scholarly journals Genetic characterization ofrec-1, a mutant ofUstilago maydisdefective in repair and recombination

1976 ◽  
Vol 27 (3) ◽  
pp. 413-453 ◽  
Author(s):  
R. Holliday ◽  
R. E. Halliwell ◽  
M. W. Evans ◽  
V. Rowell
Keyword(s):  
Genetic Recombination ◽  
Uv Light ◽  
Relative Increase ◽  
Regulatory Function ◽  
Genetic Studies ◽  
Distal Marker ◽  
Recombination Repair ◽  
Spontaneous Frequency ◽  
Size And Morphology ◽  
Mitosis And Meiosis

SUMMARYDetailed physiological and genetic studies of haploid and diploid strains have revealed a complex phenotype for therec-1 mutation inUstilago maydis. The mutant is defective in the repair of damage by UV light, ionizing radiation and nitrosoguanidine. Four alleles are all recessive and have the same sensitivity to UV, suggesting the loss of a single cellular function. A significant fraction of non-viable cells is formed during growth, and in diploid strains considerable variation in colony size and morphology is seen. The spontaneous frequency of mutation is greater than in wild-type cells, but there is little, if any, enhancement by irradiation.rec-1 also has pleiotropic effects on genetic recombination. The spontaneous level of mitotic allelic or non-allelic recombination is abnormally high, but the relative increase after irradiation is much lower than in control diploids. Allelic recombination is strongly associated with the expression of a hetozygous recessive distal marker, and it is shown that this is often due to hemizygosity rather than to homozygosity of this marker. The results indicate that allelic recombination is due to crossing over rather than gene conversion, but that the cross over is often associated with a chromatid break.rec-1 interacts with other radiation sensitive mutants, such asrec-2. Diploids homozygous for both are totally deficient in allelic recombination. In crosses betweenrec-1 strains meiosis is defective, with a low viability of meiotic products and frequent production of aneuploids or diploids among the survivors. The overall phenotype ofrec-1 strains can best be explained in terms of the loss of a regulatory function, which leads to uncontrolled recombination during mitosis and meiosis, and the loss of a recombination repair pathway which is normally induced by agents which damage DNA.

scholarly journals Requirement of DNA Polymerase η for Error-Free Bypass of UV-Induced CC and TC Photoproducts

2001 ◽  
Vol 21 (1) ◽  
pp. 185-188 ◽  
Author(s):  
Sung-Lim Yu ◽  
Robert E. Johnson ◽  
Satya Prakash ◽  
Louise Prakash
Keyword(s):  
Dna Polymerase ◽  
Uv Light ◽  
Wide Spectrum ◽  
Variant Form ◽  
Induced Mutations ◽  
Uv Mutagenesis ◽  
Genetic Studies ◽  
Human Dna ◽  
Skin Cancers ◽  
Cyclobutane Dimers

ABSTRACT The yeast RAD30-encoded DNA polymerase η (Polη) bypasses a cis-syn thymine-thymine dimer efficiently and accurately. Human DNA polymerase η functions similarly in the bypass of this lesion, and mutations in human Polη result in the cancer prone syndrome, the variant form of xeroderma pigmentosum. UV light, however, also elicits the formation ofcis-syn cyclobutane dimers and (6-4) photoproducts at 5′-CC-3′ and 5′-TC-3′ sites, and in both yeast and human DNA, UV-induced mutations occur primarily by 3′ C to T transitions. Genetic studies presented here reveal a role for yeast Polη in the error-free bypass of cyclobutane dimers and (6-4) photoproducts formed at CC and TC sites. Thus, by preventing UV mutagenesis at a wide spectrum of dipyrimidine sites, Polη plays a pivotal role in minimizing the incidence of sunlight-induced skin cancers in humans.

scholarly journals Genetic Recombination in Bacillus subtilis 168: Effect of ΔhelD on DNA Repair and Homologous Recombination

2001 ◽  
Vol 183 (19) ◽  
pp. 5772-5777 ◽  
Author(s):  
Begoña Carrasco ◽  
Silvia Fernández ◽  
Marie-Agnes Petit ◽  
Juan C. Alonso
Keyword(s):  
Dna Repair ◽  
Bacillus Subtilis ◽  
Homologous Recombination ◽  
Genetic Recombination ◽  
Methyl Methanesulfonate ◽  
Plasmid Transformation ◽  
Dna Damaging Agents ◽  
Bacillus Subtilis 168 ◽  
Recombination Repair ◽  
Helicase Iv

ABSTRACT The B. subtilis ΔhelD allele rendered cells proficient in transformational recombination and moderately sensitive to methyl methanesulfonate when present in an otherwise Rec+ strain. The ΔhelD allele was introduced into rec-deficient strains representative of the α (recF strain), β (addA addB), γ (recH), ɛ (ΔrecU), and ζ (ΔrecS) epistatic groups. The ΔhelDmutation increased the sensitivity to DNA-damaging agents ofaddAB, ΔrecU, and ΔrecS cells, did not affect the survival ofrecH cells, and decreased the sensitivity ofrecF cells. ΔhelD also partially suppressed the DNA repair phenotype of other mutations classified within the α epistatic group, namely the recL, ΔrecO, and recR mutations. The ΔhelD allele marginally reduced plasmid transformation (three- to sevenfold) of mutations classified within the α, β, and γ epistatic groups. Altogether, these data indicate that the loss of helicase IV might stabilize recombination repair intermediates formed in the absence of recFLOR and renderrecFLOR, addAB, andrecH cells impaired in plasmid transformation.

UV light-induced cyclobutane pyrimidine dimers are mutagenic in mammalian cells

1986 ◽  
Vol 6 (10) ◽  
pp. 3349-3356
Author(s):  
M Protić-Sabljić ◽  
N Tuteja ◽  
P J Munson ◽  
J Hauser ◽  
K H Kraemer ◽  
...  
Keyword(s):  
Mammalian Cells ◽  
Uv Light ◽  
Shuttle Vector ◽  
Marker Gene ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
Relative Increase ◽  
Cyclobutane Dimers ◽  
Double Base ◽  
Vector Dna

We used a simian virus 40-based shuttle vector plasmid, pZ189, to determine the role of pyrimidine cyclobutane dimers in UV light-induced mutagenesis in monkey cells. The vector DNA was UV irradiated and then introduced into monkey cells by transfection. After replication, vector DNA was recovered from the cells and tested for mutations in its supF suppressor tRNA marker gene by transformation of Escherichia coli carrying a nonsense mutation in the beta-galactosidase gene. When the irradiated vector was treated with E. coli photolyase prior to transfection, pyrimidine cyclobutane dimers were removed selectively. Removal of approximately 90% of the pyrimidine cyclobutane dimers increased the biological activity of the vector by 75% and reduced its mutation frequency by 80%. Sequence analysis of 72 mutants recovered indicated that there were significantly fewer tandem double-base changes and G X C----A X T transitions (particularly at CC sites) after photoreactivation of the DNA. UV-induced photoproducts remained (although at greatly reduced levels) at all pyr-pyr sites after photoreactivation, but there was a relative increase in photoproducts at CC and TC sites and a relative decrease at TT and CT sites, presumably due to a persistence of (6-4) photoproducts at some CC and TC sites. These observations are consistent with the fact that mutations were found after photoreactivation at many sites at which only cyclobutane dimers would be expected to occur. From these results we conclude that UV-induced pyrimidine cyclobutane dimers are mutagenic in DNA replicated in monkey cells.

scholarly journals Synthesis, Characterization, and Photocatalytic Activity of ZnO Nanomaterials Prepared by a Green, Nonchemical Route

2020 ◽  
Vol 2020 ◽  
pp. 1-8
Author(s):  
Ngoc Thinh Nguyen ◽  
Van Anh Nguyen
Keyword(s):  
Uv Light ◽  
Photocatalytic Decomposition ◽  
Illumination Time ◽  
Reaction Rate Constants ◽  
Uv Illumination ◽  
Zno Nanomaterials ◽  
Crystallite Sizes ◽  
Size And Morphology ◽  
Analytical Tools ◽  
Synthesized Materials

An eco-friendly method for the synthesis of ZnO nanoparticles was studied. Zinc acetate precursor was thermally decomposed without adding any chemical agents. The synthesized materials were thoroughly characterized by various analytical tools. The results indicated that the synthesized ZnO nanomaterials have a wurtzite structure. The estimated crystallite sizes of the materials obtained at 450, 550, 650, and 750°C (named as ZnO-450, ZnO-550, ZnO-650, and ZnO-750) were 33, 36, 38, and 42 nm, respectively. The morphology of the nanomaterials was revealed to be affected by calcination temperature, causing the formation of both nanoparticles and nanorods with different sizes and shapes. The materials were applied as photocatalysts for methylene blue (MB) decomposition under ultraviolet (UV) light. Results showed that the decomposition efficiency strongly depends on UV illumination time, size, and morphology of ZnO nanomaterials. The highest MB decomposition (99.4%) is obtained when using ZnO-750. The photocatalytic decomposition follows the first-order reaction. The reaction rate constants corresponding to the MB decomposition process with the presence of ZnO-450, ZnO-550, ZnO-650, and ZnO-750 are 0.0512, 0.0636, 0.1077, and 0.1286 min-1, respectively.

Monitoring of chromosome dynamics of single yeast cells in a microfluidic platform with aperture cell traps

Lab on a Chip ◽  
2016 ◽  
Vol 16 (8) ◽  
pp. 1358-1365 ◽  
Author(s):  
Si Hyung Jin ◽  
Sung-Chan Jang ◽  
Byungjin Lee ◽  
Heon-Ho Jeong ◽  
Seong-Geun Jeong ◽  
...  
Keyword(s):  
Dna Replication ◽  
Genetic Recombination ◽  
Yeast Cells ◽  
Chromosome Movement ◽  
Microfluidic Platform ◽  
Chromosome Dynamics ◽  
Mitosis And Meiosis

Chromosome movement plays important roles in DNA replication, repair, genetic recombination, and epigenetic phenomena during mitosis and meiosis.

scholarly journals Role of DNA Polymerase η in the Bypass of a (6-4) TT Photoproduct

2001 ◽  
Vol 21 (10) ◽  
pp. 3558-3563 ◽  
Author(s):  
Robert E. Johnson ◽  
Lajos Haracska ◽  
Satya Prakash ◽  
Louise Prakash
Keyword(s):  
Dna Polymerase ◽  
Xeroderma Pigmentosum ◽  
Uv Light ◽  
Dna Lesions ◽  
Variant Form ◽  
Replication Machinery ◽  
Genetic Studies ◽  
Induced Mutagenesis ◽  
Combined Action

ABSTRACT UV light-induced DNA lesions block the normal replication machinery. Eukaryotic cells possess DNA polymerase η (Polη), which has the ability to replicate past a cis-syn thymine-thymine (TT) dimer efficiently and accurately, and mutations in human Polη result in the cancer-prone syndrome, the variant form of xeroderma pigmentosum. Here, we test Polη for its ability to bypass a (6-4) TT lesion which distorts the DNA helix to a much greater extent than acis-syn TT dimer. Opposite the 3′ T of a (6-4) TT photoproduct, both yeast and human Polη preferentially insert a G residue, but they are unable to extend from the inserted nucleotide. DNA Polζ, essential for UV induced mutagenesis, efficiently extends from the G residue inserted opposite the 3′ T of the (6-4) TT lesion by Polη, and Polζ inserts the correct nucleotide A opposite the 5′ T of the lesion. Thus, the efficient bypass of the (6-4) TT photoproduct is achieved by the combined action of Polη and Polζ, wherein Polη inserts a nucleotide opposite the 3′ T of the lesion and Polζ extends from it. These biochemical observations are in concert with genetic studies in yeast indicating that mutations occur predominantly at the 3′ T of the (6-4) TT photoproduct and that these mutations frequently exhibit a 3′ T→C change that would result from the insertion of a G opposite the 3′ T of the (6-4) TT lesion.

Phenotypic expression of primary lesions of genetic material in Saccharomyces yeasts

Genome ◽  
1989 ◽  
Vol 31 (2) ◽  
pp. 497-502 ◽  
Author(s):  
Sergey G. Inge-Vechtomov ◽  
Marina V. Repnevskaya
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Mating Type ◽  
Uv Light ◽  
Phenotypic Expression ◽  
Genetic Material ◽  
Selective System ◽  
Spontaneous Frequency ◽  
Saccharomyces Yeasts

"Illegitmate" mating of yeasts (α × α), either spontaneous or induced by uv light or ethyl methanesulfanate, in a selective system for "cytoduction" revealed that about 95% of cytoductants expressed their original (α) mating type. Inducing the mating by treating the recipient of cytoplasm with uv light reached two orders of magnitude. An additional copy of MATα in the α recipient almost completely eliminated the effect, which means that nonheritable mating type changes observed are formally recessive and are localized within MATα complex. About 1% of cytoductants obtained were nonmating types and some of them were identified as matα1 mutants. Rad18 mutant as a recipient showed a considerably elevated spontaneous frequency of illegitimate hybridization and cytoduction. The cytoductants also preserved the original mating type. These facts suggest that nonheritable changes of mating type are due to repairable primary (premutational) lesions in MATα genetic material. The significance of these results for understanding the mechanism of nonheritable variability is discussed.Key words: mating type, nonheritable changes, primary lesions, premutational events, Saccharomyces cerevisiae, repair.

scholarly journals UV light-induced cyclobutane pyrimidine dimers are mutagenic in mammalian cells.

1986 ◽  
Vol 6 (10) ◽  
pp. 3349-3356 ◽  
Author(s):  
M Protić-Sabljić ◽  
N Tuteja ◽  
P J Munson ◽  
J Hauser ◽  
K H Kraemer ◽  
...  
Keyword(s):  
Mammalian Cells ◽  
Uv Light ◽  
Shuttle Vector ◽  
Marker Gene ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
Relative Increase ◽  
Cyclobutane Dimers ◽  
Double Base ◽  
Vector Dna

We used a simian virus 40-based shuttle vector plasmid, pZ189, to determine the role of pyrimidine cyclobutane dimers in UV light-induced mutagenesis in monkey cells. The vector DNA was UV irradiated and then introduced into monkey cells by transfection. After replication, vector DNA was recovered from the cells and tested for mutations in its supF suppressor tRNA marker gene by transformation of Escherichia coli carrying a nonsense mutation in the beta-galactosidase gene. When the irradiated vector was treated with E. coli photolyase prior to transfection, pyrimidine cyclobutane dimers were removed selectively. Removal of approximately 90% of the pyrimidine cyclobutane dimers increased the biological activity of the vector by 75% and reduced its mutation frequency by 80%. Sequence analysis of 72 mutants recovered indicated that there were significantly fewer tandem double-base changes and G X C----A X T transitions (particularly at CC sites) after photoreactivation of the DNA. UV-induced photoproducts remained (although at greatly reduced levels) at all pyr-pyr sites after photoreactivation, but there was a relative increase in photoproducts at CC and TC sites and a relative decrease at TT and CT sites, presumably due to a persistence of (6-4) photoproducts at some CC and TC sites. These observations are consistent with the fact that mutations were found after photoreactivation at many sites at which only cyclobutane dimers would be expected to occur. From these results we conclude that UV-induced pyrimidine cyclobutane dimers are mutagenic in DNA replicated in monkey cells.

VISUALIZING HOMOLOGOUS RECOMBINATION WITH INTERACTIVE COMPUTER PROGRAM

2011 ◽  
Vol 08 (04) ◽  
pp. 263-272 ◽  
Author(s):  
XIAOLI YANG ◽  
RONG GE ◽  
CHARLES TSENG
Keyword(s):  
Genetic Variation ◽  
Homologous Recombination ◽  
Computer Program ◽  
Molecular Mechanisms ◽  
Genetic Recombination ◽  
Genetic Material ◽  
Interactive Computer Program ◽  
Learning Programs ◽  
Computer Based ◽  
Mitosis And Meiosis

Homologous recombination is important for DNA repair and for increasing genetic variation, whereby it enriches the gene pool and keeps populations viable. In eukaryotes, genetic recombination takes place during meiosis. For genes on different chromosomes, mixing of paternal and maternal genes is achieved through the random formation of different chromosome configurations at metaphase I of meiosis. This process accounts for the genetic principle of the independent assortment of unlinked genes. Recombination of paternal and maternal genes on different members of the homologous chromosome pair, on the other hand, can only be achieved through the exchange of genetic material between nonsister chromatids, resulting in increased genetic variation. The molecular mechanisms of homologous recombination are complicated and often difficult for students to understand. The objective of this research is to develop an interactive computer program for teaching this important biological process. The software program, along with related computer-based genetics learning programs — for mitosis and meiosis, as well as for a cytogenetics laboratory — will be useful for genetics education at the high school and university levels.

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