Physiological aspects of Trypanosoma cruzi gene regulation during heat-shock.

Investigations on the conditions of heat-shock response in Trypanosoma cruzi, the agent of Chagas disease, showed that at 37 degrees C, one of the heat-shock temperatures employed, the parasites from 48 h culture do not display a classical response to the heat treatment, since a general increase in RNA and protein synthesis was detected. The classical heat-shock response was detected only at 40 degrees C. The data also suggest that the heat shock proteins (HSP) mRNA population is sufficient to maintain protein synthesis at a high rate for at least 1 h and, to maintain the same rate of response for a longer period, transcription is necessary. The half life of HSP 70 mRNA is less than 3 h at 37 degrees C. The protein synthesized during the first hour of the heat shock at 37 degrees C is stable for at least 24 h. The parasite seems to be able to reuse the stock of HSP mRNAs stored during the first thermal shock to respond to a second heat treatment. These data are discussed bearing in mind other cell types.