| 1. |
- Byström, Anders S, et al.
(författare)
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The nucleotide sequence of an Escherichia coli operon containing genes for the tRNA(m1G)methyltransferase, the ribosomal proteins S16 and L19 and a 21-K polypeptide
- 1983
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Ingår i: EMBO Journal. - : Oxford University Press. - 0261-4189 .- 1460-2075. ; 2:6, s. 899-905
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Tidskriftsartikel (refereegranskat)abstract
- The nucleotide sequence of a 4.6-kb SalI-EcoRI DNA fragment including the trmD operon, located at min 56 on the Escherichia coli K-12 chromosome, has been determined. The trmD operon encodes four polypeptides: ribosomal protein S16 (rpsP), 21-K polypeptide (unknown function), tRNA-(m1G)methyltransferase (trmD) and ribosomal protein L19 (rplS), in that order. In addition, the 4.6-kb DNA fragment encodes a 48-K and a 16-K polypeptide of unknown functions which are not part of the trmD operon. The mol. wt. of tRNA(m1G)methyltransferase determined from the DNA sequence is 28 424. The probable locations of promoter and terminator of the trmD operon are suggested. The translational start of the trmD gene was deduced from the known NH2-terminal amino acid sequence of the purified enzyme. The intercistronic regions in the operon vary from 9 to 40 nucleotides, supporting the earlier conclusion that the four genes are co-transcribed, starting at the major promoter in front of the rpsP gene. Since it is known that ribosomal proteins are present at 8000 molecules/genome and the tRNA-(m1G)methyltransferase at only approximately 80 molecules/genome in a glucose minimal culture, some powerful regulatory device must exist in this operon to maintain this non-coordinate expression. The codon usage of the two ribosomal protein genes is similar to that of other ribosomal protein genes, i.e., high preference for the most abundant tRNA isoaccepting species. The trmD gene has a codon usage typical for a protein made in low amount in accordance with the low number of tRNA-(m1G)methyltransferase molecules found in the cell.
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| 2. |
- Leanderson, T, et al.
(författare)
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Interferon-specific effects on protein synthesis in P3HR-1 cells.
- 1982
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Ingår i: EMBO Journal. - 0261-4189 .- 1460-2075. ; 1:12, s. 1505-11
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Tidskriftsartikel (refereegranskat)abstract
- The effect of interferon (IFN) on protein synthesis was studied in the Burkitt's lymphoma cell line P3HR-1 by [35S]methionine labelling of the cells, followed by two-dimensional gel electrophoresis of cell extracts. De novo synthesis of three proteins (mol. wts. 33 000, 62 000, and 98 000, respectively) and alterations in the rate of synthesis for a small number of additional proteins were observed during the first 12 h of treatment, while the rate of overall protein synthesis was unaffected. Treatment of P3HR-1 cells with 12-O-tetradecanoyl-phorbol-13-acetate (TPA) or hydrocortisone (HC), which induce similar changes in cell cycle distribution as does IFN, did not induce comparable changes in the rates of protein synthesis. Thus, the effects were specific for IFN and not induced by the change in cell cycle distribution per se, i.e., accumulation in G0. Treatment of cells with 2'-5' pA core did not mimic the effect of IFN at the translational level. A substrain of P3HR-1 cells, selected for resistance to the anti-proliferative effect of IFN, lacked six proteins found in the wild-type. The 62 000 mol. wt. protein was induced in this substrain as well as in native P3HR-1 cells on addition of IFN. The resistant substrain still developed an anti-viral effect in response to IFN. Thus, it seems as if the anti-proliferative and anti-viral effects of IFN, at least in some cells are mediated by different intracellular molecular mechanisms.
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| 3. |
- Lee, J Y, et al.
(författare)
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Insect immunity. Isolation of cDNA clones corresponding to attacins and immune protein P4 from Hyalophora cecropia.
- 1983
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Ingår i: EMBO Journal. - 0261-4189 .- 1460-2075. ; 2:4, s. 577-81
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Tidskriftsartikel (refereegranskat)abstract
- Diapausing pupae of the Cecropia moth (Hyalophora cecropia) respond to an injection of live bacteria by the selective synthesis of certain types of RNA and immune proteins (designated P1-P9). The in vitro translation products of RNA from both injured and infected pupae showed specific patterns with a defined number of extra bands. Some proteins characteristic of the normal RNA were reduced in the immune RNA translation products. Antibody reaction was used to show the selective synthesis of immune proteins P4 and P5 with mRNA from pupae subjected to injury or infection. The protein synthesized in vitro, which cross-reacted with P5 antibodies, is most likely a precursor of the attacins described in the preceding paper. A cDNA clone bank was prepared and two clones were isolated and shown to contain 750 bp corresponding to P4 and 250 bp of attacin information. These clones were used to estimate the sizes of the mRNAs by Northern blotting and to estimate, by RNA/DNA hybridization, the levels of P4 and P5 mRNA. In vivo incorporation of [35S]methionine into attacins and P4 during different conditions was compared with the levels of the corresponding mRNA.
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