The heat shock response in Tetrahymena thermophila: control of protein synthesis

Abstract

Tetrahymena thermophila cells that had been shifted from log growth to a non-nutrient medium (60mM Tris) were unable, during the first few hours of starvation, to mount a successful heat shock response and were killed by what should normally have been a non—lethal heat shock. An examination of the protein synthetic response of these short-starved cells during heat shock revealed that whereas they were able to initiate the synthesis of heat shock proteins, it was at a much reduced rate relative to controls and they quickly lost all capacity to synthesize any proteins. Certain pretreatments of cells, including a prior heat shock, abolished the heat shock inviability of these starved cells. Also, if cells were transferred to 10 mM Tris rather than 60 mM Tris, they were not killed by the same heat treatment. We found no abnormalities in either heat shock or non-heat shock mRNA metabolism in starved cells unable to survive a sublethal heat shock when compared with the response of those cells which can survive such a treatment. However, selective rRNA degradation occurred in the non-surviving cells during the heat shock and this presumably accounted for their inviability. A