Expression of the 39k promoter of Autographa californica nuclear polyhedrosis virus is increased by the apoptotic suppressor P35

The 39k promoter of the baculovirus Autographa californica nuclear polyhedrosis virus (AcNPV) is transactivated by the viral protein IE1 and further stimulated by viral enhancer elements and the viral coactivator IE2. To identify additional viral proteins that regulate expression from the 39k promoter, we performed cotransfection experiments with clones of viral DNA and a plasmid containing the chloramphenicol acetyltransferase (CAT) gene under the control of the 39k promoter. Our results indicated that cotransfection of a 39cat construct with plasmids containing IE1 and the EcoRI-S fragment of viral DNA stimulated CAT activity 2.5-fold as compared to cells transfected in the absence of EcoRI-S. EcoRI-S encodes P35, a protein that suppresses apoptosis in AcNPV-infected cells. Primer extension analysis showed that the increase in CAT activity was due to a corresponding increase in mRNA, indicating that P35 may increase transcription from the 39k promoter. To determine whether P35 could activate the 39k promoter in the absence of IE1, the p35 open reading frame was cloned under the control of the ie1 promoter. Cotransfections of 39cat and IE-P35 in the presence and absence of pIE1 indicated that activation of 39k by P35 required the IE1 protein. Cotransfection of plasmids encoding P35 and IE1 did not lead to an increase in the expression of IE1. This suggests that the mechanism of P35 is different than that of IE2 which activates 39k indirectly by increasing the expression of IE1. Cotransfection experiments indicated that IE2 and P35 act in a synergistic fashion.

Marek's disease virus type 1-specific phosphorylated proteins pp38 and pp24 with common amino acid termini are encoded from the opposite junction regions between the long unique and inverted repeat sequences of viral genome

The nucleotide sequence of the junction region between the long unique (UL) and terminal inverted repeat (TRL) sequences of Marek's disease (MD) virus type 1 (MDV1) DNA revealed the presence of a rightward open reading frame of 155 amino acids. The ORF inserted into an eukaryotic expression vector transiently expressed an antigen in the cytoplasm of COS7 cells which reacted with the monoclonal antibody M21 against an MDV1-specific phosphorylated protein complex consisting of at least the proteins pp38 and pp24. In addition, RNA synthesized in vitro from the ORF under the control of the T7 promoter was translated in vitro using rabbit reticulocyte lysates. A polypeptide of about 24 kDa was immunoprecipitated with M21 antibody. Thus, the MDV1-specific phosphorylated proteins pp38 and pp24 with common amino termini are encoded in the opposite junction regions between the UL and IRL and between the UL and TRL, respectively, of the MDV1 genome. The pp38 gene is transcribed leftward from the viral genome, while the pp24 gene was shown here to be transcribed rightward in a MD tumor cell line as well as in cells productively infected with MDV1.

[Epidemiology of adenovirus pneumonia in Beijing, 1976-1990]

From 1976 to 1990 for 15 consecutive epidemic years, virological examinations were carried out on 2,757 hospitalized infants and children infected with pneumonia. Ninety-nine strains of types 3 and 7 adenovirus (Ad3,Ad7) isolated from 50s to 90s were analyzed with 12 DNA restriction endonucleases. Results showed the epidemiologic characteristics of adenovirus (Adv) pneumonia in Beijing. Epidemic occurred yearly, but there was no severe outbreak of Adv pneumonia as in 1958. Ad3 and Ad7 were the main etiologic agents of Adv pneumonia. Ad7 was dominant in 1976-1980; while Ad3 was more prevalent in 1981-1990. DNA restriction endonuclease analysis revealed six genome types of Ad7 and three genotypes of Ad3. 7a1, 7a4, 7b and 7g occurred in 1958, 1965, but disappeared between 1980-1990; 3a2 was first detected in 1962. From 1980 to 1990, 7d and 3a2 were the dominant genome types. Among the Ad7 strains only one strain of 7d1 was identified; all others were 7d. 3a4 and 3a6 first appeared in 1984 and 1986, respectively. The changes of epidemic patterns seemed correlated with the variations of genome types.

Identification and molecular characterization of csrA, a pleiotropic gene from Escherichia coli that affects glycogen biosynthesis, gluconeogenesis, cell size, and surface properties

Current evidence suggests that a few global regulatory factors mediate many of the extensive changes in gene expression that occur as Escherichia coli enters the stationary phase. One of the metabolic pathways that is transcriptionally activated in the stationary phase is the pathway for biosynthesis of glycogen. To identify factors that regulate glycogen biosynthesis in trans, a collection of transposon mutants was generated and screened for mutations which independently increase or decrease glycogen levels and the expression of a plasmid-encoded glgC'-lacZ fusion. The glycogen excess mutation TR1-5 was found to be pleiotropic. It led to increased expression of the genes glgC (ADPglucose pyrophosphorylase) and glgB (glycogen branching enzyme), which are representative of two glycogen synthesis operons, and the gluconeogenic gene pckA (phosphoenolpyruvate carboxykinase), and it exhibited effects on cell size and surface (adherence) properties. The mutated gene was designated csrA for carbon storage regulator. Its effect on glycogen biosynthesis was mediated independently of cyclic AMP (cAMP), the cAMP receptor protein, and guanosine 3'-bisphosphate 5'-bisphosphate (ppGpp), which are positive regulators of glgC expression. A plasmid clone of the native csrA gene strongly inhibited glycogen accumulation and affected the ability of cells to utilize certain carbon sources for growth. Nucleotide sequence analysis, complementation experiments, and in vitro expression studies indicated that csrA encodes a 61-amino-acid polypeptide that inhibits glycogen biosynthesis. Computer-assisted data base searches failed to identify genes or proteins that are homologous with csrA or its gene product.

Helical structure of P pili from Escherichia coli

The structure of the P pili from Escherichia coli has been studied using X-ray fiber diffraction and scanning transmission electron microscopy (STEM). Analysis of the fiber diffraction data indicates that the pili are constituted largely of structural subunits arranged helically with approximately 33 subunits in 10 turns in an axial repeat of 244.5 +/- 1.8 A. Radial electron density distributions calculated from equatorial diffraction data and STEM data indicate that the pili are about 65 A in diameter with a small central cavity roughly 15 A across. The principal protein component of the pili is PapA, which has a molecular weight of 16.5 kDa. Assuming that each subunit consists of a single PapA molecule, the mass-per-unit-length of the pili predicted from the X-ray data is 2.23 kDa/A. Measurements of mass-per-unit-length were also made through the analysis of STEM images. These measurements indicate a value of 2.13 +/- 0.14 kDa/A. STEM images demonstrated the presence of thin, thread-like structures emerging from the ends of pili and spanning breaks in the pili structure. These structures, which have been observed under other conditions, have been termed fibrillae. In the STEM images the fibrillae appear about 20 A in diameter. The mass-per-unit-length of the fibrillae was estimated using the STEM data to be 0.4 kDa/A. These data are consistent with the fibrillae representing an unwound or unraveled form of the pili proteins overstretched to about five times the length they would have in the intact pili.

Intracellular trafficking of two major Epstein-Barr virus glycoproteins, gp350/220 and gp110

The processing and intracellular localization of the two predominant Epstein-Barr virus glycoproteins expressed in late lytic infection were investigated. Immune light or electron microscopy of frozen fixed sections revealed that gp110 colocalized to the endoplasmic reticulum and to the nuclear membrane with the endoplasmic reticulum-resident protein, heavy-chain-binding protein (BiP), while gp350/220 accumulated in low abundance in the endoplasmic reticulum and was present in higher abundance in cytoplasmic structures presumed to be Golgi and in plasma membranes. Consistent with endoplasmic reticulum and nuclear membrane localization, the bulk of gp110 was sensitive to endoglycosidase H, indicating high-mannose, pre-Golgi, N-linked glycosylation; while consistent with Golgi and plasma membrane localization, gp350/220 was mostly resistant to endoglycosidase H because of complex N- and O-linked glycosylation. gp350/220 was as abundant in extracellular enveloped virus as in the plasma membrane but was much less abundant or undetected in internal cytoplasmic or nuclear membranes. In contrast, gp110-specific antibodies did not label extracellular or intracellular virus. These data indicate that the major antigenic components of gp110 are not incorporated into or are occluded in virions and that gp350/220 is added to virus in cytoplasmic transit through a process of de-envelopment and re-envelopment at the plasma membrane or at post-Golgi vesicles. Consistent with cytoplasmic de-envelopment and re-envelopment at the plasma membrane was the finding of some free nucleocapsids in the cytoplasm of cells with intact nuclear membranes and nucleocapsids which appeared to bud through the plasma membrane.

Identification of the Epstein-Barr virus gp85 gene

The Epstein-Barr virus glycoprotein gp85 has been mapped to the Epstein-Barr virus DNA open reading frame BXLF2 (R. Baer, A. Bankier, M. Biggin, P. Deininger, P. Farrell, T. Gibson, G. Hatfull, G. Hudson, S. Stachwell, C. Sequin, P. Tufnell, and B. Barrell, Nature [London] 310:207-211, 1984). A gp85-specific monoclonal antibody reacts with the BXLF2 in vitro transcription-translation product. The monoclonal antibody also precipitates an 85-kilodalton protein from rodent cells transfected with the BXLF2 open reading frame DNA. In these cells, gp85 localizes to the cytoplasm and nuclear rim rather than to the plasma membrane as in lymphocytes. Northern (RNA) blot hybridization and analysis of a cDNA clone containing BXLF2 indicate that gp85 is translated from an unspliced, late, 2.5-kilobase transcript. Similarities between the predicted amino acid sequences of gp85 and herpes simplex virus gH (D. McGeoch and A. Davison, Nucleic Acids Res. 14:4281-4292, 1986) are noted.

Epstein-Barr virus glycoprotein homologous to herpes simplex virus gB

The Epstein-Barr virus DNA open reading frame BALF4 (R. Baer, A.T. Bankier, M.D. Biggin, P.L. Deininger, P.J. Farrell, T.J. Gibson, G. Hatfull, G.S. Hudson, S.C. Stachwell, C. Sequin, P.S. Tuffnell, and B.G. Barrell, Nature [London] 310:207-211, 1984), which by nucleotide sequence comparison could encode a protein similar to herpes simplex virus gB (P.E. Pellett, M.D. Biggin, B. Barrell, and B. Roizman, J. Virol. 56:807-813, 1985), has now been shown to encode a 110-kilodalton glycoprotein. Late infectious cycle RNAs of 3.0 and 1.8 kilobases are transcribed from BALF4. Translation of these RNAs in vitro, transcription and translation of BALF4 in vitro, or metabolic labeling of cells in the presence of tunicamycin and immunoprecipitation with BALF4-specific sera results in identification of a 93-kilodalton precursor to gp110. Since N-glycosidase F only reduces the size of gp110 to 105 kilodaltons, gp110 probably has both N- and O-linked glycosylation, gp110 is an abundant glycoprotein in Epstein-Barr virus-infected cells. In infected lymphocytes and in 3T3 cells, in which the gene is expressed from a recombinant expression vector, most of the protein is cytoplasmic and perinuclear. In contrast to gB, gp110 was not detected in the infected-cell plasma membrane. In cells replicating Epstein-Barr virus, gp110 localized to the inner and outer nuclear membrane lamellae and to endoplasmic reticulum structures which sometimes contained enveloped virus. gp110 may play an important role in modifying infected intracellular membranes.