The heat shock consensus sequence is not sufficient for hsp70 gene expression in Drosophila melanogaster.

A hybrid gene in which the expression of an Escherichia coli beta-galactosidase gene was placed under the control of a Drosophila melanogaster 70,000-dalton heat shock protein (hsp70) gene promoter was constructed. Mutant derivatives of this hybrid gene which contained promoter sequences of different lengths were prepared, and their heat-induced expression was examined in D. melanogaster and COS-1 (African green monkey kidney) cells. Mutants with 5' nontranscribed sequences of at least 90 and up to 1,140 base pairs were expressed strongly in both cell types. Mutants with shorter 5' extensions (of at least 63 base pairs) were transcribed and translated efficiently in COS-1 but not at all in D. melanogaster cells. Thus, in contrast to the situation in COS-1 cells, the previously defined heat shock consensus sequence which is located between nucleotides 62 and 48 of the hsp70 gene 5' nontranscribed DNA segment is not sufficient for the expression of the D. melanogaster gene in homologous cells. A second consensus-like element 69 to 85 nucleotides upstream from the cap site is postulated to be also involved in the heat-induced expression of the hsp70 gene in D. melanogaster cells.     

Heat shock and developmental regulation of the Drosophila melanogaster hsp83 gene.

In contrast to the hsp70 gene, whose expression is normally at a very low level and increases by more than 2 orders of magnitude during heat shock, the hsp83 gene in Drosophila melanogaster is expressed at high levels during normal development and increases only severalfold in response to heat shock. Developmental expression of the hsp83 gene consists of a high level of tissue-general, basal expression and a very high level of expression in ovaries. We identified regions upstream of the hsp83 gene that were required for its developmental and heat shock-induced expression by assaying beta-galactosidase activity and mRNA levels in transgenic animals containing a series of 5' deletion and insertion mutations of an hsp83-lacZ fusion gene. Deletion of sequences upstream of the overlapping array of a previously defined heat shock consensus (HSC) sequence eliminated both forms of developmental expression of the hsp83 gene. As a result, the hsp83 gene with this deletion mutation was regulated like that of the hsp70 gene. Moreover, an in vivo polymer competition assay revealed that the overlapping HSC sequences of the hsp83 gene and the nonoverlapping HSC sequences of the hsp70 gene had similar affinities for the factor required for heat induction of the two heat shock genes. We discuss the functional similarity of hsp70 and hsp83 heat shock regulation in terms of a revised view of the heat shock-regulatory sequence.     

Ecdysteroid-regulated heat-shock gene expression during Drosophila melanogaster development

Peaks in hsp 26, 28, and 83 RNA levels are correlated with peaks in ecdysteroid titers during mid-embryogenesis, pupariation, and mid-pupation, and with a peak in the level of RNA from the 74EF ecdysone puff at pupariation. Inhibition of the ecdysteroid peak at pupariation by temperature shift of the conditionally ecdysteroid-deficient strain ecd-1 was followed by a disappearance of hsp 26 RNA and a decline in hsp 83 RNA level; subsequent addition of exogeneous 20-OH-ecdysone to the temperature-shifted strain resulted in a severalfold increase in hsp 83 RNA level, and a dramatic increase in that of hsp 26. These results are consistent with the induction of the hsp 83, 28, and 26 genes by ecdysteroid at several developmental stages.     

Effect of heat shock,pretreatment and hsp70 copy number on wing development in Drosophila melanogaster

Naturally occurring heat shock (HS) during pupation induces abnormal wing development in Drosophila; we examined factors affecting the severity of this induction. The proportion of HS-surviving adults with abnormal wings varied with HS duration and intensity, and with the pupal age or stage at HS administration. Pretreatment (PT), mild hyperthermia delivered before HS, usually protected development against HS. Gradual heating resembling natural thermal regimes also protected wing development against thermal disruption. Because of the roles of the wings in flight and courtship and in view of natural thermal regimes that Drosophila experience, both HS-induction of wing abnormalities and its abatement by PT may have marked effects on Drosophila fitness in nature. Because PT is associated with expression of heat-inducible molecular chaperones such as Hsp70 in Drosophila, we compared thermal disruption of wing development among hsp70 mutants as well as among strains naturally varying in Hsp70 levels. Contrary to expectations, lines or strains with increased Hsp70 levels were no more resistant to HS-disruption of wing development than counterparts with lower Hsp70 levels. In fact, wing development was more resistant to HS in hsp70 deletion strains than control strains. We suggest that, while high Hsp70 levels may aid cells in surviving hyperthermia, high levels may also overly stimulate or inhibit numerous signalling pathways involved in cell proliferation, maturation and programmed death, resulting in developmental failure.     

Trichostatin A extends the lifespan of Drosophila melanogaster by elevating hsp22 expression

Aging can be defined as time-dependent, gradual anddetrimental changes in the structure and physiologicalfunction of an organism, ultimately leading to death [1].Factors influencing the aging process would change thelongevity. In Drosophila melanogaster, …     

The small heat shock protein Hsp22 of Drosophila melanogaster is a mitochondrial protein displaying oligomeric organization

Drosophila melanogaster has four main small heat shock proteins (Hsps), D. melanogaster Hsp22 (DmHsp22), Hsp23 (DmHsp23), Hsp26 (DmHsp26), and Hsp27 (DmHsp27). These proteins, although they have high sequence homology, show distinct developmental expression patterns. The function(s) of each small heat shock protein is unknown. DmHsp22 is shown to localize in mitochondria both in D. melanogaster S2 cells and after heterologous expression in mammalian cells. Fractionation of mitochondria indicates that DmHsp22 resides in the mitochondrial matrix, where it is found in oligomeric complexes, as shown by sedimentation and gel filtration analysis and by cross-linking experiments. Deletion analysis using a DmHsp22-EGFP construct reveals that residues 1-17 and an unknown number of residues between 17-28 are necessary for import. Site-directed mutagenesis within a putative mitochondrial motif (WRMAEE) at positions 8-13 shows that the first four residues are necessary for mitochondrial localization. Immunoprecipitation results indicate that there is no interaction between DmHsp22 and the other small heat shock proteins. The mitochondrial localization of this small Hsp22 of Drosophila and its high level of expression in aging suggests a role for this small heat shock protein in protection against oxidative stress.     

Profiling catalase gene expression in Drosophila melanogaster during development and aging

Catalase represents one of the key antioxidant enzymes (AOE) in the metabolism of oxygen free radicals. A comprehensive analysis was brought to bear on establishing catalase gene expression profiles during development and aging, with the underlying objective being to identify potential regulatory factors. Expression of the catalase gene exhibits substantial variations during development and aging in a stage- and tissue-specific manner. At the temporal level, previous observations of the coincidence of ecdysteroid pulses with peaks in catalase expression during developmental stages were largely corroborated. In adults, a small but significant decline in catalase expression was noted in adults as a function of age. Spatially, it was ascertained that catalase expression is mostly confined to tissues related to intermediary metabolism, digestive and adipose systems as well as oenocytes. By combining histochemical analysis of reporter gene expression with immunostaining of the endogenous product, it was possible to identify putative positive and negative regulatory elements that control catalase expression. Finally, when adult flies were subjected to various environmental insults, such as heat, paraquat, hyperoxia and H(2)O(2), no significant responses were observed, suggesting that catalase gene expression is largely governed by intrinsic genetic programs.