Structure and promoter analysis of the human unc-33-like phosphoprotein gene. E-box required for maximal expression in neuroblastoma and myoblasts

The human unc-33-like phosphoprotein (hUlip/CRMP-4) is a member of a family of developmentally regulated genes that are highly expressed in the nervous system. Mutations in the C. elegans unc-33 gene lead to worms with abnormal movements. The hUlip gene encodes a 570-amino acid protein with 98% homology to its murine (Ulip) (Byk, T., Dobransky, T., Cifuentes-Diaz, C., and Sobel, A. (1996) J. Neurosci. 16, 688-701) and rat (CRMP-4) (Wang, L. H., and Strittmatter, S. M. (1996) J. Neurosci. 16, 6197-6207) counterparts (Gaetano, C., Matsuo, T., and Thiele, C. J. (1997) J. Biol. Chem. 272, 12195-12201). The hUlip gene was isolated from a human genomic library. It contains 15 exons, including an exon defined by an anaplastic oligodendroglioma expressed sequence tag, and spans at least 61.7 kilobases. hUlip lacks sequences corresponding to the first six exons found in unc-33. unc-33 exons correspond to homologous hUlip exons as follows: VII to 1 and 2, VIII to 3-9, IX to 10-12, and X to 13 and 14. Using the hUlip clone 1 phage, fluorescence in situ hybridization analysis indicates that the hybridization signal localizes to human chromosome 5q32. Deletion analysis of 5'-flanking sequences delineated the sequences sufficient to express a reporter gene in both neuroblastoma cells and myoblasts. A consensus MyoD/myogenin binding site is located in a region of the downstream promoter that is nearly identical to its mouse homologue. Mutagenesis shows that this conserved MyoD/myogenin site is necessary for full promoter activity in both myoblasts and neuroblastoma cells.     

人同源框基因Lhx4 cDNA序列的获得,染色体定位和基因组分析

Lhx4基因是LIM同源框基因家族的一员 ,它在运动神经元的发育过程中发挥着重要的作用 .从人脊髓cDNA文库中筛选到了 1个人源性Lhx4基因的cDNA全长序列 ,它与鼠源性的Lhx4基因的cDNA序列有 92 %同源性 .它的基因被定位在 1号染色体 1q 2 4 .1- 1q 2 4 .3的位置 ,并包含有 6个外显子 .其中同源框结构域由外显子 4和 5表达 ,LIM结构域 1由外显子 2表达 ,LIM结构域2由外显子 3表达 .     

一种新型眼皮肤白化病——OCA4

眼皮肤白化病(OCA)在遗传学上是一组由不同基因的突变导致的具有相同或相似临床症状的遗传病。根据涉及基因的不同, OCA进一步分为4型, 即眼皮肤白化病Ⅰ~Ⅳ型(OCA1~OCA4)。OCA4为近年新发现的一种眼皮肤白化病类型, 首报病例是一名土尔其后裔。与小鼠uw基因同源的MATP基因突变导致OCA4表型的发生。MATP 基因定位于5p13.3, 由7个外显子和6个内含子构成, MATP基因在转录水平上受黑素细胞特异性转录因子调控, 编码由530个氨基酸残基构成的膜相关转运蛋白。迄今, 至少已报道了18种MATP基因病理性突变和8种DNA多态性变异。     

p80 ROKalpha binding protein is a novel splice variant of CRMP-1 which associates with CRMP-2 and modulates RhoA-induced neuronal morphology

Using antibody against the Rho binding domain of ROKalpha, two neuronal phosphoproteins of 62 and 80 kDa were co-immunoprecipitated from brain extracts. Peptide analysis revealed their identity as collapsin response mediator proteins (CRMPs); p62 was CRMP-2 whereas p80 was a novel splice form of CRMP-1 with an extended N-terminus. p80 CRMP-1 was able to complex with CRMP-2, suggesting that p80 CRMP-1 and CRMP-2 form oligomers. CRMP-2 was the major substrate of ROK. p80 CRMP-1 interacted with the kinase domain of ROKalpha, resulting in inhibition of the catalytic activity towards other substrates. Over-expression of p80 CRMP-1 and CRMP-2 together counteracted the effects of RhoA on neurite retraction, an effect enhanced by mutation of the ROK phosphorylation site in CRMP-2. p80 CRMP-1 and CRMP-2 may be modulators of RhoA-dependent signaling, through interaction with and regulation of ROKalpha.     

P16^INK4、Rb基因表达在肺癌发生中协调性研究

采用mRNA原位双杂交和免疫组织化学方法对31例非小细胞肺癌组织进行P16^INK、Rb基因、Rb基因表达水平及其相关性的研究。结果显示,以Dig-碱性磷酸酶－NBT／BCIP系统检测P16^INK4基因转录,阳性结果呈蓝色,阴性杂交率为22．6％（7／31）;以Bio－辣根过氧化物酶－AEC系统检测Rb基因转录,阳性结果为红色,阴性率为16．1％（5／31）。免疫组织化学检测显示P16^INK4蛋白质阴性率为42％（13／31）;Rb蛋白表达阴性率为19．4％（6／31）。Rb、P16^INK4基因在非小细胞肺癌发生中起协同调控作用,以P16^INK4基因表达异常为主。     

Neurofibromin interacts with CRMP-2 and CRMP-4 in rat brain

Neurofibromin, encoded by the neurofibromatosis type 1 (NF1) gene, regulates the Ras and cAMP pathways and plays a role in proliferation and neuronal morphogenesis. The details of the molecular mechanism of neurofibromin action in these processes are still unclear. In this study, immunoprecipitation and proteomics were used to identify novel proteins from rat brain that interact with neurofibromin. Mass spectrometry analysis showed that two proteins, the collapsin response mediator protein-2 (CRMP-2) and propionyl-CoA carboxylase alpha chain (PCCA), associated with neurofibromin. Immunoprecipitation-immunoblotting analysis confirmed the interactions between neurofibromin and CRMP-2 and CRMP-4, but not CRMP-1, in rat brain. CDK5, a kinase that regulates CRMP-2 in axonal outgrowth, was required for the interaction between neurofibromin and CRMP-2. Since both neurofibromin and CRMP proteins are involved in proliferation and axonal morphogenesis, these results suggest that the interaction with CRMPs contributes to the function of neurofibromin in tumorigenesis and neuronal morphogenesis.     

大肠癌中p53基因突变的研究

应用聚合酶链反应(PCR)──单链构型多态性(SSCP)结合银染法对14例大肠癌p53基因的第4、第5─6和第7外显子进行了点突变的研究,结果共检测出6例点突变,而且发现各外显子的突变频率存在差异。另外,利用购自ATCC的两个探针 (p53cDNA探针和pYNZ22探针)对大肠癌中p53基因的杂合性失去进行了研究,在14例大肠癌中共检出6例杂合性丢失。将点突变检测结果同杂合性丢失结果进行比较分析, 并着重探讨了大肠癌中p53基因失活导致肿瘤的作用方式。 Abstract:The exons 4-7 of p53 gene were examined in 14 colorectal Cancer patients by using PCR-SSCP-silver staining method.The results showed 6 cases of point mutation and the mutation frequencies of exons were different from each other.p53 cDNA and pYNZ22 VNTR were used as probes to examine LOH(Loss of heterozygosity)of 14 colorectal cancers.6 cases with LOH were found.The results of present research suggest that mutation and LOH of p53 gene are critical events in the progress and development of Cancer.There were different kinds of inactivation model of p53 gene in the process of development of cancer and transformation of cells.     

Structure of the human retinoblastoma-related p107 gene and its intragenic deletion in a B-cell lymphoma cell line

The human p107 protein shares many structural and functional features with the retinoblastoma gene product and retinoblastoma-related p130 protein. In this study, we have cloned and elucidated the complete intron-exon organization of the gene encoding the p107 protein. The gene contains 22 exons spanning over 100kilobase pairs of genomic DNA. The length of individual exons ranges from 50 to 840base pairs. The arrays of exons in the p107 gene are rather similar among members of the gene family, especially to those of the p130 gene, while the length of introns is extensively diverse. This study will provide a molecular basis for implementing comprehensive screening for p107 mutations using genomic DNAs from human malignancies.We also show a detailed structure of an intragenic deletion of the p107 gene found in a human B-cell lymphoma cell line, KAL-1, which was shown to occur by homologous recombination between the two directly repeated Alu family sequences.     

人肝癌细胞p53基因的表达及其对细小病毒H-1的敏感性

本文利用单链构象多态性分析,17号染色体短臂等位基因杂合性分析,Northern印迹,免疫沉淀,p53基因第7外显子酶切等技术检测了两个中国人肝癌细胞系SMMC-7721,YY-8103和一个自发转化的人肝细胞系L-02的p53基因结构与表达。实验表明,这三个细胞系中没有出现17号染色体短臂等位基因杂合性缺失,第4—9外显子也没发生突变,但其mRNA和蛋白表达水平很低。利用MTT比色分析法研究了这三个细胞系和其他已知p53基因背景的八个人肝癌细胞系(QGY-7703、PLC/PRF/5、Huh-7、Hep3B、FOCUS、Tong/ HCC、SK-Hep-1、HepG2)对自主性细小病毒H-1的敏感性。除HepG2细胞外,其他十个细胞系p53基因的结构和/或表达都不正常。经H-1感染(moi=20)后,其敏感性均高于HepG2细胞。本研究初步表明了p53基因结构或表达的不正常可能导致人肝癌或转化细胞对H-1的敏感性的提高。     

The structure of human collapsin response mediator protein 2, a regulator of axonal growth

Axonal growth cone guidance is a central process in nervous system development and repair. Collapsin response mediator protein 2 (CRMP-2) is a neurite extension-promoting neuronal cytosolic molecule involved in the signalling of growth inhibitory cues from external stimuli, such as semaphorin 3A and the myelin-associated glycoprotein. We have determined the crystal structure of human tetrameric CRMP-2, which is structurally related to the dihydropyriminidases; however, the active site is not conserved. The wealth of earlier functional mapping data for CRMP-2 are discussed in light of the three-dimensional structure of the protein. The differences in oligomerisation interfaces between CRMP-1 and CRMP-2 are used to model CRMP-1/2 heterotetramers.     

Structure of the human lck gene: differences in genomic organisation within src-related genes affect only N-terminal exons

Although cDNA sequences coding for several Rous sarcoma virus Src-related protein tyrosine kinases (PTKs) have been reported for several years, knowledge of the structure and organisation of genes of the src family is still limited. In this work, a detailed structure and organisation of the human lck gene is reported. A 17-kb genomic clone encoding human p56 Lck, a lymphocyte-specific PTK of the Src-related subfamily, has been isolated. The human lck gene is organized in 13 exons, one more than in the human cellular (c)-src gene. The twelve coding exons are located in this clone, whereas the putative 5'-noncoding exon is probably located very far upstream from the second exon. Splicing sites for exons 4 to 12, which encode both conserved phospholipase-C-like and catalytic domains of the Src-like PTKs, arise exactly at the same position for the human lck, human c-src and c-fgr genes. The only differences concern the splice sites of exons 1' and 2, which encode the unique N-terminal domain of human Lck. These results give further evidence that the different PTKs of the Src-like family have probably evolved through the mechanism of exon shuffling.     

Collapsin response mediator protein-4 regulates F-actin bundling

Collapsin response mediator proteins (CRMPs) form a family of cytosolic phosphoproteins which are involved in the signal transduction of semaphorin 3A leading to growth cone collapse. These proteins interact with a variety of cytosolic proteins including tubulin heterodimers. Here, we show that CRMP-4 co-localizes with F-actin in regular rib-like structures within lamellipodia of B35 neuroblastoma cells. Furthermore, depolymerization of actin fibers changed the distribution of GFP-CRMP-4 in vivo. In vitro, recombinant CRMP-4 formed homo-oligomers, bound to F-actin and organized F-actin into tight bundles. Both oligomerization and F-actin bundling depended on the C-terminal part of CRMP-4. The stoichiometry of actin and CRMP-4 in bundles was approximately 1:1 and the apparent equilibrium constant of the microfilament-CRMP-4 interaction was estimated from bundling assays as K(app) = 730 mM(-1). CRMP-4 was abundant in the cytosol of B35 neuroblastoma cells and its concentration was measured as approximately 1.7 microM. Overexpression of CRMP-4 inhibited the migration of B35 neuroblastoma cells, while knockdown of CRMP-4 enhanced cell migration and disturbed rib-like actin-structures in lamellipodia. Taken together, our data indicate that CRMP-4 promotes bundling of F-actin in vitro, that it is an important component of rib-like actin bundles in lamellipodia in vivo and that it functionally regulates the actin cytoskeleton in motile cells. These findings suggest a specific regulatory role of CRMP-4 towards the actin cytoskeleton which may by be relevant for growth cone collapse.     

Isolation, characterization, and localization of human genomic DNA encoding the beta 1 subunit of the GABAA receptor (GABRB1).

Genomic DNA that encodes the beta 1 subunit of the human gamma-aminobutyric acidA (GABAA) receptor was cloned and mapped. Exons and flanking introns (greater than 14 kb) were sequenced to determine the structural organization of the gene. The gene was localized on human chromosome 4, in bands p12-13. The beta 1 subunit is encoded by a relatively large gene (greater than 65 kb) on nine exons. In contrast to other conserved regions of the subunit polypeptide, the proposed channel-forming domain (M2) is derived from more than one exon. The organization of exons was compared with that of the genes that code for subunits of nicotinic acetylcholine receptors. There is no evidence for conservation of gene structure between these two members of the proposed gene superfamily. However, intron-exon junctions were found to be conserved precisely between subtypes of GABAA receptor subunits.     

Molecular characterization of p53 mutations in primary and secondary liver tumors: diagnostic and therapeutic perspectives

p53 is one of the most mutated genes in human cancer. We have performed the molecular characterization of p53 and have searched for correlations with etiological factors and clinical parameters in primary and secondary liver tumors. A systematic study was carried out, innovative in many respects, to determine the mutational pattern of all 11 exons of p53 and analysis was extended also to exons 1–4 and 9–11 and the exon/intron junctions. Our analyses were performed on case histories of 114 patients from the European area and highlighted p53 mutation patterns different from those reported in the literature for the same tumors. In our case history, different tumors of the same organ showed a different frequency and distribution of mutations. In analyzed tumor types, gene status was a prognostic indicator of survival because patients undergoing liver resection without mutated p53 had a more favorable prognosis than mutated patients. This suggests p53 molecular diagnosis could become a further criterion in the decision for surgery and possible therapies. We describe the ideal conditions for polymerase chain reaction (PCR), single-strand conformation polymorphism (SSCP), and direct sequencing, which we have set in order to optimize yields, sensitivity, and time of what might become a massive molecular screening.     

Organization and nucleotide sequences of the human tyrosinase gene and a truncated tyrosinase-related segment

We have isolated and sequenced the gene encoding human tyrosinase, the key enzyme in pigment biosynthesis. The human tyrosinase gene contains five exons and spans more than 50 kb of DNA on chromosome segment 11q14----q21. We have also isolated a second segment in the human genome that is closely related to tyrosinase. The tyrosinase-related segment, located on 11p11.2----cen, contains only exons 4 and 5 plus adjacent noncoding regions. This segment is present in all human ethnic groups analyzed, and the noncoding nucleotide sequences shared by the 11q tyrosinase gene and the 11p tyrosinase-related segment differ by only 2.6%. This suggests that this segment of the tyrosinase gene was duplicated approximately 24 million years ago.     

Genomic structures and sequences of two closely linked genes (AMT, TCTA) on dog chromosome 20q15.1-->q15.2

Analysis of genomic sequence from canine chromosome 20q15.1-->q15.2 revealed the presence of two closely linked genes. The two genes represent the corresponding canine orthologs of human aminomethyltransferase (AMT) and the human T-cell leukemia translocation associated (TCTA) gene. Aminomethyltransferase or glycine cleavage system T-protein is an important enzyme in glycine metabolism. The reported canine AMT gene spans 5 kb and consists of nine exons. It encodes a protein of 403 amino acids with 88% identity to human aminomethyltransferase. Human TCTA is located on 3p21 near the breakpoint of a t(1;3) translocation observed in some cancer cell lines. The 4-kb canine TCTA gene consists of three exons and probably represents a pseudogene. It is located adjacent to AMT and very close to DAG1 and BSN.     

Collapsin response mediator protein-2 accelerates axon regeneration of nerve-injured motor neurons of rat

The rat collapsin response mediator protein-2 (CRMP-2) is a member of CRMP family (CRMP-1-5). The functional consequence of CRMP-2 during embryonic development, particularly in neurite elongation, is relatively understood; however, the role in nerve regeneration is unclear. Here we examined the role of CRMP-2 during nerve regeneration using rat hypoglossal nerve injury model. Among the members, CRMP-1, CRMP-2, CRMP-5 mRNA expressions increased after nerve injury, whereas CRMP-3 and CRMP-4 mRNA did not show any significant change. In the N1E-115 cells, CRMP-2 has the most potent neurite elongation activity among the CRMP family members. In dorsal root ganglion (DRG) organ culture, CRMP-2 overexpression by adenoviral vector demonstrated substantial neurite elongation. On the other hand, CRMP-2 (DeltaC381), which acts as a dominant negative form of CRMP-2, inhibited neurite formation. Collectively, it would be plausible that CRMP-2 has potent nerve regeneration activity after nerve injury. We therefore examined whether CRMP-2 overexpression in the injured hypoglossal motor neurons accelerates nerve regeneration. A retrograde-tracer, Fluoro-Gold (FG), was used to evaluate the number of reprojecting motor neurons after nerve injury. CRMP-2-overexpressing motor neurons demonstrated the accelerated reprojection. The present study suggests that CRMP-2 has potent neurite elongation activity in nerve regeneration in vivo.