A rearranged junD transforms chicken embryo fibroblasts.

A complementary DNA clone synthesized from the chicken junD mRNA, containing 5'- and 3'-untranslated sequences, was inserted in the retroviral expression vector RCAS to yield the construct JD. A second RCAS construct (DDDD) contained only the coding domains of JunD. DDDD did not transform upon primary transfection, but JD produced small numbers of transformed cell foci in chicken embryo fibroblast cultures. The virus recovered from these foci, JDV, was moderately transforming for chicken fibroblasts and weakly oncogenic in the animal. Its genome was rearranged, showing evidence for two recombination events. The first crossover was located between 5'-untranslated and coding sequences of junD and incorporated part of the 5'-untranslated region into an open reading frame. The second crossover occurred between junD and gag. The two crossovers generate a single open reading frame of 2064 nucleotides that encodes an 85 kilodalton protein in which sequences in the amino-terminal region of JunD are duplicated. This gag junD reading frame was recloned and then reconstituted into a replication-defective but transformation-competent retrovirus, indicating that the Gag-JunD fusion protein is the effector of transformation. A construct containing this rearranged coding sequence of JunD in Rc/RSV transactivated the collagenase promoter in chicken cells. Southern blot analysis of several independently isolated JunD transformants and deletion analysis of JDV indicated that duplication of a domain in the amino-terminal region of JunD is crucial for transformation and transactivation.     

A novel 24-kDa microtubule-associated protein purified from sea urchin eggs.

Chromatographic fractionation of a crude extract of sea urchin eggs on a hydrophobic column enabled us to find a new 24-kDa microtubule-associated protein (SU-MAP24) that bound tightly to the column and was eluted under alkaline conditions. Biochemical studies using the purified protein showed its direct binding to microtubules reconstituted from tubulin purified from starfish sperm outer fibers. SU-MAP24 promoted tubulin polymerization in a dose-dependent manner. Immunoblotting analysis showed that SU-MAP24 is present in a microtubule protein fraction obtained from a crude extract using taxol, and immunostaining of paraffin-sectioned metaphase eggs showed its localization in the mitotic apparatus. These results show that SU-MAP24 is a newly identified microtubule-associated protein.     

Cytoskeleton-associated glycoproteins from chicken sympathetic neurons and chicken embryo brain

A non-ionic detergent-insoluble fraction was obtained from pure cultures of chicken sympathetic neurons and further purified at the 10%-30% interface of a discontinuous density gradient. This fraction contains actin as its major component and approximately 20 further polypeptides some of which are glycosylated. Two conspicuous glycoproteins in this fraction, of molecular masses 130 kDa and 90 kDa, have been shown to bind to concanavalin A; in cultured neurons the 130-kDa glycoprotein may also be labelled with [3H]glucosamine and [3H]fucose. Both are restricted to one interface of the stepped sucrose gradient when cells are lysed in low ionic strength buffer and eluted with actin in the void volume of a Sepharose 6B column. Glycoproteins of the same molecular weight have been obtained by the same isolation procedure from 10-day-old chicken embryo brains. One-dimensional peptide maps show that the carbohydrate-containing peptides from brain and sympathetic neurons are closely similar if not identical. The glycoproteins are also present in sciatic nerve but cannot be detected in a detergent-insoluble form in rounded neurons - lacking axons - or fibroblasts. They might, therefore, be involved in the linkage of the axonal cytoskeleton to the plasma membrane.     

A functional 125-kDa core polypeptide of fission yeast DNA topoisomerase II.

We purified fission yeast DNA topoisomerase II (topo II) to apparent homogeneity. It consists of a single 165-kDa polypeptide in sodium dodecyl sulfate-polyacrylamide gel electrophoresis and, upon treatment with a bifunctional reagent, doubles its molecular weight. Limited proteolysis of intact topo II by papain produces a 125-kDa core, which lacks the N-terminal 75 and the C-terminal approximately 260 amino acids but still contains regions similar to those of bacterial or phage T4 topo II subunits. The core retains relaxing and unknotting activities. Further digestion inactivates the core, cleaving it at the middle of the GyrB-like domain and at the beginning of the GyrA-like domain. Therefore, papain appears to cleave spatially distinct subdomains of topo II. We made top2 mutant genes deleted of the C-terminal 286 or N-terminal 74 amino acids, which can substitute for the wild-type top2+ gene in mitosis and meiosis. However, a mutant containing deletions of both termini cannot rescue the top2 null mutant, despite the fact that the product is enzymatically active. Therefore, the top2 product of the doubly truncated gene may not fulfill all of the in vivo requirements for top2+ function.     

Endothelial monocyte-activating polypeptide II. A novel tumor-derived polypeptide that activates host-response mechanisms.

An important means by which tumor cells influence the vasculature is through the production of soluble mediators altering vascular properties. A approximately 22-kDa polypeptide was purified to homogeneity from conditioned medium of murine methylcholanthrene A (meth A) fibrosarcoma cells by ion-exchange chromatography and preparative sodium dodecyl sulfate-polyacryl-amide gel electrophoresis (SDS-PAGE), based on its ability to induce tissue factor procoagulant activity in endothelial cells (ECs). The final product migrated as a broad band on reduced and nonreduced SDS-PAGE and had an unique amino-terminal sequence. This meth A-derived polypeptide modulated EC coagulant properties through the induction of tissue factor, induced monocyte migration and tissue factor expression, and was also chemotactic for granulocytes. Injection of the polypeptide into mouse footpads resulted in an inflammatory response with tissue swelling and polymorphonuclear leukocyte infiltration. The ability of this mediator to activate ECs and monocytes has led us to name it EMAP II (endothelial monocyte-activating polypeptide). EMAP II is distinct from a previously described approximately 40-kDa meth A-derived polypeptide termed EMAP I. Through its potential to activate host effector mechanisms, EMAP II could contribute to the biology of immunogenic tumors, such as the meth A fibrosarcoma.     

Sex determination in the chicken embryo.

The chicken embryo represents a suitable model for studying vertebrate sex determination and gonadal sex differentiation. While the basic mechanism of sex determination in birds is still unknown, gonadal morphogenesis is very similar to that in mammals, and most of the genes implicated in mammalian sex determination have avian homologues. However, in the chicken embryo, these genes show some interesting differences in structure or expression patterns to their mammalian counterparts, broadening our understanding of their functions. The novel candidate testis-determining gene in mammals, DMRT1, is also present in the chicken, and is expressed specifically in the embryonic gonads. In chicken embryos, DMRT1 is more highly expressed in the gonads and Müllerian ducts of male embryos than in those of females. Meanwhile, expression of the orphan nuclear receptor, Steroidogenic Factor 1 (SF1) is up-regulated during ovarian differentiation in the chicken embryo. This contrasts with the expression pattern of SF1 in mouse embryos, in which expression is down-regulated during female differentiation. Another orphan receptor initially implicated in mammalian sex determination, DAX1, is poorly conserved in the chicken. A chicken DAX1 homologue isolated from a urogenital ridge library lacked the unusual DNA-binding motif seen in mammals. Chicken DAX1 is autosomal, and is expressed in the embryonic gonads, showing somewhat higher expression in female compared to male gonads, as in mammals. However, expression is not down-regulated at the onset of testicular differentiation in chicken embryos, as occurs in mice. These comparative data shed light on vertebrate sex determination in general.     

Identification of microRNAs from different tissues of chicken embryo and adult chicken

We report for the first time the identification of 25 microRNAs from tissues originating from chicken embryo and adult chicken. Most of the cloned microRNAs are expressed in both adult chickens and chicken embryos. Fourteen were identified without any prior prediction. One microRNA, miR-757, is thought to be chicken-specific. Three of the microRNAs appear to be extremely tissue specific.     

Ethidium bromide-induced loss of mitochondrial DNA from primary chicken embryo fibroblasts.

Chicken embryo fibroblasts in uridine-containing medium are inherently resistant to the growth-inhibitory effect of ethidium bromide. The drug was found to inhibit the incorporation of [3H]thymidine into mitochondrial DNA circular molecules. Mitochondrial DNA was quantitated by DNA-DNA reassociation kinetics with a probe of chicken liver mitochondrial DNA. A mean number of 604 copies of mitochondrial DNA per cell was found. This number decreased progressively in cells exposed to ethidium bromide, and by day 13 ca. one copy of mitochondrial DNA was detected per cell. When the cells were then transferred to drug-free medium, the number of copies increased very slowly as a function of time. On the other hand, analyses of DNA extracted from cell populations exposed to ethidium bromide for 20 or more days, with or without subsequent transfer to drug-free medium, revealed very little or no mitochondrial DNA by reassociation kinetics or by Southern blot hybridization of AvaI- or HindIII-digested total cellular DNA. As a result of the elimination of mitochondrial DNA molecules, the establishment of cell populations with a respiration-deficient phenotype was confirmed by measuring cytochrome c oxidase activity as a function of the number of cell generations and the absorption spectrum of mitochondrial cytochromes.     

A novel form of rhodopsin kinase from chicken retina and pineal gland.

The G protein-coupled receptor kinases (GRKs) are important enzymes in the desensitization of activated G protein-coupled receptors (GPCR). Seven members of the GRK family have been identified to date. Among these enzymes, GRK1 is involved in phototransduction and is the most specialized kinase of the family. GRK1 phosphorylates photoactivated rhodopsin (Rho*), initiating steps in its deactivation. In this study, we found that chicken retina and pineal gland express a novel form of GRK that has sequence features characteristic of GRK1. However, unlike bovine GRK1 which is farnesylated, chicken GRK1 contains a consensus sequence for geranylgeranylation. Peptides corresponding to the C-terminal sequence of chicken GRK1 are geranylgeranylated by a cytosolic extract of chicken liver. Based on results of molecular cloning and immunolocalization, it appears that both rod and cone photoreceptors express this novel GRK1. These data indicate a larger sequence diversity of photoreceptor GRKs than anticipated previously.     

Tryptic peptides from the beta polypeptide chain of AII component of chicken hemoglobin.

The aminoethylated beta polypeptide chain in AII component from the hemoglobin of adult chicken was digested with trypsin [EC 3.4.21.4] and the resulting peptides were separated and purified by ion exchange chromatography, paper chromatography, and gel filtration. Eighteen tryptic peptides, which were nonoverlapping, accounted for all of the amino acid residues in the beta polypeptide chain. The amino acid sequences of the tryptic peptides were established by a combination of enzymatic digestion and subtractive Edman degradation.     

Isolation and characterization of a 70-kDa metalloprotease (gelatinase) that is elevated in Rous sarcoma virus-transformed chicken embryo fibroblasts.

Chicken embryo fibroblasts (CEF) transformed by Rous sarcoma virus (RSVCEF) secrete a 70-kDa metallo-gelatinase at elevated levels over that of normal CEF. The 70-kDa enzyme has been purified from RSVCEF conditioned medium and represents 1-3% of the total protein in the RSVCEF conditioned medium. A 22-kDa protein, which appears to be the avian form of the tissue inhibitor of metalloproteases (TIMP), is co-isolated in association with the 70-kDa enzyme and can be separated from the enzyme by gel filtration carried out under denaturing conditions. The isolated 70-kDa species is in the zymogen form. It can be activated by treatment with the organomercurial, p-aminophenylmercuric acetate (APMA), yielding a 62-kDa active species derived by an apparent autoproteolytic cleavage from the 70-kDa proenzyme as determined by both substrate gel analysis and immunoblots using a monospecific antibody to the 70-kDa proenzyme. The proenzyme is poorly activated by trypsin and not activated by plasmin. The APMA-activated enzyme rapidly degrades denatured collagens but under identical conditions is unable to degrade native collagens, including basement membrane type IV collagen. Only at very high enzyme to substrate ratios (1:2) will native type IV collagen be hydrolyzed. Partial N-terminal amino acid sequencing of both the 70-kDa proenzyme and the 62-kDa active enzyme indicates that the avian enzyme is a member of the matrix metalloprotease family (MMP-2). When CEF cultures, infected with a temperature sensitive mutant of RSV, conditional for the expression of the transforming src oncogene, were incubated at the permissive and nonpermissive temperatures, differential levels of the 70-kDa enzyme were produced in direct proportion to the functioning of the src oncogene.     

Isolation and characterization of tropomyosin kinase from chicken embryo

Tropomyosin kinase is partially purified from 14-day-old chicken embryos using DEAE-cellulose, cellulose phosphate and gel filtration chromatography. The purest enzyme preparation consists of two major bands of Mr = 76,000 and 43,000 on SDS-polyacrylamide gel electrophoresis. The molecular weight of the enzyme is 250,000 determined by gel filtration chromatography. It phosphorylates casein and skeletal tropomyosin equally well but histone and phosvitin at a much slower rate. Smooth muscle myosin light chain, tropomyosin from platelet, erythrocyte and smooth muscle are not phosphorylated. The apparent Km for skeletal alpha-tropomyosin and ATP is 50 microM and 200 microM, respectively. Vmax varies between 100-300 nmol/min per mg depending on the purity of the preparation. Mg2+ and dithiothreitol are essential for activity but Ca+, calmodulin and cAMP are not required. The optimum temperature is 37 degrees C and optimum pH is about 7.5. Heparin, a potent inhibitor of casein kinase II, has no inhibitory effect on the enzyme. Similar tropomyosin kinase activity is not detected in skeletal muscle in adult rabbit and chicken. The tropomyosin kinase described here represents a hitherto uncharacterized kinase responsible for phosphorylation of tropomyosin in the chicken embryo.     

Fibronectin from chicken embryo fibroblasts contains covalently bound phosphate

Fibronectin isolated from cultures of chicken embryo fibroblasts (CEF) contains phosphorus linked to serine and threonine by monoester bonds. Normal and Rous sarcoma virus (RSV)-transformed cells were incubated with [32P]orthophosphate, and fibronectin was isolated from the cell surfaces and conditioned media. 32P was stably associated with fibronectin during immunoprecipitation, SDS-polyacrylamide gel electrophoresis, phospholipid solvent extraction, and hot acid but not alkaline treatment. After a limited acid hydrolysis of fibronectin, both phosphoserine and phosphothreonine were found. The specific radioactivity of the 32P-labeled fibronectin from the conditioned medium of normal CEF was higher than that from the cultures of transformed CEF.     

Isolation and characterization of an abundant and novel 22-kDa protein (SM22) from chicken gizzard smooth muscle

Chicken gizzard smooth muscle contains a highly abundant protein (SM22) with an apparent Mr on sodium dodecyl sulfate-polyacrylamide electrophoretic gels of 23,000. The ratio of actin:SM22:tropomyosin in this tissue is estimated to be 6.5(+/- 0.8):2.0(+/- 0.2):1.0. At least three isoelectric isoforms are present in ratios of alpha:beta:gamma of 14:5:1 with alpha the most basic and gamma the most acidic. A method for the purification of SM22 and partial separation of its isoforms is described. Amino acid analyses of purified alpha and beta demonstrate the presence of 1 and 2 half-cystines, respectively, and a lower content of basic amino acids in beta. A value of 22,000 for the Mr of alpha estimated by sedimentation equilibrium indicated its presence as a monomer at physiological ionic strengths. Estimates of the translational frictional coefficient (f/fmin) of alpha calculated from its Stokes radius (25.5 A) and Mr were consistent with its existence as a moderately asymmetric globular protein. Calculations based on its far-ultraviolet CD spectrum provided values of 37% alpha-helix, 31% beta-sheet, 5% beta-turn, and 27% random coil. SM22 was shown not to share functional properties with several proteins of similar Mr and isoelectric point such as myokinase, brain 23-kDa protein, and troponin I. We conclude that it is a novel protein not previously isolated or characterized from any tissue.     

A 60-kDa polypeptide in mammalian cells with epitopes related to actin

We have identified a novel actin-related 60-kDa polypeptide in mammalian cells. The relatedness of this polypeptide to actin is indicated by its affinity for DNase I, two monoclonal anti-actin antibodies, and two independent peptide-specific anti-actin antibodies which bind to actin at around amino acid 244. It is not incorporated into cytoskeletal stress fibers, although it is a stable protein. Its expression (60-kDa polypeptide, pI of 5.4 to 5.5) is inhibited by the K+ ionophore, nonactin, which is known to collapse the energy-dependent translocation of cytoplasmically synthesized proteins into mitochondria.     

Solubilization of adenylate cyclase from normal and Rous sarcoma-transformed chicken embryo fibroblasts.

Adenylate cyclase activities in membranes prepared from Rous sarcoma-transformed chicken embryo fibroblasts are 2 to 4 times lower than in membranes prepared from normal chicken embryo fibroblasts. Adenylate cyclase activities were solubilized from normal and transformed membranes with five different nonionic detergents. In all cases, the specific activities of the enzyme solubilized from normal and transformed preparations were essentially identical. These data suggest that the microenvironment of adenylate cyclase in transformed membranes may be wholly or partially responsible for the decreased activities of this enzyme.     

A novel 40-kDa membrane-associated EF-hand calcium-binding protein in Plasmodium falciparum.

A 40-kDa sexual stage radiolabeled surface protein of Plasmodium falciparum, Pfs40, was previously identified as a potential target antigen of transmission blocking immunity by an immunogenetic approach. Synthetic oligonucleotide "guessmers," based on microsequenced tryptic peptides of Pfs40 purified by two-dimensional gel electrophoresis, were used to clone the full length cDNA and genomic DNA encoding Pfs40. The deduced amino acid sequence predicted an integral membrane protein containing five EF-hand calcium-binding domains. The biological activity of one or more of these domains was confirmed by binding of 45Ca to both native and recombinant Pfs40. Antisera to recombinant Pfs40 immunoprecipitated the native radiolabeled 40-kDa surface protein. The predicted noncytosolic membrane-associated localization of Pfs40 is unique within the EF-hand calcium-binding protein superfamily.