Cloning and characterization of MDDX28, a putative dead-box helicase with mitochondrial and nuclear localization.

A cDNA encoding a novel member of the helicase family, MDDX28, has been cloned from a human testis library. This apparently intronless gene was transcribed in all tissues studied. MDDX28 encodes a protein of 540 amino acids, with approximately 30% homology to other helicases over the core region, containing all the conserved DEAD-box helicase motifs. No homologue is known. MDDX28 has RNA and Mg(2+)-dependent ATPase activity. Subcellular localization studies of MDDX28 using oligoclonal antibodies raised against the protein as well as its enhanced green fluorescence protein (EGFP) demonstrated that the protein is localized in the mitochondria and the nucleus. To our knowledge, MDDX28 is the first member of the RNA helicase described with this dual location. The nuclear localization of MDDX28 depended on active RNA polymerase II transcription, suggesting that the protein could be transported to and from the nucleus. This was confirmed further in an interspecies heterokaryon assay, in which MDDX28 was seen to translocate to the nucleus and mitochondria. The mitochondrial uptake of the MDDX28-EGFP-N1 fusion protein was inhibited by carbonyl cyanide p-(trichloromethoxy)phenylhydrazone. Our results indicate that MDDX28 can be transported between the mitochondria and the nucleus.

[Gene transfer--ways of administration, advantages, possible unsuitability and hazards]. / Genoverføring--administrasjonsmåter, fordeler, mulige ulemper og farer.

BACKGROUND: Reports about successful gene therapy are now published after a period of more than ten years of trial and error. The key problem is to get DNA from genes or gene fragments into the target cells to be transcribed. MATERIAL AND METHODS: A brief review of transfer techniques is given, based upon the authors' own research and the literature in the field. RESULTS: In most cases, a vector (modified virus DNA or RNA, or plasmid DNA) is used as a vehicle. Retrovirus (RNA virus), adenovirus (DNA virus) and adeno-associated virus (DNA virus) are frequently used. Non-viral vectors such as plasmid DNA, liposome-linked DNA, protein DNA conjugates and artificial chromosomes are also relevant. Retrovirus has been used in about 60% of all gene therapy protocols. One problem is how to produce enough modified retrovirus for clinical use, hence retrovirus has mainly been used in ex vivo gene therapy, in which the number of target cells to be infected with the vector is limited and much lower than in in vivo therapy. INTERPRETATION: Increased insight into the genome has taught us that genes can partially or totally replace each other with regard to function, but they will not be expressed at the same time in the patient's life or in the same organ. In the future it may not be necessary to transfer a new gene; instead we may interfere with the regulation of another gene with a similar function.

Characterization of PSKH1, a novel human protein serine kinase with centrosomal, golgi, and nuclear localization.

We report here the characterization of PSKH1, a novel human protein serine kinase with multiple intracellular localizations. The gene consists of three exons distributed over 35 kb of genomic DNA in region 16q22.1. The 3.4-kb cDNA predicts a protein of 424 amino acids with a calculated molecular mass of 48.1 kDa and pI of 9.6. PSKH1 is expressed in all tissues and cell lines tested as shown by Northern blots, with the highest level of abundance in testis. PSKH1 displays the highest level of similarity with rat CaM kinase I (50. 2%) over 259 amino acids in the conserved catalytic region, but lacks significant homology with proteins in the database outside the catalytic core. Polyclonal antibodies have been raised, and indirect immunofluorescence microscopy of untransfected COS-1 cells suggests that PSKH1 is localized in the Brefeldin A-sensitive Golgi compartment, at centrosomes, in the nucleus with a somewhat speckle-like presence, and more diffusely in the cytoplasm. The presence in the centrosome appears to be enhanced during osmotic stress. Immunoisolated PSKH1 does not phosphorylate any of the common kinase substrates in vitro, but autophosphorylates exclusively serines within its COOH-terminal region in an intermolecular fashion. Furthermore, autophosphorylation activity is repressed upon addition of Ca(2+)/CaM, suggesting that PSKH1 activity depends on Ca(2+) concentration in vivo.

Secondary structure prediction and in vitro accessibility of mRNA as tools in the selection of target sites for ribozymes.

We have investigated the relative merits of two commonly used methods for target site selection for ribozymes: secondary structure prediction (MFold program) and in vitro accessibility assays. A total of eight methylated ribozymes with DNA arms were synthesized and analyzed in a transient co-transfection assay in HeLa cells. Residual expression levels ranging from 23 to 72% were obtained with anti-PSKH1 ribozymes compared to cells transfected with an irrelevant control ribozyme. Ribozyme efficacy depended on both ribozyme concentration and the steady state expression levels of the target mRNA. Allylated ribozymes against a subset of the target sites generally displayed poorer efficacy than their methylated counterparts. This effect appeared to be influenced by in vivo accessibility of the target site. Ribozymes designed on the basis of either selection method displayed a wide range of efficacies with no significant differences in the average activities of the two groups of ribozymes. While in vitro accessibility assays had limited predictive power, there was a significant correlation between certain features of the predicted secondary structure of the target sequence and the efficacy of the corresponding ribozyme. Specifically, ribozyme efficacy appeared to be positively correlated with the presence of short stem regions and helices of low stability within their target sequences. There were no correlations with predicted free energy or loop length.

Overexpression of human lecithin:cholesterol acyltransferase in mice offers no protection against diet-induced atherosclerosis.

Human lecithin:cholesterol acyltransferase (LCAT) is a key enzyme in the metabolism of cholesterol. We have used homozygous transgenic mice overexpressing the human LCAT transgene to study the effect of a "Western-type" atherogenic diet (30% fat, 5% cholesterol and 2% cholic acid) on their LCAT expression, activity, lipoprotein profile and tendency to develop atherosclerosis. The LCAT activity was 35-fold higher in serum of the homozygous transgenic mice than in murine control serum, and decreased 11-20% in the transgenic mice when fed the atherogenic diet. The total cholesterol and high-density lipoprotein cholesterol (HDL-C) concentrations were approximately doubled in the transgenic mice compared with the controls when both groups were fed a regular chow diet. In mice on the atherogenic diet, the triglyceride concentration decreased about 50% to the same level in transgenic and control mice. Total cholesterol and HDL-C concentrations increased and were 60-80% higher in the transgenic mice. The expression of LCAT mRNA in the liver was decreased by 49-60% in the transgenic mice when fed the atherogenic diet. The development of atherosclerosis was similar in transgenic and control mice. Thus, the 14- to 27-fold higher LCAT activity and the higher HDL-C concentrations in the homozygous LCAT transgenic mice had no significant protective influence on the development of diet-induced atherosclerosis.

Modular bacterial artificial chromosome vectors for transfer of large inserts into mammalian cells.

To facilitate the use of large-insert bacterial clones for functional analysis, we have constructed new bacterial artificial chromosome vectors, pPAC4 and pBACe4. These vectors contain two genetic elements that enable stable maintenance of the clones in mammalian cells: (1) The Epstein-Barr virus replicon, oriP, is included to ensure stable episomal propagation of the large insert clones upon transfection into mammalian cells. (2) The blasticidin deaminase gene is placed in a eukaryotic expression cassette to enable selection for the desired mammalian clones by using the nucleoside antibiotic blasticidin. Sequences important to select for loxP-specific genome targeting in mammalian chromosomes are also present. In addition, we demonstrate that the attTn7 sequence present on the vectors permits specific addition of selected features to the library clones. Unique sites have also been included in the vector to enable linearization of the large-insert clones, e. g., for optical mapping studies. The pPAC4 vector has been used to generate libraries from the human, mouse, and rat genomes. We believe that clones from these libraries would serve as an important reagent in functional experiments, including the identification or validation of candidate disease genes, by transferring a particular clone containing the relevant wildtype gene into mutant cells or transgenic or knock-out animals.

Effects of binding of ligand (FVIIa) to induced tissue factor in human endothelial cells.

The tissue factor protein is structurally related to the cytokine receptors and ligand binding (factor VIIa) has been reported to give an intracellular calcium signal, thus indicating that tissue factor is a true receptor. In view of the attempts to use recombinant factor VIIa as a therapeutic agent in hemophilia, its binding effects may be of clinical interest. We have studied the effect of ligand binding to human endothelial cells that were stimulated with interleukin-1 to express tissue factor. Human umbilical cord vein endothelial cells produce and release a wide variety of proteins that participate in coagulation and fibrinolysis, and we have investigated whether binding of recombinant factor VIIa to tissue factor altered the release of some of these compounds. Three main findings are reported. (1) After an initial increase, the measurable tissue factor activity in endothelial cells decreased more rapidly in the presence of factor VIIa (half-life 3.7+/-0.7 hours) than in its absence (half-life 7.4+/-1.5 hours). This difference was not seen when tissue factor antigen was measured, indicating that ligand binding did not increase the degradation of the protein. (2) Tissue factor pathway inhibitor was detected on the cell surface, in cell homogenates, and in cell medium. When recombinant factor VIIa was added to the cells there was a significant decrease in the release of tissue factor pathway inhibitor to the medium. Four hours after recombinant factor VIIa was added, the levels were 7.5-fold higher in the medium of untreated cells compared to the medium of cells treated with recombinant factor VIIa. (3) We observed increased release of von Willebrand factor (vWF). After 1 and 6 hours with recombinant FVIIa the release was significantly greater than in controls without FVIIa. We did not detect significant differences in the release of tissue plasminogen activator or tissue factor pathway inhibitor.

Binding of factor VIIa to tissue factor on keratinocytes induces gene expression.

Binding of the zymogen serine protease Factor VII (FVII) to its cellular cofactor tissue factor (TF) triggers blood coagulation. Several recent reports have suggested that the formation of this complex may serve additional functions. We have used cDNA arrays to study differential gene expression in response to the interaction of activated FVII (FVIIa) with TF on a human keratinocyte cell line. Of 931 mRNA species observed up to 6 h after FVIIa (10 nM) addition, 24 were significantly up-regulated in what may resemble a wound-type response. Responders included mRNA species coding for transcription regulators (c-fos, egr-1, ETR101, BTEB2, c-myc, fra-1, and tristetraproline), growth factors (amphiregulin, hbEGF, CTGF, and FGF-5), proinflammatory cytokines (IL-1beta, IL-8, LIF, and MIP2alpha), proteins involved in cellular reorganization/migration (RhoE, uPAR, and collagenases 1 and 3), and others (PAI-2, cyclophilin, GADD45, Jagged1, and prostaglandin E(2) receptor). The transcriptional response to FVIIa was abrogated by antibodies to TF and left unaffected by hirudin. The pattern of genes induced suggests that the FVIIa.TF complex may play an active role in early wound repair as well as hemostasis. The former is a novel function ascribed to the complex that may also be contributing to the pathophysiology of unwarranted TF expression.

Cellular effects of initiation of the extrinsic pathway of blood coagulation.

In the initial phase of scientific research into blood clotting around 50 years ago, most studies focused on investigating blood samples to find out what took place in the flowing blood. With the purification and cloning of Tissue Factor (TF) it was realized that TF was an integral membrane protein sitting in the cell surface membrane. This shifted the emphasis to investigations of what happened on the cell surface, and later to the cell biology of TF and its inducibility in monocytes/macrophages and endothelial cells. During the last 8 years, researchers have become increasingly interested in studying the processes going on inside the cells that carry TF when coagulation is initiated on their surface. Cells carrying TF have been incriminated in tumorigenesis, metastasis, angiogenesis, and a number of other cellular phenotypes. That binding of the plasma clotting Factor VIIa upregulates a number of genes involved in regulation of growth, transcription, and cellular motility, as well as cytokines, makes it possible to suggest a link between the formation of the TF/Factor VIIa complex and these cellular processes.

High-resolution integrated map encompassing the breast cancer loss of heterozygosity region on human chromosome 16q22.1.

Loss of heterozygosity (LOH) on the long arm of human chromosome 16 is a common genetic alteration observed in both invasive ductal and invasive lobular breast carcinomas. We have generated a high-resolution integrated map encompassing the smallest region of LOH overlap within chromosome 16q22.1 (SRO2). Southern hybridization experiments using more than 140 probes resulted in the assembly of 152 bacterial large-insert clones into a 2.8-Mb contig covering SRO2. The structure of the contig was verified by long-range mapping using total human genomic DNA, and the contig orientation was determined by fluorescence in situ hybridization. A total of 68 transcripts have been identified in the map. One of the genes residing within SRO2 is the E-cadherin gene, CDH1, which has previously been shown to be mutated in lobular breast carcinomas, resulting in loss of E-cadherin expression. In most cases of ductal carcinoma, which is the major mammary cancer type, E-cadherin is normally expressed, suggesting that other genes within 16q22.1 are involved in the development of this tumor subtype. The high-resolution map presented in this study provides a valuable resource for identification of tumor suppressor genes expected to be involved in the etiology of breast carcinomas.

Coagulation factors VIIa and Xa induce cell signaling leading to up-regulation of the egr-1 gene.

Intracellular signaling induced by the coagulation factors (F) VIIa and Xa is poorly understood. We report here studies on these processes in a human keratinocyte line (HaCaT), which is a constitutive producer of tissue factor (TF) and responds to both FVIIa and FXa with elevation of cytosolic Ca(2+), phosphorylation of extracellular signal-regulated kinase (Erk) 1/2, p38(MAPK), and c-Jun N-terminal kinase, and up-regulation of transcription of the early growth response gene-1 (egr-1). Using egr-1 as end point, we observed with both agonists that phosphatidylinositol-specific phospholipase C and the mitogen-activated protein kinase/Erk kinase/Erk pathway were mediators of the responses. The responses to FVIIa were TF-dependent and up-regulation of egr-1 mRNA did not require presence of the TF cytoplasmic domain. Antibodies to EPR-1 and factor V had no effect on the response to FXa. We have provided evidence that TF is not the sole component of the FVIIa receptor. The requirement for proteolytic activity of both FVIIa and FXa suggests that protease-activated receptors may be involved. We now report evidence suggesting that protease-activated receptor 2 or a close homologue may be a necessary but not sufficient component of this particular signal transduction pathway. The up-regulation of egr-1 describes one way by which the initiation of blood coagulation may influence gene transcription. The ability of these coagulation proteases to induce intracellular signals at concentrations at or below the plasma concentrations of their zymogen precursors suggests that these processes may occur also in vivo.

Interferon regulatory factor 1 mediates the interferon-gamma induction of the human immunoproteasome subunit multicatalytic endopeptidase complex-like 1.

Proteasomes generate antigenic peptides from intracellular proteins for presentation to the immune system by the major histocompatibility complex class I molecules. The antiviral cytokine IFN-gamma alters the catalytic specificity of proteasomes by inducing the synthesis of an alternative set of three proteolytically active proteasome subunits. We have analyzed the mechanism of IFN-gamma induction for the IFN-gamma-induced subunit multicatalytic endopeptidase complex-like 1 (MECL1). The human MECL1 promoter contains two interferon-stimulated response elements (ISREs), generally known to bind members of the interferon regulatory factor (IRF) family. The importance of these elements for IFN-gamma induction of MECL1 was addressed by transfecting an endothelial cell line with MECL1 promoter constructs. By deletions and mutations of the ISRE sequences, we demonstrated that both ISREs were needed for full IFN-gamma induction of the reporter gene. The second (downstream) ISRE was essential for both IFN-gamma-induced and basal transcriptional activity of the promoter. In electrophoretic mobility shift assays, anti-IRF-1 antibodies supershifted an IFN-gamma-induced protein binding specifically to both ISRE sequences, whereas IRF-2 bound the second ISRE before induction. Co-transfection of IRF-1 resulted in induced MECL1 promoter activity in the absence of IFN-gamma. These data indicate that the IFN-gamma induction of human MECL1 is mediated by IFN-gamma-induced IRF-1.

Oral contraceptives highlight the genotype-specific association between serum phospholipids and activated factor VII.

The present analysis was undertaken to study the effect of oral contraceptive (OC) use on activated factor VII (FVIIa) in subjects characterized by FVII genotypes, with the further aim of evaluating the role of lipids in this pharmacological interaction. In OC users (n=42) and nonusers (n=130) of comparable age, we examined the FVII phenotypic variables (FVII coagulant activity [FVIIc], FVII antigen, and FVIIa), FVII genotypes (the 353R/Q and 5'F7 polymorphisms analyzed in combination; alleles M1/M2 and A1/A2, respectively), and a number of lipid and lipoprotein parameters: serum concentrations of total cholesterol (chol), low density lipoprotein and high density lipoprotein-chol, triglycerides, phospholipids (PhLs), apolipoprotein A1, and lipoprotein(a). PhLs, triglycerides, apolipoprotein A1, chol, FVII antigen, FVIIc, and high density lipoprotein-chol levels were shown to be statistically higher in users than nonusers. FVII levels, particularly those of FVIIa and FVIIc, were much higher in homozygotes for the A1 and M1 alleles (A11 M11), especially in OC users. A strong association was found between PhL and FVIIa: in the multiple regression analysis, women taking OCs who had elevated PhL concentrations also had very high levels of FVIIa, but only if their genotype was A11 M11. These results indicate that the increased FVII levels in OC users depend on the FVII genotype and that high PhL concentrations predict very high levels of FVIIa and FVIIc.

Serum phospholipids are the main environmental determinants of activated factor VII in the most common FVII genotype. European Union Concerted Action "Clotart".

BACKGROUND AND OBJECTIVE: Numerous studies have emphasized the role of triglyceride-rich lipoproteins and of Factor VII (FVII) polymorphisms in determining levels of FVII activity. DESIGN AND METHODS: This study was undertaken to evaluate the role of other lipid fractions and the interaction between lipids and FVII in subjects with recognised genotypes. Volunteer subjects (n=459) from 5 European countries were studied. Blood samples were drawn irrespective of the time of day or fasting status. Levels of FVII activity (FVIIc), activated FVII (FVIIa) and FVII antigen (FVIIAg) were evaluated with reference to a number of lipid parameters (HDL-, LDL- and total cholesterol, triglycerides, phospholipids, lipoprotein(a), and apoliproptein A1). The two most common FVII polymorphisms were analyzed in combination (353R/Q and 5'F7; alleles M1/M2 and A1/A2, respectively). RESULTS: Homozygotes for the A1 and M1 alleles (M11/A11) had significantly higher FVII levels. At multiple regression analysis the strongest predictor of FVIIa and FVIIc was the concentration of phospholipids. This interaction was confined to the A11M11 genotype subjects. INTERPRETATION AND CONCLUSIONS: These data indicate that lipids contribute mainly to FVIIa levels through their phospholipid content, and that the degree of this contribution is strictly dependent on FVII genotypes.

Effects of hTNFalpha expression in T cells on haematopoiesis in transgenic mice.

A transgenic line of mice carrying one copy of the hTNFalpha gene under the control of its own promoter and the CD2 locus control region has been analysed for the effects of TNFalpha on haematopoiesis. A low level constitutive expression of hTNFalpha in lymphoid tissue was observed. Human TNFalpha binds to and activates the murine p55 receptor, but not the p75 receptor. This implies that the observed effects of hTNFalpha in mice were mediated only through the p55 receptor. Various lymphoid tissues were depleted of lymphocytes, especially thymus, spleen and peripheral blood. Effects on thymus development were detected already at 3 wk of age, more general effects on haematopoiesis were evident by 5 wk: a drop in total blood leukocytes, mainly due to a 67% decline in lymphocytes. At 16 wk the mice had developed anaemia, whereas platelets, neutrophils and monocytes had increased. The fall in lymphocytes was due to lowered levels of T cells as well as B cells. The cause of the shortened lifespan of the transgenic mice was probably not the haematological effects of hTNFalpha directly. Absence of trophic factors supplied by the normal T cell population remains possible.

Hammerhead ribozyme design and application.

The emerging knowledge about RNA-based enzymes has already had great impact on our concept of evolutionary history, making the 'RNA world' more likely. It may well have an equally important impact on the diagnostic and therapeutic practices of human and veterinary medicine in the next decade. We are not quite there yet. This review addresses the design and application of hammerhead ribozymes, two aspects of a conserved and most commonly studied and used enzymatically active entity among the RNA enzymes. The emerging picture is one of great diversity. There is at this stage no general cell model nor a clearly preferable ribozyme structure. Each and every cell line (and tissue) may be unique in that they vary with respect to structural requirements for optimal uptake, activity and stability of ribozymes. We may have seen only the tip of the iceberg when it comes to RNA-based enzymes and their roles in biology and medicine.