Disease relevance of Hsp27

• During development, each of the four members of the small heat shock protein family (Hsp27, Hsp26 Hsp23 and Hsp22), which are coordinately induced in response to a heat stress, shows a specific pattern of expression in diverse tissues and cells [1].
• The most prominent site maps 100 base-pairs upstream of hsp26 in a very pyrimidine-rich region adjacent to a known region of chromatin DNAase I hypersensitivity [2].
• In the central nervous system, hsp23 and hsp26 were present in the neurocytes of the brain and the thoracic ganglion [3].
• In addition, expression of Hsp27 seems to be a negative prognostic factor for gastric cancer [4].
• In patients with cervical cancer, Hsp27 is predominantly expressed in well-differentiated and moderately differentiated squamous cell carcinomas [4].

High impact information on Hsp27

• Several of the tissue-specific mutations have also been shown to induce an hsp26-Adh fusion gene in trans [5].
• We conclude that most, or all, of the cis-acting regulatory sequences required for hsp26 gene expression during oogenesis are physically separable from those required for heat-inducible expression [6].
• We have constructed and transformed into the D. melanogaster germ line a series of hsp26 deletion variants [6].
• The accumulation in normal oogenesis of mRNAs for only three of the seven heat shock proteins indicates the existence of differential, possibly multiple controls of heat shock gene expression, and suggests that heat shock proteins hsp83, hsp28 and hsp26 function in the oocyte or early embryo [7].
• During normal development in D. melanogaster, messenger RNAs for three of the seven heat shock proteins (hsp83, hsp28 and hsp26) accumulate in adult ovaries and are abundant in embryos until blastoderm [7].

Chemical compound and disease context of Hsp27

• In endometrial carcinomas, the presence of Hsp27 is correlated with the degree of tumor differentiation as well as with the presence of estrogen and progesterone receptors [4].
• A synthetic, 23-bp ecdysterone regulatory element (EcRE), derived from the upstream region of the Drosophila melanogaster hsp27 gene, was inserted adjacent to the herpes simplex virus thymidine kinase promoter fused to a bacterial gene for chloramphenicol acetyltransferase (CAT) [8].

Biological context of Hsp27

• 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 [9].
• The developmental and heat-shock-induced expression of two small heat-shock proteins (Hsp23 and Hsp27) was investigated during spermatogenesis in Drosophila melanogaster [9].
• Hsp27 is expressed throughout oogenesis, but its intracellular localization is stage-specific, being nuclear from germarium to stage 6 and cytoplasmic from stage 8 onwards [1].
• The other site is located approximately 800 base-pairs upstream of hsp28 in an area devoid of such chromatin-specific features [2].
• By testing a series of 5' deletion mutants in hsp22/HSV-tk, a homologous sequence located adjacent to the TATA box in both the hsp22 and hsp26 genes was identified as being responsible for their heat-shock activation [10].

Anatomical context of Hsp27

• Hsp27 was expressed in some somatic cells (cyst cells and epithelial cells of the accessory glands) and, in addition, was also visible in the maturing spermatocytes of the germline [9].
• In response to heat stress, Hsp27 is expressed in all cells of the ommatidium including the cone, pigment and photoreceptor cells [11].
• The transcriptional regulation of the Drosophila melanogaster hsp27 (also called hsp28) gene was studied by introducing altered genes into the germ line by P element-mediated transformation [12].
• In contrast, the maximum expression of hsp26 was seen in gonads of young flies, and it was only lightly detected in the brain [3].
• On the other hand, hsp26 was essentially detected in ovaries and testes of these young flies [3].

Associations of Hsp27 with chemical compounds

• We have determined the DNA sequence of the intergenic region separating hsp23 and hsp27 and have located putative heat shock and ecdysterone consensus sequences [12].
• 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 [13].
• Unlike the glucocorticoid-response element and the estrogen-response element, the base pairs placed at positions -3, -4 and +1, +3, +4 of the hsp27 EcRE palindrome can be mutated without effect on the EcR binding [14].
• The second step involved the use of a magnetic DNA affinity technique where the double stranded hsp 27 oligonucleotide containing EcdR binding sequence was biotin 5'-end labelled and bound to monodisperse superparamagnetic particles coated with streptavidin (Dynabeads M-280 Streptavidin) giving magnetic DNA affinity beads [15].
• The ecdysone-responsive DNA sequence of the Drosophila hsp27 gene promoter contains four direct and inverted repeats reminiscent of those that compose the vertebrate palindromic estrogen response element (ERE) and the thyroid hormone/retinoic acid response element (TRE/RRE) [16].

Physical interactions of Hsp27

• Competition experiments indicated that the affinity of the Ddc EcRE for the ecdysone receptor complex was at least four-fold less than that of the canonical EcRE of the hsp27 gene [17].
• CucB also prevents the formation of the Drosophila ecdysteroid receptor/Ultraspiracle/20E complex with the hsp27 ecdysteroid response element as demonstrated by gel-shift assay [18].

Other interactions of Hsp27

• Further, two-hybrid system analysis reveals DmUbc9 interaction with Drosophila and mammalian Hsp27 [19].
• We have investigated interaction of EcR and Usp DNA-binding domains (EcRDBD and UspDBD, respectively) with the palindromic response element from the hsp27 gene promoter (hsp27pal) [20].
• Electrophoretic mobility shift assays indicated that CcEcR binds specifically to the Drosophila hsp27 ecdysone response element as a heterodimer with Drosophila USP, the product of the ultraspiracle gene [21].
• DHR96 is also 20E-inducible, and its encoded protein binds selectively to the hsp27 20E response element [22].
• Genes for small heat shock proteins (hsp27 to hsp22) are activated in late third-instar larvae of Drosophila melanogaster in the absence of heat stress [23].

Analytical, diagnostic and therapeutic context of Hsp27

• A gel-filtration assay has been developed with which the specific interaction between Drosophila melanogaster ecdysteroid receptor and the 20-hydroxy-ecdysone responsive element of the hsp27 gene promoter region was characterized in terms of complex formation, saturation of DNA binding and the apparent molecular mass of the complex [24].
• While silencing does decrease the accessibility of some restriction enzyme sites to some extent, it does not prevent the binding of TBP, RNA polymerase, or the heat shock factor to the hsp26 promoter, as shown by chromatin immunoprecipitation [25].
• Under all these conditions, hsp27 appears to be concentrated in the nuclear region as revealed by immunofluorescence [26].
• The developmental and heat shock-induced expression of the small heat shock protein Hsp27 was investigated by confocal microscopy of whole-mount immunostained preparations of ovarioles during oogenesis in Drosophila melanogaster [27].
• Southern blot analyses showed that the heterochromatic hsp26 transgenes are underrepresented 1.3- to 33-fold in polytene tissue relative to the endogenous euchromatic hsp26 gene [28].

References