囊萼花属─—中国玄参科新记录属及—新种

报道了我国玄参科的一个新记录属──囊萼花属ＣｙｒｔａｎｄｒｏｍｏｅａＺｏｌｌ，该属为印度－马来西亚分布，它经过泰国北部，缅甸与我国发生连系，到达我国云南贡山、屏边、金平。全世界有１１—１２种，我国（云南）首次记录两种，其中一种为新种。     

转基因大豆MON89788芯片式数字PCR定量方法的建立

针对抗虫耐除草剂大豆转基因品系MON89788,从转基因植物基因组DNA的提取、核酸模板的质量和浓度控制、引物探针的筛选、PCR反应过程的建立等方面建立了一套完整的转基因大豆芯片式dPCR定量检测方法。本实验也对该方法的重复性和定量检测限进行考察。10组5%转基因品系大豆MON89788样品定量重复性RSD在1.17%-9.97%之间,均满足国际上转基因定量结果RSD小于25%的要求。用该方法对转基因含量为5%、1%、0.1%的大豆MON89788进行定量检测,其定量结果为5.20%、0.94%和0.11%,RSD分别为6.2%、3.6%和15.2%。该检测方法的定量限达到0.1%,能满足欧盟对转基因定量标识0.9%的要求。将本实验建立的方法用于转基因大豆的定量检测,能为规范我国转基因监管工作的实施提供强有力的技术支撑。     

Certain biochemical characteristics of an insulin-like substance from the bivalve mollusk Anodonta cygnea

An insulin-like substance (ILS) was isolated from the visceral organs of the bivalve mollusc Anodonta cygnea by chromatography on a sulfocationite CU-23 and purified by reverse phase liquid chromatography. ILS was shown to be made up to several fractions with Mr ranging from 9 to 20 kDa which have identical amino acid composition but different hydrophobicity and N-terminal amino acids. It was supposed that the heterogeneity of ILS fractions is due to its genetical or posttranslational polymorphism. ILS has a low (0.02%) affinity for the mammalian insulin receptor and a low immune affinity for mammalian insulin and possesses a mitogenic activity which is commensurate with that of the epidermal growth factor. The data obtained suggest that Anodonta cygnea ILS represents a separate branch of a relatively ancient family of insulin-like hormones and growth factors responsible for metabolism and proliferation of invertebrate tissues.     

Novel Interaction of the Z-DNA Binding Domain of Human ADAR1 with the Oncogenic c-Myc Promoter G-Quadruplex

Both G-quadruplex and Z-DNA can be formed in G-rich and repetitive sequences on genome, and their formation and biological functions are controlled by specific proteins. Z-DNA binding proteins, such as human ADAR1, have a highly conserved Z-DNA binding domain having selective affinity to Z-DNA. Here, our study identifies the Z-DNA binding domain of human ADAR1 (hZα_ADAR1) as a novel G-quadruplex binding protein that recognizes c-myc promoter G-quadruplex formed in NHEIII₁ region and represses the gene expression. An electrophoretic migration shift assay shows the binding of hZα_ADAR1 to the intramolecular c-myc promoter G-quadruplex-forming DNA oligomer. To corroborate the binding of hZα_ADAR1 to the G-quadruplex, we conducted CD and NMR chemical shift perturbation analyses. CD results indicate that hZα_ADAR1 stabilizes the parallel-stranded conformation of the c-myc G-quadruplex. The NMR chemical shift perturbation data reveal that the G-quadruplex binding region in hZα_ADAR1 was almost identical with the Z-DNA binding region. Finally, promoter assay and Western blot analysis show that hZα_ADAR1 suppresses the c-myc expression promoted by NHEIII₁ region containing the G-quadruplex-forming sequence. This finding suggests a novel function of Z-DNA binding protein as a regulator of G-quadruplex-mediated gene expression.     

The strength of SMAD1/5 activity determines the mode of stem cell division in the developing spinal cord

The different modes of stem cell division are tightly regulated to balance growth and differentiation during organ development and homeostasis. However, the mechanisms controlling such events are not fully understood. We have developed markers that provide the single cell resolution necessary to identify the three modes of division occurring in a developing nervous system: self-expanding, self-renewing, and self-consuming. Characterizing these three modes of division during interneuron generation in the developing chick spinal cord, we demonstrated that they correlate to different levels of activity of the canonical bone morphogenetic protein effectors SMAD1/5. Functional in vivo experiments showed that the premature neuronal differentiation and changes in cell cycle parameters caused by SMAD1/5 inhibition were preceded by a reduction of self-expanding divisions in favor of self-consuming divisions. Conversely, SMAD1/5 gain of function promoted self-expanding divisions. Together, these results lead us to propose that the strength of SMAD1/5 activity dictates the mode of stem cell division during spinal interneuron generation.     

An assessment of the role of domain F and pest sequences in estrogen receptor half-life and bioactivity

The estrogen receptor (ER) is a rapidly turning over protein, with a half-life of ca. 3–4 h in estrogen target cells. Sequence analysis of the human ER reveals a putative PEST sequence, sequences rich in proline (P), glutamic acid (E), serine (S) and threonine (T), in the carboxy-terminal F domain of the protein. Since PEST sequences have been implicated in the rapid turnover of some proteins, we have used site-directed mutagenesis to investigate the role of the F region containing PEST residues in the stability and bioactivity of the receptor. A truncated form of ER lacking the last 41 amino acids of the protein and encompassing the PEST sequences (amino acids 555 to 567) was made by mutagenesis of the ER cDNA. Pulse-chase experiments, involving immunoprecipitation of [³⁵S]methionine/[³⁵]Scysteine labeled receptors or of receptors covalently labeled with tamoxifen aziridine followed by gel electrophoresis, were used to determine the half-life of the wild-type and truncated ERs. These experiments showed that the turnover rate of the receptors expressed in Chinese hamster ovary and monkey kidney (COS-1) cells was 3 to 5 h and that elimination of the PEST residues did not have a significant effect on the degradation rate of the protein. Moreover, deletion of the last 41 amino acids (F domain) of the ER did not affect transactivation ability, ligand binding affinity, or the phosphorylation pattern of the receptor. Therefore, the role of domain F in ER function remains unclear, but it is not a determinant of the relatively rapid rate of ER turnover in cells.