Use of antibodies directed against synthetic peptides for identifying cDNA clones, establishing reading frames, and deducing the gene order of measles virus

Mechanism of CD150 (SLAM) down regulation from the host cell surface by measles virus hemagglutinin protein

Measles virus has been reported to enter host cells via either of two cellular receptors, CD46 and CD150 (SLAM). CD46 is found on most cells of higher primates, while SLAM is expressed on activated B, T, and dendritic cells and is an important regulatory molecule of the immune system. Previous reports have shown that measles virus can down regulate expression of its two cellular receptors on the host cell surface during infection. In this study, the process of down regulation of SLAM by measles virus was investigated. We demonstrated that expression of the hemagglutinin (H) protein of measles virus was sufficient for down regulation. Our studies provided evidence that interactions between H and SLAM in the endoplasmic reticulum (ER) can promote the down regulation of SLAM but not CD46. In addition, we demonstrated that interactions between H and SLAM at the host cell surface can also contribute to SLAM down regulation. These results indicate that two mechanisms involving either intracellular interactions between H and SLAM in the ER or receptor-mediated binding to H at the surfaces of host cells can lead to the down regulation of SLAM during measles virus infection.

Stat5a serine phosphorylation. Serine 779 is constitutively phosphorylated in the mammary gland, and serine 725 phosphorylation influences prolactin-stimulated in vitro DNA binding activity

The activity of transcription factors of the Stat family is controlled by phosphorylation of a conserved, carboxyl-terminal tyrosine residue. Tyrosine phosphorylation is essential for Stat dimerization, nuclear translocation, DNA binding, and transcriptional activation. Phosphorylation of Stats on specific serine residues has also been described. We have previously shown that in HC11 mammary epithelial cells Stat5a is phosphorylated on Tyr(694) in a prolactin-sensitive manner, whereas serine phosphorylation is constitutive (Wartmann, M., Cella, N., Hofer, P., Groner, B., Xiuwen, L., Hennighausen, L., and Hynes, N. E. (1996) J. Biol. Chem. 271, 31863-31868). By using mass spectrometry and site-directed mutagenesis, we have now identified Ser(779), located in a unique Stat5a SP motif, as the site of serine phosphorylation. By using phospho-Ser(779)-specific antiserum, we have determined that Ser(779) is constitutively phosphorylated in mammary glands taken from different developmental stages. Stat5a isolated from spleen, heart, brain, and lung was also found to be phosphorylated on Ser(779). Ser(725) in Stat5a has also been identified as a phosphorylation site (Yamashita, H., Xu, J., Erwin, R. A., Farrar, W. L., Kirken, R. A., and Rui, H. (1998) J. Biol. Chem. 273, 30218-30224). Here we show that mutagenesis of Ser(725), Ser(779), or a combination of Ser(725/779) to an Ala had no effect on prolactin-induced transcriptional activation of a beta-casein reporter construct. However, following prolactin induction the Ser(725) mutant displayed sustained DNA binding activity compared with that of wild type Stat5a. The results suggest that Ser(725) phosphorylation has an impact on signal duration.

A single amino acid change in the hemagglutinin protein of measles virus determines its ability to bind CD46 and reveals another receptor on marmoset B cells

This paper provides evidence for a measles virus receptor other than CD46 on transformed marmoset and human B cells. We first showed that most tissues of marmosets are missing the SCR1 domain of CD46, which is essential for the binding of Edmonston measles virus, a laboratory strain that has been propagated in Vero monkey kidney cells. In spite of this deletion, the common marmoset was shown to be susceptible to infections by wild-type isolates of measles virus, although they did not support Edmonston measles virus production. As one would expect from these results, measles virus could not be propagated in owl monkey or marmoset kidney cell lines, but surprisingly, both a wild-type isolate (Montefiore 89) and the Edmonston laboratory strain of measles virus grew efficiently in B95-8 marmoset B cells. In addition, antibodies directed against CD46 had no effect on wild-type infections of marmoset B cells and only partially inhibited the replication of the Edmonston laboratory strain in the same cells. A direct binding assay with insect cells expressing the hemagglutinin (H) proteins of either the Edmonston or Montefiore 89 measles virus strains was used to probe the receptors on these B cells. Insect cells expressing Edmonston H but not the wild-type H bound to rodent cells with CD46 on their surface. On the other hand, both the Montefiore 89 H and Edmonston H proteins adhered to marmoset and human B cells. Most wild-type H proteins have asparagine residues at position 481 and can be converted to a CD46-binding phenotype by replacement of the residue with tyrosine. Similarly, the Edmonston H protein did not bind CD46 when its Tyr481 was converted to asparagine. However, this mutation did not affect the ability of Edmonston H to bind marmoset and human B cells. The preceding results provide evidence, through the use of a direct binding assay, that a second receptor for measles virus is present on primate B cells.

Artificial mutations and natural variations in the CD46 molecules from human and monkey cells define regions important for measles virus binding

CD46 was previously shown to be a primate-specific receptor for the Edmonston strain of measles virus. This receptor consists of four short consensus regions (SCR1 to SCR4) which normally function in complement regulation. Measles virus has recently been shown to interact with SCR1 and SCR2. In this study, receptors on different types of monkey erythrocytes were employed as "natural mutant proteins" to further define the virus binding regions of CD46. Erythrocytes from African green monkeys and rhesus macaques hemagglutinate in the presence of measles virus, while baboon erythrocytes were the least efficient of the Old World monkey cells used in these assays. Subsequent studies demonstrated that the SCR2 domain of baboon CD46 contained an Arg-to-Gln mutation at amino acid position 103 which accounted for reduced hemagglutination activity. Surprisingly, none of the New World monkey erythrocytes hemagglutinated in the presence of virus. Sequencing of cDNAs derived from the lymphocytes of these New World monkeys and analysis of their erythrocytes with SCR1-specific polyclonal antibodies indicated that the SCR1 domain was deleted in these cells. Additional experiments, which used 35 different site-specific mutations inserted into CD46, were performed to complement the preceding studies. The effects of these artificial mutations were documented with a convenient binding assay using insect cells expressing the measles virus hemagglutinin. Mutations which mimicked the change found in baboon CD46 or another which deleted the SCR2 glycosylation site reduced binding substantially. Another mutation which altered GluArg to AlaAla at positions 58 and 59, totally abolished binding. Finally, the epitopes for two monoclonal antibodies which inhibit measles virus attachment were mapped to the same regions implicated by mutagenesis.

Trophinin and tastin, a novel cell adhesion molecule complex with potential involvement in embryo implantation

Two human epithelial cell lines, trophoblastic teratocarcinoma HT-H and endometrial adenocarcinoma SNG-M cells, adhere to each other at their respective apical cell surfaces in a divalent cation-independent manner. Two novel molecules responsible for the adhesion between these two cell types were identified by expression cDNA cloning. One, named trophinin, is an intrinsic membrane protein and mediates homophilic self-binding. Another, named tastin, is a cytoplasmic protein and is necessary for trophinin to function as a cell adhesion molecule. Trophinin and tastin appear to be associated with the cytoskeleton in HT-H and SNG-M cells. These molecules are normally not expressed in various types of human cells in tissues, with the exception of macrophages. Strong expression of these molecules was detected in the trophectoderm surface of monkey blastocyst. These molecules are also expressed in human endometrial surface epithelium on day 16/17 at the early secretory phase of human endometrium, the time consistent with that expected for the "implantation window."

Double-stranded RNA adenosine deaminase activity during measles virus infection

It has been postulated that the cellular double-stranded (ds) RNA adenosine deaminase enzyme is responsible for biased hypermutation during persistent SSPE measles infections in humans. As a test of this hypothesis we studied the effect of negative-strand RNA virus infection on enzyme activity. The adenosine deaminase activity was found in nuclear extracts of both uninfected CV-1 and A549 cells and in cytoplasmic extracts of A549, but not CV-1, cells. During measles or Sendai virus infection of either CV-1 or A549 cells the adenosine deaminase activity in the nucleus remained fairly constant up to 24 h post infection, and there was no apparent re-partitioning of the enzyme between the nucleus and the cytoplasm. Transcription complexes of Sendai virus in vitro or measles virus in vivo did not serve as substrates for the enzyme. These data suggest that even though some portion of the adenosine deaminase enzyme may be present in the cytoplasm of at least some cells during virus infection, modification of the viral RNAs by this enzyme, if it occurs at all, must be at a very low level not directly detectable by biochemical analysis.

The extracellular domain of the epidermal growth factor receptor. Studies on the affinity and stoichiometry of binding, receptor dimerization and a binding-domain mutant

The binding of epidermal growth factor (EGF) or an EGF-like growth factor to the EGF receptor is the initial event which leads to receptor activation, and consequently the induction of cell growth. In order to study this binding interaction in detail, we produced the extracellular domain of the EGF receptor (EGFR) using the baculovirus expression system. Affinity-labeling and Western-blot analyses revealed that the baculovirus-infected insect cells secrete active EGFR extracellular domain relatively efficiently, however a significant amount of inactive EGFR extracellular domain is retained within the cells. The apparent dissociation constant (Kd) of the secreted EGFR extracellular domain for EGF and transforming growth factor alpha (TGF-alpha), as determined using an immobilized receptor binding assay, was approximately 200 nM. Interestingly, this Kd value is 30-40-fold lower than that of the full-length EGFR derived from detergent-solubilized A431 cell membranes. The stoichiometry of binding of the EGFR extracellular domain to EGF and TGF-alpha was examined by band-shift analysis on non-denaturing PAGE and was estimated to be 1:1. We have also shown, using sedimentation equilibrium analysis, that ligand binding induces significant dimerization of the EGFR extracellular domain. Finally, we carried out site-specific mutagenesis on the EGFR extracellular domain in order to define the ligand-binding region. We identified amino acid residues which are close to the binding site since they are common to the epitopes of several ligand-competitive monoclonal antibodies. However, these residues do not contribute directly to ligand binding since the affinity of the mutated EGFR extracellular domain for EGF and TGF-alpha was unaffected.

The regulation of alpha 5 beta 1 integrin expression in human muscle cells

The expression of alpha 5 beta 1 integrin was examined in either cloned or fluorescence-activated cell-sorted satellite cells derived from human biceps muscle. Removal of serum and factors required for muscle cell growth and proliferation both induced terminal differentiation and resulted in a coordinate downregulation of mRNA transcripts encoding alpha 5 and beta 1 integrin subunits. A corresponding downregulation of the alpha 5 subunit occurred at the protein level. Treatment of cultures with 5-bromo-2'-deoxyuridine (BUdR), a thymidine analog which inhibits muscle cell differentiation, resulted in increased expression of alpha 5 integrin subunit at both the mRNA and protein levels. However, levels of alpha 5 subunit message and protein were still markedly downregulated on removal of serum and growth factors from BUdR-treated cultures, indicating that downregulation of alpha 5 beta 1 integrin during myogenesis does not require and is not a consequence of muscle cell terminal differentiation. Downregulation of alpha 5 integrin subunit expression could be prevented by maintenance of cells in medium supplemented with serum and growth factors, although no single defined component of this medium could on its own prevent the downregulation of alpha 5 integrin subunit expression. Collectively, these results suggest that downregulation of alpha 5 beta 1 integrin expression is not a consequence of muscle cell terminal differentiation, but is dependent on a combination of exogenous growth factors which are also required for muscle cell growth and proliferation.

Functional analysis of N-linked glycosylation mutants of the measles virus fusion protein synthesized by recombinant vaccinia virus vectors

The role of N-linked glycosylation in the biological activity of the measles virus (MV) fusion (F) protein was analyzed by expressing glycosylation mutants with recombinant vaccinia virus vectors. There are three potential N-linked glycosylation sites located on the F2 subunit polypeptide of MV F, at asparagine residues 29, 61, and 67. Each of the three potential glycosylation sites was mutated separately as well as in combination with the other sites. Expression of mutant proteins in mammalian cells showed that all three sites are used for the addition of N-linked oligosaccharides. Cell surface expression of mutant proteins was reduced by 50% relative to the wild-type level when glycosylation at either Asn-29 or Asn-61 was abolished. Despite the similar levels of cell surface expression, the Asn-29 and Asn-61 mutant proteins had different biological activities. While the Asn-61 mutant was capable of inducing syncytium formation, the Asn-29 mutant protein did not exhibit any significant cell fusion activity. Inactivation of the Asn-67 glycosylation site also reduced cell surface transport of mutant protein but had little effect on its ability to cause cell fusion. However, when the Asn-67 mutation was combined with mutations at either of the other two sites, cleavage-dependent activation, cell surface expression, and cell fusion activity were completely abolished. Our data show that the loss of N-linked oligosaccharides markedly impaired the proteolytic cleavage, stability, and biological activity of the MV F protein. The oligosaccharide side chains in MV F are thus essential for optimum conformation of the extracellular F2 subunit that is presumed to bind cellular membranes.

Transcription inhibition and other properties of matrix proteins expressed by M genes cloned from measles viruses and diseased human brain tissue

Ribonucleoprotein (RNP) cores extracted from virions of wild-type (Edmonston strain) measles virus (MV) or obtained from MV-infected cells (cRNP) were shown to be capable of transcribing RNA in vitro but at relatively low efficiency. The tightly bound matrix (M) protein could be effectively removed from virion RNP (vRNP) and from cRNP by exposure to buffers of high ionic strength (0.5 to 1.0 M KCl) but only at pH 8.0 or higher. The vRNP and cRNP cores complexed with M protein exhibited markedly reduced transcriptional activity at increasing concentrations, whereas vRNP and cRNP cores free of M protein exhibited linear and substantially higher transcriptional activity; these data suggest that M protein is the endogenous inhibitor of MV RNP transcription. M-gene cDNA clones derived from three strains of wild-type (wt) MV and 10 clones from mRNAs isolated from the brain tissue of patients who had died from subacute sclerosing panencephalitis (SSPE) and from measles inclusion body encephalitis (MIBE) were recloned in the pTM-1 expression vector driven by the bacteriophage T7 RNA polymerase expressed by a coinfecting vaccinia virus recombinant. All 10 mutant SSPE and MIBE clones expressed in vitro and in vivo M proteins that reacted with monospecific anti-M polyclonal antibody and migrated on polyacrylamide gels to positions identical to or only slightly different from those of the M proteins expressed by wt MV clones. When reconstituted with cRNP cores, the three expressed wt M proteins and 6 of the 10 mutant-expressed M proteins showed equivalent capacity to down-regulate MV transcription. Three of the M proteins from SSPE clones and one from the MIBE clone showed little or no capacity to down-regulate transcription when reconstituted with cRNP cores. The only plausible explanations for loss of transcription inhibition activity by the four SSPE/MIBE M proteins were exceedingly high degrees of hypermutations leading to U-->C transitions and cloning-corrected mutations in the initiator codon (ATG-->ACG) of the four M genes. However, only the hypermutated M protein expressed by the MIBE cDNA clone exhibited virtually no capacity to bind cRNP cores in a reconstitution assay. These experiments provide some preliminary data to support the hypothesis that MV encephalitis may result from certain selective mutations in the M gene.

The 1,629-nucleotide open reading frame located downstream of the Autographa californica nuclear polyhedrosis virus polyhedrin gene encodes a nucleocapsid-associated phosphoprotein

A 78-kDa protein was produced in bacteria from a clone of the 1,629-nucleotide open reading frame located immediately downstream from the polyhedrin gene of Autographa californica nuclear polyhedrosis virus. The identity of this protein was confirmed by its reactivity with peptide antiserum and amino terminal peptide sequencing after purification from transformed bacteria. The polypeptide was used to produce polyclonal antisera in rabbits. Immunoblot analysis of insect cells infected with the baculovirus indicated that two related proteins with molecular masses of 78 and 83 kDa were synthesized late in infection. Biochemical fractionation studies indicated that both of these proteins were present in purified nucleocapsids from budded and occluded virus preparations. Immunoprecipitation of 32P-labeled proteins and treatment of purified nucleocapsids with alkaline phosphatase demonstrated that the 83-kDa protein was a phosphorylated derivative of the 78-kDa protein. Furthermore, immunoelectron microscopy revealed that the proteins were localized to regions of nucleocapsid assembly within the infected cell and appeared to be associated with the end structures of mature nucleocapsids.

Ebola protein analyses for the determination of genetic organization

Amino-acid sequencing of the purified major nucleoprotein (NP), VP35 and VP40 from purified Ebola virus proved that they are the protein products of the first three genes, and that the open reading frame (ORF) of the NP begins at nucleotide 470. Because of the many unusual features of the ORFs of Ebola virus, we thought that our conclusions should be substantiated. Comparisons of in vitro-translation products to purified viral proteins were used to demonstrate conclusively that the NP, VP35 and VP40 were the protein products of genes one, two, and three, respectively. Studies using antibodies to synthetic peptides matching the N- and C-termini of the deduced sequences from these genes confirmed these conclusions and that the ORF for the NP begins at nucleotide 470. Subsequent studies confirmed that VP30 is encoded by the fifth gene.

N-cadherin mediates Sertoli cell-spermatogenic cell adhesion

The complex topological association of Sertoli cells and spermatogenic cells in the testis suggests the existence of cell surface adhesion molecules that regulate cellular interactions within the seminiferous epithelium. The recent report of N-cadherin mRNA expression in the mouse testis implies the involvement of this known adhesion molecule in testicular cell binding. Accordingly, here we report that (1) N-cadherin is found on the surface membranes of rat spermatogenic cells and on Sertoli cells, and (2) that N-cadherin is a partial mediator of Sertoli cell-germ cell adhesion as tested in an vitro cell-cell binding assay. Antiserum directed against the N-cadherin cell adhesion recognition sequence was used for Western blot anlaysis of purified plasma membranes from Sertoli cells and from spermatogenic cells. Both membrane preparations exhibited reactivity at an appropriate M(r) of about 130 kDa. In addition, immunofluorescence assays demonstrated that both germ cells and Sertoli cells were labeled by anti-N-cadherin. Finally, the antiserum was included in a cytometer-assisted cell-cell binding test to determine its inhibitory ability. The antiserum consistently reduced specific testicular cell-cell adhesion by 30%-50%. This is the first demonstration that antibodies directed against the cadherin cell adhesion recognition sequence are capable of inhibiting cell-cell interactions. Pre-incubation of either rat Sertoli cells or spermatogenic cells alone was sufficient to achieve statistically significant inhibition of intercellular adhesion. We conclude, therefore, that N-cadherin is expressed by both Sertoli cells and spermatogenic cells and that N-cadherin is one of a number of regulatory molecules mediating local cellular associations in the mammalian seminiferous tubule.

Iscom immunization with synthetic peptides representing measles virus hemagglutinin

Synthetic peptides representing the measles virus (MV) hemagglutinin (MVH) were incorporated into immunostimulating complexes (iscoms) and used for immunization of rabbits. Nine regions of MVH were selected on the basis of hydropathy and antigenicity profiles, by use of the known primary structure of MVH. Six linear and three branched types of peptides were synthesized and conjugated to palmitic acid before incorporation into the iscom structure. Five of the anti-peptide sera reacted by ELISA with the homologous peptide but did not react with MV in the native state, indicating that either the selected sites are not represented on the surface of MV, or they could be a conformational epitope. Human-anti MV and rabbit anti-MV did not react with the peptides.

The levels and biologic action of the human neutrophil granule peptide HP-1 in lung tumors

HP-1 is the most abundant human representative of a recently discovered class of neutrophil cystine- and arginine-rich peptides. These peptides have many potentially regulatory activities expressed at nanomolar concentrations. To establish the levels of HP-1 that can accumulate in human lung tumors and nondiseased lung fragments, tissues were extracted for their peptide content. The extracts were purified on reverse phase HPLC, and HP-1 and related peptides were identified by sequence analysis and their concentrations in the tissue quantitated by amino acid analysis. Immunohistochemistry was performed and strongly suggests that HP-1 is confined to granulocytes under most circumstances, and indicates that the levels of HP-1 measured in the tumors reflect the levels obtained when solid tissue is infiltrated by neutrophils. The maximum observed levels were 26 nanomoles per gram wet weight of tissue. Attempts were then made to correlate this level to the cytotoxic potential of HP-1 by performing in vitro cytotoxicity dose-response curves on several cell lines. Most cells were killed at between 1 and 8 microM, and the response depended on the growth conditions of the cells. The levels of HP-1 that accumulate in tumors can exceed the in vitro cytolytic concentrations. The levels are also considerably in excess of those required to exert in vitro regulatory actions.

Synthesis of leader RNA and editing of the P mRNA during transcription by purified measles virus

A transcription system with detergent-disrupted purified measles virus was developed. Synthesis of authentic, full-length measles virus N, P, M, and F mRNAs by purified virus occurred as identified by dot-blot hybridization analysis of individual measles virus clones and gel electrophoresis. The relative abundance of the first five viral mRNAs synthesized in vitro decreased significantly with their distance from the 3' end. The addition of the soluble protein fraction from uninfected A549 cells stimulated overall viral RNA synthesis but did not alter the relative abundance of each of the mRNAs. Measles virus synthesized in vitro a leader RNA of approximately 55 nucleotides in length, suggesting that like other negative-strand viruses, transcription initiated only at the 3' end of the genome RNA. Purified measles virus also catalyzed RNA editing during the synthesis of the P mRNA as shown by modified primer extension analysis of the mRNA products and by translation of the modified RNA into the V protein in rabbit reticulocyte lysates. These data suggested that the RNA editing activity was virus encoded.

Vaccinia virus recombinants expressing either the measles virus fusion or hemagglutinin glycoprotein protect dogs against canine distemper virus challenge

cDNA clones of the genes encoding either the hemagglutinin (HA) or fusion (F) proteins of the Edmonston strain of measles virus (MV) were expressed in vaccinia virus recombinants. Immunofluorescence analysis detected both proteins on the plasma membranes of unfixed cells as well as internally in fixed cells. Immunoprecipitation of metabolically radiolabeled infected-cell extracts by using specific sera demonstrated a 76-kDa HA polypeptide and gene products of 60, 44, and 23 kDa which correspond to a MV F precursor and cleavage products F0, F1, and F2, respectively. Neither recombinant induced cell fusion of Vero cells when inoculated individually, but efficient cell fusion was readily observed upon coinfection of cells with both recombinants. Inoculation of dogs with the vaccinia virus-MV F recombinant (VV-MVF) did not give rise to detectable MV-neutralizing antibody. Inoculation of dogs with the vaccinia virus-MV HA recombinant (VV-MVHA) or coinoculation with both recombinants (VV-MVF and VV-MVHA) induced significant MV-neutralizing titers that were increased following a booster inoculation. Inoculation of dogs with the vaccinia virus recombinants or with MV failed to induce canine distemper virus (CDV)-neutralizing antibodies. Upon challenge with a lethal dose of virulent CDV, signs of infection were observed in dogs inoculated with (VV-MVF). No symptoms of disease were observed in dogs that had been vaccinated with VV-MVHA or with VV-MVHA and VV-MVF and then challenged with CDV. All dogs vaccinated with the recombinant viruses as well as those inoculated with MV or a vaccine strain of CDV survived CDV challenge.

Involvement of the C-terminus of the inositol 1,4,5-trisphosphate receptor in Ca2+ release analysed using region-specific monoclonal antibodies

We have studied the effects of monoclonal antibodies that recognize different epitopes of the cerebellar Ins(1,4,5)P3 receptor on Ins(1,4,5)P3-induced Ca(2+)-release activity. Ins(1,4,5)P3 stimulated Ca2+ flux from cerebellar microsomes, and half-maximal Ca2+ release occurred at 112 +/- 8 nM-Ins(1,4,5)P3 [concentration causing half-maximal effect (EC50) = 112.8 nM]. The minimum concentration of Ins(1,4,5)P3 necessary to initiate Ca2+ release (threshold concentration) was 20 +/- 5 nM. A monoclonal antibody (mAb) 18A10 (50 micrograms/ml), which recognizes the C-terminal region of the Ins(1,4,5)P3 receptor, suppressed Ins(1,4,5)P3-induced Ca2+ release: the EC50 and threshold concentration shifted to 460 +/- 56 nM and 61 +/- 6 nM respectively. On the other hand, the antibody at the same concentration raised the affinity of the receptor for binding to Ins(1,4,5)P3, and the Kd value decreased from 43 +/- 12 nM to 25 +/- 4 nM without a change in the number of Ins(1,4,5)P3-binding sites. However, mAbs that recognize the N-terminal domain affected neither Ca2+ release nor Ins(1,4,5)P3 binding. Among the various synthetic peptides, only the 12-residue-long peptide from the most C-terminal portion of the receptor (amino acid residues 2736-2747) reacted strongly with mAb18A10. From these findings, combined with the Immunogold localization of the cerebellar Ins(1,4,5)P3 receptor [Otsu, Yamamoto, Maeda, Mikoshiba & Tashiro (1990) Cell Struct. Funct. 15, 163-173], we concluded that the C-terminus of the Ins(1,4,5)P3 receptor is exposed to the cytoplasmic side of the smooth endoplasmic reticulum and plays an important role in the regulation of both Ins(1,4,5)P3-binding affinity and channel gating.

Characterization of V protein in measles virus-infected cells

An edited mRNA transcribed from the phosphoprotein (P) gene of measles virus (MV) has been predicted to encode a cysteine-rich protein designated V. This mRNA contains a single additional nontemplated G residue which permits access to an additional protein-coding reading frame. Such an edited P gene-specific mRNA has been detected in MV-infected cells, but no corresponding protein has yet been identified in vivo. We report the use of antisera directed against synthetic peptides corresponding to five different regions of the predicted MV V protein amino acid sequence to analyse MV-specific proteins synthesized in vivo and in vitro. The MV V protein (40 kDa) was detected in MV-infected cells in a diffuse cytoplasmic distribution, a predominant subcellular localization distinct from that of virus nucleocapsids. The protein was found to be phosphorylated and to be maximally synthesized at 16 h postinfection, when MV-specific structural protein synthesis was also maximal. Antiserum directed against a peptide (PV2) corresponding to amino acids 65 to 87 of the V protein amino acid recognized the P protein but not the V protein, indicating that the P and V proteins may be folded differently at or near this region so that the PV2 sequence is in an exposed position at the surface of the P protein but not at the surface of the V protein.

Effects of the 'fusion peptide' from measles virus on the structure of N-methyl dioleoylphosphatidylethanolamine membranes and their fusion with Sendai virus

31P nuclear magnetic resonance spectroscopy (31P-NMR) was used to study phospholipid organization in hydrated preparations of N-methyl dioleoylphosphatidylethanolamine and a 'fusion peptide' with the sequence: FAGV-VLAGAALGVAAAAQI, which corresponds to the amino terminus of the F1 subunit of the membrane fusion protein of measles virus. These amino acids are believed to mediate syncytia formation, host-cell penetration and hemolysis by infectious virus. The presence of the peptide at 0.5 mole percent significantly facilitated the formation of isotropic 31P resonances. The effects at 1 mole percent peptide were substantially enhanced over the effects observed at 0.5 mole percent, leading to a decrease in the onset temperature of the formation of the isotropic 31P-NMR resonances by about 30 degrees C. The formation of such isotropic 31P-NMR resonances has been previously associated with an increased rate of fusion of large unilamellar vesicles composed of N-methyl dioleoylphosphatidylethanolamine. Enhanced fusion of octadecyl rhodamine-labelled Sendai virus with N-methyl dioleoylphosphatidylethanolamine large unilamellar vesicles was observed when the 'fusion peptide' was incorporated into the large unilamellar vesicles.

Anti-peptide antibodies to cathepsins B, L and D and type IV collagenase. Specific recognition and inhibition of the enzymes

Anti-peptide antibodies were raised against synthetic peptides selected from the sequences of human cathepsins B and L, porcine cathepsin D and human type IV collagenase. Sequences were selected from the active site clefts of the cathepsins in the expectation that these would elicit immunoinhibitory antibodies. In the case of type IV collagenase a sequence unique to this metalloproteinase subclass and suitable for immunoaffinity purification, was chosen. Antibodies against the chosen cathepsin B sequence were able to recognize the peptide but were apparently unable to recognise the whole enzyme. Antibodies against the chosen cathepsin L sequence were found to recognise and inhibit the native enzyme and were also able to discriminate between denatured cathepsins L and B on Western blots. Antibodies against the chosen cathepsin D sequence recognised native cathepsin D in a competition ELISA, but did not inhibit the enzyme. Native type IV collagenase was purified from human leukocytes by immuno-affinity purification with the corresponding anti-peptide antibodies.

Identification and characterization of a baculovirus occlusion body glycoprotein which resembles spheroidin, an entomopoxvirus protein

A 37-kDa polypeptide specified by Autographa californica nuclear polyhedrosis virus was found to share significant homology with Choristoneura biennis entomopoxyvirus spheroidin protein, which is the major component of entomopoxvirus occlusion bodies. Antibodies raised against spheroidin cross-reacted with the 37-kDa protein and confirmed its expression in the late phase of wild-type baculovirus infection. Immunoblot analysis and fluorescence microscopy demonstrated that the protein was associated with purified A. californica nuclear polyhedrosis virus occlusion bodies and was absent in purified virions. Immunofluorescence studies localized the protein to the periphery of occlusion bodies and the internal membranes of cells infected with wild-type baculovirus. The open reading frame encoding this spheroidinlike protein was inserted into a baculovirus expression vector, and recombinant protein was synthesized under control of the polyhedrin promoter. Studies of the recombinant protein demonstrated that it was heterogeneous in molecular mass as a result of N-linked glycosylation. Tunicamycin inhibited carbohydrate addition and yielded proteins of 34 and 33 kDa.

Purification of the 110-kilodalton glycoprotein receptor for mouse hepatitis virus (MHV)-A59 from mouse liver and identification of a nonfunctional, homologous protein in MHV-resistant SJL/J mice

The receptor for mouse hepatitis virus strain A59 (MHV-A59) is a 110- to 120-kilodalton (kDa) glycoprotein which is expressed in MHV-susceptible mouse strains on the membranes of hepatocytes, intestinal epithelial cells, and macrophages. SJL/J mice, which are highly resistant to MHV-A59, were previously shown to lack detectable levels of receptor by using either solid-phase virus receptor assays or binding of a monoclonal anti-receptor antibody (MAb) which blocks infection of MHV-susceptible mouse cells. This MAb was used for affinity purification of the receptor glycoprotein from livers of MHV-susceptible Swiss Webster mice. The MHV receptor and an antigenically related protein of 48 to 58 kDa were copurified and then separated by preparative sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The first 15 amino acids of the receptor were sequenced, and a synthetic peptide of this amino acid sequence was prepared. Rabbit antiserum made against this peptide bound to the MHV receptor glycoprotein and the 48- to 58-kDa protein from livers of MHV-susceptible BALB/c mice and Swiss Webster mice and from the intestinal brush border of BALB/c mice. In immunoblots of intestinal brush border and hepatocyte membranes of MHV-resistant SJL/J mice, the antibody against the amino terminus of the receptor identified proteins that are 5 to 10 kDa smaller than the MHV receptor and the 48- to 58-kDa related protein from Swiss Webster or BALB/c mice. Thus, SJL/J mice express a protein which shares some sequence homology with the MHV receptor but which lacks virus-binding activity and is not recognized by the blocking anti-receptor MAb. These results suggest that resistance of SJL/J mice to MHV-A59 may be due to absence or mutation of the virus-binding domain in the nonfunctional receptor homolog in SJL/J mice.

Molecular analysis of structural protein genes of the Yamagata-1 strain of defective subacute sclerosing panencephalitis virus. II. Nucleotide sequence of a cDNA corresponding to the P plus M dicistronic mRNA

The nucleotide sequence of a cloned cDNA corresponding to the P + M dicistronic mRNA of a subacute sclerosing panencephalitis (SSPE) virus was determined and compared with data of measles virus (MV). The dicistronic mRNA of the SSPE virus consisted of the 3' proximal 626 nucleotides of P mRNA, intercistronic trinucleotides, a full length of M mRNA, and 75 poly A nucleotides. The part encoding the P protein had a high homology to MV, except at the noncoding region. The terminating consensus sequence of the P gene and the intercistronic trinucleotides of the SSPE virus were CTAC(A)6 and CCT; in MV they are TTAT(A)6 and CTT, respectively. In the M gene, the starting consensus sequence was exactly the same as MV, but at the 5' proximal end, one third of this gene was different: The first ATG codon of the MV M gene signaling opening of the reading frame was changed to ACG in the SSPE virus and one long open reading frame started from the third ATG codon. The stop codon (TAG) of the MV M gene was also changed to CAG in the SSPE virus. Thus, the deduced SSPE-virus M protein lacked 50 amino acids at the amino terminal and had 15 extra amino acids at the carboxyl end when compared with the MV M protein.

Diversity of matrix protein in subacute sclerosing panencephalitis and measles virus-infected cells

Expression of the viral matrix (M) proteins in Vero cells infected with 18 strains of subacute sclerosing panencephalitis (SSPE) virus and measles virus was examined by immunocytochemistry and Western blot analysis using an anti-M monospecific serum and two sera against the M protein specific synthetic peptides. By immunocytochemistry using the anti-M monospecific serum, M protein was detected in all of the virus-infected cells regardless of cell-free virus production. M proteins of the seven non-productive strains were found to vary significantly in their epitope, in their reactivity to different assay systems, and in their molecular weight, whereas M proteins of the other 11 productive strains were detected consistently. These results suggest diversification of M protein of the non-productive strains.

Different roles of individual N-linked oligosaccharide chains in folding, assembly, and transport of the simian virus 5 hemagglutinin-neuraminidase

The role of N-linked glycosylation in protein maturation and transport has been studied by using the simian virus 5 hemagglutinin-neuraminidase (HN) protein, a model class II integral membrane glycoprotein. The sites of N-linked glycosylation on HN were identified by eliminating each of the potential sites for N-linked glycosylation by oligonucleotide-directed mutagenesis on a cDNA clone. Expression of the mutant HN proteins in eucaryotic cells indicated that four sites are used in the HN glycoprotein for the addition of N-linked oligosaccharide chains. These functional glycosylation sites were systematically eliminated in various combinations from HN to form a panel of mutants in which the roles of individual carbohydrate chains and groups of carbohydrate chains could be analyzed. Alterations in the normal glycosylation pattern resulted in the impairment of HN protein folding and assembly which, in turn, affected the intracellular transport of HN. The severity of the consequences on HN maturation depended on both the number of deleted carbohydrate sites and their position in the HN molecule. Analysis of the reactivity pattern of HN conformation-specific monoclonal antibodies with the mutant HN proteins indicated that one specific carbohydrate chain plays a major role in promoting the correct folding of HN. Another carbohydrate chain, which is not essential for the initial folding of HN was found to play a role in preventing the aggregation of HN oligomers. The HN molecules which were misfolded, owing to their altered glycosylation pattern, were retained in the endoplasmic reticulum. Double-label immunofluorescence experiments indicate that misfolded HN and folded HN are segregated in the same cell. Misfolded HN forms disulfide-linked aggregates and is stably associated with the resident endoplasmic reticulum protein, GRP78-BiP, whereas wild-type HN forms a specific and transient complex with GRP78-BiP during its folding process.

Different roles of individual N-linked oligosaccharide chains in folding, assembly, and transport of the simian virus 5 hemagglutinin-neuraminidase

The role of N-linked glycosylation in protein maturation and transport has been studied by using the simian virus 5 hemagglutinin-neuraminidase (HN) protein, a model class II integral membrane glycoprotein. The sites of N-linked glycosylation on HN were identified by eliminating each of the potential sites for N-linked glycosylation by oligonucleotide-directed mutagenesis on a cDNA clone. Expression of the mutant HN proteins in eucaryotic cells indicated that four sites are used in the HN glycoprotein for the addition of N-linked oligosaccharide chains. These functional glycosylation sites were systematically eliminated in various combinations from HN to form a panel of mutants in which the roles of individual carbohydrate chains and groups of carbohydrate chains could be analyzed. Alterations in the normal glycosylation pattern resulted in the impairment of HN protein folding and assembly which, in turn, affected the intracellular transport of HN. The severity of the consequences on HN maturation depended on both the number of deleted carbohydrate sites and their position in the HN molecule. Analysis of the reactivity pattern of HN conformation-specific monoclonal antibodies with the mutant HN proteins indicated that one specific carbohydrate chain plays a major role in promoting the correct folding of HN. Another carbohydrate chain, which is not essential for the initial folding of HN was found to play a role in preventing the aggregation of HN oligomers. The HN molecules which were misfolded, owing to their altered glycosylation pattern, were retained in the endoplasmic reticulum. Double-label immunofluorescence experiments indicate that misfolded HN and folded HN are segregated in the same cell. Misfolded HN forms disulfide-linked aggregates and is stably associated with the resident endoplasmic reticulum protein, GRP78-BiP, whereas wild-type HN forms a specific and transient complex with GRP78-BiP during its folding process.

Diazepam binding inhibitor (DBI) processing: immunohistochemical studies in the rat brain

Diazepam Binding Inhibitor (DBI) is an endogenous 11-kDa peptide originally isolated from rat brain. In rat brain DBI coexists with at least three different processing products and the members of this peptide family have been shown to displace benzodiazepines and beta carbolines from recognition sites located on the allosteric modulatory centers of GABAA receptors. Immunocytochemical methods were used to study the location of DBI and two of the processing products, octadecaneuropeptide (ODN) DBI 33-50 and triakontatetraneuropeptide (TTN) DBI 17-50, in rat brain. DBI-LI was found in selected neuronal perikarya and in many glia and glial-like cells. All circumventricular organs displayed a strong DBI like immunoreactivity (LI). The distribution and cellular location of the ODN-LI and TTN-LI differed from that of DBI because they were preferentially associated with DBI in neurons, but not in glia or glial-like cells. The presence of DBI, but not of its processing products, in glial cells, circumventricular organs, and cells of peripheral tissues suggests that the function of this peptide may extend to other yet unknown function in addition to an action on the allosteric modulatory center of GABAA receptors located in neurons.

Synthesis of the membrane fusion and hemagglutinin proteins of measles virus, using a novel baculovirus vector containing the beta-galactosidase gene

An improved baculovirus expression vector was developed to expedite screening and facilitate oligonucleotide-directed mutagenesis. This vector contained twin promoters derived from the P10 and polyhedrin genes of Autographica californica nuclear polyhedrosis virus. The P10 promoter directed the synthesis of beta-galactosidase, whereas the polyhedrin promoter controlled the synthesis of foreign gene products. These two genes recombined with wild-type virus genome to yield recombinants which were polyhedrin negative, produced the foreign gene product, and formed blue plaques when beta-galactosidase indicator was present in the agarose overlay. An origin of replication derived from M13 or f1 bacteriophage was also included in the plasmid to permit the synthesis of single-stranded DNA. This template DNA was used to introduce or delete sequences through the process of site-specific mutagenesis. The measles virus virion possesses a membrane envelope which contains two glycoproteins: the hemagglutinin (H) and membrane fusion (F) proteins. The H polypeptide has receptor-binding and hemagglutinating activity, whereas the F protein mediates virus penetration of the host cell, formation of syncytia, and hemolysis of erythrocytes. Genes for these two glycoproteins were inserted into the NheI cloning site of the modified expression vector described above. The vector and purified wild-type viral DNA were introduced into Sf9 insect cells by calcium phosphate precipitation. A mixture of wild-type and recombinant virus was generated and used to infect Sf9 cells, which were subsequently overlaid with agarose. After 3 days, 0.1 to 1% of the plaques became blue in the presence of beta-galactosidase indicator. At least 70% of these blue viral colonies contained the foreign gene of interest as determined by dot blot analysis. Recombinant virus was separated from contaminating wild-type virus through several rounds of plaque purification. Insect cells were then infected with the purified recombinants, and synthesis of H and F proteins were verified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis followed by immunoblot detection and Coomassie blue staining. Glycosylation of the proteins appeared to be impaired somewhat, and the precursor to the F protein was not completely cleaved by the proteases present in insect host cells. On the other hand, both proteins appeared to be active in hemagglutination, hemolysis, and cell fusion assays. Levels of synthesis were in the order of 50 to 150 mg of protein per 10(8) cells.

Estradiol stimulates cadherin expression in rat granulosa cells

We have investigated the ability of hormones to modulate cadherin expression by differentiating cells. Immunocytochemical and immunoblot techniques were employed to analyze the effects of estradiol and follicle-stimulating hormone on cadherin expression in rat granulosa cells. Estradiol was shown to stimulate the expression of cadherin by these cells. This is the first report of a hormone regulating the levels of cadherin in differentiating cells.

Progressive restriction in the distribution of the Hox-1.3 homeodomain protein during embryogenesis

Expression of the murine homeobox containing gene Hox-1.3 was analyzed in mouse embryos using polyclonal antisera to peptides predicted from cDNA and genomic sequences. At the earliest stage examined, 7.5 days gestation, cell nuclei throughout the three embryonic germ layers and in extraembryonic structures derived from the fertilized ovum were strongly immunoreactive. Rostro-caudal gradients or other patterns of regional differentiation in levels of expression could not be seen. Surrounding maternal tissue showed only weak immunoreactivity. At 8.5 days gestation, immunoreactivity was present in all embryonic structures including neural tube, somites and lateral plate mesoderm, ectoderm and endoderm. Immunoreactivity was progressively restricted thereafter. At 17 days gestation, strong immunoreactivity was largely restricted to the nervous system, both central and peripheral. Spinal cord was well stained, with a dramatic reduction in intensity near the junction of spinal cord and brain. In addition to this overall pattern, enhanced immunoreactivity appeared in limited populations of newly-formed neuroblasts of spinal cord and brain, suggesting that Hox-1.3 might serve to regulate the development of specific types of neurons following cessation of precursor cell mitosis.

The Hox-1.3 homeo box protein is a sequence-specific DNA-binding phosphoprotein

We report that the murine Hox-1.3 homeo domain protein is a nuclear phosphoprotein capable of binding to specific DNA sequences. DNase I protection of the Hox-1.3 gene promoter region with the Hox-1.3 protein identifies a binding site 144 bp upstream from the start of transcription. Both phosphorylated and nonphosphorylated forms bind DNA directly in a sequence-specific manner. Electrophoretic mobility shift assays were performed with a set of synthetic oligonucleotides representing either the DNase I-protected region of the Hox-1.3 gene or partially homologous sequences present in promoter regions of other characterized viral, yeast, and mammalian genes. From the results, we deduce a consensus binding motif of CPyPyNATTAT/GPy. Base substitutions in the core ATTA sequence severely reduce or abolish binding. In the SV40 enhancer, the Hox-1.3 binding motif overlaps both the octamer (Octa2) and the transactivator protein-1 (AP-1) binding sites. The Hox-1.3 binding motif also overlaps the nuclear factor III (NF-III) octamer motif in the adenovirus-2 origin of DNA replication. Overlap among DNA-binding sites suggests that regulation imparted by certain cis-elements may be integrated by these different factors.

Isolation and biological activity of corticostatic peptides (anti-ACTH)

Corticostatins (CS's) are a family of low molecular weight peptides, rich in arginine and cysteine with the ability to inhibit ACTH stimulated adrenocortical steroidogenesis. They show a high degree of specificity in that they do not inhibit the action of angiotensin II in the adrenal cortex. Four corticostatins have been isolated from rabbit lung extracts and peritoneal neutrophil extracts and one from human neutrophils. Among them corticostatin I, CSI, is the most potent with an I.D.50 of 25 nM. Corticostatin activity is different from other published inhibitory factors such as TGF-B and ANF, which inhibit basal and angiotensin II stimulated steroidogenesis. Other factors such as macrophage secreted products, and septic shock plasma factors which have not been fully characterized also have suppressive activity on ACTH induced adrenocortical steroidogenesis in vitro. It is not yet clear whether there is any relationship between corticostatins and these macrophage products and shock plasma factor. Corticostatins do not inhibit dbcAMP induced steroidogenesis, however they do inhibit the accumulation of cAMP in response to ACTH in rat adrenal cell suspensions. Binding studies show that CSI is a competitive inhibitor of ACTH, probably acting by blocking, the address recognition site of the receptor. There is wide variation in the potency of the corticostatins ranging from an ID50 of 100 ng/ml for CSI to a completely inactive analog, HP1. In this paper we will describe the purification of the corticostatins and some recent results obtained on their mechanism of action.

Developmental profile and differential localization of mRNAs of myelin proteins (MBP and PLP) in oligodendrocytes in the brain and in culture

We applied the in situ hybridization technique to localize the mRNAs for two myelin proteins: proteolipid protein (PLP) and myelin basic protein (MBP). In the oligodendrocyte in primary culture, PLP mRNA was located exclusively in the cell body throughout development. However, MBP mRNA was first located in the cell body and was rapidly distributed to the processes but not to the membranous sheets formed from the tips and lengths of the processes. Expression of PLP and MBP genes progressed in the caudo-cranial direction in the brain as far as we examined it in the tissue sections up to the 30th postnatal day: mRNAs of both genes were first detected in the pons and the medulla oblongata on the 3rd postnatal day and then in the cerebellum and the anterior part of the brain. PLP mRNA was located exclusively in the cell body throughout development. The number of PLP mRNA-positive cells reached a plateau in the posterior part of the brain on the 18th postnatal day, whereas it continued to increase in the anterior part of the brain by the 30th day. MBP mRNA was first expressed in the cell body, but later, it was found along the myelin sheath.

Expression of bicistronic measles virus P/C mRNA by using hybrid adenoviruses: levels of C protein synthesized in vivo are unaffected by the presence or absence of the upstream P initiator codon

The measles virus (MV) P/C mRNA is functionally bicistronic. Translation is presumed to initiate at both the first and second 5'-proximal AUG codons, leading, respectively, to synthesis of the P and C polypeptides from different overlapping reading frames. To study the function and differential expression of these polypeptides, we have constructed hybrid human adenoviruses capable of expressing high levels of P and C together or of C alone. Cloned cDNA corresponding to the MV P/C gene was coupled to the adenovirus type 2 (Ad2) major late promoter, most of the Ad2 tripartite leader sequence, and the simian virus 40 3'-end processing signal and then used to replace most of the E1a-E1b region of the Ad5 genome in two hybrid adenoviruses: one (Ad5MV/PC13) which contained both 5'-proximal AUG codons of the P/C mRNA and another (Ad5MV/C3) which retained only the second. The sequence context for the P protein initiator AUG codon in Ad5MV/PC13 was made more favorable (GAGAUGG) than the relatively unfavorable context (CCGAUGG) seen in the native MV P/C mRNA. After infection of 293 cells (which provide complementary E1a-E1b functions), both viruses directed equal amounts of P/C-specific mRNA transcription. Ad5MV/PC13 directed the synthesis of both P and C proteins, while Ad5MV/C3 directed the synthesis of C protein alone. Ad5-expressed P protein was phosphorylated, while C was not. C protein had a similar diffuse cytoplasmic localization in both MV and Ad5-infected cells. Ad5MV/C3 and Ad5MV/PC13 directed equal amounts of C protein expression in 293 cells at a level approximately 15 times greater than that seen in MV-infected cells. Thus the level of C protein expression was unaffected by the presence or absence of an out-of-frame upstream AUG codon in a favorable sequence context. This observation cannot be explained by the scanning model for ribosomal initiation and suggests that ribosomes may be binding directly at an internal mRNA site at or near the initiator AUG codon for the C protein.

Cell surface expression of glycosylated, nonglycosylated, and truncated forms of a cytoplasmic protein pyruvate kinase

The soluble cytoplasmic protein pyruvate kinase (PK) has been expressed at the cell surface in a membrane-anchored form (APK). The hybrid protein contains the NH2-terminal signal/anchor domain of a class II integral membrane protein (hemagglutinin/neuraminidase, of the paramyxovirus SV5) fused to the PK NH2 terminus. APK contains a cryptic site that is used for N-linked glycosylation but elimination of this site by site-specific mutagenesis does not prevent cell surface localization. Truncated forms of the APK molecule, with up to 80% of the PK region of APK removed, can also be expressed at the cell surface. These data suggest that neither the complete PK molecule nor its glycosylation are necessary for intracellular transport of PK to the cell surface, and it is possible that specific signals may not be needed in the ectodomain of this hybrid protein to specify cell surface localization.

Influenza A virus M2 protein: monoclonal antibody restriction of virus growth and detection of M2 in virions

The influenza A virus M2 protein is an integral membrane protein of 97 amino acids that is expressed at the surface of infected cells with an extracellular N-terminal domain of 18 to 23 amino acid residues, an internal hydrophobic domain of approximately 19 residues, and a C-terminal cytoplasmic domain of 54 residues. To gain an understanding of the M2 protein function in the influenza virus replicative pathway, we produced and characterized a monoclonal antibody to M2. The antibody-binding site was located to the extracellular N terminus of M2 as shown by the loss of recognition after proteolysis at the infected-cell surface, which removes 18 N-terminal residues, and by the finding that the antibody recognizes M2 in cell surface fluorescence. The epitope was further defined to involve residues 11 and 14 by comparing the predicted amino acid sequences of M2 from several avian and human strains and the ability of the M2 protein to be recognized by the antibody. The M2-specific monoclonal antibody was used in a sensitive immunoblot assay to show that M2 protein could be detected in virion preparations. Quantitation of the amount of M2 associated with virions by two unrelated methods indicated that in the virion preparations used there are 14 to 68 molecules of M2 per virion. The monoclonal antibody, when included in a plaque assay overlay, considerably showed the growth of some influenza virus strains. This plaque size reduction is a specific effect for the M2 antibody as determined by an analysis of recombinants with defined genome composition and by the observation that competition by an N-terminal peptide prevents the antibody restriction of virus growth.

Sequence of the 3386 3' nucleotides of the genome of the AVO1 strain rabies virus: structural similarities in the protein regions involved in transcription

DNA fragments complementary to the genome of an avirulent strain (AVO1) of the rabies virus were cloned and sequenced. The sequence of the 3386 nucleotides from the 3' end covers the genes encoding the leader RNA, the nucleoprotein N, the phosphoprotein M1 and the matrix protein M2, as well as the intergenic regions. Comparison of the AVO1 sequence with those of other rabies strains reveals a very high conservation at both the nucleotide and the amino acid levels. The non-protein coding regions of the genome (leader gene, untranslated regions flanking mRNAs, untranscribed intergenic regions) are discussed in terms of their possible involvement in the rabies virus biology. Comparison of the rabies genome with those of other unsegmented negative strand RNA viruses (rhabdoviruses and paramyxoviruses) indicates that the start and stop transcription signals, located at the border of each gene encoding a protein, and the regions of the phosphoprotein and matrix proteins that could be implicated in the transcription process, retain a similar overall structure. Thus, it appears that during evolution, these virus genomes have diverged while keeping the protein structures and regulatory sequence important in transcription. These results prompt us to propose that the major distinctive feature of the rabies transcription may arise from the highly variable intergenic regions where the attenuation of transcription is assumed to take place.

High-level eucaryotic in vivo expression of biologically active measles virus hemagglutinin by using an adenovirus type 5 helper-free vector system

The entire measles virus (MV) hemagglutinin (HA)-coding region was reconstructed from cloned cDNAs and used as part of a hybrid transcription unit to replace a region of the adenovirus type 5 genome corresponding to the entire E1a transcription unit and most of the E1b transcription unit. The resulting recombinant virus was stable and able to replicate to high titers in 293 cells (which constitutively express the complementary E1a-E1b functions) in the absence of helper virus. During infection of 293 cells, the hybrid virus expressed MV HA protein which was indistinguishable from that expressed in MV-infected cells in terms of immunoreactivity, gel mobility, glycosylation, subcellular localization, and biologic activity. Infection of 293 cells with the hybrid virus led to high-level synthesis of the MV HA protein (equivalent to 65 to 130% of the level seen in MV-infected cells). At late times after high-multiplicity hybrid virus infection of HeLa and Vero cells (which do not express E1 functions), the level of HA protein synthesis was at least 35% of that seen in 293 cells. This MV-adenovirus recombinant will be useful in the study of the biologic properties of the MV HA protein and in assessment of the potential usefulness of hybrid adenoviruses as live-virus vaccine vectors.

Cell surface expression and orientation in membranes of the 44-amino-acid SH protein of simian virus 5

Antiserum was raised against a synthetic peptide containing the N-terminal hydrophilic domain of the small hydrophobic protein (SH) of simian virus 5 (SV5) and used to characterize properties of the SH protein. SH demonstrated properties of an integral membrane protein. Indirect immunofluorescence experiments showed that the protein is involved in the exocytotic pathway, and isolation of plasma membranes from SV5-infected cells showed an enrichment of SH, indicating that SH is transported to the infected-cell surface. Biochemical analysis of the orientation of SH in membranes by proteolysis of intact SV5-infected cell surfaces and intracellular microsomal vesicles indicated that SH is oriented in membranes with its N-terminal hydrophilic domain exposed on the cytoplasmic face of the plasma membrane and the C terminus of approximately five amino acid residues exposed at the cell surface. These data are discussed with respect to positive-acting signals being necessary in the ectodomain of SH for cell surface expression.

Protein sorting between mitochondrial membranes specified by position of the stop-transfer domain

Recently, we fused a matrix-targeting signal to a large fragment of vesicular stomatitis virus G protein, which contains near its COOH-terminus a well-characterized endoplasmic reticulum (ER) stop-transfer sequence; the hybrid G protein was sorted to the inner mitochondrial membrane (Nguyen, M., and G. C. Shore. 1987. J. Biol. Chem. 262:3929-3931). Here, we show that the 19 amino acid G stop-transfer domain functions in an identical fashion when inserted toward the COOH-terminus of an otherwise normal matrix precursor protein, pre-ornithine carbamyl transferase; after import, the mutant protein was found anchored in the inner membrane via the stop-transfer sequence, with its NH2 terminus facing the matrix and its short COOH-terminal tail located in the intermembrane space. However, when the G stop-transfer sequence was placed near the NH2 terminus, the protein was inserted into the outer membrane, in the reverse orientation (NH2 terminus facing out, with a large COOH-terminal fragment located in the intermembrane space). These observations for mitochondrial topogenesis can be explained by a simple extension of existing models for ER sorting.

Analysis of the polypeptides synthesized in rinderpest virus-infected cells

We have identified, by [35S]methionine labeling, eight major induced proteins and a number of minor proteins in rinderpest virus-infected bovine kidney cells. The polypeptides ranged in molecular weight from 212 to 21.5 kDa. The majority of these polypeptides are virus specific, as demonstrated by immunoprecipitation with rabbit hyperimmune serum against rinderpest. Infected cells radiolabeled with glucosamine contained a 75-kDa polypeptide and a broad band migrating at 80 kDa, both identified as virus specific by immunoprecipitation. Phosphorylated virus-specific proteins of 65 kDa and a complex of polypeptides at 92.5 kDa were also identified. Monospecific and monoclonal antibodies against measles virus and canine distemper virus hemagglutinin, fusion protein, nucleocapsid protein, and phosphoproteins confirmed the identity of the corresponding rinderpest virus-specific polypeptides.

Construction and characterization of complementary DNA libraries from Vero cells infected with measles virus

Several cDNA libraries have been generated from poly(A)RNA from Vero cells infected for 24 hours with measles virus. Different protocols for cDNA library construction were compared and some critical steps were evaluated. From these libraries, a measles virus specific sequence corresponding to 885 of 1600 nucleotides of the measles virus phosphoprotein gene has been cloned. The phosphoprotein gene accounts for 1% of the total cDNA library after 24 hours of infection at 37 degrees C. The technique of differential colony hybridization was used to analyze the distribution and change of the poly(A)-RNA expression in uninfected Vero cells and in cells infected with measles virus for 24 hours.

Intergenic sequences of the vesicular stomatitis virus genome (New Jersey serotype): evidence for two transcription initiation sites within the L gene

The intergenic sequences of vesicular stomatitis virus of the New Jersey serotype [VSV (NJ): Ogden strain] have been determined by dideoxy sequencing across the gene junctions of the viral RNA genome using deoxyoligonucleotide primers. The N-NS, NS-M, and M-G intergenic sequences of VSV (NJ) are identical to the consensus intergenic sequence for VSV of the Indiana serotype [VSV (IND)]: 3'-AUACU7GAUUGUCNNNAG-5' (genome sense; N denotes any nucleotide), where 3'-AUACU7-5' encodes the 3' terminus and the start of the polyadenylate tract of the preceding mRNA, 3'-UUGUCNNNAG-5' encodes the 5' terminus of the succeeding mRNA, and 3'-GA-5' is a nontranscribed dinucleotide. Notably, the NS-M junction of VSV (NJ) does not contain the anomalous dinucleotide 3'-CA-5' which is found at the NS-M junction of VSV (IND). In striking contrast to VSV (IND), the G-L intergenic sequence of VSV (NJ) contains a 19-base insertion between the nontranscribed dinucleotide and the consensus mRNA start sequence. During in vitro transcription, the L mRNA of VSV (NJ) may initiate at two distinct sites: the first start site (3'-CCUUAUCUUC-5') is that flanking the nontranscribed dinucleotide, and the second start site is a consensus mRNA start sequence located 20 bases downstream from the nontranscribed dinucleotide. However, the L mRNA isolated form VSV (NJ)-infected cells appears to initiate only at the consensus start sequence. The possible role of these start sites in L mRNA synthesis is discussed.

Expression of a homeo domain protein in noncontact-inhibited cultured cells and postmitotic neurons

The murine Hox 1.3 gene is one of six homeo box genes clustered on chromosome 6. Our analysis of Hox 1.3 cDNA and genomic clones indicates that the gene is organized into two exons and encodes a 270-amino-acid homeo domain protein. The predicted protein is rich in serine, glycine, and proline residues, and its homeo domain is identical to the Hox 2.1 domain. During embryogenesis, the gene is maximally expressed at midgestation but is also expressed to a lesser extent in many adult tissues possessing different cell lineages. Hox 1.3 transcripts are also present in cultured fibroblasts. The Hox 1.3 protein accumulates in the nuclei of nonconfluent cultured fibroblasts but is greatly diminished in contact-inhibited nongrowing cells. Thus, the expression of the Hox 1.3 gene correlates with growth in embryos and cultured cells. Paradoxically, it is also expressed in certain subsets of postmitotic, fully differentiated neurons, most notably the Purkinje neurons of the cerebellum, the pyramidal and dentate neurons of the hippocampus, and the motor neurons of the spinal cord. This complex pattern of expression suggests that Hox 1.3 may provide a function required by many cell types in addition to any role it may have in morphogenesis.

Identification of the product of dnaB gene in Bacillus subtilis

In order to detect the product of dnaB gene in B. subtilis, a gene which is involved in the initiation of DNA replication and the formation of the DNA-membrane complex, we synthesized an origopeptide of 15 amino acids which corresponds to a region near the carboxyl-terminal of the gene product, and raised antibody against the synthetic peptide. We have also employed a filter binding assay to measure the predicted DNA binding activity of the product of the dnaB gene, using the plasmid pUB110. The binding activity was detected after fractionation of cell lysates of B. subtilis on sucrose-density gradients. When the active fraction was prepared from a mutant which was temperature-sensitive for the dnaB gene, the DNA binding activity in the fraction showed significant thermolability. Furthermore, the binding activity was inhibited by the purified antibody raised against the synthetic peptide. These results suggest that the product of the dnaB gene does indeed have DNA binding activity, and that the filter binding assay and the antibody can be used for the detection and characterization of the gene product.