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Regulation of RNA polymerase II activity in a mutant rat myoblast cell line resistant to α amanitin


A MUTANT cell line, Ama102, resistant to the cytotoxic effects of a amanitin, the specific inhibitor of RNA polymerase II (refs 1 and 2), has been selected3 from cultures of Yaffe's4 rat skeletal muscle myoblast cell line, L6, treated with mutagen. Ama102 cells have similar doubling times for growth in the absence or presence of 3 μg ml−1 α amanitin whereas the Ama+ parent does not survive in this concentration of α amanitin. Studies in vitro (ref. 3 and D.S. et al., manuscript in preparation) indicate that Ama102 cells possess an RNA polymerase II which, retains about 30% of its activity in 0.1 μg ml−1 α amanitin, a concentration sufficient to inactivate completely the Ama+ polymerase II. If α amanitin has a similar inhibitory action in vivo and in vitro, the normal growth of Ama102 cells in α amanitin coupled with the partial resistance of its RNA polymerase II activity to α amanitin in vitro seems paradoxical. Does the mutant Ama102 cell grow normally in α amanitin with only 30% of its normal RNA polymerase II active, or can the RNA polymerase II activity increase when the mutant is grown in α amanitin? The experiments reported here indicate that Ama102 cells can compensate for the partial inactivation of RNA polymerase II by α amanitin by increasing the RNA polymerase II activity.

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SOMERS, D., PEARSON, M. & INGLES, C. Regulation of RNA polymerase II activity in a mutant rat myoblast cell line resistant to α amanitin. Nature 253, 372–374 (1975).

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