Interactions of a laminin-binding peptide from a 33-kDa protein related to the 67-kDa laminin receptor with laminin and melanoma cells are heparin-dependent.

A laminin-binding peptide (peptide G), predicted from the cDNA sequence for a 33-kDa protein related to the 67-kDa laminin receptor, specifically inhibits binding of laminin to heparin and sulfatide. Since the peptide binds directly to heparin and inhibits interaction of another heparin-binding protein with the same sulfated ligands, this inhibition is due to direct competition for binding to sulfated glycoconjugates rather than an indirect effect of interaction with the binding site on laminin for the 67-kDa receptor. Direct binding of laminin to the peptide is also inhibited by heparin. This interaction may result from contamination of the laminin with heparan sulfate, as binding is enhanced by the addition of substoichiometric amounts of heparin but inhibited by excess heparin and two heparin-binding proteins. Furthermore, laminin binds more avidly to a heparin-binding peptide derived from thrombospondin than to the putative receptor peptide. Adhesion of A2058 melanoma cells on immobilized peptide G is also heparin-dependent, whereas adhesion of the cells on laminin is not. Antibodies to the beta 1-integrin chain or laminin block adhesion of the melanoma cells to laminin but not to peptide G. Thus, the reported inhibition of melanoma cell adhesion to endothelial cells by peptide G may result from inhibition of binding of laminin or other proteins to sulfated glycoconjugate receptors rather than from specific inhibition of laminin binding to the 67-kDa receptor.     

Conformational preference and ligand binding properties of DNA junctions are determined by sequence at the branch

Four-arm DNA branched junctions are stable analogues of Holliday recombinational intermediates. A number of four-arm DNA junctions synthesized from oligonucleotides have now been studied. Gel mobility or chemical footprinting experiments on several immobile four-arm junctions indicate that in the presence of Mg2+, they assume a preferred conformation consisting of two helical domains, each formed by stacking a particular pair of arms on each other. We show here that a junction we designate as J1c that has the same chemical composition as one we have previously studied in detail, J1, but is formed from the four strands complementary to those of the latter, exhibits the reverse stacking preference. The pattern of self-protection of the strands of J1c exposed to Fe(II).EDTA-induced scission reveals that twofold symmetry is preserved, but the opposite pair of strands preferentially cross over. Moreover, the Fe(II).EDTA scission profiles of J1c indicate that this junction exhibits a weaker bias as to which strands cross over than is observed in J1. The preference for the dominant species in J1 is 1.3 times greater than in J1c at 4 degrees C and in the presence of 10 mM Mg2+, based on chemical reactivity data. This is confirmed by a cleavage experiment using the resolvase enzyme, endonuclease I, from bacteriophage T7. This difference could reflect either sequence-dependent differences in the equilibrium among isomers, or in the structure of these junctions. Chemical footprinting experiments using the probes MPE.Fe(II) and (OP)2Cu(I) show that the high-affinity ligand binding site in immobile junctions is determined by junction geometry.     

Tumor necrosis factor-alpha enhances inhibitory effects of interleukin-1 beta on Leydig cell steroidogenesis

Human recombinant tumor necrosis factor-alpha (rTNF alpha) alone (up to 1000 units/ml) did not alter either basal or human chorionic gonadotropin (hCG)-induced testosterone formation in primary culture of rat Leydig cells. However, concomitant addition of rTNF alpha with human recombinant interleukin-1 beta (rIL-1 beta) enhanced the inhibitory effects of rIL-1 beta. The rIL-1 beta dose response curve was shifted to the left (IC50 changed from 1 ng/ml to 0.3 ng/ml). Even though rTNF alpha had no effect on testosterone formation, hCG-stimulated cyclic AMP formation was inhibited by rTNF alpha in a dose dependent manner. In the presence of both rTNF alpha and rIL-1 beta, hCG-induced cyclic AMP formation and binding of [125I]-hCG to Leydig cells were further inhibited. Testicular macrophages represent about 20% of the interstitial cells. TNF alpha and IL-1 may be produced locally by interstitial macrophages and have paracrine effects on Leydig cell function.     

Five polymorphic microsatellite VNTRs on the human X chromosome

The human genome contains approximately 50,000 copies of an interspersed repeat with the sequence (dT.dG/dA.dC)n, where n = approximately 10-60. We and others have found that several of these repeats have variable lengths in different individuals, with allelic fragments varying in size by multiples of 2 bp. These "microsatellite" variable number of tandem repeats (VNTRs) may be scored by PCR, using unique flanking primers to amplify the repeat-containing regions and resolving the products on DNA sequencing gels. Since few VNTRs have been found on the X chromosome, we screened a flow-sorted X chromosome-specific genomic library for microsatellites. Approximately 25% of the phage clones hybridized to a poly (dT-dG).poly(dA-dC) probe. Of seven X-linked microsatellites present in positive phages, five are polymorphic and three have both eight or more alleles and heterozygosities exceeding 75%. Using PCR to amplify genomic DNAs from hybrid cell panels, we confirmed the X localization of these VNTRs and regionally mapped four of them. The fifth VNTR was regionally mapped by virtue of its tight linkage to DXS87 in Centre du Polymorphisme Humain families. We conclude that whatever factors limit the occurrence of "classical" VNTRs and RFLPs on the X chromosome do not appear to operate in the case of microsatellite VNTRs.     

若尔盖沙化土地治理土壤微生物群落与功能基因比较研究

【目的】在高寒沙地中建立以赖草和沙生苔草等先锋植物为主的人工草方格,探究其土壤微生物群落动态变化以及养分循环过程。【方法】采用宏基因组测序和qPCR方法进行土壤微生物群落结构组成分析、功能基因注释和绝对丰度测定,并结合土壤理化因子数据进行冗余分析。【结果】人工建立草方格后,沙地土壤中全氮、速效磷以及有机碳含量分别提高了20%-68%、10%-247%、19%-56%;细菌和真菌的群落数量分别提高了17%-81%和2%-95%,与植物促生长相关的鞘氨醇单胞菌属(Sphingomonas)、慢生根瘤菌属(Bradyrhizobium)、硝化螺旋菌属(Nitrospira)、Solirubrobacter属和类诺卡氏菌属(Nocardioides)等细菌种类的相对丰度呈上升趋势;氮循环中与氨氧化和亚硝酸盐氧化相关的amoCAB基因簇和nxrAB基因簇显著富集,发现了完全氨氧化的基因标志。【结论】人工建立草方格有效提升了高寒沙地土壤养分和微生物群落数量,促进了养分循环。适度放牧可以增加沙地生态系统的氮汇扩散性,有助于本土先锋植物定植,为今后在同等高海拔地区采取沙地生态修复措施提供理论参考。     

Rapid improvement of rice eating and cooking quality through gene editing toward glutelin as target

Rice eating and cooking quality(ECQ) is a major concern of breeders and consumers, determining market competitiveness worldwide. Rice grain protein content(GPC) is negatively related to ECQ,making it possible to improve ECQ by manipulating GPC. However, GPC is genetically complex and sensitive to environmental conditions; therefore, little progress has been made in traditional breeding for ECQ. Here, we report that CRISPR/Cas9-mediated knockout of genes encoding the grain storage protein gluteli...     

Rhizosphere soil bacterial communities and nitrogen cycling affected by deciduous and evergreen tree species

Deciduous and evergreen trees differ in their responses to drought and nitrogen (N) demand. Whether or not these functional types affect the role of the bacterial community in the N cycle during drought remains uncertain. Two deciduous tree species (Alnus cremastogyne, an N₂‐fixing species, and Liquidambar formosana) and two evergreen trees (Cunninghamia lanceolata and Pinus massoniana) were used to assess factors in controlling rhizosphere soil bacterial community and N cycling functions. Photosynthetic rates and biomass production of plants, 16S rRNA sequencing and N‐cycling‐related genes of rhizosphere soil were measured. The relative abundance of the phyla Actinobacteria and Firmicutes was higher, and that of Proteobacteria, Acidobacteria, and Gemmatimondaetes was lower in rhizosphere soil of deciduous trees than that of evergreen. Beta‐diversity of bacterial community also significantly differed between the two types of trees. Deciduous trees showed significantly higher net photosynthetic rates and biomass production than evergreen species both at well water condition and short‐term drought. Root biomass was the most important factor in driving soil bacterial community and N‐cycling functions than total biomass and aboveground biomass. Furthermore, 44 bacteria genera with a decreasing response and 46 taxa showed an increased response along the root biomass gradient. Regarding N‐cycle‐related functional genes, copy numbers of ammonia‐oxidizing bacteria (AOB) and autotrophic ammonia‐oxidizing archaea (AOA), N₂ fixation gene (nifH), and denitrification genes (nirK, nirS) were significantly higher in the soil of deciduous trees than in that of the evergreen. Structural equation models explained 50.2%, 47.6%, 48.6%, 49.4%, and 37.3% of the variability in copy numbers of nifH, AOB, AOA, nirK, and nirS, respectively, and revealed that root biomass had significant positive effects on copy numbers of all N‐cycle functional genes. In conclusion, root biomass played key roles in affecting bacterial community structure and soil N cycling. Our findings have important implications for our understanding of plants control over bacterial community and N‐cycling function in artificial forest ecosystems.     

Design,synthesis, and biological evaluation of novel carbazole derivatives as potent DNMT1 inhibitors with reasonable PK properties

The DNA methyltransferases (DNMTs) were found in mammals to maintain DNA methylation. Among them, DNMT1 was the first identified, and it is an attractive target for tumour chemotherapy. DC_05 and DC_517 have been reported in our previous work, which is non-nucleoside DNMT1 inhibitor with low micromolar IC₅₀ values and significant selectivity towards other S-adenosyl-_L-methionine (SAM)-dependent protein methyltransferases. In this study, through a process of similarity-based analog searching, a series of DNMT1 inhibitors were designed, synthesized, and evaluated as anticancer agents. SAR studies were conducted based on enzymatic assays. And most of the compounds showed strong inhibitory activity on human DNMT1, especially WK-23 displayed a good inhibitory effect on human DNMT1 with an IC₅₀ value of 5.0 µM. Importantly, the pharmacokinetic (PK) profile of WK-23 was obtained with quite satisfying oral bioavailability and elimination half-life. Taken together, WK-23 is worth developing as DNMT1-selective therapy for the treatment of malignant tumour.     

羊草草原枯枝落叶分解的研究——主要优势植物的分解速率和损失率

分解速率和损失率从不同侧面反映了枯枝落叶分解动态,羊草草原主要优势植物,羊草（Leymus chinensis),拂子茅（Calamagrostis epigejos),减蓬（Suaeda glauca),碱茅（Puccinellia tenuiflora),五脉山黎豆（Lathyrus quinqueneruivs),碱蒿（Artemisia anethifolia)分解速率的季节变化动态近似倒“V”字型,损失率的季节变化呈S型,反了枯枝落叶的失重情况,枯枝落叶的化学组成成分是造成不同种植物间分解差异的主要原因,特别是C／N比与分解快慢有密切关系,分解初期,枯枝落叶的损失符合指数衰减模型,枯枝落叶损失95％所需时间,羊草群落约为8．8a,杂类草群落约为9．7a,碱茅群落约为7．1a,碱蓬群落约为4．7a。