Analysis of RNA and protein synthesis in temperature-sensitive mutants of Tetrahymena pyriformis

Abstract

Temperature-sensitive mutants of Tetrahymena pyriformis which had previously been selected for their inability to grow at 38°C but which grew normally (or near normally) at 30°C were characterized with respect to their patterns of RNA and protein accumulation at both the permissive and nonpermissive temperatures. Out of 116 such mutants, the majority (72) acted like wild type for these accumulations during a 3 h labelling period although some of them stopped dividing during this time. The remainder exhibited a variety of altered phenotypes for the rate, extent, and timing of RNA and/or protein accumulation. Those mutants which exhibited selective inhibition of RNA accumulation, and were thus potential ribosomal RNA (rRNA) mutants, were further characterized by examining patterns of protein and RNA synthesis in cells starved at the permissive temperature, but re-fed at the permissive and non-permissive temperatures. At least five different types of mutants as defined by patterns of protein and RNA synthesis in refed cells were identified. Direct analysis of the RNA synthesized in cells from 2 of these types of mutants showed that in 5 out of 6 cases rRNA synthesis and/or processing was inhibited within 30 min after shifting to the non-permissive temperature. The other mutant examined was found to show a delayed inhibition of rRNA synthesis.