A Caenorhabditis elegans RNA polymerase II gene, ama-1 IV, and nearby essential genes
Rogalski, T.M.; Riddle, D.L.
Genetics 118(1): 61-74
1988
ISSN/ISBN: 0016-6731 PMID: 8608933 Document Number: 318990
The amanitin-binding subunit of RNA polymerase II in C. elegans is encoded by the ama-1 gene, located approximately 0.05 map unit to the right of dpy-13 IV. Using the amanitin-resistant ama-1(m118) strain as a parent, amanitin-sensitive mutants that carry recessive-lethal ama-1 alleles were isolated. Of the 6 ethyl methanesulfonate-induced mutants examined, 2 were arrested late in embryogenesis. One of these was a large deficiency, mDf9, but the second might be a novel point mutation. The 4 other mutants were hypomorphs, and presumably produced altered RNA polymerase II enzymes with some residual function. Two of these mutants developed into sterile adults at 20 degrees C but were arrested as larvae at 25 degrees C, and 2 others were fertile at 20 degrees C and sterile at 25 degrees C. Temperature-shift experiments performed with the adult sterile mutant, ama-1(m118m238ts), revealed a temperature-sensitive period that began late in gonadogenesis and was centered around the initiation of egg-laying. Postembryonic development at 25 degrees C was reduced by 30%. In contrast, the amanitin-resistant allele of ama-1 had very little effect on developmental rate or fertility. Fifteen essential genes in an interval of 4.5 map units surrounding ama-1, as well as 4 gamma -ray-induced deficiencies and 2 duplications that included the ama-1 gene were identified. The larger duplication, mDpl, might include the entire left arm of chromosome IV, and it recombined with the normal homologue at a low frequency. The smallest deficiency, mDf10, complemented all but 3 identified genes: let-278, dpy-13 and ama-1, which defined an interval of only 0.1 map unit. The terminal phenotype of mDf10 homozygotes was developmental arrest during the 1st larval stage, suggesting that there was sufficient maternal RNA polymerase II to complete embryonic development.