Hydrogen peroxide activates immediate binding of a Drosophila factor to DNA heat‐shock regulatory element in vivo and in vitro

Abstract

The synthesis of heat-shock proteins via activation of heat-shock genes occurs in response to heat and various physical or chemical stressing agents. Transcriptional activation of heat-shock genes requires a heat-shock regulatory element in their promoter, to which a heat-shock specific transcription factor binds. In Drosophilu cells, the heat-shock factor already exists in unstressed cells in an inactive form and acquires the capacity to bind to the heat-shock element following stress. The mechanism of this activation is not known ; neither is it known whether the different stressing agents induce the heat-shock response through a common mechanism. We previously proposed that many agents known to induce the heat-shock response (substances interfering with respiratory metabolism, agents reacting with sulphydryl groups, metals, recovery from anaerobiosis and ischemia) might act via accumulation of reactive oxygen species, i.e. superoxide ion or H202. We show here that H202, introduced either in Drosophilu cell cultures or in cell extracts, was able to activate heat-shock-element binding. Activation was rapid and H 2 0 2 concentration dependent, with a threshold of 1 pM. These results were confirmed with mouse fibroblast cells. This very rapid activation, in vivo or in vitro, suggests a direct effect of H 2 0 2 either on the heatshock factor itself or on its activator.The synthesis of heat-shock or more generally termed stress proteins in response to elevation of temperature or to a large variety of physical and chemical stressing agents seems to be common to all living organisms, from bacteria to man [l -41. A puzzling question is the mechanism by which the numerous stressing agents lead to the transcriptional activation of the same set of heat-shock genes and to what extent they might act through a common pathway.We previously proposed a hypothesis based on the following observation : reoxygenation after a period of anoxia without elevation of temperature, is sufficient to induce the heatshock proteins in Drosophila Kc cells [5] and other biological systems [6 -lo]. At the time of reoxygenation, O2 consumption is increased twofold over the control [5]. It is known that this situation, deprivation of oxygen followed by an excess, generates byproducts of the partial reduction of oxygen, i.e. free radicals or reactive oxygen species [l 11, among which two have been particularly studied, the superoxide ion (0;) and H 2 0 2 . These reactive oxygen species are involved in many diseases, in the inflammation process, and in carcinogenesis [12-141. We hypothesized that the reactive oxygen species might also be involved in the mechanism of induction of heatshock proteins [5]. Indeed, heat-shock is accompanied by an elevation of O2 consumption [5, 101 and many factors which induce the heat-shock protein response could act via accumulation of reactive oxygen species or more generally via modification of the redox equilibrium of the cell [I, 3, 15, 161. This is the case, for example, for substances interfering with the [19]...

The deubiquitinase ataxin-3 requires Rad23 and DnaJ-1 for its neuroprotective role in Drosophila melanogaster

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Larval regulation of adult longevity in a genetically-selected long-lived strain of Drosophila

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Hydrogen peroxide- and glutathione-associated mechanisms of acclimatory stress tolerance and signalling

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