Chinese hamster cell variants resistant to the A chain of ricin carry altered ribosome function.
Ricin, a toxic lectin from Ricinus communis, is composed of two different polypeptide chains, A and B, and the ricin A chain (RA) blocks protein synthesis. We studied cell lines resistant to cytotoxic action of RA. One low-RA-resistant cell line, AR10, isolated from Chinese hamster ovary (CHO) cells, was resistant to a low dose of RA (1 microgram/ml) and showed a 10-fold-higher resistance to RA and ricin than that of CHO. We further mutagenized AR10 to isolate high-RA-resistant cell lines AR100-6, AR100-9, and AR100-13, which were resistant to higher doses of RA and ricin (100- to 1,000-fold) than CHO was. The binding of [125I]ricin to AR10, AR100-6, AR100-9, and AR100-13 cells was decreased to about 30% of that of CHO. The internalization of [125I]ricin in AR10 cells and in the high-RA-resistant clones was the same. Polyuridylate-dependent polyphenylalanine synthesis, using S-30 extracts from either AR100-9 or AR100-13, was about 100-fold more resistant to the inhibitory action of RA than when CHO, AR10, and AR100-6 cells extracts were used. The protein synthesis with ribosomes (80S) from AR100-9 or AR100-13 was 10- to 100-fold more resistant to RA than it was with parental ribosomes when combined with the S-100 fraction of CHO cells. The polyphenylalanine synthesis assay using the ribosomes constituted from the 60S subunit of AR100-9 and the 40S subunit of CHO indicated that the resistant phenotype of AR100-9 cells is due to an alteration of the 60S ribosomal subunit.
Department of Biochemistry, Oita Medical School, Hazama-cho, Oita 879-56, Japan.
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M
Ono
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M
Kuwano
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K
Watanabe
G
G
Funatsu
D000818:Animals; D016466:CHO Cells; D016923:Cell Death / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D002999:Clone Cells / Q000187:drug effects / Q000378:metabolism; D006224:Cricetinae; D004305:Dose-Response Relationship, Drug; D004351:Drug Resistance / Q000235:genetics*; D004705:Endocytosis; D009154:Mutation; D012270:Ribosomes / Q000187:drug effects* / Q000378:metabolism*; D012276:Ricin / Q000378:metabolism / Q000494:pharmacology* / Q000633:toxicity
D012276:Ricin