A quantitative, non-radioactive single-nucleotide insertion assay for analysis of DNA replication fidelity by using an automated DNA sequencer

A method to determine the steady-state kinetic parameters of single-nucleotide insertion in replication was developed using an automated DNA sequencer. The insertion of nucleoside 5'-triphosphates into a 6-carboxyfluorescein-labeled primer by DNA polymerase was quantified from the band pattern on a gel using GeneScan software. The parameters determined by this method were consistent with those obtained by the conventional radioisotope-labeling method. This non-radioactive, fluorescent-based method is rapid and can handle a large number of samples to assess cognate or non-cognate base pair formation between natural or unnatural bases in replication.     

Use of apple seed meal as a new source of beta-glucosidase for enzymatic glucosylation of 4-substituted benzyl alcohols and tyrosol in monophasic aqueous-dioxane medium

A facile method for enzymatic glycosylation of 4-substituted benzyl alcohols and tyrosol with glucose in a monophasic aqueous-dioxane medium was reported, using a crude meal of apple seed as a new catalyst. The corresponding beta-d-glucosides were synthesized in moderate yields (13.1-23.1%), among which the salidroside was obtained in 15.8% yield.     

Structural basis of sugar-recognizing ubiquitin ligase

SCF(Fbs1) is a ubiquitin ligase that functions in the endoplasmic reticulum (ER)-associated degradation pathway. Fbs1/Fbx2, a member of the F-box proteins, recognizes high-mannose oligosaccharides. Efficient binding to an N-glycan requires di-N-acetylchitobiose (chitobiose). Here we report the crystal structures of the sugar-binding domain (SBD) of Fbs1 alone and in complex with chitobiose. The SBD is composed of a ten-stranded antiparallel beta-sandwich. The structure of the SBD-chitobiose complex includes hydrogen bonds between Fbs1 and chitobiose and insertion of the methyl group of chitobiose into a small hydrophobic pocket of Fbs1. Moreover, NMR spectroscopy has demonstrated that the amino acid residues adjoining the chitobiose-binding site interact with the outer branches of the carbohydrate moiety. Considering that the innermost chitobiose moieties in N-glycans are usually involved in intramolecular interactions with the polypeptide moieties, we propose that Fbs1 interacts with the chitobiose in unfolded N-glycoprotein, pointing the protein moiety toward E2 for ubiquitination.     

The N- and C-terminal mutations in tryptophan permease Tat2 confer cell growth in<Emphasis Type="Italic"> Saccharomyces cerevisiae</Emphasis> under high-pressure and low-temperature conditions

Tryptophan uptake appears to be the limiting factor in growth of tryptophan auxotrophic Saccharomyces cerevisiae strains under the conditions of high hydrostatic pressure and low temperature. When the cells are subjected to a pressure of 25 MPa, tryptophan permease Tat2 is degraded in a manner dependent on ubiquitination by Rsp5. One of the high-pressure growth-conferring genes, HPG2, was shown to be allelic to TAT2. The HPG2-1 (Tat2^E27F) mutation site is located within the ExKS motif in the N-terminus, and the HPG2-2 (Tat2^D563N) and HPG2-3 (Tat2^E570K) mutation sites are located at the KQEIAE sequence in the C-terminus. The HPG2 mutations enhance the stability of Tat2 during high-pressure or low-temperature incubation, leading to cell growth under these stressful conditions. These results suggest that the cytoplasmic tails are involved in Rsp5-mediated ubiquitination of Tat2 under high-pressure or low-temperature conditions.Communicated by K. Horikoshi     

Intermediate fertile Triticum aestivum （＋）Agropyron elongatum somatic hybrids are generated by low doses of UV irradiation

We report the production and characterization of somatic hybrids between Triticum aestivum L. and Agropyron elongatum (Host) Nevishi (the synonym is Thinopyrum ponticum). Asymmetric protoplast fusion was performed between Agropyron elongatum protoplasts irradiated with a low UV dose and protoplasts of wheat taken from nonregenerable suspension cultures. More than 40 green plantlets were obtained from 15 regenerated clones and one of them produced seeds. The phenotypes of the hybrid plants and seeds were intermediate between wheat and Agropyron elongatum. All of the regenerated calli and plants were verified as intergeneric hybrids on the basis of morphological observation and analysis of isozyme, cytological, 5SrDNA spacer sequences and random amplified polymorphic DNA (RAPD). RFLP analysis of the mitochondrial genome revealed evidence of random segregation and recombination of mtDNA.     

Soluble expression and characterization of a GFP-fused pea actin isoform（PEAc1）

A pea actin isoform PEAcl with green fluorescent protein (GFP) fusion to its C-terminus and His-tag to its Nterminus, was expressed in prokaryotic cells in soluble form, and highly purified with Ni-Chelating Sepharose^TM Fast Flow column. The purified fusion protein (PEAcl-GFP) efficiently inhibited DNase I activities before polymerization,and activated the myosin Mg-ATPase activities after polymerization. The PEAcl-GFP also polymerized into green fluorescent filamentous structures with a critical concentration of 0.75μM. These filamentous structures were labeled by TRITC-phalloidin, a specific agent for staining actin microfilaments, and identified as having 9 nm diameters by negative staining. These results indicated that PEAc 1 preserved the essential characteristics of actin even with His-tag and GFP fusion, suggesting a promising potential to use GFP fusion protein in obtainning soluble plant actin isoform to analyze its physical and biochemical properties in vitro. The PEAcl-GFP was also expressed in tobacco BY2 cells,which offers a new pathway for further studying its distribution and function in vivo.     

代谢性谷氨酸受体配体(s)-4C3HPG对大鼠脑缺血耐受性诱导的影响

目的：观察侧脑室注射代谢型谷氨酸受体1／5亚型（mGluR1/5)配体（s)-4C3HPG对海马脑缺血耐受（BIT）诱导的影响,以探讨mGLUR1/5在BIT诱导中的作用。方法：采用大鼠四血管闭塞全脑缺血模型（4－vessel occlusion,4VO),应用硫堇染色和GFAP免疫组化法。36只大鼠椎动脉凝闭后分为sham组、单纯缺血组、BIT组和（s)-4C3HPG组,其中（s)-4C3HPG组又按所给药物剂量不同,分为0．2、0．04和0．008mg三个亚组。所有动物均在手术后或末次缺血后7d处死取材观察。结果：（1）单纯8min缺血可使海马CA1区组织学分级升高、锥体神经元密度降低和胶质纤维酸性蛋白（glial fibrillary acidic protein,GFAP)阳性表达增加（P＜0．05vs sham）.(2)BIT组未见单纯缺血组的上述变化,表明CIP可防止后续8min缺血造成的神经元损伤。（3）CIP的这种保护作用可被（s)-4C3HPG阻断,表现为海马CA1区组织学分级升高和锥体神经元密度降低（P＜0．05 vs sham)。这种变化与（s)-4C3HPG的剂量呈现明显的相关性,即剂量越大,上述改变越明显。结论：（s)-4C3HPG可阻断CIP诱导BIT的作用,提示mGluR1/5参与BIT的诱导。     

GnRH-II analogs for selective activation and inhibition of non-mammalian and type-II mammalian GnRH receptors

Recently, we identified three types of non-mammalian gonadotropin-releasing hormone receptors (GnRHR) in the bullfrog (designated bfGnRHR-1-3), and a mammalian type-II GnRHR in green monkey cell lines (denoted gmGnRHR-2). All these receptors responded better to GnRH-II than GnRH-I, while mammalian type-I GnRHR showed greater sensitivity to GnRH-I than GnRH-II. In the present study, we designed new GnRH-II analogs and examined whether they activated or inhibited non-mammalian and mammalian type-II GnRHRs. [D-Ala6]GnRH-II, with D-Ala substituted for Gly6 in GnRH-II, increased inositol phosphate (IP) production in cells stably expressing non-mammalian GnRHRs more effectively than native GnRH-II. However, it exhibited lower activity for mammalian type-I GnRHR than GnRH-I itself. Trptorelix-1, a GnRH-II antagonist, inhibited GnRH-induced IP production in cells expressing non-mammalian GnRHRs more effectively than Cetrorelix, a GnRH-I antagonist. Trptorelix-1, however, had lower potency for mammalian type-I GnRHR than Cetrorelix. Ligand-receptor binding assays revealed that [D-Ala6]GnRH-II and Trptorelix-1 have higher affinities for non-mammalian GnRHRs but lower affinities for mammalian type-I GnRHR than GnRH-II and Cetrorelix, respectively. Moreover, [D-Ala6]GnRH-II and Trptorelix-1 had a higher affinity for gmGnRHR-2 than GnRH-II and Cetrorelix, respectively. These results indicate that [D-Ala6]GnRH-II and Trptorelix-1 are highly effective agonist and antagonist, respectively, for non-mammalian and type-II mammalian GnRHRs.     

Microtubule-associated [corrected] protein 7 increases the membrane expression of transient receptor potential vanilloid 4 (TRPV4)

The molecular mechanism of the transmission of changes in the shape of the cell surface to ion channels remains obscure. Ca2+ influx induced by cell deformity is inhibited by actin-freezing reagents, suggesting that the actin microfilament couples with an ion channel. Transient receptor potential vanilloid 4 (TRPV4) is a candidate in the calcium-permeable, swelling-activated mechanosensitive channel in heterogeneously expressed cells. To investigate the mechanosensitive molecular complex, we found that microtubule-associated protein 7 (MAP7) is the mouse TRPV4 C-terminal binding protein. MAP7 was coimmunoprecipitated with TRPV4. The results of a pull-down assay demonstrated that the alignment of amino acids 798-809 of TRPV4 was important in this interaction. TRPV4 and MAP7 colocalized in the lung and kidney. The coexpression of these two molecules resulted in the redistribution of TRPV4 toward the membrane and increased its functional expression. The alignment of amino acids 798-809 of TRPV4 was also important in the functional expression. The activated current was abolished by actin-freezing but not by microtubule-freezing reagents. We therefore believe that MAP7 may enhance the membrane expression of TRPV4 and possibly link cytoskeletal microfilaments.     

QSulf1 remodels the 6-O sulfation states of cell surface heparan sulfate proteoglycans to promote Wnt signaling

The 6-O sulfation states of cell surface heparan sulfate proteoglycans (HSPGs) are dynamically regulated to control the growth and specification of embryonic progenitor lineages. However, mechanisms for regulation of HSPG sulfation have been unknown. Here, we report on the biochemical and Wnt signaling activities of QSulf1, a novel cell surface sulfatase. Biochemical studies establish that QSulf1 is a heparan sulfate (HS) 6-O endosulfatase with preference, in particular, toward trisulfated IdoA2S-GlcNS6S disaccharide units within HS chains. In cells, QSulf1 can function cell autonomously to remodel the sulfation of cell surface HS and promote Wnt signaling when localized either on the cell surface or in the Golgi apparatus. QSulf1 6-O desulfation reduces XWnt binding to heparin and HS chains of Glypican1, whereas heparin binds with high affinity to XWnt8 and inhibits Wnt signaling. CHO cells mutant for HS biosynthesis are defective in Wnt-dependent Frizzled receptor activation, establishing that HS is required for Frizzled receptor function. Together, these findings suggest a two-state "catch or present" model for QSulf1 regulation of Wnt signaling in which QSulf1 removes 6-O sulfates from HS chains to promote the formation of low affinity HS-Wnt complexes that can functionally interact with Frizzled receptors to initiate Wnt signal transduction.