Characteristics of concanavalin A‐resistant Chinese hamster ovary cells and certain revertants

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Abstract
Clones of Chinese hamster ovary (CHO) cells were isolated by single‐step selection for resistance to killing by Concanavalin A (ConA) and certain cellular and membrane properties were examined. The ConA‐resistant isolates were only about 2‐fold more resistant than wild type cells to the selecting lectin, but exhibited pleiotropic temperature‐sensitivity for growth, markedly altered morphology and adherence, and significant differences in susceptibility to other agents such as colchicine. Two revertants to full temperature‐resistance were isolated from different ConA‐resistant mutants. One revertant clone had reacquired wild type sensitivity to ConA while the other revertant remained ConA‐resistant. The two series of wild type, ConA‐resistant, and temperature revertant clones were analyzed for altered mobility of cell surface glycoproteins using lactoperoxidase/125I and galactose oxidase/[3H]borohydride labelling procedures. The ConA‐resistant clones showed increased mobility on polyacrylamide gels of three classes of labelled proteins, in the molecular weight ranges 225,000, 200,000, and 130,000 daltons. These changes persisted in the temperature‐revertant that remained ConA‐resistant, while two of the altered protein classes were restored to wild type mobility in the revertant that regained ConA‐sensitivity. Cell hybridization experiments indicated that the temperature‐sensitive phenotypes of different ConA‐resistant isolates are recessive and noncomplementing, implying that the same gene is affected in each case. The reversions to temperature resistance appear to be recessive suppressor mutations in different genes.