S. Brandau et al., HIGH CONSTITUTIVE LEVELS OF HEAT-SHOCK PROTEINS IN HUMAN-PATHOGENIC PARASITES OF THE GENUS LEISHMANIA, Biochemical journal, 310, 1995, pp. 225-232
We have analysed the transcription of three heat-shock genes, HSP70, H
SP83 and ClpB, in the protozoan parasite Leishmania. All three heat-sh
ock genes are transcribed constitutively and not heat-inducibly. Howev
er, we find that two major heat-shock proteins, HSP70 and HSP83, are s
ynthesized at elevated rates during heat stress. We conclude that the
cellular stress response in Leishmaniae is regulated exclusively on a
post-transcriptional level much in contrast with all other eukaryotes
examined so far. The induced synthesis of HSP70 and HSP83, however, do
es not increase the steady-state level of either protein significantly
. This is compensated by high constitutive levels of both proteins: HS
P70 and HSP83, however, does not increase the steady-state level of ei
ther protein significantly. This is compensated by high constitutive l
evels of both proteins: HSP70 and HSP83 make up 2.1% and 2.8%, respect
ively, of the total protein in unstressed Leishmania promastigotes. Al
so, HSP70 is a strictly cytoplasmic protein in Leishmania and does not
relocate into the nucleus during heat stress, as it does in other euk
aryotes examined in the past.