Unligated Okazaki Fragments Induce PCNA Ubiquitination and a Requirement for Rad59-Dependent Replication Fork Progression

Deficiency in DNA ligase I, encoded by CDC9 in budding yeast, leads to the accumulation of unligated Okazaki fragments and triggers PCNA ubiquitination at a non-canonical lysine residue. This signal is crucial to activate the S phase checkpoint, which promotes cell cycle delay. We report here that a pol30-K107 mutation alleviated cell cycle delay in cdc9 mutants, consistent with the idea that the modification of PCNA at K107 affects the rate of DNA synthesis at replication forks. To determine whether PCNA ubiquitination occurred in response to nicks or was triggered by the lack of PCNA-DNA ligase interaction, we complemented cdc9 cells with either wild-type DNA ligase I or a mutant form, which fails to interact with PCNA. Both enzymes reversed PCNA ubiquitination, arguing that the modification is likely an integral part of a novel nick-sensory mechanism and not due to non-specific secondary mutations that could have occurred spontaneously in cdc9 mutants. To further understand how cells cope with the accumulation of nicks during DNA replication, we utilized cdc9-1 in a genome-wide synthetic lethality screen, which identified RAD59 as a strong negative interactor. In comparison to cdc9 single mutants, cdc9 rad59Δ double mutants did not alter PCNA ubiquitination but enhanced phosphorylation of the mediator of the replication checkpoint, Mrc1. Since Mrc1 resides at the replication fork and is phosphorylated in response to fork stalling, these results indicate that Rad59 alleviates nick-induced replication fork slowdown. Thus, we propose that Rad59 promotes fork progression when Okazaki fragment processing is compromised and counteracts PCNA-K107 mediated cell cycle arrest.     

牛β-乳球蛋白基因的克隆及部分序列测定

为了制备乳腺生物反应器所需要的乳腺特异性表达的调控序列,用ＰＣＲ法从奶牛染色体上分５段扩增出了全长的牛 ＢＬＧ基因约 ８ ｋｂ,包括 １．８ ｋｂ的 ５’侧翼区、１．７ ｋｂ的 ３’侧翼区及 ４．７ ｋｂ的ｇＤＮＡ区。扩增出的各片段克隆到Ｔ－Ｖｅｃｔｏｒ上,酶切鉴定及序列分析均证实了所扩增片段的正确性。     

一类生化反应模型的定性分析

本文讨论了Babloyantz-Hiernaux生化反应模型及其特殊情况下的Glerer-Meinhardt数学模型,得到了前者的平衡位置的局部稳定位和后者的极限环的存在性即振荡反应的存在性以及其平衡位置的大范围稳定性.     

Effect of different iron loads on serum and tissue biochemical parameters and liver hepcidin mRNA abundance of neonatal piglets

Iron (Fe) is an essential and important trace element for animals. In order to study its metabolism and relationship with hepcidin, piglet models of Fe-deficiency and Fe-overload were established by intramuscular injection with different doses of Fe-dextran (150 mg Fe/ml) within 1 week of age. Twelve piglets were divided into three groups of four animals: deficiency, regular and overload group, receiving 0 ml, 1 ml and 6 ml Fe-dextran, respectively. The piglets were euthanised at the age of 7 days for analysis. The results showed that the Fe-concentrations in liver, spleen and serum of piglets in the overload group were higher than in the regular and deficiency groups (p < 0.05). In the overload group, several serum biochemical parameters, e.g. globulin, total bilirubin, total cholesterol, high density lipoprotein (HDL), malondialdehyde, glutathione peroxidase (GPx), peroxidase and xanthine oxidase were higher, while alkaline phosphatase (AKP) and triglycerides were lower, compared with the regular group (p < 0.05). The serum concentrations of AKP, total bilirubin and peroxidase in the deficiency group were lower, while HDL and GPx were higher, compared with the regular group (p < 0.05). Hepcidin mRNA abundance was 131 times lower in the liver of piglets with Fe-deficiency, and 7 times higher in the overloaded group than that in the regular group (p < 0.05). In conclusion, Fe-overload and deficiency would influence Fe-metabolism, serum biochemical indexes, oxidation state and hepcidin mRNA abundance in piglet liver.     

Hydrogen protects against hyperoxia-induced apoptosis in type II alveolar epithelial cells via activation of PI3K/Akt/Foxo3a signaling pathway

Oxidative stress is regarded as a key regulator in the pathogenesis of prolonged hyperoxia-induced lung injury, which causes injury to alveolar epithelial cells and eventually leads to development of bronchopulmonary dysplasia (BPD). Many studies have shown that hydrogen has a protective effect in a variety of cells. However, the mechanisms by which hydrogen rescues cells from damage due to oxidative stress in BPD remains to be fully elucidated. This study sought to evaluate the effects of hydrogen on hyperoxia-induced lung injury and to investigate the underlying mechanism. Primary type II alveolar epithelial cells (AECIIs) were divided into four groups: control (21% oxygen), hyperoxia (95% oxygen), hyperoxia + hydrogen, and hyperoxia + hydrogen + LY294002 (a PI3K/Akt inhibitor). Proliferation and apoptosis of AECIIs were assessed using MTS assay and flow cytometry (FCM), respectively. Gene and protein expression were detected by quantitative polymerase chain reaction (q-PCR) and western blot analysis. Stimulation with hyperoxia decreased the expression of P-Akt, P- FoxO3a, cyclinD1 and Bcl-2. Hyperoxic conditions increased levels of Bim, Bax, and Foxo3a, which induced proliferation restriction and apoptosis of AECIIs. These effects of hyperoxia were reversed with hydrogen pretreatment. Furthermore, the protective effects of hydrogen were abrogated by PI3K/Akt inhibitor LY294002. The results indicate that hydrogen protects AECIIs from hyperoxia-induced apoptosis by inhibiting apoptosis factors and promoting the expression of anti-apoptosis factors. These effects were associated with activation of the PI3K/Akt/FoxO3a pathway.     

Different fermentation strategies by Schizochytrium mangrovei strain pq6 to produce feedstock for exploitation of squalene and omega‐3 fatty acids

Schizochytrium mangrovei strain PQ 6 was investigated for coproduction of docosahexaenoic acid (C22: 6ω‐3, DHA ) and squalene using a 30‐L bioreactor with a working volume of 15 L under various batch and fed‐batch fermentation process regimes. The fed‐batch process was a more efficient cultivation strategy for achieving higher biomass production rich in DHA and squalene. The final biomass, total lipid, unsaponifiable lipid content, and DHA productivity were 105.25 g · L^?1, 43.40% of dry cell weight, 8.58% total lipid, and 61.66 mg · g^?1 · L^?1, respectively, after a 96 h fed‐batch fermentation. The squalene content was highest at 48 h after feeding glucose (98.07 mg · g^?1 of lipid). Differences in lipid accumulation during fermentation were correlated with changes in ultrastructure using transmission electron microscopy and Nile Red staining of cells. The results may be of relevance to industrial‐scale coproduction of DHA and squalene in heterotrophic marine microalgae such as Schizochytrium .     

A new genus and species of turtle blood fluke (Digenea: Schistosomatoidea) from the Mekong snail-eating turtle, <Emphasis Type="Italic">Malayemys subtrijuga</Emphasis> (Schlegel &amp; Müller) (Testudines: Geoemydidae) in Vietnam,with a reassessment of related Asiatic turtle blood flukes and molecular phylogeny

Platt sinuosus Roberts & Bullard n. g., n. sp. (type-species) infects the kidney and mesenteric blood vessels of Mekong snail-eating turtles, Malayemys subtrijuga (Schlegel & Müller), in the Mekong River Basin. Species of Platt Roberts & Bullard n. g. are unique by the combination of having a papillate ventral sucker, vasa efferentia that are dorsal to the gonads, a massive cirrus-sac that is directed anteriad or laterad, and a vitellarium that surrounds the intestinal caeca. The new species resembles Platt ocadiae (Takeuti, 1942) Roberts & Bullard n. comb. but differs from it by having an external seminal vesicle that overlaps with or is immediately posterior to the level of the ventral sucker. Seven species previously of Hapalorhynchus Stunkard, 1922 are reassigned herein to Platt: P. odhnerensis (Mehra, 1933) Roberts & Bullard n. comb.; P. yoshidai (Ozaki, 1939) Roberts & Bullard n. comb.; P. ocadiae; P. oschmarini (Belous, 1963) Roberts & Bullard n. comb.; P. sutlejensis (Mehrotra, 1973) Roberts & Bullard n. comb.; P. synderi (Platt & Sharma, 2012) Roberts & Bullard n. comb.; and P. tkachi (Platt & Sharma, 2012) Roberts & Bullard n. comb. A dichotomous key to Platt spp. is provided. Hapalorhynchus sheilae (Mehrotra, 1973) Bourgat, 1990 and Hapalorhynchus mica (Oshmarin, 1971) Bourgat, 1990 are considered as species inquirendae, and Hapalorhynchus indicus (Thapar, 1933) Price, 1934 and Hapalorhynchus macrotesticularis (Rohde, Lee, & Lim, 1968) Brooks & Sullivan, 1981 are considered as species incertae sedis. Phylogenetic analysis of the large subunit rDNA (28S) showed P. sinuosus and P. snyderi to be sister taxa distinct from a monophyletic Hapalorhynchus and Coeuritrema platti Roberts & Bullard, 2016.