Microbial transformation of 8-chloro-10,11-dihydrodibenz(b,f)(1,4)oxazepine by fungi.

The microbial transformation of 8-chloro-10,11-dihydrodibenz(b,f)(1,4)oxazepine (compound I) was undertaken to obtain new derivatives. Compound I was transformed by Hormodendrum sp. (NRRL 8133) to 8-chloro-10,11-dihydrodibenz(b,f)(1,4)oxazepine-11-one (compound II) and 2-(2-amino-4-chlorophenoxy)benzyl alcohol (compound IV). Microbial cleavage of the nonaromatic ring to form compound IV was accomplished by several other fungi. Compound I was transformed to 8-chlorodibenz(b,f)(1,4)oxazepine (compound III) by Hormodendrum cladosporioides (NRRL 8132).     

Down-regulating GRP78 reverses pirarubicin resistance of triple negative breast cancer by miR-495-3p mimics and involves the p-AKT/mTOR pathway

Due to the lack of known therapeutic targets for triple-negative breast cancer (TNBC), chemotherapy is the only available pharmacological treatment. Pirarubicin (tetrahydropyranyl Adriamycin, THP) is the most commonly used anthracycline chemotherapy agent. However, TNBC has a high recurrence rate after chemotherapy, and the mechanisms of chemoresistance and recurrence are not entirely understood. To study the chemoresistance mechanisms, we first screened compounds on a pirarubicin-resistant cell line (MDA-MB-231R) derived from MDA-MB-231. The drug resistance index of MDA-MB-231R cells was approximately five times higher than that of MDA-MB-231 cells. MDA-MB-231R cells have higher GRP78 and lower miR-495-3p expression levels than MDA-MB-231 cells. Transfecting MDA-MB-231R cells with a siGRP78 plasmid reduced GRP78 expression, which restored pirarubicin sensitivity. Besides, transfecting MDA-MB-231R cells with miR-495-3p mimics increased miR-495-3p expression, which also reversed pirarubicin chemoresistance. Cell counting kit-8 (CCK-8), EdU, wound healing, and Transwell assays showed that the miR-495-3p mimics also inhibited cell proliferation and migration. Based on our results, miR-495-3p mimics could down-regulate GRP78 expression via the p-AKT/mTOR signaling pathway in TNBC cells. Remarkably, chemo-resistant and chemo-sensitive TNBC tissues had opposite trends in GRP78 and miR-495-3p expressions. The lower the GRP78 and the higher the miR-495-3p expression, the better prognosis in TNBC patients. Therefore, the mechanism of pirarubicin resistance might involve the miR-495-3p/GRP78/Akt axis, which would provide a possible strategy for treating TNBC.     

Previously Unrecognized Ornithuromorph Bird Diversity in the Early Cretaceous Changma Basin,Gansu Province,Northwestern China

Here we report on three new species of ornithuromorph birds from the Lower Cretaceous Xiagou Formation in the Changma Basin of Gansu Province, northwestern China: Yumenornis huangi gen. et sp. nov., Changmaornis houi gen. et sp. nov., and Jiuquanornis niui gen. et sp. nov.. The last of these is based on a previously published but unnamed specimen: GSGM-05-CM-021. Although incomplete, the specimens can be clearly distinguished from each other and from Gansus yumenensis Hou and Liu, 1984. Phylogenetic analysis resolves the three new taxa as basal ornithuromorphs. This study reveals previously unrecognized ornithuromorph diversity in the Changma avifauna, which is largely dominated by Gansus but with at least three other ornithuromorphs. Body mass estimates demonstrate that enantiornithines were much smaller than ornithuromorphs in the Changma avifauna. In addition, Changma enantiornithines preserve long and recurved pedal unguals, suggesting an arboreal lifestyle; in contrast, Changma ornithuromorphs tend to show terrestrial or even aquatic adaptions. Similar differences in body mass and ecology are also observed in the Jehol avifauna in northeastern China, suggesting niche partitioning between these two clades developed early in their evolutionary history.     

Conservation of structure and mechanism by Trm5 enzymes

Enzymes of the Trm5 family catalyze methyl transfer from S-adenosyl methionine (AdoMet) to the N¹ of G37 to synthesize m¹G37-tRNA as a critical determinant to prevent ribosome frameshift errors. Trm5 is specific to eukaryotes and archaea, and it is unrelated in evolution from the bacterial counterpart TrmD, which is a leading anti-bacterial target. The successful targeting of TrmD requires detailed information on Trm5 to avoid cross-species inhibition. However, most information on Trm5 is derived from studies of the archaeal enzyme Methanococcus jannaschii (MjTrm5), whereas little information is available for eukaryotic enzymes. Here we use human Trm5 (Homo sapiens; HsTrm5) as an example of eukaryotic enzymes and demonstrate that it has retained key features of catalytic properties of the archaeal MjTrm5, including the involvement of a general base to mediate one proton transfer. We also address the protease sensitivity of the human enzyme upon expression in bacteria. Using the tRNA-bound crystal structure of the archaeal enzyme as a model, we have identified a single substitution in the human enzyme that improves resistance to proteolysis. These results establish conservation in both the catalytic mechanism and overall structure of Trm5 between evolutionarily distant eukaryotic and archaeal species and validate the crystal structure of the archaeal enzyme as a useful model for studies of the human enzyme.     

Gephyromycinifex aptenodytis gen. nov., sp. nov., isolated from gut of Antarctic emperor penguin Aptenodytes forsteri

Antonie van Leeuwenhoek - A novel actinobacterium NJES-13T was isolated from the gut of Antarctic emperor penguin Aptenodytes forsteri. The new isolate produces bioactive gephyromycin metabolites...     

Age-Related CD4+CD25+Foxp3+ Regulatory T-Cell Responses During Plasmodium berghei ANKA Infection in Mice Susceptible or Resistant to Cerebral Malaria

Different functions have been attributed to CD4⁺CD25⁺Foxp3⁺ regulatory T-cells (Tregs) during malaria infection. Herein, we describe the disparity in Treg response and pro- and anti-inflammatory cytokines during infection with Plasmodium berghei ANKA between young (3-week-old) and middle-aged (8-month-old) C57BL/6 mice. Young mice were susceptible to cerebral malaria (CM), while the middle-aged mice were resistant to CM and succumbed to hyperparasitemia and severe anemia. The levels of pro-inflammatory cytokines, such as TNF-α, in young CM-susceptible mice were markedly higher than in middle-aged CM-resistant mice. An increased absolute number of Tregs 3-5 days post-inoculation, co-occurring with elevated IL-10 levels, was observed in middle-aged CM-resistant mice but not in young CM-susceptible mice. Our findings suggest that Treg proliferation might be associated with the suppression of excessive pro-inflammatory Th1 response during early malaria infection, leading to resistance to CM in the middle-aged mice, possibly in an IL-10-dependent manner.     

秦岭中段野生动物多样性的红外相机监测数据库平台介绍

秦岭地处我国中西部, 生物地理位置重要, 拥有丰富的生物多样性, 有大熊猫(Ailuropoda melanoleuca)、秦岭羚牛(Budorcas bedfordi)、金丝猴(Rhinopithecus roxellana)和朱鹮(Nipponia nippon)等4个秦岭森林旗舰物种, 被称为“秦岭四宝”。利用红外相机技术开展秦岭野生动物的非损伤性监测不仅可以为秦岭山系提供物种名录信息, 还可以为了解秦岭野生动物的行为和活动格局提供科学数据。清华大学环境学院生态团队自2009-2020年在秦岭中段南坡先后实施了7个项目, 对秦岭南坡的4个保护区进行了野生动物监测, 面积达1,113 km ²(26.5 km × 42 km), 红外相机位点数267个, 相机日数152,160天, 共获取红外相机照片855,260张。共鉴定出27种野生兽类和63种野生鸟类, 并应用这些照片数据开展了信息挖掘工作, 对野生动物行为、稀有物种、与生境的关系, 以及人为活动对野生动物的影响等领域进行了研究, 已取得部分成果。在此基础上建立了“秦岭中段野生动物多样性的红外相机监测数据库平台”, 供团队内部及合作者使用。通过10年的监测, 我们提出未来研究建议: (1)对于非常偶见的物种, 还需要更长的时间并在更多样化的生境布设相机, 以获取更多影像数据评估其现状; (2)数据库需要在更大程度和深度上进行信息挖掘, 尤其在种间关系、物种-生境关系、种群动态等方面; (3)对典型大种群数量的物种(如秦岭羚牛和野猪Sus scrofa)及食物链顶端大型捕食动物(如金钱豹Panthera pardus)进行种群动态研究, 为整个秦岭生态系统的健康持续提供科学支撑; (4)利用数据库的数据及今后红外相机监测数据进行野生动物疾病的发生发展监测研究。     

Circulating exosomal long non‐coding RNAs in patients with acute myocardial infarction

Exosomes are attracting considerable interest in the cardiovascular field as the wide range of their functions is recognized in acute myocardial infarction (AMI). However, the regulatory role of exosomal long non‐coding RNAs (lncRNAs) in AMI remains largely unclear. Exosomes were isolated from the plasma of AMI patients and controls, and the sequencing profiles and twice qRT‐PCR validations of exosomal lncRNAs were performed. A total of 518 differentially expressed lncRNAs were detected over two‐fold change, and 6 kinds of lncRNAs were strikingly elevated in AMI patients with top fold change and were selected to perform subsequent validation. In the two validations, lncRNAs ENST00000556899.1 and ENST00000575985.1 were significantly up‐regulated in AMI patients compared with controls. ROC curve analysis revealed that circulating exosomal lncRNAs ENST00000556899.1 and ENST00000575985.1 yielded the area under the curve values of 0.661 and 0.751 for AMI, respectively. Moreover, ENST00000575985.1 showed more significant relationship with clinical parameters, including inflammatory biomarkers, prognostic indicators and myocardial damage markers. Multivariate logistic model exhibited positive association of ENST00000575985.1 with the risk of heart failure in AMI patients. In summary, our data demonstrated that circulating exosomal lncRNAs ENST00000556899.1 and ENST00000575985.1 are elevated in patients with AMI, functioning as potential biomarkers for predicting the prognosis of pateints with AMI.     

Pyrophosphorolysis of CCA addition: implication for fidelity

In nucleic acid polymerization reaction, pyrophosphorolysis is the reversal of nucleotide addition, in which the terminal nucleotide is excised in the presence of inorganic pyrophosphate (PPi). The CCA enzymes are unusual RNA polymerases, which catalyze CCA addition to positions 74-76 at the tRNA 3′ end without using a nucleic acid template. To better understand the reaction mechanism of CCA addition, we tested pyrophosphorolysis of CCA enzymes, which are divided into two structurally distinct classes. Here, we show that only class II CCA enzymes catalyze pyrophosphorolysis and that the reaction can initiate from all three CCA positions and proceed processively until the removal of nucleotide C74. Pyrophosphorolysis of class II enzymes establishes a fundamental difference from class I enzymes, and it is achieved only with the tRNA structure and with specific divalent metal ions. Importantly, pyrophosphorolysis enables class II enzymes to efficiently remove an incorrect A75 nucleotide from the 3′ end, at a rate much faster than the rate of A75 incorporation, suggesting the ability to perform a previously unexpected quality control mechanism for CCA synthesis. Measurement of kinetic parameters of the class II Escherichia coli CCA enzyme reveals that the enzyme catalyzes pyrophosphorolysis slowly relative to the forward nucleotide addition and that it exhibits weak binding affinity to PPi relative to NTP, suggesting a mechanism in which PPi is rapidly released after each nucleotide addition as a driving force to promote the forward synthesis of CCA.     

Receptor tyrosine kinases positively regulate BACE activity and Amyloid-β production through enhancing BACE internalization

Amyloid-β （Aβ） peptide, the primary constituent of senile plaques in Alzheimer＇s disease （AD）, is generated by β-secretase- and y-secretase-mediated sequential proteolysis of the amyloid precursor protein （APP）. The aspartic protease, β -site APP cleavage enzyme （BACE）, has been identified as the main β-secretase in brain but the regulation of its activity is largely unclear. Here, we demonstrate that both BACE activity and subsequent Aβ production are enhanced after stimulation of receptor tyrosine kinases （RTKs）, such as the receptors for epidermal growth factor （EGF） and nerve growth factor （NGF）, in cultured cells as well as in mouse hippocampus. Furthermore, stimulation of RTKs also induces BACE internalization into endosomes and Golgi apparatus. This enhancement of BACE activity and A β production upon RTK activation could be specifically inhibited by Src family kinase inhibitors and by depletion of endogenous c-Src with RNAi, and could be mimicked by over-expressed c-Src. Moreover, blockage of BACE internalization by a dominant negative form of Rab5 also abolished the enhancement of BACE activity and Aβ production, indicating the requirement of BACE internalization for the enhanced activity. Taken together, our study presents evidence that BACE activity and Aβ production are under the regulation of RTKs and this is achieved via RTK-stimulated BACE internalization, and suggests that an aberration of such regulation might contribute to pathogenic Aβ production.