Specific protection from phenocopy induction by heat shock

Abstract

Mild heat treatments applied to whole animals or cell cultures of Drosophila prior to lethal heat shocks result in increased survival and protection against phenocopy induction. The optimal condition for the preliminary mild heat treatment is that which induces the synthesis of heat-shock proteins but does not turn off the protein synthesis that is in progress. Recovery of protein synthesis but not RNA synthesis following a drastic heat shock is much enhanced by the pretreatments. The results suggest that the protection for survival and against phenocopy induction is due to storage of messenger RNA.Key words: drosophila, gene regulation, heat shock, protection phenocopies, survival I NTROD UCTl ON We recently described [ I ] a series of phenocopies that are induced in Drosophila melanogaster by subjecting pupa to heat shock at specific stages of development. Three of the phenocopies produced by shocks at successive intervals closely resemble the mutants hook and javelin which are involved in determining the structure of the scutellar bristles of the adult fly. We have also shown that the conditions used for phenocopy induction, turn off, for a time, both transciptional and translational activities in Drosophila tissues [ 1 , 2 ] . Subsequently, translation resumes long before reactivation of transcription [ l ] . These findings show that heat shock can result in storage of mRNAs in keeping with the observations of McKenzie et a1 [ 131 and Mirault et a1 [14] . Furthermore these observations provide a reasonable basis for interpretation of the heat-shock protection phenomenon described by Milkman several years ago [3,4] . Milkman and collaborators demonstrated that when Drosophila pupa (24 hours) were subjected to a mild heat shock prior to one that would be lethal alone, some animals would survive. They also reported that a pretreatment of this kind would prevent the induction of a phenocopy of the mutant crossveinless.

Expression and localization of Drosophila melanogaster hsp70 cognate proteins.

“…The mechanism of induction common to these inducers and the functions of the hsps are unknown. There is good evidence that the stress response is an adaptive mechanism that enables cells to survive a variety of environmental conditions that would otherwise be lethal (2,17,34,36,38).It is clear that the D. melanogaster heat shock genes are not coordinately expressed during normal development. hsp83 is probably present in all normal cells, and its induction after heat shock results in only a few fold increase in protein (33,40,76).…”

“…The mechanism of induction common to these inducers and the functions of the hsps are unknown. There is good evidence that the stress response is an adaptive mechanism that enables cells to survive a variety of environmental conditions that would otherwise be lethal (2,17,34,36,38).…”

Induced thermal tolerance and heat shock protein synthesis in Chinese hamster ovary cells

“…It has been suggested that hsp may perform a function which is essential to cell survival following certain kinds of stress (Loomis & Wheeler, 1980;Ashburner & Bonner, 1979;Guttman et al, 1980). Synthesis of hsp has been associated with acquisition of transient, heat-induced heat resistance in Drosophila and yeast (Mitchell et al, 1979;McAlister & Finkelstein, 1980). We have performed experiments to determine the kinetics of induction of thermal tolerance in Chinese hamster HA-1 cells, and the effects of heat treatments on the recovery of protein synthesis, with particular attention to whether or not "heat shock" induces specific proteins.…”

“…,uCi/ml 35S-methionine and labelled for 1 h. Cells were pelleted, rinsed in ethanol. dissolved in sample buffer and run on 7-20% acrylamide gels as described previously (Tissieres et al, 1974 here and the kinetics of recovery of protein synthesis in Drosophila are intriguing (Mitchell et al, 1979;Peterson & Mitchell, 1981 (Henle & Leeper, 1979). However, since one does not know the function of hsp, it is also possible that the effects of heat shock on RNA and protein synthesis may be simply reflecting the "state" of the cell after heating.…”

Starved Tetrahymena thermophila cells that are unable to mount an effective heat shock response selectively degrade their rRNA.

“…This thermoprotection (probably not analagous to acquired thermotolerance [18,20,22]) required a full hour of prior heat shock to manifest itself fully (Table 2). Moreover, this protection was transient.…”