Meiotic association between Spo11 regulated by Rec102, Rec104 and Rec114

Meiotic recombination is initiated by DNA double-stranded break (DSB) formation catalyzed by Spo11, a type-II topoisomerase-like transesterificase, presumably via a dimerization-mediated mechanism. We demonstrate the existence of in vivo interactions between Spo11 proteins carrying distinct tags, and the chromatin-binding and DSB activity of tagged Spo11 at innate and targeted DSB sites upon fusion to the Gal4 DNA-binding domain. First we identified the interaction between Spo11-3FLAG and Gal4BD-Spo11 proteins, and established that this interaction specifically occurs at the time of DSB formation. We then observed that presence of the Gal4BD-spo11Y135F (nuclease-deficient) protein allows Spo11-3FLAG recruitment at the GAL2 locus, indicative of the formation of a hetero-complex near the GAL2 UAS sites, but no formation of double- or single-strand breaks. Spo11 self-interaction around the GAL2 DSB site depends on other proteins for DSB formation, in particular Rec102, Rec104 and Rec114. Together, these results suggest that in vivo self-association of Spo11 during meiosis is genetically regulated. The results are discussed in relation to possible roles of Spo11 self-interaction in the control of the cleavage activity

Population genomics of the fission yeast Schizosaccharomyces pombe.

The fission yeast Schizosaccharomyces pombe has been widely used as a model eukaryote to study a diverse range of biological processes. However, population genetic studies of this species have been limited to date, and we know very little about the evolutionary processes and selective pressures that are shaping its genome. Here, we sequenced the genomes of 32 worldwide S. pombe strains and examined the pattern of polymorphisms across their genomes. In addition to introns and untranslated regions (UTRs), intergenic regions also exhibited lower levels of nucleotide diversity than synonymous sites, suggesting that a considerable amount of noncoding DNA is under selective constraint and thus likely to be functional. A number of genomic regions showed a reduction of nucleotide diversity probably caused by selective sweeps. We also identified a region close to the end of chromosome 3 where an extremely high level of divergence was observed between 5 of the 32 strains and the remain 27, possibly due to introgression, strong positive selection, or that region being responsible for reproductive isolation. Our study should serve as an important starting point in using a population genomics approach to further elucidate the biology of this important model organism

Early and Definitive Diagnosis of Toxic Shock Syndrome by Detection of Marked Expansion of T-Cell-Receptor Vβ2-Positive T Cells

We describe two cases of early toxic shock syndrome, caused by the superantigen produced from methicillin-resistant Staphylococcus aureus and diagnosed on the basis of an expansion of T-cell-receptor Vβ2-positive T cells. One case-patient showed atypical symptoms. Our results indicate that diagnostic systems incorporating laboratory techniques are essential for rapid, definitive diagnosis of toxic shock syndrome

ヨウレイリン ノ ジュカンシャダンリョウ ソクテイ ノ タメ ノ オオガタ ウリョウケイ ノ ケンテイ

幼齢林における樹冠遮断量の測定上の問題点を解決できるような大型雨量計のデザインを提示し,実際に作製した大型雨量計を用いてその実用性を検討した。雨量計の重要な要素である受水面積は,我が国の一般的な幼齢林の植栽密度,植物への影響,メンテナンス性,既往の大型雨量計を用いた樹冠遮断研究における受水面積の決定基準などを参考にして,約5m^2が適当であると決めた。大型雨量計の実用性は,次の各実験により確認した。まず,降雨強度の大きい降雨イベントにおいても雨量計からの排水水量を正確に測定できるようするために,本研究で用いた500mLの転倒マス型量水計を対象に大流量を含めた流量検定を行い,流量と1転倒に要する水量との関係を求めた。次に,大型雨量計の初期損失量を求めたところ0.2mm以下であり,大型雨量計の排水性は良好であった。さらに,大型雨量計の受水面積を厳密に求めるために,自然降雨を対象にした大型雨量計と貯留型雨量計の比較観測を行った。転倒マス型量水計の検定結果を考慮して補正した大型雨量計からの排水水量と,貯留型雨量計が示した雨量の関係は,良好な直線関係を示しており,その直線の傾きから大型雨量計の厳密な受水面積を決めた。また,その直線関係は,通常の降雨イベントだけでなく強度の大きい降雨イベントにおいても成り立っていたため,本研究で提示した大型雨量計は降雨強度の大きいイベントにも耐えうる実用性の高い雨量計であることがわかった。We proposed a design of a large plastic-sheet net-rainfall gauge for measurements of interception loss at young forests in Japan, and calibrated the proposed gauge with a standard rain gauge. The appropriate orifice area of the proposed gauge was suggested to be approximately 5m^2, considering the prevalent stand density of young forests in Japan, negative influences of water-logging on nearby plants, and the standard method to determine orifice areas in previous studies. The calibration of the proposed gauge was made by the following three steps. First, in order to examine robustness of the proposed gauge under strong rain conditions, we made a dynamic calibration of an attached tipping bucket flow meter under a variety of inflow water fluxes. This calibration provided a correction function revealing accurate water volume which is necessary to register a tip of the flow meter, as a function of the inflow water flux. Second, we found that initial loss of water, being retained on the proposed gauge, was less than 0.2 mm, indicating good drainage of the proposed gauge. Third, to calculate the accurate orifice areas of the proposed gauges, we made comparative measurements of rainfall using three proposed gauges and a standard gauge. Good linear relationships were found between total drainage water volumes from the proposed gauges, which were corrected by the above correction function, and rainfall observed by the standard gauge. By making use of the slopes of lines, we determined the accurate orifice areas of the proposed gauges. The line successfully fitted to a rainfall event with strong rainfall intensity, indicating that the proposed gauge was applicable to monitor rainfall interception even in strong rainfall conditions

Critical amino acids in human DNA polymerases η and κ involved in erroneous incorporation of oxidized nucleotides

Oxidized DNA precursors can cause mutagenesis and carcinogenesis when they are incorporated into the genome. Some human Y-family DNA polymerases (Pols) can effectively incorporate 8-oxo-dGTP, an oxidized form of dGTP, into a position opposite a template dA. This inappropriate G:A pairing may lead to transversions of A to C. To gain insight into the mechanisms underlying erroneous nucleotide incorporation, we changed amino acids in human Polη and Polκ proteins that might modulate their specificity for incorporating 8-oxo-dGTP into DNA. We found that Arg61 in Polη was crucial for erroneous nucleotide incorporation. When Arg61 was substituted with lysine (R61K), the ratio of pairing of dA to 8-oxo-dGTP compared to pairing of dC was reduced from 660:1 (wild-type Polη) to 7 : 1 (R61K). Similarly, Tyr112 in Polκ was crucial for erroneous nucleotide incorporation. When Tyr112 was substituted with alanine (Y112A), the ratio of pairing was reduced from 11: 1 (wild-type Polκ) to almost 1: 1 (Y112A). Interestingly, substitution at the corresponding position in Polη, i.e. Phe18 to alanine, did not alter the specificity. These results suggested that amino acids at distinct positions in the active sites of Polη and Polκ might enhance 8-oxo-dGTP to favor the syn conformation, and thus direct its misincorporation into DNA