Plexin-B2 Mediates Physiologic and Pathologic Functions of Angiogenin.

Angiogenin (ANG) is a secreted ribonuclease (RNase) with cell-type- and context-specific roles in growth, survival, and regeneration. Although these functions require receptor-mediated endocytosis and appropriate subcellular localization, the identity of the cell surface receptor remains undefined. Here, we show that plexin-B2 (PLXNB2) is the functional receptor for ANG in endothelial, cancer, neuronal, and normal hematopoietic and leukemic stem and progenitor cells. Mechanistically, PLXNB2 mediates intracellular RNA processing that contribute to cell growth, survival, and regenerative capabilities of ANG. Antibodies generated against the ANG-binding site on PLXNB2 restricts ANG activity in vitro and in vivo, resulting in inhibition of established xenograft tumors, ANG-induced neurogenesis and neuroprotection, levels of pro-self-renewal transcripts in hematopoietic and patient-derived leukemic stem and progenitor cells, and reduced progression of leukemia in vivo. PLXNB2 is therefore required for the physiological and pathological functions of ANG and has significant therapeutic potential in solid and hematopoietic cancers and neurodegenerative diseases.

Angiogenin Promotes Hematopoietic Regeneration by Dichotomously Regulating Quiescence of Stem and Progenitor Cells.

Regulation of stem and progenitor cell populations is critical in the development, maintenance, and regeneration of tissues. Here, we define a novel mechanism by which a niche-secreted RNase, angiogenin (ANG), distinctively alters the functional characteristics of primitive hematopoietic stem/progenitor cells (HSPCs) compared with lineage-committed myeloid-restricted progenitor (MyePro) cells. Specifically, ANG reduces the proliferative capacity of HSPC while simultaneously increasing proliferation of MyePro cells. Mechanistically, ANG induces cell-type-specific RNA-processing events: tRNA-derived stress-induced small RNA (tiRNA) generation in HSPCs and rRNA induction in MyePro cells, leading to respective reduction and increase in protein synthesis. Recombinant ANG protein improves survival of irradiated animals and enhances hematopoietic regeneration of mouse and human HSPCs in transplantation. Thus, ANG plays a non-cell-autonomous role in regulation of hematopoiesis by simultaneously preserving HSPC stemness and promoting MyePro proliferation. These cell-type-specific functions of ANG suggest considerable therapeutic potential.

Myeloid cells protect intestinal epithelial barrier integrity through the angiogenin/plexin-B2 axis.

Communication between myeloid cells and epithelium plays critical role in maintaining intestinal epithelial barrier integrity. Myeloid cells interact with intestinal epithelial cells (IECs) by producing various mediators; however, the molecules mediating their crosstalk remain incompletely understood. Here, we report that deficiency of angiogenin (Ang) in mouse myeloid cells caused impairment of epithelial barrier integrity, leading to high susceptibility to DSS-induced colitis. Mechanistically, myeloid cell-derived angiogenin promoted IEC survival and proliferation through plexin-B2-mediated production of tRNA-derived stress-induced small RNA (tiRNA) and transcription of ribosomal RNA (rRNA), respectively. Moreover, treatment with recombinant angiogenin significantly attenuated the severity of experimental colitis. In human samples, the expression of angiogenin was significantly down-regulated in patients with inflammatory bowel disease (IBD). Collectively, we identified, for the first time to our knowledge, a novel mediator of myeloid cell-IEC crosstalk in maintaining epithelial barrier integrity, suggesting that angiogenin may serve as a new preventive agent and therapeutic target for IBD.

Angiogenin and plexin-B2 axis promotes glioblastoma progression by enhancing invasion, vascular association, proliferation and survival.

BACKGROUND: Angiogenin is a multifunctional secreted ribonuclease that is upregulated in human cancers and downregulated or mutationally inactivated in neurodegenerative diseases. A role for angiogenin in glioblastoma was inferred from the inverse correlation of angiogenin expression with patient survival but had not been experimentally investigated. METHODS: Angiogenin knockout mice were generated and the effect of angiogenin deficiency on glioblastoma progression was examined. Angiogenin and plexin-B2 genes were knocked down in glioblastoma cells and the changes in cell proliferation, invasion and vascular association were examined. Monoclonal antibodies of angiogenin and small molecules were used to assess the therapeutic activity of the angiogenin-plexin-B2 pathway in both genetic and xenograft animal models. RESULTS: Deletion of Ang1 gene prolonged survival of PDGF-induced glioblastoma in mice in the Ink4a/Arf-/-:Pten-/- background, accompanied by decreased invasion, vascular association and proliferation. Angiogenin upregulated MMP9 and CD24 leading to enhanced invasion and vascular association. Inhibition of angiogenin or plexin-B2, either by shRNA, monoclonal antibody or small molecule inhibitor, decreases sphere formation of patient-derived glioma stem cells, reduces glioblastoma proliferation and invasion and inhibits glioblastoma growth in both genetic and xenograft animal models. CONCLUSIONS: Angiogenin and its receptor, plexin-B2, are a pair of novel regulators that mediate invasion, vascular association and proliferation of glioblastoma cells. Inhibitors of the angiogenin-plexin-B2 axis have therapeutic potential against glioblastoma.

Management Strategy and Radiologic Outcomes of Symptomatic Spontaneous Isolated Superior Mesenteric Artery Dissection Based on Angiographic Classification: The Follow-Up Experience in a Single Center.

PURPOSE: To investigate the demographics, clinical features, radiologic measurement, treatment, and outcomes of symptomatic spontaneous isolated superior mesenteric artery dissection (SISMAD) according to computed tomography (CT) classification. METHODS: This retrospective study included 201 patients diagnosed with symptomatic SISMAD from November 2014 to December 2020. Symptomatic spontaneous isolated superior mesenteric artery dissection was categorized into four types based on CT images by Yun's angiographic classification. Their clinical characteristics, images features, treatment methods, and radiological outcomes were comparatively analyzed by CT angiographic types. RESULTS: SISMADs were categorized into type I (13.9%) patent false lumen (FL) with both entry and re-entry; type IIa (37.3%), blind pouch of FL; type IIb (43.3%), thrombosed FL; and type III (5.5%), and the occlusion of superior mesenteric artery (SMA). Type IIb, the most common SISMAD, showed the largest true lumen (TL) residual diameter and the lowest percentage of TL stenosis. Type III positioned most proximally to SMA origin and had the maximum dissection length. Symptomatic spontaneous isolated superior mesenteric artery dissections underwent conservative (75.1%), endovascular (22.4%), and surgical (2.5%) treatment. Conservative treatment was more frequent in type I (85.7%) and type IIb (83.9%) than in type IIa (65.3%) and type III (45.5%). Endovascular intervention was more commonly utilized in type IIa (32.0%) and type III (36.4%) than in type I (14.3%) and type IIb (14.9%). Conservative patients achieved FL vanishment/shrinkage (57.8%), stabilization (26.6%), and enlargement (15.6%). After conservative treatment, type I showed angiographic FL stabilization; type IIa achieved FL shrinkage (48.1%), stabilization (22.2%), and enlargement (29.6%); type IIb exhibited FL vanishment/shrinkage (92.0%) and enlargement (8.0%). Cumulative rate of stent patency was 92.3% during 6-year follow-up. CONCLUSIONS: Conservative management with close follow-up is initially provided especially for types I and IIb. Morphological stabilization is more frequent in type I of patent FL with entry and re-entry. False lumen vanishment or shrinkage was more likely to occur in type IIb due to the thrombus absorption. Endovascular intervention has excellent long-term in-stent patency and is predominantly utilized in types IIa and III. Blood flow sustained into a blind-ending FL causes the TL compression and stenosis in type IIa. Type III with the occlusion of SMA has the high risk of bowel ischemia. CLINICAL IMPACT: According to Yun's angiographic classification of spontaneous isolated superior mesenteric artery dissection (SISMAD), type I (13.9%) has patent true and false lumen and the morphological pattern is maintained stable; type IIa (37.3%) possesses a patent blind-ending false lumen which might shrink, remain unchanged, or enlarge; and endovascular intervention is suggested when conservative treatment failed; type IIb (43.3%) recovers spontaneously due to the absorption of false lumen thrombus and conservative treatment is preferentially considered; type III (5.5%) with the occlusion of main trunk carries a high risk of bowel necrosis, early endovascular intervention is proposed, and open surgery might be necessary.

Angiogenin maintains gut microbe homeostasis by balancing α-Proteobacteria and Lachnospiraceae.

OBJECTIVE: Antimicrobial peptides (AMPs) play essential roles in maintaining gut health and are associated with IBD. This study is to elucidate the effect of angiogenin (ANG), an intestine-secreted AMP, on gut microbiota and its relevance with IBD. DESIGN: The effect of ANG on microbiota and its contribution to colitis were evaluated in different colitis models with co-housing and faecal microbiota transplantation. ANG-regulated bacteria were determined by 16S rDNA sequencing and their functions in colitis were analysed by bacterial colonisation. The species-specific antimicrobial activity of ANG and its underlying mechanism were further investigated with microbiological and biochemical methods. ANG level and the key bacteria were characterised in IBD faecal samples. RESULTS: ANG regulated microbiota composition and inhibited intestinal inflammation. Specifically, Ang1 deficiency in mice led to a decrease in the protective gut commensal strains of Lachnospiraceae but an increase in the colitogenic strains of α-Proteobacteria. Direct binding of ANG to α-Proteobacteria resulted in lethal disruption of bacterial membrane integrity, and consequently promoted the growth of Lachnospiraceae, which otherwise was antagonised by α-Proteobacteria. Oral administration of ANG1 reversed the dysbiosis and attenuated the severity of colitis in Ang1-deficient mice. The correlation among ANG, the identified bacteria and IBD status was established in patients. CONCLUSION: These findings demonstrate a novel role of ANG in shaping gut microbe composition and thus maintaining gut health, suggesting that the ANG-microbiota axis could be developed as a potential preventive and/or therapeutic approach for dysbiosis-related gut diseases.

De novo transcriptome in roots of switchgrass (Panicum virgatum L.) reveals gene expression dynamic and act network under alkaline salt stress.

BACKGROUND: Soil salinization is a major limiting factor for crop cultivation. Switchgrass is a perennial rhizomatous bunchgrass that is considered an ideal plant for marginal lands, including sites with saline soil. Here we investigated the physiological responses and transcriptome changes in the roots of Alamo (alkaline-tolerant genotype) and AM-314/MS-155 (alkaline-sensitive genotype) under alkaline salt stress. RESULTS: Alkaline salt stress significantly affected the membrane, osmotic adjustment and antioxidant systems in switchgrass roots, and the ASTTI values between Alamo and AM-314/MS-155 were divergent at different time points. A total of 108,319 unigenes were obtained after reassembly, including 73,636 unigenes in AM-314/MS-155 and 65,492 unigenes in Alamo. A total of 10,219 DEGs were identified, and the number of upregulated genes in Alamo was much greater than that in AM-314/MS-155 in both the early and late stages of alkaline salt stress. The DEGs in AM-314/MS-155 were mainly concentrated in the early stage, while Alamo showed greater advantages in the late stage. These DEGs were mainly enriched in plant-pathogen interactions, ubiquitin-mediated proteolysis and glycolysis/gluconeogenesis pathways. We characterized 1480 TF genes into 64 TF families, and the most abundant TF family was the C2H2 family, followed by the bZIP and bHLH families. A total of 1718 PKs were predicted, including CaMK, CDPK, MAPK and RLK. WGCNA revealed that the DEGs in the blue, brown, dark magenta and light steel blue 1 modules were associated with the physiological changes in roots of switchgrass under alkaline salt stress. The consistency between the qRT-PCR and RNA-Seq results confirmed the reliability of the RNA-seq sequencing data. A molecular regulatory network of the switchgrass response to alkaline salt stress was preliminarily constructed on the basis of transcriptional regulation and functional genes. CONCLUSIONS: Alkaline salt tolerance of switchgrass may be achieved by the regulation of ion homeostasis, transport proteins, detoxification, heat shock proteins, dehydration and sugar metabolism. These findings provide a comprehensive analysis of gene expression dynamic and act network induced by alkaline salt stress in two switchgrass genotypes and contribute to the understanding of the alkaline salt tolerance mechanism of switchgrass and the improvement of switchgrass germplasm.

Integrated Analysis of the Transcriptome and Metabolome Revealed Candidate Genes Involved in GA3-Induced Dormancy Release in Leymus chinensis Seeds.

Leymus chinensis is a perennial forage grass that has good palatability, high yield and high feed value, but seed dormancy is a major problem limiting the widespread cultivation of L. chinensis. Here, we performed transcriptomic and metabolomic analysis of hulled and de-hulled seeds of L. chinensis treated with or without GA3 to investigate the changes in gene and metabolites associated with dormancy release induced by GA3. The germination test revealed that the optimum concentration of GA3 for disruption of L. chinensis seed dormancy was 577 µM. A total of 4327 and 11,919 differentially expressed genes (DEGs) and 871 and 650 differentially abundant metabolites were identified in de-hulled and hulled seeds treated with GA3, respectively, compared with seeds soaked in sterile water. Most of the DEGs were associated with starch and sucrose metabolism, protein processing in the endoplasmic reticulum, endocytosis and ribosomes. Furthermore, isoquinoline alkaloid biosynthesis, tyrosine metabolism, starch and sucrose metabolism, arginine and proline metabolism, and amino sugar and nucleotide sugar metabolism were significantly enriched pathways. Integrative analysis of the transcriptomic and metabolomic data revealed that starch and sucrose metabolism is one of the most important pathways that may play a key role in providing carbon skeletons and energy supply for the transition of L. chinensis seeds from a dormant state to germination by suppressing the expression of Cel61a, egID, cel1, tpsA, SPAC2E11.16c and TPP2, enhancing the expression of AMY1.1, AMY1.2, AMY1.6 and GLIP5, and inhibiting the synthesis of cellobiose, cellodextrin, and trehalose while promoting the hydrolysis of sucrose, starch, cellobiose, cellodextrin, and trehalose to glucose. This study identified several key genes and provided new insights into the molecular mechanism of seed dormancy release induced by GA3 in L. chinensis. These putative genes will be valuable resources for improving the seed germination rate in future breeding studies.

Angiogenin regulates PKD activation and COX-2 expression induced by TNF-α and bradykinin in the colonic myofibroblast.

INTRODUCTION: The myofibroblast is a gastrointestinal stromal cell that is a target of tumor necrosis factor-alpha (TNF-α), a pro-inflammatory cytokine strongly implicated in colitis-associated cancer. Crosstalk between TNF-α and other pro-inflammatory mediators amplify inflammatory signaling but the mechanism is unknown. Angiogenin (ANG) is a 14-kDa angiogenesis protein that is regulated in patients with inflammatory bowel disease. However, the role of ANG on inflammatory mediator crosstalk in the myofibroblast is unknown. METHODS: The human colonic myofibroblast cell line 18Co, as well as primary mouse and human colonic myofibroblasts, were exposed to TNF-α (10 ng/ml) and bradykinin (BK, 100 nM). ANG was quantified by ELISA. The expression of cyclo-oxygenase-2 (COX-2) and phosphorylation of PKD was assessed by Western Blot. RESULTS: Primary mouse and human colonic myofibroblasts exposed to TNF-α/BK led to enhanced PKD phosphorylation and synergistic COX-2 expression. 18Co cells secrete high levels of ANG (24h, 265 ± 5 pg/ml). The monoclonal antibody 26-2F, which neutralizes ANG, inhibited TNF-α/BK-mediated PKD phosphorylation and synergistic COX-2 expression in primary human myofibroblasts. Likewise, in primary mouse myofibroblasts that do not express ANG (ANG-KO), TNF-α/BK failed to enhance PKD phosphorylation and COX-2 expression. CONCLUSIONS: TNF-α/BK enhance PKD phosphorylation and COX-2 expression in primary mouse and human colonic myofibroblasts. Angiogenin is produced by the myofibroblast, and inhibition of ANG signaling, either by its absence (ANG-KO) or by pharmacologic inhibition, blocks enhanced PKD phosphorylation and synergistic COX-2 expression induced by TNF-α/BK. ANG mediates crosstalk signaling between TNF-α/BK in the regulation of stroma-derived COX-2 and may be a novel therapeutic target for the management of colitis-associated cancer.

Full-length transcriptome sequencing reveals the low-temperature-tolerance mechanism of Medicago falcata roots.

BACKGROUND: Low temperature is one of the main environmental factors that limits crop growth, development, and production. Medicago falcata is an important leguminous herb that is widely distributed worldwide. M. falcata is related to alfalfa but is more tolerant to low temperature than alfalfa. Understanding the low temperature tolerance mechanism of M. falcata is important for the genetic improvement of alfalfa. RESULTS: In this study, we explored the transcriptomic changes in the roots of low-temperature-treated M. falcata plants by combining SMRT sequencing and NGS technologies. A total of 115,153 nonredundant sequences were obtained, and 8849 AS events, 73,149 SSRs, and 4189 lncRNAs were predicted. A total of 111,587 genes from SMRT sequencing were annotated, and 11,369 DEGs involved in plant hormone signal transduction, protein processing in endoplasmic reticulum, carbon metabolism, glycolysis/gluconeogenesis, starch and sucrose metabolism, and endocytosis pathways were identified. We characterized 1538 TF genes into 45 TF gene families, and the most abundant TF family was the WRKY family, followed by the ERF, MYB, bHLH and NAC families. A total of 134 genes, including 101 whose expression was upregulated and 33 whose expression was downregulated, were differentially coexpressed at all five temperature points. PB40804, PB75011, PB110405 and PB108808 were found to play crucial roles in the tolerance of M. falcata to low temperature. WGCNA revealed that the MEbrown module was significantly correlated with low-temperature stress in M. falcata. Electrolyte leakage was correlated with most genetic modules and verified that electrolyte leakage can be used as a direct stress marker in physiological assays to indicate cell membrane damage from low-temperature stress. The consistency between the qRT-PCR results and RNA-seq analyses confirmed the validity of the RNA-seq data and the analysis of the regulatory mechanism of low-temperature stress on the basis of the transcriptome. CONCLUSIONS: The full-length transcripts generated in this study provide a full characterization of the transcriptome of M. falcata and may be useful for mining new low-temperature stress-related genes specific to M. falcata. These new findings could facilitate the understanding of the low-temperature-tolerance mechanism of M. falcata.

HDAC3 modulates cancer immunity via increasing PD-L1 expression in pancreatic cancer.

Pancreatic ductal adenocarcinoma (PDAC) is the second leading cause of cancer-related deaths worldwide. Despite immune checkpoints based immunotherapy highlights a new therapeutic strategy and achieves a remarkable therapeutic effect in various types of malignant tumors. Pancreatic cancer is one of the non-immunogenic cancers and is resistant to immunotherapy. Programmed death ligand 1 (PD-L1) is expressed on the surface of tumor cells and its level is a key determinant of the checkpoint immunotherapy efficacy. Here, we reported that the specific inhibitor of histone deacetylase 3 (HDAC3) decreased the protein and mRNA level of PD-L1 in pancreatic cancer cells. Furthermore, we showed that HDAC3 was critical for PD-L1 regulation and positively correlated with PD-L1 in PDAC patient specimens. Finally, we demonstrated that HDAC3/signal transducer and activator of transcription 3 (STAT3) pathway transcriptionally regulated PD-L1 expression. Collectively, our data contributes to a better understanding of the function of HDAC3 in cancer immunity and the regulatory mechanism of PD-L1. More importantly, these data suggest that the HDAC3 inhibitors might be used to improve immunotherapy in pancreatic cancer.

Sub-chronic 90-day toxicity of neamine in SD rats and its anti-liver cancer activity in vitro and in vivo.

Neamine, an inhibitor of angiogenin (ANG), is a new investigative anticancer drug currently in preclinical stage. Here we report the 90-day sub-chronic toxicity of neamine in SD rats and its anti-liver cancer activity in vitro and in vivo. Neamine has a No Observed Adverse Effect Level (NOAEL) of 12 and 16mg·kg-1·d-1 for female and male rats, respectively. No mortality was found. The adverse effects included increased organ coefficients of spleen and kidney, increased BUN in both female and male rats at high dose, increased CR and decreased organ coefficients of heart and liver in male rats at high dose. All of which, except the kidney coefficient and BUN in males, returned to normal levels after 28-day recovery. Histopathological examination revealed vacuolar degeneration of glomerulus, degeneration of renal tubules and cast in the kidneys, which were also recovered except in males of high-dosing group. These results indicate that kidney is the most susceptible organ for neamine toxicity. Tissue microarray analysis validated that ANG is up-regulated in hepatocellular carcinoma accompanied by increased nuclear translocation, suggesting that ANG is a possible target for drug development in liver cancer treatment. Neamine blocked nuclear translocation of ANG in HUVEC and HepG2 cells, and inhibited ANG-stimulated cell proliferation without affecting basal level cell proliferation. Neamine also inhibited progression of HepG2 xenografts in athymic mice accompanied by decreased angiogenesis and cancer cell proliferation. These results suggest that neamine is a specific ANG inhibitor with low toxicity and high anti-liver cancer efficacy.

Angiogenin Mediates Cell-Autonomous Translational Control under Endoplasmic Reticulum Stress and Attenuates Kidney Injury.

Endoplasmic reticulum (ER) stress is involved in the pathophysiology of kidney disease and aging, but the molecular bases underlying the biologic outcomes on the evolution of renal disease remain mostly unknown. Angiogenin (ANG) is a ribonuclease that promotes cellular adaptation under stress but its contribution to ER stress signaling remains elusive. In this study, we investigated the ANG-mediated contribution to the signaling and biologic outcomes of ER stress in kidney injury. ANG expression was significantly higher in samples from injured human kidneys than in samples from normal human kidneys, and in mouse and rat kidneys, ANG expression was specifically induced under ER stress. In human renal epithelial cells, ER stress induced ANG expression in a manner dependent on the activity of transcription factor XBP1, and ANG promoted cellular adaptation to ER stress through induction of stress granules and inhibition of translation. Moreover, the severity of renal lesions induced by ER stress was dramatically greater in ANG knockout mice (Ang(-/-)) mice than in wild-type mice. These results indicate that ANG is a critical mediator of tissue adaptation to kidney injury and reveal a physiologically relevant ER stress-mediated adaptive translational control mechanism.

Transcription of angiogenin and ribonuclease 4 is regulated by RNA polymerase III elements and a CCCTC binding factor (CTCF)-dependent intragenic chromatin loop.

Angiogenin (ANG) and ribonuclease 4 (RNASE4), two members of the secreted and vertebrate-specific ribonuclease superfamily, play important roles in cancers and neurodegenerative diseases. The ANG and RNASE4 genes share genetic regions with promoter activities, but the structure and regulation of these putative promotes are unknown. We have characterized the promoter regions, defined the transcription start site, and identified a mechanism of transcription regulation that involves both RNA polymerase III (Pol III) elements and CCCTC binding factor (CTCF) sites. We found that two Pol III elements within the promoter region influence ANG and RNASE4 expression in a position- and orientation-dependent manner. We also provide evidence for the presence of an intragenic chromatin loop between the two CTCF binding sites located in two introns flanking the ANG coding exon. We found that formation of this intragenic loop preferentially enhances ANG transcription. These results suggest a multilayer transcriptional regulation of ANG and RNASE4 gene locus. These data also add more direct evidence to the notion that Pol III elements are able to directly influence Pol II gene transcription. Furthermore, our data indicate that a CTCF-dependent chromatin loop is able to differentially regulate transcription of genes that share the same promoters.

Ribonuclease/angiogenin inhibitor 1 regulates stress-induced subcellular localization of angiogenin to control growth and survival.

Angiogenin (ANG) promotes cell growth and survival. Under growth conditions, ANG undergoes nuclear translocation and accumulates in the nucleolus where it stimulates rRNA transcription. When cells are stressed, ANG mediates the production of tRNA-derived stress-induced small RNA (tiRNA), which reprograms protein translation into a survival mechanism. The ribonucleolytic activity of ANG is essential for both processes but how this activity is regulated is unknown. We report here that ribonuclease/angiogenin inhibitor 1 (RNH1) controls both the localization and activity of ANG. Under growth conditions, ANG is located in the nucleus and is not associated with RNH1 so that the ribonucleolytic activity is retained to ensure rRNA transcription. Cytoplasmic ANG is associated with and inhibited by RNH1 so that random cleavage of cellular RNA is prevented. Under stress conditions, ANG is localized to the cytoplasm and is concentrated in stress granules where it is not associated with RNH1 and thus remains enzymatically active for tiRNA production. By contrast, nuclear ANG is associated with RNH1 in stressed cells to ensure that the enzymatic activity is inhibited and no unnecessary rRNA is produced to save anabolic energy. Knockdown of RNH1 abolished stress-induced relocalization of ANG and decreased cell growth and survival.

Angiogenin stimulates ribosomal RNA transcription by epigenetic activation of the ribosomal DNA promoter.

Angiogenin (ANG) undergoes nuclear translocation and promotes ribosomal RNA (rRNA) transcription thereby enhancing cell growth and proliferation. However, the mode of action of ANG in stimulating rRNA transcription is unclear. Here, we show that ANG enhances the formation of RNA polymerase I (Pol I) pre-initiation complex at the ribosomal DNA (rDNA) promoter. ANG binds at the upstream control element (UCE) of the promoter and enhances promoter occupancy of RNA Pol I as well as the selectivity factor SL1 components TAFI 48 and TAFI 110. We also show that ANG increases the number of actively transcribing rDNA by epigenetic activation through promoter methylation and histone modification. ANG binds to histone H3, inhibits H3K9 methylation, and activates H3K4 methylation as well as H4 acetylation at the rDNA promoter. These data suggest that one of the mechanisms by which ANG stimulates rRNA transcription is through an epigenetic activation of rDNA promoter.

Metagenomics study of soil microorganisms involved in the carbon cycle in a saline-alkaline meadow steppe in the Songnen Plain in Northeast China.

Soil microorganisms play an important role in regulating and contributing to carbon cycling processes in grassland ecosystems. Soil salinization is one of the major problems causing soil degradation, and its effects on carbon cycle immobilization-related functional genes in soil microorganisms remain unknown. Therefore, we took Songnen salinization grassland as the research object, selected grasslands with different salinization levels, and explored the diversity of soil microorganisms and functional genes related to carbon cycling in Songnen grassland with different salinization levels through metagenomic technology. The results showed that with the increase of salinity, the relative abundance of Ascomycetes increased, while the relative abundance of Proteus and Firmicutes decreased. In addition, the relative abundance of functional genes related to carbon cycling fixation has also decreased. As the degree of soil salinization increases, the relative abundance of glycoside hydrolases (GH)130 family significantly increases, while the relative abundance of soil carbohydrate enzymes belonging to GH3 and GH55 families significantly decreases. Using structural equation modeling (SEM), it was found that soil pH and conductivity (EC) have a significant impact on soil microbial diversity and functional genes related to carbon cycling fixation. The increase in soil pH directly reduces the Shannon diversity of soil microbial diversity and functional genes related to carbon cycling fixation. Therefore, it can be concluded that the intensification of grassland salinization reduces the diversity of bacteria and fungi, and affects the diversity of functional genes related to carbon cycling fixation by reducing the total diversity of bacteria. The increase in salinity has a negative feedback effect on grassland soil carbon cycling. This study provides a theoretical framework for grassland soil carbon sequestration and degradation restoration.

Effect of Growth Stage on Nutrition, Fermentation Quality, and Microbial Community of Semidry Silage from Forage Soybean.

Soybean (Glycine max (Linn.) Merr.) is highly suitable as animal feed. The silage quality and microbial characteristics of soybean silage are still unclear. Forage soybean (HN389), at six different growth stages (R2-R7), were used as experimental materials to investigate the changes in fermentation, nutritional quality, and microbial characteristics of semidry silage after 0, 7, 14, 30, and 45 d. As the growth period extended, the content of crude protein (CP) and crude fat (EE) gradually increased, while the neutral detergent fiber (NDF) and the acid detergent fiber (ADF) content decreased. The pH value also decreased gradually with fermentation time, accompanied by increases in the proportion of ammonia-N and the content of lactic acid (LA) and acetic acid (AA). In addition, competitive inhibition was observed in the microbial fermentation. With the process of ensiling, Lactobacillus became the dominant bacterial species. The results indicate that the most active stage of fermentation during ensiling occurred within the first 7 days, the fermentation and nutritional quality of the soybean forage were improved, and the optimal mowing stage was the grain stage. Comparison of the microbial abundance showed that all microorganisms entered a stable stage at 30 days of silage. After storage, the dominant bacteria were Lactobacillus, Enterobacter, and Pantoea.

CDK6 inhibits de novo lipogenesis in white adipose tissues but not in the liver.

Increased de novo lipogenesis (DNL) in white adipose tissue is associated with insulin sensitivity. Under both Normal-Chow-Diet and High-Fat-Diet, mice expressing a kinase inactive Cyclin-dependent kinase 6 (Cdk6) allele (K43M) display an increase in DNL in visceral white adipose tissues (VAT) as compared to wild type mice (WT), accompanied by markedly increased lipogenic transcriptional factor Carbohydrate-responsive element-binding proteins (CHREBP) and lipogenic enzymes in VAT but not in the liver. Treatment of WT mice under HFD with a CDK6 inhibitor recapitulates the phenotypes observed in K43M mice. Mechanistically, CDK6 phosphorylates AMP-activated protein kinase, leading to phosphorylation and inactivation of acetyl-CoA carboxylase, a key enzyme in DNL. CDK6 also phosphorylates CHREBP thus preventing its entry into the nucleus. Ablation of runt related transcription factor 1 in K43M mature adipocytes reverses most of the phenotypes observed in K43M mice. These results demonstrate a role of CDK6 in DNL and a strategy to alleviate metabolic syndromes.

Genome-wide identification and quantitative analysis of cleaved tRNA fragments induced by cellular stress.

Certain stress conditions can induce cleavage of tRNAs around the anticodon loop via the use of the ribonuclease angiogenin. The cellular factors that regulate tRNA cleavage are not well known. In this study we used normal and eIF2α phosphorylation-deficient mouse embryonic fibroblasts and applied a microarray-based methodology to identify and compare tRNA cleavage patterns in response to hypertonic stress, oxidative stress (arsenite), and treatment with recombinant angiogenin. In all three scenarios mouse embryonic fibroblasts deficient in eIF2α phosphorylation showed a higher accumulation of tRNA fragments including those derived from initiator-tRNA(Met). We have shown that tRNA cleavage is regulated by the availability of angiogenin, its substrate (tRNA), the levels of the angiogenin inhibitor RNH1, and the rates of protein synthesis. These conclusions are supported by the following findings: (i) exogenous treatment with angiogenin or knockdown of RNH1 increased tRNA cleavage; (ii) tRNA fragment accumulation was higher during oxidative stress than hypertonic stress, in agreement with a dramatic decrease of RNH1 levels during oxidative stress; and (iii) a positive correlation was observed between angiogenin-mediated tRNA cleavage and global protein synthesis rates. Identification of the stress-specific tRNA cleavage mechanisms and patterns will provide insights into the role of tRNA fragments in signaling pathways and stress-related disorders.