[Physical mapping of the Bombyx mori nuclear polyhedrosis virus genome]. / Fizicheskoe kartirovanie genoma virusa iadernogo poliédroza Bombyx mori.

The restriction map of the nuclear polyhedrosis DNA virus of Bombyx mori has been determined with the use of four restriction endonucleases: NotI, BamHI, SmaI and KpnI. 18 cleavage sites have been localized on the viral DNA. Total length of the viral DNA is about 130 kb. The fragment containing a polyhedrin gene has been localized on the map by the blot hybridization technique.

Characterization of 3'----5' exonuclease associated with DNA polymerase of silkworm nuclear polyhedrosis virus.

3'----5' Exonuclease specific for single-stranded DNA copurified with DNA polymerase of nuclear polyhedrosis virus of silkworm Bombyx mori (BmNPV Pol). BmNPV Pol has no detectable 5'----3' exonuclease activity on single-stranded or duplex DNA. Analysis of the products of 3'----5' exonucleolytic reaction showed that deoxynucleoside monophosphates were released during the hydrolysis of single-stranded DNA. The exonuclease activity cosedimented with the polymerase activity during ultracentrifugation of BmNPV Pol in glycerol gradient. The polymerase and the exonuclease activities of BmNPV Pol were inactivated by heat with nearly identical kinetics. The mode of the hydrolysis of single-stranded DNA by BmNPV Pol-associated exonuclease was strictly distributive. The enzyme dissociated from single-stranded DNA after the release of a single dNMP and then reassociated with a next polynucleotide being degradated.

[Studies on protein biosynthesis in the silk gland of Bombyx mori L. silkworm]. / Issledovanie biosinteza belkov v shelkootdelitel'noi zheleze tutovogo shelkopriada Bomby x mori L

The incorporation of (14C) lysine (to characterize the biosynthesis of cellular proteins) and (14C) glycine (for silk fibroin) in free and membrane-bound polyribosomes was studied in fibroin portion of the silk gland of Bombyx mori silkworm in the V instar. It was shown that although the membrane-bound polyribosomes are found in posterior silk gland from the beginning of the V instar, the fibroin biosynthesis in the membranebound polyribosomes takes place predominantly in the second part of the V instar. On the other hand the cellular proteins are synthesized mostly in the free polyribosomes in the first half of the V instar. In the second half of the V instar in the sucrose gradient zone corresponding to free polyribosomes, monoribosomes unable to synthesize protein for the absence of mRNA are present. Nevertheless, these ribosomes isolated from the fibroin part of the silk gland in the end of the V instar do synthesize polyphenylalanine in the presence of poly (U), and aminoacyl-t-RNA-synthetases and tRNA's obtained from the posterior silk gland.

[Properties of the cell-free protein synthesizing system from the fibroin region of the Bombyx mori silkgland]. / Svoistva beskletochnoi sistemy belkovogo sinteza iz fibroinovogo otdela shelkootdelitel'noi zhelezy tutovogo shelkopriada Bomby x mori.

Microsomes isolated from the fibroin region of the Bombyx mori silkgland synthesize in the cell-free system a glycin rich polypeptide or polypeptides presumably representing fibroin precursors. Besides microsomes the system requires ATP and ATP-generating system, GTP, soluble protein fraction and tRNA, glycine incorporation is inhibited by puromycin and cycloheximide. It is shown that the synthesis of a polypeptide with high Gly/Lys ratio requires soluble protein fraction isolated from the silk gland at the end of the instar V. When the soluble protein fraction from the larvoe at the early instar V is used the Gly/Lys ratio in the product is markedly lower. These results permit to suggest that fibroin synthesis may be regulated at the level of tRNA aminoacylation.

RNA-polymerase activity in isolated nuclei of developing silkworm embryos.

Nuclei isolated from developing embryos of the silkworm (Bombyx mori) are capable of RNA synthesis in vitro. The incorporation of C-14-uridine triphosphate (C-14-UTP) into the acid-insoluble fraction requires the presence of the other three ribonucleoside triphosphates; it is inhibited by actinomycin, olivomycin, and ethidium bromide, and is stimulated by ammonium sulfate. In a medium of moderate ionic strength C-14-UTP incorporation is slightly inhibited by alpha-amanitine (4 mug/ml), whereas in the presence of 0.2 M ammonium sulfate the same alpha-amanitine concentration reduces the incorporation by 90%. These data indicate that silkworm embryo nuclei, like nuclei from several other sources, contain two different RNA-polymerase fractions.