental study of the radiation monitoring system based on evaluation of DNA lesions.

The biological dosemeter that measures biological responses to ionising radiation is useful for radiation protection. This paper presents the development and characterisation of a gamma ray irradiation dosimetry system based on real-time PCR (polymerase chain reaction) methodology. Real-time PCR is used to amplify and simultaneously quantify a targeted DNA molecule.

Orientation of paramecium swimming in a static magnetic field: Dependence on membrane lipid fluidity.

We studied the swimming orientation of the ciliated protozoan Paramecium aurelia in a static magnetic field (0.78 T). P.

Microchamber arrays for the identification of individual cells exposed to an X-ray microbeam.

To identify individual cells exposed to a X-ray microbeam in a cell population, we developed a biocompatible microchamber-array chip using UV lithography of photopolymer SU-8. The center-to-center distance between microchambers is 50 mum including a wall of 15 mum height. Using the microchamber-array chip, we performed tracking of individual exposed cells.

AtREV1, a Y-family DNA polymerase in Arabidopsis, has deoxynucleotidyl transferase activity in vitro.

To clarify the functions of the Arabidopsis thaliana REV1 (AtREV1) protein, we expressed it in Escherichia coli and purified it to near homogeneity. The deoxynucleotidyl transferase activity of the recombinant AtREV1 was examined in vitro using a primer extension assay. The recombinant AtREV1 transferred one or two nucleotides to the primer end.

Specificity of mutations induced by carbon ions in budding yeast Saccharomyces cerevisiae.

To investigate the nature of mutations induced by accelerated ions in eukaryotic cells, the effects of carbon-ion irradiation were compared with those of gamma-ray irradiation in the budding yeast Saccharomyces cerevisiae. The mutational effect and specificity of carbon-ion beams were studied in the URA3 gene of the yeast. Our experiments showed that the carbon ions generated more than 10 times the number of mutations induced by gamma-rays, and that the types of base changes induced by carbon ions include transversions (68.

Fidelity of DNA polymerase delta holoenzyme from Saccharomyces cerevisiae: the sliding clamp proliferating cell nuclear antigen decreases its fidelity.

DNA polymerases delta and epsilon (pol delta and epsilon) are the two major replicative polymerases in the budding yeast Saccharomyces cerevisiae. The fidelity of pol delta is influenced by its 3'-5' proofreading exonuclease activity, which corrects misinsertion errors, and by enzyme cofactors. PCNA is a pol delta cofactor, called the sliding clamp, which increases the processivity of pol delta holoenzyme.

Orientation of paramecium swimming in a DC magnetic field.

We found that a ciliated protozoan, Paramecium, swam perpendicular to a static (DC) magnetic field (0.68 T). The swimming orientation was similar even when the ionic current through the cell membrane disappeared after saponin treatment.

Fidelity of DNA polymerase epsilon holoenzyme from budding yeast Saccharomyces cerevisiae.

DNA polymerases delta and epsilon (pol delta and epsilon) are the major replicative polymerases and possess 3'-5' proofreading exonuclease activities that correct errors arising during DNA replication in the yeast Saccharomyces cerevisiae. This study measures the fidelity of the holoenzyme of wild-type pol epsilon, the 3'-5' exonuclease-deficient pol2-4, a +1 frameshift mutator for homonucleotide runs, pol2C1089Y, and pol2C1089Y pol2-4 enzymes using a synthetic 30-mer primer/100-mer template. The nucleotide substitution rate for wild-type pol epsilon was 0.

The fifth essential DNA polymerase phi in Saccharomyces cerevisiae is localized to the nucleolus and plays an important role in synthesis of rRNA.

We report that POL5 encodes the fifth essential DNA polymerase in Saccharomyces cerevisiae. Pol5p was identified and purified from yeast cell extracts and is an aphidicolin-sensitive DNA polymerase that is stimulated by yeast proliferating cell nuclear antigen (PCNA). Thus, we named Pol5p DNA polymerase phi.