The Drosophila nuclear receptors: new insight into the actions of nuclear receptors in development.

In Drosophila melanogaster, an increasing number of members of the steroid hormone receptor superfamily are being identified and characterized. Molecular and genetic analysis of receptor function provides evidence for a set of functions underlying the determination of pattern formation, metamorphosis, eye development, and reproduction. Many of the Drosophila receptor genes show striking homologies to mammalian receptor genes. This suggests that genetic analysis in flies could facilitate the generation of biological models that pertain to complex hormonal responses in development and which are relevant to both vertebrate and invertebrate systems.     

番茄乙烯受体结构和功能研究进展

综述了近年来番茄乙烯受体研究方面的最新进展。以拟南芥的乙类受体为探针,从番茄加筛选得到Le-ETR1、Le-ETR2、Le-ETR3、Le-ETR4、Le-ETR55个有功能的乙烯受体基因。番茄乙类受体与细菌的双组分感受系统高度相似,同乙烯结合需要铜离子的协同作用。植物株发育期间通过激活某些受体基因的表达和（或）控制铜离子的转运调节乙烯敏感性。调节乙烯受体表达的基因工程显示了广阔的前景。但各个受体的功能及基因分析与活体标记的关系还需进一步研究。     

Phage receptors of Escherichia coli. Basic components of the outer membrane of E. coli as phage receptors

Major outer membrane components which determine the structure and the barrier function of membrane Gram-negative bacteria are receptors for many bacteriophages. LPS--the major component of the outer membrane of Enterobacteria can be used by some phages with wide host range specificity. The other component of the outer membrane frequently include phage receptor component is OmpA protein. OmpA protein different areas can be used as receptors for different phages T--even group. A large group of phage receptors compose porin proteins, which are discovered in 32 species of bacteria. The synthesis of major porin proteins, which a receptor for several phages, are regulated by sufficiently complex system of some genes. These genes are sensitive to the changes of environment.     

Persistence of duplicated PAC<Subscript>1</Subscript> receptors in the teleost, <Emphasis Type="Italic">Sparus auratus</Emphasis>

Background:  

Duplicated genes are common in vertebrate genomes. Their persistence is assumed to be either a consequence of gain of novel function (neofunctionalisation) or partitioning of the function of the ancestral molecule (sub-functionalisation). Surprisingly few studies have evaluated the extent of such modifications despite the numerous duplicated receptor and ligand genes identified in vertebrate genomes to date. In order to study the importance of function in the maintenance of duplicated genes, sea bream (Sparus auratus) PAC₁ receptors, sequence homologues of the mammalian receptor specific for PACAP (Pituitary Adenylate Cyclase-Activating Polypeptide), were studied. These receptors belong to family 2 GPCRs and most of their members are duplicated in teleosts although the reason why both persist in the genome is unknown.     

Bidirectional communication between the pineal gland and the immune system

The pineal gland is a vertebrate neuroendocrine organ converting environmental photoperiodic information into a biochemical message (melatonin) that subsequently regulates the activity of numerous target tissues after its release into the bloodstream. A phylogenetically conserved feature is increased melatonin synthesis during darkness, even though there are differences between mammals and birds in the regulation of rhythmic pinealocyte function. Membrane-bound melatonin receptors are found in many peripheral organs, including lymphoid glands and immune cells, from which melatonin receptor genes have been characterized and cloned. The expression of melatonin receptor genes within the immune system shows species and organ specificity. The pineal gland, via the rhythmical synthesis and release of melatonin, influences the development and function of the immune system, although the postreceptor signal transduction system is poorly understood. Circulating messages produced by activated immune cells are reciprocally perceived by the pineal gland and provide feedback for the regulation of pineal function. The pineal gland and the immune system are, therefore, reciprocally linked by bidirectional communication.     

Plant immunity: the origami of receptor activation

Mutations in plant cytosolic HSP90 genes have been found to impair the immune responses triggered by host pathogen receptors. HSP90 links the plant receptors to other components essential for receptor function. The new findings suggest mechanistic parallels with steroid receptor regulation in animals.     

Construction of a series of ompF-ompC chimeric genes by in vivo homologous recombination in Escherichia coli and characterization of the translational products.

OmpF and OmpC are major outer membrane proteins. Although they are homologous proteins, they function differently in several respects. As an approach to elucidate the submolecular structures that determine the difference, a method was developed to construct a series of ompF-ompC chimeric genes by in vivo homologous recombination between these two genes, which are adjacent on a plasmid. The genomic structures of these chimeric genes were determined by restriction endonuclease analysis and nucleotide sequence determination. In almost all cases, recombination took place between the corresponding homologous regions of the ompF and ompC genes. Many of the chimeric genes produced proteins that migrated to various positions between the OmpF and OmpC proteins on polyacrylamide gel. On the basis of the results, a domain contributing to the mobility difference the OmpF and OmpC proteins was identified. Some chimeric genes did not accumulate outer membrane proteins, despite the fact that the fusion of the ompF and ompC genes was in frame. Bacterial cells possessing the chimeric proteins were also tested as to their sensitivity to phages which require either OmpF or OmpC as a receptor component. The chimeric proteins were either of the OmpF or OmpC type with respect to receptor activity. Based on the observations, the roles of submolecular domains in the structure, function, and biogenesis of the OmpF and OmpC proteins are discussed.     

Inactivation of erythropoietin receptor function by point mutations in a region having homology with other cytokine receptors.

The cytoplasmic domain of the erythropoietin receptor (EpoR) contains a region, proximal to the transmembrane domain, that is essential for function and has homology with other members of the cytokine receptor family. To explore the functional significance of this region and to identify critical residues, we introduced several amino acid substitutions and examined their effects on erythropoietin-induced mitogenesis, tyrosine phosphorylation, and expression of immediate-early (c-fos, c-myc, and egr-1) and early (ornithine decarboxylase and T-cell receptor gamma) genes in interleukin-3-dependent cell lines. Amino acid substitution of W-282, which is strictly conserved at the middle portion of the homology region, completely abolished all the functions of the EpoR. Point mutation at L-306 or E-307, both of which are in a conserved LEVL motif, drastically impaired the function of the receptor in all assays. Other point mutations, introduced into less conserved amino acid residues, did not significantly impair the function of the receptor. These results demonstrate that conserved amino acid residues in this domain of the EpoR are required for mitogenesis, stimulation of tyrosine phosphorylation, and induction of immediate-early and early genes.     

海马学习记忆功能有关基因及六味地黄汤益智作用与基因表达关系的研究

运用逆转录 多聚酶链反应 (RT PCR)技术及学习记忆行为实验 ,通过快速老化模型小鼠 (SAM )、氢化可的松处理小鼠及正常小鼠 ,研究发现海马糖皮质激素受体 (GR)、盐皮质激素受体 (MR)、bcl 2、c fos、神经细胞粘附分子 (NCAM )、早老蛋白 2 (PS 2 )及apoE与中枢学习记忆功能具有密切的关系。应用mRNA差异显示技术研究发现 ,SAM的快速老化亚系SAMP8和抗快速老化亚系SAMR1海马有 6条明显差异的基因片段 ,其中二个为新基因。口服六味地黄汤 (LW )对模型动物学习记忆功能衰退具有明显的改善作用 ,同时对海马基因表达异常具有明显纠正作用。应用胚胎大鼠原代培养的海马神经元研究发现皮质酮对学习记忆有关基因表达具有明显影响。上述结果提示 ,中枢学习记忆过程与海马多种基因表达存在密切的关系 ,纠正海马基因表达异常、调节下丘脑 垂体 肾上腺 (HPA)轴的平衡是LW益智作用的重要机制之一。     

Interaction of the glucocorticoid receptor with the chromatin landscape

The generality and spectrum of chromatin-remodeling requirements for nuclear receptor function are unknown. We have characterized glucocorticoid receptor (GR) binding events and chromatin structural transitions across GR-induced or -repressed genes. This analysis reveals that GR binding invariably occurs at nuclease-accessible sites (DHS). A remarkable diversity of mechanisms, however, render these sites available for GR binding. Accessibility of the GR binding sites is either constitutive or hormone inducible. Within each category, some DHS sites require the Brg1-containing Swi/Snf complex, but others are Brg1 independent, implicating a different remodeling complex. The H2A.Z histone variant is highly enriched at both inducible and constitutive DHS sites and is subject to exchange during hormone activation. The DHS profile is highly cell specific, implicating cell-selective organization of the chromatin landscape as a critical determinant of tissue-selective receptor function. Furthermore, the widespread requirement for chromatin remodeling supports the recent hypothesis that the rapid exchange of receptor proteins occurs during nucleosome reorganization.