Disease relevance of Hsp23

• Hsp23 was found to be expressed in the brain, thoracic ganglion, fat body and gonads of young (0-12 h) males and females [1].

High impact information on Hsp23

• We have used the P-element-mediated transformation of Drosophila germ line to study the 5' DNA sequences involved in the thermal inducibility of the genes for heat shock proteins hsp23 and 26 [2].
• For hsp23, each successive shortening of the promoter region from 618 to 402, 321 and 263 bp clearly decreased the expression [2].
• Several hundred base pairs upstream of Drosophila hsp23 and 26 genes are required for their heat induction in transformed flies [2].
• The regulation of the Drosophila melanogaster hsp23 gene by heat shock and ecdysterone has been analysed by measuring activities of hsp--Escherichia coli beta-galactosidase hybrid genes in transfected hormone-sensitive D. melanogaster cells [3].
• A sequence element, which also occurs in the promoters of several other developmentally regulated Drosophila genes, is present in regions of the hsp23 promoter that are essential for its ecdysterone, but not its heat-regulated activity; this element may represent a binding site for an ecdysterone--receptor complex [3].

Biological context of Hsp23

• The same cell-specific pattern of expression was observed after heat shock, and cells which did not express Hsp23 and Hsp27 in the absence of stress were similarly unable to mount a heat shock response for these s-Hsps [4].
• The developmental and heat-shock-induced expression of two small heat-shock proteins (Hsp23 and Hsp27) was investigated during spermatogenesis in Drosophila melanogaster [4].
• In germ line tissues such as testes, Hsp23 and 27 are both readily expressed in the absence of stress (albeit in distinct cell lineages) and cannot be further induced by heat shock [5].
• We have determined the DNA sequence of the intergenic region separating hsp23 and hsp27 and have located putative heat shock and ecdysterone consensus sequences [6].
• Drosophila melanogaster is polymorphic for a specific repeated (CATA) sequence in the regulatory region of hsp23 [7].

Anatomical context of Hsp23

• Immunostaining of whole-mount organs and thin sections of testes showed that an anti-Hsp23 antibody specifically decorated cells of the somatic lineage, such as the cyst cells and the epithelial cells of the testis and of the seminal vesicle [4].
• In the central nervous system, hsp23 and hsp26 were present in the neurocytes of the brain and the thoracic ganglion [1].
• In addition, hsp23 (but not hsp26) was also detected in the central neuropile of these two organs [1].
• Induction of the other hs gene RNAs was </=3-fold, except for hsp23, which was induced approximately 5-fold in thorax. hsp22 protein was detected using rat anti-hsp22 polyclonal antisera and was induced >150-fold, with particularly abundant expression in eye tissue [8].
• The expression of Drosophila melanogaster hsp23-Escherichia coli beta-galactosidase hybrid genes containing different segments of the 5' non-transcribed sequence of the hsp23 gene has been examined at the RNA and protein levels in Xenopus oocytes [9].

Associations of Hsp23 with chemical compounds

• Hybridization of a nick-translated genomic clone containing the hsp23 gene to a total RNA blot showed that ecdysterone stimulation of hsp23 synthesis was the result of an increase in the hsp23 RNA content of S3 cells [10].
• Poly(A) removal is highly regulated: poly(A) is (i) removed much more rapidly from Hsp70 RNAs than from Hsp23 RNAs, (ii) removed more rapidly after mild heat shocks than after severe heat shocks, and (iii) removed more rapidly after a severe heat shock if cells have first been conditioned by a mild heat treatment [11].
• Purified receptor binds specifically to several sequences in the promoters of the developmentally active hsp27 and hsp23 heat shock genes that were previously implied in ecdysterone regulation of the genes and that share limited homology among themselves and with mammalian steroid receptor binding sites [12].
• Although the four small hsps show considerable sequence homology in their coding sequences, antisense hsp 23 RNA was shown to specifically inhibit hsp 23 mRNA translation under both high (formamide, 45 degrees C) and low stringency (37 degrees C) conditions [13].

Regulatory relationships of Hsp23

• Thus, BR-C regulates hsp23 expression via direct interaction of the predominant isoform with the distal regulatory element [14].

Other interactions of Hsp23

• Here, we investigated the transcriptional regulation of other heat-shock-responsive genes (Hsp23, Hsp26, Hsp83 and Hsrw) in D. triauraria with relation to diapause [15].
• The cell-specific induction of Hsp23 under stress conditions does not seem to be regulated by the Drosophila melanogaster heat shock transcriptional factor (DmHSF) [16].
• The inhibition was highly specific: expression of the closely related heat shock proteins hsp22, hsp23, and hsp28 was unaffected [17].
• The induced proteins appear to be identical to three of the heat shock proteins (hsp 23, 22a, and 22b), as shown by electrophoretic mobilities and peptide mapping by partial proteolysis [18].
• The deletion of binding site 5 in a reporter gene construct reproduced the effect of the npr class mutations, that is, hsp23 is no longer expressed in any tissue tested except brain [14].

Analytical, diagnostic and therapeutic context of Hsp23

• Thus the immunofluorescence observations reported here unambiguously confirm for hsp 23 earlier reports that heat shock proteins are mainly found in nuclei after heat shock and that upon return to 25 degrees C, they move to the cytoplasm [19].

References