Response to heat shock of gene 1, a Drosophila melanogaster small heat shock gene, is developmentally regulated

Abstract

The expression of gene 1, a member of the small heat shock gene family from the Drosophila melanogaster chromosomal locus 67B was studied. In contrast to the other heat shock genes, the response of gene 1 to stress was modulated during development. In the absence of stress, gene 1 was expressed at the beginning of pupation, and at a very low level in adult males. Expression of gene 1 was substantially increased by heat shock in pupae, but was one to two orders of magnitude lower in adults or in embryos. Under the same conditions, hsp70 or hsp26 were induced to similar levels in all stages. This developmental effect could be mimicked in cultured Drosophila cells: expression of gene 1 was stimulated by heat shock in the presence, but not in the absence, of the moulting hormone ecdysterone, while the level of expression of hsp26 and hsp70 in response to heat shock was independent of the presence of the hormone. Thus, the presence and activity of the heat shock transcription factor are not sufficient for the maximal response of gene 1 to stress. These results suggest that the heat shock activator protein requires additional factors, which are developmentally regulated, to activate transcription of gene 1. Furthermore, S1 nuclease mapping analysis revealed several gene 1 mRNA species, which are generated by the use of alternative polyadenylation sites and by the use of differentially regulated transcriptional initiation sites.

Alternative polyadenylation and the stress response

“…The most prominent member of the HSP family, HSP70, is tightly regulated and has many protein isoforms encoded by separate gene loci which have distinct regulatory characteristics allowing them to help cells respond to various types of assaults (Daugaard et al, 2007;Tranter et al, 2011). Early studies on HSPs demonstrated that during heat shock various mRNAs encoding HSP proteins, including HSP70, were subject to APA (Lowe & Moran, 1986;Vazquez, 1991). Despite being overlooked for decades, a number of recent studies have begun to investigate the role of APA in regulating HSP70 expression (Kraynik et al, 2015;Tranter et al, 2011).…”

Lipoproteins and heat shock proteins as measures of reproductive physiology in the soft shell clam, Mya arenaria

“…One family of heat shock proteins, the low molecular weight hsps, are known to be developmentally regulated, at least in part through the action of hormones Vazquez, 1991;Billoud et al, 1993;de Jong et al, 1993). The induction of hsps is uncoupled during development, in contrast to the coordinate induction during heat shock .…”