RNA polymerase II from wild type and alpha-amanitin-resistant strains of Caenorhabditis elegans.

DNA-dependent RNA polymerases I, II, and III have been isolated from the soil nematode, Caenorhabditis elegans, and RNA polymerase II has been partially purified. The sensitivities of these enzymes to alpha-amanitin resemble those of the cognate enzymes from vertebrates. RNA polymerase II from C. elegans is 50% inhibited by 7 ng/ml of the amatoxin and RNA polymerase III by 80 micrograms/ml, whereas RNA polymerase I is insensitive to 500 micrograms/ml. We have obtained mutants of C. elegans which can grow and reproduce in concentrations of alpha-amanitin which arrest development of wild type animals. One of these mutants (DR432) has an altered RNA polymerase II which in partially purified extracts is 150 times less sensitive to the drug than the wild type enzyme. The mutation, ama-1(m130), in DR432 is dominant and maps near dpy-13 on linkage group IV. RNA polymerase II isolated from ama-1/+ heterozygotes contains equal proportions of two components, corresponding in alpha-amanitin sensitivity to the enzymes from DR432 and wild type. Thus, ama-1 appears to affect a subunit of RNA polymerase II.