| Autor: |
Lewis, John A., Falcoff, Ernersto, Falcoff, Rebecca |
| Předmět: |
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| Zdroj: |
European Journal of Biochemistry; 5/16/78, Vol. 86 Issue 2, p497-509, 13p |
| Abstrakt: |
We have investigated the mechanism by which double-stranded RNA (dsRNA) inhibits protein synthesis in ceil-free extracts prepared from mouse L cells which had been pre-treated with purified interferon. Preincubation of such extracts for a determined period of time causes inactivation of tRNA species and hence an inhibition of protein synthesis with either Mengo RNA or poly(U,C) as mRNA. This inhibition can be overcome by addition of tRNA. We show that dsRNA inhibits the translation of Mengo RNA irrespective of the period of preincubation and that this inhibition is not overcome by tRNA. Translation of poly(U,C) is unaffected by dsRNA. Thus dsRNA does not act at the level of peptide chain elongation and does not cause inactivation of tRNA species, indicating that dsRNA inhibits protein synthesis in extracts of interferon-treated cells by a mechanism which is different from that responsible for the inhibition observed in the absence of dsRNA. The addition of dsRNA to extracts prepared from interferon-treated cells causes two modifications which are expected to inhibit protein synthesis, (a) An enhancement of the level of nuclease activity, causing Mengo [3H]RNA to be degraded more rapidly in interferon-treated cell extracts than control extracts, even when association of Mengo RNA with ribosomes is inhibited by the addition of pactamycin. (b) An impairment in the formation of methionyl-tRNA - 40-S-ribosomal- subunit complexes. The reduced binding of methionyl-tRNA to 40-S subunits can be overcome by the addition of a crude initiation factor preparation suggesting that dsRNA causes inactivation of an endogenous initiation factor(s). In the early stages of translation of Mengo RNA (10–15 min) dsRNA causes a reduction in the incorporation of [35S]methionine into the N-terminal position of polypeptides suggesting that initiation of protein synthesis is impaired, presumably as a result of the block of methionyl- tRNA-40-S-subunit complex formation. At a later stage (30–45 rain) Mengo RNA is almost completely destroyed under the normal conditions of protein synthesis. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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