Vaccinia virus cores contain an activity which is able to relax both left-and right-handed superhelical DNA. This virus-specific nicking-closing enzyme has been highly purified and differs from the corresponding host enzyme in salt optimum, in sedimentation coefficient, and in polypeptide composition as determined on sodium dodecyl sulfate/polyacrylamide gels. The enzyme is probably newly synthesized after the cessation of host protein synthesis which follows virus infection. The most highly purified preparation contains two polypeptides, one of molecular weight 24,000 and the other 35,000. The former polypeptide is a major constituent of the virus (7% of total protein by weight), whereas the latter is present in a much smaller amount (0.2%). Chromatography with denatured DNA-cellulose reveals that the activity is predominately associated with those fractions enriched in the polypeptide of greater molecular weight. Many fundamental biological processes are associated with changes in the duplex winding of DNA. These include DNA replication; transcription; recombination; formation of nucleosomes; packaging of DNA in organelles, such as mitochondria or chloroplasts; formation of complex prokaryotic chromosomes (1); and encapsidation into viruses. Enzymes from several sources have recently been discovered which are able to relieve torsional stress on the DNA duplex. None of these appears to require a cofactor, and their primary function is to introduce a transient local swivel that allows the DNA to rotate in response to a torque.The prokaryotic enzymes, termed omega proteins (2), have been purified from Escherichia coli 1100 (2, 3) and from E. coli B (4) and are able to catalyze duplex rotation in the righthanded (overwinding) direction only. The eukaryotic enzymes are able to catalyze rotation in both directions and have so far been discovered in several animal cell nuclei (5-9). In the present report we show that such an activity is encapsidated in mature vaccinia virions and is active in viral cores, which are able to carry out transcription as intact complexes. The activity is not identical to the corresponding host protein and is newly synthesized following infection. This result, representing a virus-specific nicking-closing enzymet, confirms the widespread distribution of this activity.The only presently available assay for nicking-closing activity is based upon the ability of the enzyme to remove superhelical turns from closed circular duplex DNA. Such DNA molecules are subject to the topological constraint (11) that the net interstrand winding, a, is a constant and is the sum of the number MATERIALS AND METHODS Reagents. Yeast alcohol dehydrogenase and horse heart cytochrome c were obtained from Worthington and Sigma, respectively. Ethidium bromide (EtdBr) was obtained from Calbiochem, and [35S]methionine was purchased from New England Nuclear. All other chemicals were of reagent grade.Preparation of Virus. Vaccinia virus strain WR, grown in HeLa S cells, was purified by the method of Joklik (14). ...

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The synthesis of a series of 5-substituted uracil derivatives is described. 5-Bromoacetyluracil (2a) was converted to the glycolyl (2b), glycyl (2c), N,N-dimethylglycyl (2d), 4-imidazolyl (3), and 2-amino-4-thiazolyl (4) derivatives. 5-Formyluracil (5) was used in the preparation of the 2-imidazolyl (6), the 3-acrylic acid (7b), the ester (7a), and the 3-N,N-dimethylacrylamide (8) derivatives. A Mannich reaction converted 5-acetyluracil to the amino ketone 9 which was reduced to give the 3-dimethylamino-1-propanol derivative 10. Compounds 2b,d,3,4,6, and 7b failed to inhibit the growth of Escherichia coli B and Staphylococcus aureus.

5‐Acetyluracil (I) wird zu (IIa) bromiert, aus dem die Folgeprodukte (IIb)‐(IId) zugänglich sind.