Small RNAs of Rous Sarcoma Virus: Characterization by Two-Dimensional Polyacrylamide Gel Electrophoresis and Fingerprint Analysis

Approximately 15 to 20 different species of small (4 to 7S) RNAs have been purified by two-dimensional polyacrylamide gel electrophoresis of RNA isolated from virions of Schmidt-Ruppin D strain of Rous sarcoma virus. Each species of small RNA has been isolated free of 70S RNA; nine of them, including 5S and 7S RNAs, were also found associated with the 70S genomic RNA. Most of the 4S RNAs are present at an average of less than one copy per virion. The 4S RNAs have T1 RNase (EC 2.7.7.26) fingerprints, which are very similar to those of tRNAs. One of the smallest 4S RNAs, which can act as a primer for initiation of RNA-directed DNA synthesis, is associated with the 70S RNA in 1 to 2 copies per complex, whereas an additional 6 to 8 copies of this molecule are free.     

Stability in vitro of uridine diphosphoglucose pyrophosphorylase in Dictyostelium discoideum

The stability of uridine diphosphoglucose pyrophosphorylase was examined in extracts prepared at different stages of development in Dictyostelium discoideum. In the early stages, the kinetics of inactivation were nonlinear, and, therefore, it was not possible to determine the specific enzyme activity. In the later stages of development, the enzyme was stable, but it could be rapidly inactivated by a heat-labile inhibitor present in extracts prepared at an early stage.     

Low-molecular-weight RNAs of Moloney murine leukemia virus: identification of the primer for RNA-directed DNA synthesis.

The small RNAs of Moloney murine leukemia virus (M-MuLV) were fractionated into at least 15 species by two-dimensional polyacrylamide gel electrophoresis. The pattern of small RNAs is significantly different from that of Rous sarcoma virus. A subset of the virion small RNAs is associated with the genome RNA in the 70S complex. One of the associated molecules, a cellular tRNA, is tightly bound to the genome RNA and serves as the major primer for M-MuLV RNA-directed DNA synthesis in vitro.     

Biochemical properties of the bromodeoxyuridine-induced guinea pig virus.

The biophysical and biochemical properties of the virus particles released by guinea pig embryo cells treated with 5-bromo-2'-deoxyuridine (BUdR) have been compared to those of the B-type mouse mammary tumor virus (MMTV) and the C-type Rauscher murine leukemia virus. The high-molecular-weight (60 to 70S) RNA of the BUdR-induced guinea pig virus (GPV) has a molecular weight of 8 X 106 when measred by mixed agarose polyacylamide gel electrophoresis. The virus particles isolated from the tissue culture medium of BUdR-induced guniea pig cells have the following properties in common with MMTV: (i) a buoyant density of 1.18 g/ml in sucrose and 1.21 g/ml in CsCl, and (ii) a DNA polymerase that prefers Mg2+ over Mn2+ in an assay using the synthetic template poly(rC):oligo(dG). No nucleic acid sequence homology between GPV RNA and the viral RNAs of the MMTV, murine leukemia virus, hamster sarcoma virus, or Mason-Pfizer monkey virus could be observed in a competition hybridization assay using the radioactive-labeled GPV 60 to 70S RNA. By this same competition by hybridization assay the frequency of GPV proviral sequences was estimated to be at least 83 per haploid cellular genome of guniea pig cells. No nucleic acid sequences related to be GPV RNA were detected in the DNA of normal tissues of mice, rats, cats, dogs, baboons, or humans by direct RNA-DNA hybridization using radioactive GPV60 to 70S RNA.     

Virion-Associated RNA Primer for Rous Sarcoma Virus DNA Synthesis: Isolation from Uninfected Cells

Uninfected chicken, duck, rat, and human fibroblast cells in culture contained a tRNA-like RNA molecule which was structurally identical to a virion-associated RNA primer for in vitro Rous sarcoma virus DNA synthesis. This primer RNA appeared to be a normal tRNA of these cells. It was not found in a number of lower eukaryotic cells or in Escherichia coli.     

Characterization and quantification of the androgen and glucocorticoid receptors in cytosol from rat skeletal muscle

The binding of the radioactive synthetic hormonal steroids [3H]dexamethasone (9 alpha-fluoro-11 beta, 17 alpha, 21-trihydroxy-16 alpha-methyl-1,4-pregnadiene-3,20-dione) and [3H]methyltrienolone (17 beta-hydroxy-17 alpha-methyl-4,9,11-estratien-3-one) to cytosol from rat skeletal muscle was studied using dextran-coated charcoal to separate unbound and receptor-bound steroid. The rates of association, dissociation, and degradation of the complexes of dexamethasone and methyltrienolone with receptor were highly dependent on temperature. The temperature dependence of association was greater for dexamethasone, and that of degradation was greater for methyltrienolone. Dissociation rates were insignificant for both steroid-receptor complexes compared to association and degradation rates. The apparent equilibrium dissociation constants for the binding of dexamethasone and methyltrienolone to their receptor binding sites were about 7 and 0.3 nM, respectively, regardless of temperature (0. 15 or 23 degrees C). The lack of influence of temperature on the equilibrium constants indicate that the binding was of hydrophobic character, and the corresponding free energy changes upon binding of dexamethasone and methyltrienolone to their respective binding sites were -41 and -49 kJ mol-1 under equilibrium conditions at 0 degrees C. The apparent maximum number of binding sites determined from Scatchard plots under these conditions was about 1900 fmol/g of tissue, 3500 fmol/mg of DNA or 30 fmol/mg of protein in the case of the dexamethasone receptor, and the corresponding figures for the methyltrienolone were about 100 fmol/g of tissue, 200 fmol/mg of DNA or 2 fmol/mg of protein. The ligand specificities of the binding sites for dexamethasone and methyltrienolone were typical of a glucocorticoid and an androgen receptor, respectively. Both steroid-receptor complexes were retained on DNA-cellulose columns, and were eluted by NaCl at an ionic strength of 0.1. The DNA-cellulose step purified about 20 times, and was used to allow gel exclusion chromatography and electrofocusing. Both steroid-receptor complexes were excluded from a column of Sephadex G-150. Electrofocusing in preparative columns gave reproducible patterns consisting of three peaks for each receptor. The apparent isoelectric points were 5.4, 5.6 and 6.2 for the glucocorticoid receptor, and 5.9, 6.2 and 8.5 for the androgen receptor.     

Immunological relationships of an endogenous guinea pig retrovirus with prototype mammalian type B and type D retroviruses.

A retrovirus endogenous to guinea pig cells was earlier shown to be morphologically similar to type B and type D prototype retroviruses. Molecular hybridization techniques were used to show that guinea pig virus nucleotide sequences are endogenous to both domestic (Cavia porcellus) and indigenous (Cavia aperea) guinea pigs, but cannot be detected in the DNA of either other hystricomorph rodents or other mammals tested. Using radioimmunological techniques designed to detect interspecies relationships, the major internal polypeptide of guinea pig virus (p26) was shown to share three different sets of interspecies antigenic determinants with squirrel monkey retrovirus, viper retrovirus, and mouse mammary tumor virus. Thus, guinea pig virus appears to provide an evolutionary link between type B and D retroviruses.     

Variation in the convexity of the human maxillary incisor labial surface

Labial surface convexity of the maxillary central incisors (ILC) is classified with a new five grade ranked scale. More than 2,000 individuals representing 20 worldwide populations were studied. Principle findings are 1) sexual dimorphism is not significant, 2) antimere asymmetry is moderate, 3) labial convexity is negatively associated (r = ?0.48) with labial surface double-shovelling, and 4) significant differences occur between several populations. Convexity is most marked in African and Asiatic Indian populations, particularly Bushmen. Europeans have intermediate degrees of convexity, and American Indians the least; Eskimos have the highest amount of convexity among Native Americans. Pacific Islanders are intermediate; Melanesians show the strongest expression of incisor labial convexity in the Pacific.     

Thermostable xylanolytic enzymes from Rhodothermus marinus grown on xylan

The thermophilic eubacterium Rhodothermus marinus was cultivated in a fermentor and studied with respect to activities of induced xylanolytic enzymes. Growth in the fermentor on xylan occurred with a maximum specific growth rate of 0.43 h^–1 for a batch culture. The final cell concentration was 4 g cell dry weight (CDW)/l for cells grown on xylan compared to 2 g CDW/l for cells grown without xylan in the cultivation medium. At least two xylanolytic enzymes, endo-1,4--xylanase and xylan 1,4--xylosidase, were secreted into the culture medium when cells were cultivated on xylan. Of the three cellulolytic enzymes tested for activity, -glucosidase activity was in the range of the xylanolytic enzyme activities whereas cellulose-1,4--cellobiosidase and cellulase activities were hardly detectable. The expression of endo-1,4--xylanase activities during cultivation indicates the existance of more than one xylanase in R. marinus. This is also observed in fractions from gel filtration. The xylanolytic enzymes are heat-stable. At 90°C and at pH 7.0 the half-life of the endo-1,4--xylanase was about 14 h and that of xylan 1,4--xylosidase was 45 min. Correspondence to: L. Dahlberg     

A pre-export U1 snRNP in Xenopus laevis oocyte nuclei.

We demonstrate that precursors of U1 snRNA are associated with nuclear proteins prior to export to the cytoplasm. The approximately 15S complexes containing pre-U1 RNA, which we call pre-export U1 snRNPs, were identified in extracts of Xenopus laevis oocyte nuclei that were synthesizing U1 RNAs from injected U1 genes. The U1 snRNP-specific A protein was associated with nuclear pre-U1 RNA since both this protein and the RNA were co-precipitated by antibodies directed against either the m7G-cap of the precursor RNA or the U1-A protein. The interaction of the U1-A protein with pre-U1 RNA required sequences in the loop II region although this region of U1 RNA was not necessary for the association of U1 A protein with mature U1 snRNPs. The U1 A protein helps protect pre-U1 RNA against degradation in the nucleus.