Spatial restriction in expression of a mouse homoeo box locus within the central nervous system

A common feature of Drosophila homoeo box genes appears to be their spatially restricted expression patterns during morphogenesis. Using Northern blot analysis and in situ hybridization to mouse tissue sections, the spatially restricted expression of a newly identified mouse homoeo box locus, Hox-3, within the central nervous system of newborn and adult mice has been demonstrated.     

Non-function of a Moloney murine leukaemia virus regulatory sequence in F9 embryonal carcinoma cells

Moloney murine leukaemia virus (M-MuLV) infection of embryonal carcinoma (EC) cells results in the integration of proviral DNA into the host cell genome, but not in virus production. One suggested explanation for the lack of viral gene expression in EC cells has been methylation of the integrated viral DNA. However, subsequent reports indicated that integration of the M-MuLV DNA occurs soon after infection, but that viral DNA methylation occurs considerably later. Nevertheless, viral gene expression is not observed even at early times. One possible explanation is that certain M-MuLV regulatory sequences do not function in EC cells. We now present evidence which supports this hypothesis.     

Comparative chromosome mapping of a conserved homoeo box region in mouse and human

Specific genes are assumed to regulate pattern formation in the mammalian embryo, but as yet none has been identified unequivocally. It is possible that such genes in mammals may be identified by virtue of a conserved coding sequence, because many of the Drosophila melanogaster homoeotic and segmentation genes, which have crucial roles in the regulation of segmental pattern formation during embryonic development, contain a 180-base pair (bp) DNA sequence, the homoeo box, and that sequences homologous to the Drosophila homoeo box are also present in 6-10 copies in higher animals, including mammals. Although the assumption that the homoeo box identifies genes responsible for pattern formation in mammals remains to be validated, it is a particularly attractive hypothesis given the strong conservation of homoeo boxes over vast evolutionary distances. Here we report the localization of a human homoeo box region, previously cloned and shown to contain two homoeo boxes within a sequence of 5-kilobases (kb), to the long arm of chromosome 17. We show that two single-copy homoeo box-flanking probes derived from this region strongly hybridize to single-copy restriction fragments in mouse genomic DNA and that these conserved homoeo box-flanking sequences map to mouse chromosome 11. This may be significant as several genes that map to chromosome 17 in human also map to chromosome 11 in the mouse, implying that a segment of mouse chromosome 11 is homologous to a region of human chromosome 17. Taken together, these data suggest that the homoeo box region detected with our probes is highly conserved in human and mouse.     

Sequential activation of HOX2 homeobox genes by retinoic acid in human embryonal carcinoma cells

RETINOIC acid had been implicated as a natural morphogen in chicken and frog embryogenesis, and is presumed to act through the gene regulatory activity of a family of nuclear receptors. Homeobox genes, which specify positional information in Drosophila and possibly in vertebrate embryogenesis, are among the candidate responsive genes. We previously reported that retinoic acid specifically induces human homeobox gene (HOX) expression in the embryonal carcinoma cell line NT2/D1. We now show that the nine genes of the HOX2 cluster are differentially activated in NT2/D1 cells exposed to retinoic acid concentrations ranging from 10(-8) to 10(-5) M. Genes located in the 3' half of the cluster are induced at peak levels by 10(-8) M retinoic acid, whereas a concentration of 10(-6) to 10(-5) M is required to fully activate 5' genes. At both high and low retinoic acid concentrations, HOX2 genes are sequentially activated in embryonal carcinoma cells in the 3' to 5' direction.     

Virus-specific effects of interferon in embryonal carcinoma cells

Embryonal carcinoma (EC) cells are susceptible to infection by a variety of viruses, but do not become resistant to infection by Semliki Forest virus or vesicular stomatitis virus (VSV) on treatment with interferon. These observations have led to the conclusion that interferon does not induce an antiviral state in EC cells. We report here, however, that EC cells treated with interferon become resistant to infection by two picornaviruses and two ts mutants of VSV, whereas they remain sensitive to wild-type VSV, Sindbis and influenza virus infectin. These results suggest that a partial antiviral state is induced in EC cells by interferon and that the induced antiviral protein(s) interferes with the replication of specific viruses. A significant common feature of these viruses is their replication through structures containing double-stranded RNA (dsRNA).     

Chi-linker-Glu融合基因双价植物表达载体的构建及其相关鉴定

将木霉几丁质酶基因Chi和β-1,3-葡聚糖酶基因Glu通过8个中性氨基酸连接起来,形成Chi-linker-Glu融合基因．其中编码区基因长2376bp,共编码792个氨基酸和一个终止子．将该融合基因克隆到中间载体pAHC25中,然后将整个ubi-chi-linker-glu-nos表达盒插入用ubi-bar-nos表达盒代替CaMV35S-gus-nos的高效植物表达载体pBI121中,构建了双价抗真菌基因的重组质粒pBIb-CG,并通过根癌农杆菌介导,采用叶盘法转化烟草．PCR扩增和PCR-Southern分析证明已将Chi-linker-Glu融合基因整合到烟草基因组中．     

ITER校正场线圈馈线系统干盒的结构设计与分析

校正场线圈馈线系统的干盒用于容纳高温超导电流引线室温端与外部室温电力系统的过渡连接接头,并为此过渡连接以及外部电缆提供可靠的支撑。其设计的合理可靠与否将会直接影响ITER装置的正常运行。文章根据ITER装置对干盒设计的要求,对CC干盒的整体结构进行了详细设计说明,并对相关结构的受力、热传导及结构模态进行计算和分析,为干盒结构的进一步研制提供了理论依据。     

Structural relationship of the SB beta-chain gene to HLA-D-region genes and murine I-region genes

The major histocompatibility complex (MHC) regulates several aspects of the immune response. Class II antigens of the MHC control cellular interactions between lymphocytes. In man, at least three class II antigens (DR, DC and SB), consisting of distinct alpha- and beta-chains, are encoded in the HLA complex. Sequence analysis has established that the DR and DC antigens are the respective structural counterparts of the murine I-E and I-A antigens. Molecular cloning of the SB beta-chain gene has now enabled us to define its relationship to other class II genes. The DR, DC and SB beta genes have diverged from each other to the same extent. In murine DNA and in cloned genes from the I region, the best hybridization of SB beta DNA is with the E beta 2 sequence. E beta 2 may belong to a complete gene (E' beta) because first domain sequences were found adjacent to it.     

Interferon enhances 2-5A synthetase in embryonal carcinoma cells

Mouse teratocarcinomas provide a useful model of mammalian differentiation, because the malignant embryonal carcinoma (EC) stem cells of such tumours may produce various differential cell types in vivo or in vitro. Many EC cell lines have now been established and classified on the basis of their ability to differentiate in vivo into cell types characteristically derived from any of the three germ layers. There is convincing evidence that EC cells can neither produce interferon, nor respond to it by becoming resistant to virus, whereas differentiated cells derived from EC lines behave normally in both respects. We investigated the lack of responsiveness of EC cells towards interferon by measuring the levels of two double-stranded RNA-dependent enzyme activities recently shown to be enhanced by interferon. We report here that on treatment with interferon, EC cells show increased 2-5A synthetase levels comparable to those found in differentiated cells, while there is little or no effect on kinase activity in EC cells, in contrast to their differentiated counterparts.     

人tPA基因真核表达质粒载体构建及其生物学功能研究

构建携带组织纤溶酶原激活物(tPA)基因真核表达质粒pcDNA3.1( )/tPA,并研究其有无生物学活性.用RT-PCR法从人心脏组织中克隆tPA基因并将其克隆至真核表达质粒pcDNA3.1( )中,对pcDNA3.1( )/tPA进行酶切鉴定和测序.脂质体介导pcDNA3.1( )/tPA转染血管平滑肌细胞,分别用Nothern Blot和斑点印迹法从mRNA和蛋白质水平检测tPA的表达,并用纤维蛋白板法测定表达产物的生物学活性.成功克隆了人tPA基因并构建了pcDNA3.1( )/tPA真核表达质粒,pcDNA3.1( )/tPA转染VSMC后,tPA mRNA和蛋白质表达增加,所表达的tPA蛋白质具有纤溶活性.     

Differential expression of myc family genes during murine development

The myc family of cellular oncogenes contains three known members. The N-myc and c-myc genes have 5'-noncoding exons, strikingly homologous coding regions, and display similar oncogenic potential in an in vitro transformation assay. The L-myc gene is less well characterized, but shows homology to N-myc and c-myc (ref. 6; also see below). c-myc is expressed in most dividing cells, and deregulated expression of this gene has been implicated in the development of many classes of tumours. In contrast, expression of N-myc has been found only in a restricted set of tumours, most of which show neural characteristics; these include human neuroblastoma, retinoblastoma and small cell lung carcinoma (SCLC). L-myc expression has so far been found only in SCLC. Activated N-myc and L-myc expression has been implicated in oncogenesis; for example, although N-myc expression has been found in all neuroblastomas tested, activated (greatly increased) N-myc expression, resulting from gene amplification, is correlated with progression of the tumour. We now report that high-level expression of N- and L-myc is very restricted with respect to tissue and stage in the developing mouse, while that of c-myc is more generalized. Furthermore, we demonstrate that N-myc is not simply a neuroectoderm-specific gene; both N- and L-myc seem to be involved in the early stages of multiple differentiation pathways. Our findings suggest that differential myc gene expression has a role in mammalian development and that the normal expression patterns of these genes generally predict the types of tumours in which they are expressed or activated.