Smed-betacatenin-1 is required for anteroposterior blastema polarity in planarian regeneration

Planarian flatworms can regenerate heads at anterior-facing wounds and tails at posterior-facing wounds throughout the body. How this regeneration polarity is specified has been a classic problem for more than a century. We identified a planarian gene, Smed-betacatenin-1, that controls regeneration polarity. Posterior-facing blastemas regenerate a head instead of a tail in Smed-betacatenin-1(RNAi) animals. Smed-betacatenin-1 is required after wounding and at any posterior-facing wound for polarity. Additionally, intact Smed-betacatenin-1(RNAi) animals display anteriorization during tissue turnover. Five Wnt genes and a secreted Frizzled-related Wnt antagonist-like gene are expressed in domains along the anteroposterior axis that reset to new positions during regeneration, which suggests that Wnts control polarity through Smed-betacatenin-1. Our data suggest that beta-catenin specifies the posterior character of the anteroposterior axis throughout the Bilateria and specifies regeneration polarity in planarians.     

Basal localization of the presumptive auxin transport carrier in pea stem cells

By means of an indirect immunofluorescence technique with the use of monoclonal antibodies, the location of the presumptive auxin transport carrier of pea stem tissue was identified in the plasma membranes at the basal ends of parenchyma cells sheathing the vascular bundles. The results represent what is believed to be the first direct evidence for the hypothesized basal efflux carrier conferring polarity to auxin transport in plant stems.     

dSarm/Sarm1 is required for activation of an injury-induced axon death pathway

Axonal and synaptic degeneration is a hallmark of peripheral neuropathy, brain injury, and neurodegenerative disease. Axonal degeneration has been proposed to be mediated by an active autodestruction program, akin to apoptotic cell death; however, loss-of-function mutations capable of potently blocking axon self-destruction have not been described. Here, we show that loss of the Drosophila Toll receptor adaptor dSarm (sterile α/Armadillo/Toll-Interleukin receptor homology domain protein) cell-autonomously suppresses Wallerian degeneration for weeks after axotomy. Severed mouse Sarm1 null axons exhibit remarkable long-term survival both in vivo and in vitro, indicating that Sarm1 prodegenerative signaling is conserved in mammals. Our results provide direct evidence that axons actively promote their own destruction after injury and identify dSarm/Sarm1 as a member of an ancient axon death signaling pathway.     

The sor gene of HIV-1 is required for efficient virus transmission in vitro

The genome of the human immunodeficiency virus HIV-1 contains at least eight genes, of which three (sor, R, and 3' orf) have no known function. In this study, the role of the sor gene was examined by constructing a series of proviral genomes of HIV-1 that either lacked the coding sequences for sor or contained point mutations in sor. Analysis of four such mutants revealed that although each clone could generate morphologically normal virus particles upon transfection, the mutant viruses were limited in their capacity to establish stable infection. Virus derived from transfection of Cos-1 cells (OKT4-) with sor mutant proviral DNA's was resistant to transmission to OKT4+ "susceptible" cells under cell-free conditions, and was transmitted poorly by coculture. In contrast, virus derived from clones with an intact sor frame was readily propagated by either approach. Normal amounts of gag-, env-, and pol-derived proteins were produced by all four mutants and assays in both lymphoid and nonlymphoid cells indicated that their trans-activating capacity was intact and comparable with wild type. Thus the sor gene, although not absolutely required in HIV virion formation, influences virus transmission in vitro and is crucial in the efficient generation of infectious virus. The data also suggest that sor influences virus replication at a novel, post-translational stage and that its action is independent of the regulatory genes tat and trs.     

酿酒酵母中磷脂合成相关基因突变对细胞自噬和液泡形态的影响

[目的]探讨酿酒酵母中磷脂合成相关基因突变对细胞自噬和液泡形态的影响.[方法]通过尼罗红染色观察酵母中磷脂合成相关基因突变后脂滴的形态;用绿色荧光蛋白(GFP)标记细胞自噬蛋白Atg8后,采用荧光显微镜和免疫印迹试验检测突变体细胞自噬的发生情况,并使用荧光染料FM4-64检测液泡形态;此外,检测相关突变体对吩嗪-1-羧酸(申嗪霉素)的敏感性.[结果]在营养有限条件下,酿酒酵母中磷脂合成相关基因突变体中脂滴的大小或数量受到不同程度的影响,但细胞自噬在常规检测条件下正常;其中磷脂酸胞苷转移酶编码基因CDS1突变导致液泡形态异常(碎片化),而其他磷脂合成相关基因突变不影响液泡形态;回补CDS1后,cds1-DAmP突变体中液泡形态恢复正常;此外,cds 1-DAmP突变体对吩嗪-1-羧酸处理更为敏感.[结论]酿酒酵母中脂滴和液泡形态异常不一定影响细胞自噬的正常进行,但可能影响其对外界环境的响应.     

Human chromosome 12 is required for elevated HIV-1 expression in human-hamster hybrid cells

Host cell factors act together with regulatory genes of the human immunodeficiency virus (HIV) to control virus production. Human-Chinese hamster ovary hybrid cell clones were used to probe for human chromosomes involved in regulating HIV gene expression. DNA transfection experiments showed that 4 of 18 clones had high levels of HIV gene expression measured by both extracellular virus production and transactivation of the HIV long terminal repeat in the presence of the trans-activator (tat) gene. Karyotype analyses revealed a 94% concordance (17/18) between human chromosome 12 and HIV gene expression. Other chromosomes had an 11 to 72% concordance with virus production.     

Phosphatidylserine receptor is required for clearance of apoptotic cells

Cells undergoing apoptosis during development are removed by phagocytes, but the underlying mechanisms of this process are not fully understood. Phagocytes lacking the phosphatidylserine receptor (PSR) were defective in removing apoptotic cells. Consequently, in PSR-deficient mice, dead cells accumulated in the lung and brain, causing abnormal development and leading to neonatal lethality. A fraction of PSR knockout mice manifested a hyperplasic brain phenotype resembling that of mice deficient in the cell death-associated genes encoding Apaf-1, caspase-3, and caspase-9, which suggests that phagocytes may also be involved in promoting apoptosis. These data demonstrate a critical role for PSR in early stages of mammalian organogenesis and suggest that this receptor may be involved in respiratory distress syndromes and congenital brain malformations.     

GRK2-dependent S1PR1 desensitization is required for lymphocytes to overcome their attraction to blood

Lymphocytes egress from lymphoid organs in response to sphingosine-1-phosphate (S1P); minutes later they migrate from blood into tissue against the S1P gradient. The mechanisms facilitating cell movement against the gradient have not been defined. Here, we show that heterotrimeric guanine nucleotide-binding protein-coupled receptor kinase-2 (GRK2) functions in down-regulation of S1P receptor-1 (S1PR1) on blood-exposed lymphocytes. T and B cell movement from blood into lymph nodes is reduced in the absence of GRK2 but is restored in S1P-deficient mice. In the spleen, B cell movement between the blood-rich marginal zone and follicles is disrupted by GRK2 deficiency and by mutation of an S1PR1 desensitization motif. Moreover, delivery of systemic antigen into follicles is impaired. Thus, GRK2-dependent S1PR1 desensitization allows lymphocytes to escape circulatory fluids and migrate into lymphoid tissues.     

ABP1参与BY2细胞生长素响应的Ca2+信号转导过程

将Ca2+响应实时荧光报告系统引入雌二醇诱导生长素结合蛋白(ABP1)调控表达的BY2细胞中,获得了 ABP1过表达(ABP1-ox)、抑制表达(ABP1-anti)同时对Ca2+标记的几个BY2细胞株.对这些细胞株进行雌二醇诱导调控其ABP1过表达或抑制表达后,分析ABP1的表达量,并通过在细胞外添加IAA处理,实时...     

The protein kinase domain of the ANP receptor is required for signaling

A plasma membrane form of guanylate cyclase is a cell surface receptor for atrial natriuretic peptide (ANP). In response to ANP binding, the receptor-enzyme produces increased amounts of the second messenger, guanosine 3',5'-monophosphate. Maximal activation of the cyclase requires the presence of adenosine 5'-triphosphate (ATP) or nonhydrolyzable ATP analogs. The intracellular region of the receptor contains at least two domains with homology to other proteins, one possessing sequence similarity to protein kinase catalytic domains, the other to regions of unknown function in a cytoplasmic form of guanylate cyclase and in adenylate cyclase. It is now shown that the protein kinase-like domain functions as a regulatory element and that the second domain possesses catalytic activity. When the kinase-like domain was removed by deletion mutagenesis, the resulting ANP receptor retained guanylate cyclase activity, but this activity was independent of ANP and its stimulation by ATP was markedly reduced. A model for signal transduction is suggested in which binding of ANP to the extracellular domain of its receptor initiates a conformational change in the protein kinase-like domain, resulting in derepression of guanylate cyclase activity.     

Calcium: is it required for transmitter secretion?

Ethanol multiplies miniature end-plate potential frequency independently of calcium ion concentrations and also multiplies calcium-dependent depolarization-evoked quantal release, to the same extent. This result implies a final common pathway, requiring little or no calcium, for both kinds of transmitter secretion. Chlorpromazine and hypertonicity act similarly to ethanol, but also depress depolarization-secretion coupling.     

The new effector AbSCP1 of foliar nematode (Aphelenchoides besseyi) is required for parasitism rice

Plant parasitic nematodes secrete effector proteins to parasitize hosts successfully. Of these proteins, serine carboxypeptidases have critical roles in pathogenicity. This study investigated the role of new effector AbSCP1 in Aphelenchoides besseyi pathogenicity. In situ hybridization and qRT-PCR analyses indicated that AbSCP1 was exclusively expressed in the esophageal glands and upregulated in juveniles. Subcellular localization assays indicated that the protein was expressed in the nucleus. The ability to hydrolyze C-terminal amino acid residues was proven for AbSCP1. Moreover, RNAi significantly reduced the expression of AbSCP1 and RNAi-treated nematodes’ reproductive potential. Pathogenicity assays on rice showed that RNAi-treated nematodes were less pathogenic than the untreated control groups. These results suggest the important role of AbSCP1 in the A. besseyi infection process.     

CHD1 motor protein is required for deposition of histone variant H3.3 into chromatin in vivo

The organization of chromatin affects all aspects of nuclear DNA metabolism in eukaryotes. H3.3 is an evolutionarily conserved histone variant and a key substrate for replication-independent chromatin assembly. Elimination of chromatin remodeling factor CHD1 in Drosophila embryos abolishes incorporation of H3.3 into the male pronucleus, renders the paternal genome unable to participate in zygotic mitoses, and leads to the development of haploid embryos. Furthermore, CHD1, but not ISWI, interacts with HIRA in cytoplasmic extracts. Our findings establish CHD1 as a major factor in replacement histone metabolism in the nucleus and reveal a critical role for CHD1 in the earliest developmental instances of genome-scale, replication-independent nucleosome assembly. Furthermore, our results point to the general requirement of adenosine triphosphate (ATP)-utilizing motor proteins for histone deposition in vivo.