The articles below (they are abstracts the complete articles are available online) seem to indicate that it's the opposite... where the hell did I read this?
MD?
http://www.jcb.org/cgi/content/abstract/109/4/1467Protein synthesis and protein phosphorylation during heat stress, recovery, and adaptation
RF Duncan and JW Hershey
Department of Biological Chemistry, University of California School of Medicine, Davis 95616.
Incubating cells at elevated temperatures causes an inhibition of protein synthesis. Mild heat stress at 41-42 degrees C inhibits the fraction of active, polysomal ribosomes from greater than 60% (preheating) to less than 30%. A return to 37 degrees C leads to an increase in protein synthesis, termed "recovery." Continuous incubation at 41-42 degrees C also leads to a gradual restoration of protein synthesis (greater than 70% of ribosomes reactivated by 2-4 h), termed "adaptation". Protein synthesis inhibition and reactivation is prestressed, recovered cells that contain elevated levels of the heat stress proteins occur to the same extent and at the same rate as in "naive" cells. The adaptation response requires transcription of new RNA whereas recovery does not. A large number of phosphorylation changes are induced by severe heat stress and occur with kinetics similar to the inhibition of protein synthesis. These include phosphorylation of eukaryotic protein synthesis initiation factor (eIF)- 2 alpha and dephosphorylation of eIF-4B and eIF-4Fp25 (eIF-4E). However, the extent to which the modification occurs is proportional to the severity of the stress, and, under mild (41-42 degrees C) heat stress conditions, these initiation factor phosphorylation changes do not occur. Similarly, under conditions of severe heat stress eIF-2 alpha and eIF-4B frequently recover to their prestress phosphorylation state before the recovery of protein synthesis. eIF-4E dephosphorylation likewise does not occur under mild heat stress conditions. Therefore, these changes in phosphorylation states, which are thought to be sufficient cause, are not necessary for the inhibition of protein synthesis observed.
http://www3.interscience.wiley.com/cgi-bin/abstract/109903799/ABSTRACT?CRETRY=1&SRETRY=0 Article
Effect of continuous heat stress on cell growth and protein synthesis in Aedes albopictus
Maria da Gloria da Costa Carvalho *, Marcia Soares Freitas
Laboratório de Virologia Molecular, Departamento de Biofísica Molecular, Instituto de Biofísica Carlos Chagas Filho, U.F.R.J. Centro de Ciências de Saúde, 21 941, Rio de Janeiro, R. J. Brazil
*Correspondence to Maria da Gloria da Costa Carvalho, Laboratório de Virologia Molecular, Departamento de Biofísica Molecular, Instituto de Biofísica Carlos Chagas Filho, U.F.R.J. Centro de Ciências de Saúde, 21 941, Rio de Janeiro, R. J. Brazil
Abstract
Aedes albopictus (clone C6/36) cells, which normally grow at 28°C, were maintained at a supraoptimal temperature of 37°C. The effect of continuous heat stress (37°C) on cell growth was analyzed as were the modifications occurring with protein synthesis during short- and long-term heat stress. We observed that cells in lag or exponential growth phase, present inhibition of cell growth, and cells in the lag phase showed more sensitivity to death than cells growing exponentially. During the first hour of exposing the cells to 37°C, they synthesized two heat shock proteins (hsps) of 82 kd and 70 kd, respectively, concomitant with inhibition of normally produced proteins at control temperature (28°C). However, for incubations longer than 2 hr at 37°C, a shift to the normal pattern of protein synthesis occurred. During these transitions, two other hsps of 76 kd and 90 kd were synthesized. Pulse chase experiments showed that the 70-kd hsp is stable at least for 18 hr, when the cells are returned to 28°C. However, if cells were incubated at 37°C, the 70-kd hsp is stable for at least 48 hr. The 70-kd hsp was localized in the cytoplasmic and in the nuclear compartment. OUr results indicate a possible role of hsp 70-kd protein in the regulation of cell proliferation.
