Expression in Escherichia coli of open reading frame gene segments of HTLV-III

Human T-cell lymphotropic virus type III (HTLV-III), the causative agent of the acquired immune deficiency syndrome (AIDS), was recently isolated and its genomic structure analyzed by DNA cloning methods. In the studies reported here a combined cloning and expression system was used to identify HTLV-III encoded peptides that react immunologically with antibodies in sera from AIDS patients. Cloned HTLV-III DNA was sheared into approximately 500-base-pair fragments and inserted into an "open reading frame" expression vector, pMR100. The inserted DNA was expressed in Escherichia coli transformants as a polypeptide fused to the lambda CI protein at its amino terminus and to beta-galactosidase at its carboxyl terminus. Sera from AIDS patients containing antibodies to HTLV-III were then used to screen for immunoreactive fusion proteins. Twenty clones, each specifying a fusion protein strongly reactive with AIDS serum, were identified. DNA sequence analysis indicated that the HTLV-III fragments were derived from the open reading frame DNA segments corresponding to the gag and pol gene coding regions and also the large open reading frame region (env-lor) located near the 3' end of the viral genome.     

Fertilization events induced by neurotransmitters after injection of mRNA in Xenopus eggs

Fertilization initiates in the egg a dramatic increase in intracellular calcium that opens ion channels and causes exocytosis. To explore the possibility that these events might involve a receptor-mediated pathway, receptors for serotonin or acetylcholine (M1 muscarinic) were expressed in the Xenopus egg; serotonin or acetylcholine then could initiate a series of responses similar to those normally initiated by sperm. Thus, there may be an endogenous receptor in the egg membrane that is activated by sperm, and the serotonin or M1 muscarinic receptor may replace the sperm receptor in this pathway.     

利用mRNA差异显示技术克隆恶疫霉侵染诱导表达的草莓基因

为了解草莓与恶疫霉互作的分子机制,以接种后3、5和7 d的感病草莓品种‘FDP821’的冠部为材料,利用mRNA差异显示技术研究‘FDP821’与恶疫霉亲和互作前后基因表达的差异,获得78条差异表达的cDNA片段,通过分析从中分离出恶疫霉侵染诱导表达的10个草莓基因cDNA片段。BLASTX在线分析表明,这些草莓基因的功能涉及呼吸作用、衰老和核苷运输与代谢等。为阐明草莓与恶疫霉互作的分子机制提供了重要的线索。     

URF6, last unidentified reading frame of human mtDNA, codes for an NADH dehydrogenase subunit

The polypeptide encoded in URF6, the last unassigned reading frame of human mitochondrial DNA, has been identified with antibodies to peptides predicted from the DNA sequence. Antibodies prepared against highly purified respiratory chain NADH dehydrogenase from beef heart or against the cytoplasmically synthesized 49-kilodalton iron-sulfur subunit isolated from this enzyme complex, when added to a deoxycholate or a Triton X-100 mitochondrial lysate of HeLa cells, specifically precipitated the URF6 product together with the six other URF products previously identified as subunits of NADH dehydrogenase. These results strongly point to the URF6 product as being another subunit of this enzyme complex. Thus, almost 60% of the protein coding capacity of mammalian mitochondrial DNA is utilized for the assembly of the first enzyme complex of the respiratory chain. The absence of such information in yeast mitochondrial DNA dramatizes the variability in gene content of different mitochondrial genomes.     

Initial function determination for the open reading frame (ORF) region of Pib gene via rice transformation

Three plant binary expression vectors—pNAR501, pNAR502 and pNAR503—were constructed, carrying fragments of exon2-exon3, 5′partial deletion exon1 and 5′partial deletion exon1-exon2-exon3 of Pib gene driven by 35S. These three vectors were transformed into the japonica rice variety Nipponbare through agrobacterium-mediated transformation. More than 30 transgenic rice plants were obtained and confirmed by polymerase chain reaction (PCR), Southern hybridization and the hygromycin resistance test in seed germination of their progeny. A rice blast resistance test for in vitro leaves of T_o transgenic plants in the tillering stage showed higher resistance to the races of E1, F1 and G1 of rice blast than that of the control Nipponbare. However, results of rice blast resistance test for seedlings of T₁ transgenic plants in the 3-to 4-leaf stage were different. All T₁ transgenic seedlings had a lower level of resistance to E1, F1 and G1 races than that of the control Nipponbare. Translated from Journal of Nanjing Agricultural University, 2006, 29(3): 1–5 [译自: 南京农业大学学报]     

Memory disruption by electrical stimulation of substantia nigra, pars compacta

Electrical stimulation of the substantia nigra, pars compacta, of albino rats while they were learning a simple foot shock task of withdrawal and response suppression disrupted retention of that task 24 hours after original learning. Stimulation in the reticular zone of the substantia nigra was without effect on retention performance. Stimulation through electrodes in the medial lemniscus, red nucleus, or brainstem regions surrounding the substantia nigra, pars compacta, was also ineffective. Original learning performance, measured as time to criterion, was unimpaired by the stimulation. Posttrial stimulation in the substantia nigra, pars compacta, but not in adjacent structures, also disrupted retention performance.     

Control of mRNA decay by heat shock-ubiquitin-proteasome pathway

Cytokine and proto-oncogene messenger RNAs (mRNAs) are rapidly degraded through AU-rich elements in the 3' untranslated region. Rapid decay involves AU-rich binding protein AUF1, which complexes with heat shock proteins hsc70-hsp70, translation initiation factor eIF4G, and poly(A) binding protein. AU-rich mRNA decay is associated with displacement of eIF4G from AUF1, ubiquitination of AUF1, and degradation of AUF1 by proteasomes. Induction of hsp70 by heat shock, down-regulation of the ubiquitin-proteasome network, or inactivation of ubiquitinating enzyme E1 all result in hsp70 sequestration of AUF1 in the perinucleus-nucleus, and all three processes block decay of AU-rich mRNAs and AUF1 protein. These results link the rapid degradation of cytokine mRNAs to the ubiquitin-proteasome pathway.     

Plant UVR8 photoreceptor senses UV-B by tryptophan-mediated disruption of cross-dimer salt bridges

The recently identified plant photoreceptor UVR8 (UV RESISTANCE LOCUS 8) triggers regulatory changes in gene expression in response to ultraviolet-B (UV-B) light through an unknown mechanism. Here, crystallographic and solution structures of the UVR8 homodimer, together with mutagenesis and far-UV circular dichroism spectroscopy, reveal its mechanisms for UV-B perception and signal transduction. β-propeller subunits form a remarkable, tryptophan-dominated, dimer interface stitched together by a complex salt-bridge network. Salt-bridging arginines flank the excitonically coupled cross-dimer tryptophan "pyramid" responsible for UV-B sensing. Photoreception reversibly disrupts salt bridges, triggering dimer dissociation and signal initiation. Mutation of a single tryptophan to phenylalanine retunes the photoreceptor to detect UV-C wavelengths. Our analyses establish how UVR8 functions as a photoreceptor without a prosthetic chromophore to promote plant development and survival in sunlight.     

Active disruption of an RNA-protein interaction by a DExH/D RNA helicase

All aspects of cellular RNA metabolism and the replication of many viruses require DExH/D proteins that manipulate RNA in a manner that requires nucleoside triphosphates. Although DExH/D proteins have been shown to unwind purified RNA duplexes, most RNA molecules in the cellular environment are complexed with proteins. It has therefore been speculated that DExH/D proteins may also affect RNA-protein interactions. We demonstrate that the DExH protein NPH-II from vaccinia virus can displace the protein U1A from RNA in an active adenosine triphosphate-dependent fashion. NPH-II increases the rate of U1A dissociation by more than three orders of magnitude while retaining helicase processivity. This indicates that DExH/D proteins can effectively catalyze protein displacement from RNA and thereby participate in the structural reorganization of ribonucleoprotein assemblies.     

Germ-line transmission of a c-abl mutation produced by targeted gene disruption in ES cells

A substitution mutation has been introduced into the c-abl locus of murine embryonic stem cells by homologous recombination between exogenously added DNA and the endogenous gene, and these cells have been used to generate chimeric mice. It is shown that the c-abl mutation was transmitted to progeny by several male chimeras. This work demonstrates the feasibility of germ-line transmission of a mutation introduced into a nonselectable autosomal gene by homologous recombination.     

利用阳畦育苗进行玉米当地加代的探讨

研究表明 ,郑州地区可利用阳畦营养钵育苗移栽、田间地膜覆盖的方法 ,对玉米材料进行加代。此法可以加快育种速度 ,同时也可以节省科研费用。     

用竞争PCR方法定量检测猪MHC-DM mRNA

根据GenBank中猪MHC-DM基因序列,用RT-PCR技术从猪肺泡巨噬细胞中扩增和克隆了猪DM基因部分片段,经测序鉴定后,用反向PCR技术构建了其缺失竞争cDNA分子。通过竞争PCR方法,建立了猪DM标准竞争曲线,并得到其直线回归方程。本方法操作简便,特异性和敏感性高,可用于猪DM mRNA水平的定量检测。     

A 200-second quasi-periodicity after the tidal disruption of a star by a dormant black hole

Supermassive black holes (SMBHs; mass is greater than or approximately 10(5) times that of the Sun) are known to exist at the center of most galaxies with sufficient stellar mass. In the local universe, it is possible to infer their properties from the surrounding stars or gas. However, at high redshifts we require active, continuous accretion to infer the presence of the SMBHs, which often comes in the form of long-term accretion in active galactic nuclei. SMBHs can also capture and tidally disrupt stars orbiting nearby, resulting in bright flares from otherwise quiescent black holes. Here, we report on a ~200-second x-ray quasi-periodicity around a previously dormant SMBH located in the center of a galaxy at redshift z = 0.3534. This result may open the possibility of probing general relativity beyond our local universe.     

Angiogenesis induced by degradation products of hyaluronic acid

Partial degradation products of sodium hyaluronate produced by the action of testicular hyaluronidase induced an angiogenic response (formation of new blood vessels) on the chick chorioallantoic membrane. Neither macromolecular hyaluronate nor exhaustively digested material had any angiogenic potential. Fractionation of the digestion products established that the activity was restricted to hyaluronate fragments between 4 and 25 disaccharides in length.     

利用mRNA差异显示技术筛选棉纤维发育相关基因

优良品种的选育对棉花生产有着其他技术不可替代的作用.研究细胞分化的内在机理,可为通过遗传工程途径人为控制棉纤维生长发育,选育优良农艺性状的新种质提供依据[1].     

半定量RT-PCR检测PERV mRNA在姜曲海猪不同器官与组织中的表达

猪内源性反转录病毒(PERV)为反转录病毒科哺乳动物C型反转录病毒属成员,它以前病毒DNA的形式整合进猪细胞基因组中,并随细胞染色体复制而复制.本试验利用半定量RT-PCR方法分析姜曲海猪的肝、心、胰、脾、肺、胆、腿肌等器官与组织中PERV基因3种亚型的mRNA表达情况.结果表明:在所检测的器官与组织中,PERV-A在肝中表达丰度最高,胰中表达丰度最低;PERV-和PERV-C均在腿肌中表达丰度最高,脾中表达丰度最低.