Steroid and high-temperature induction of the small heat-shock protein genes in Drosophila

Hsp70 and small Hsps are the major heat shock protein members involved in midgut metamorphosis in the common cutworm, Spodoptera litura

Heat shock proteins (Hsps) are important chaperones, which are involved in various signal pathways and regulate lots of physiological processes. Early research suggested that some Hsps are involved in insect development. However, few studies have been carried out to explore the roles of Hsps, especially in larval-pupal metamorphosis. In the present study, 49 Hsp unigenes were identified in the Spodoptera litura transcriptome and their mRNA expression profiles during midgut metamorphosis were examined using a tag-based digital gene expression system. The genes with the most different levels of expression were then cloned and their expression patterns in midguts from sixth instar larvae to pupae were analysed using real time quantitative PCR. The responses of these genes to juvenile hormone (JH) and 20-hydroxyecdysone (20E) were also studied. The results showed that the mRNA levels of 22 Hsp unigenes changed significantly during midgut metamorphosis. Amongst these 22 unigenes, hsp70, hsp20.4 and hsp20.8 were the most up-regulated members, and hsp15.9, hsp19.3 and hsp22.0 were the most down-regulated ones. Further studies showed that hsp70, hsp20.4 and hsp20.8 were remarkably up-regulated by JH. In addition, 20E slightly increased the mRNA levels of both hsp20.4 and hsp20.8. However, hsp15.9, hsp19.3 and hsp22.0 did not respond to either JH or 20E. These results indicate that Hsp70 and small Hsps (sHsps) are probably the major players in midgut metamorphosis in S. litura. The current findings provide valuable insights into the roles of the Hsp superfamily in insect metamorphosis.

Two hsp23 genes in the Mediterranean fruit fly, Ceratitis capitata: structural characterization, heat shock regulation and developmental expression

In the present study, we characterized a 3320-bp genomic DNA fragment encoding two medfly (Ceratitis capitata) homologues of the Drosophila melanogaster heat shock protein 23 (hsp23) gene, named Cchsp23-alphaand -beta. The two medfly hsp23 genes are transcribed in opposite directions and encode two almost identical proteins. Furthermore, the two genes exhibit a very high degree of similarity in their 5' untranslated and proximal promoter regions. Phylogenetic analysis indicated that the CcHsp23 proteins are orthologous to Drosophila Hsp23 and Sarcophaga crassipalpis Hsp23. Structural analysis of the 5' flanking regions of the Cchsp23 genes revealed the presence of several putative heat shock elements. Both CcHsp23 genes are induced by heat in a similar manner. In addition to heat-induction, the Cchsp23 genes are expressed at several stages of normal development as well as in ovaries and testes. In general, the developmental expression patterns of the medfly genes are similar, suggesting that they are under similar regulatory mechanisms. However, the expression of the Cchsp23 genes differs significantly from the expression of the Drosophila hsp23 gene in certain embryonic and larval stages, suggesting differential regulation of the hsp23 genes in the two dipteran species. The expression of both Cchsp23 genes in adult flies is increased with age, especially in males.

The hsp27 gene of the Mediterranean fruit fly, Ceratitis capitata: structural characterization, regulation and developmental expression

In the present study, a genomic DNA clone encoding the medfly homolog of Drosophila melanogaster hsp27 gene, named Cchsp27, was isolated. We sequenced a part of the clone containing the coding region, the 5' untranslated region and approximately 2.8 Kb of the 5' flanking region of the gene. Phylogenetic analysis of several insect small heat shock proteins, suggested that CcHsp27 is orthologous to Drosophila Hsp27 and Sarcophaga crassipalpis Hsp25. The Cchsp27 gene was mapped at the 81A division of the sixth chromosome which coincides with one of the major heat shock puffs of medfly. Structural analysis of the 5' flanking region of the Cchsp27 gene revealed the presence of five putative heat shock elements and one putative ecdysone response element. In addition to heat induction, the Cchsp27 gene was expressed at several stages of normal medfly development. In general, the developmental expression pattern of the Cchsp27 gene was similar to the respective pattern of Drosophila hsp27 gene. However, there were some important differences in certain developmental stages suggesting differential regulation of the hsp27 gene in the two dipterans species. Salivary gland culture experiments showed that the Cchsp27 gene is regulated by 20-hydroxyecdysone.

Temporal regulation of microRNA expression in Drosophila melanogaster mediated by hormonal signals and broad-Complex gene activity

lin-4 and let-7 are founding members of an extensive family of genes that produce small transcripts, termed microRNAs (miRNAs). In Caenorhabditis elegans, lin-4 and let-7 control the timing of postembryonic events by translational repression of target genes, permitting progression from early to late developmental programs. To identify Drosophila melanogaster miRNAs that could play similar roles in the control of developmental timing, we characterized the developmental expression profile of 24 miRNAs in Drosophila, and found 7 miRNAs that are either upregulated or downregulated in conjunction with metamorphosis. The upregulation of three of these miRNAs (mir-100, mir-125, and let-7), and the downregulation of a fourth (mir-34) requires the hormone ecdysone (Ecd) and the activity of the Ecd-inducible gene Broad-Complex. Interestingly, mir-125 is a putative homologue of lin-4. mir-100, -125, and let-7 are clustered within an 800-bp region on chromosome 2L, suggesting that these three miRNAs may be coordinately regulated via common cis-acting elements during metamorphosis. In S2 cells, Ecd and the juvenile hormone analog methoprene exert opposite effects on the expression of these four miRNAs, indicating the participation of both these hormones in the temporal regulation of mir-34, -100, -125, and let-7 expression in vivo.

The expression of the let-7 small regulatory RNA is controlled by ecdysone during metamorphosis in Drosophila melanogaster

In Caenorhabditis elegans, the heterochronic pathway controls the timing of developmental events during the larval stages. A component of this pathway, the let-7 small regulatory RNA, is expressed at the late stages of development and promotes the transition from larval to adult (L/A) stages. The stage-specificity of let-7 expression, which is crucial for the proper timing of the worm L/A transition, is conserved in Drosophila melanogaster and other invertebrates. In Drosophila, pulses of the steroid hormone 20-hydroxyecdysone (ecdysone) control the timing of the transition from larval to pupal to adult stages. To test whether let-7 expression is regulated by ecdysone in Drosophila, we used Northern blot analysis to examine the effect of altered ecdysone levels on let-7 expression in mutant animals, organ cultures, and S2 cultured cells. Experiments were conducted to test the role of Broad-Complex (BR-C), an essential component in the ecdysone pathway, in let-7 expression. We show that ecdysone and BR-C are required for let-7 expression, indicating that the ecdysone pathway regulates the temporal expression of let-7 in Drosophila. These results demonstrate an interaction between steroid hormone signaling and the heterochronic pathway in insects.

Apolipoprotein E acts to increase nitric oxide production in macrophages by stimulating arginine transport

Previous studies have shown that apolipoprotein E (apoE) plays a role in immune function by modulating tissue redox balance. Using a mouse macrophage cell line (RAW 264.7), we have examined the mechanism by which apoE regulates nitric oxide (NO) production in macrophages. ApoE potentiates NO production in immune activated RAW cells in combination with lipopolysaccharide or polyinosinic:polycytidylic acid (PIC), agents known to induce expression of inducible nitric oxide synthase mRNA and protein. The effect is not observed with apolipoprotein B or heat-inactivated apoE. The combination of PIC plus apoE produced more NO than the level expected from an additive effect of PIC and apoE alone. Furthermore, this increase was observed at submaximal extracellular arginine concentrations, suggesting that apoE altered arginine (substrate) availability. Examination of [(3)H]arginine uptake across the cell membrane demonstrated that arginine uptake was increased by PIC but further increased by PIC plus apoE. Treatment of RAW cells with apoE was associated with an increased apparent V(max) and decreased affinity for arginine as well as a switch in the induction of mRNA for subtypes of cationic amino acid transporters (CAT). Treatment of RAW cells with PIC plus apoE resulted in the loss of detectable CAT1 mRNA and expression of CAT2 mRNA. Regulation of arginine availability is a novel action of apoE on the regulation of macrophage function and the immune response.

Effects of the overexpression of the small heat shock protein, HSP27, on the sensitivity of human fibroblast cells exposed to oxidative stress

The role of the human small heat shock protein (HSP27) in oxidative stress was examined using stable transformants of an immortalized human fibroblast cell line (KMST-6) isolated by transfection of HSP27 expression vectors. Several stable transformants that expressed high or low levels of HSP27 protein were obtained. Clones expressing high levels of HSP27 were more sensitive to growth inhibition by a low dose of hydrogen peroxide (0.1 mM) than those expressing low levels. Clones expressing high levels of HSP27 did not acquire obvious resistance to hyperthermy and cytotoxic agents, except for one (#13), in which resistance to cytotoxic agents was increased. The level of phosphorylated HSP27 in clones expressing high levels of this protein increased at 30 min and was sustained even 4 hours after exposing the cells to 0.1 mM of hydrogen peroxide. On the other hand, the levels in clones expressing low levels of HSP27 were reduced within 4 hours after exposure to hydrogen peroxide. Furthermore, overexpression of nonphosphorylatable mutant HSP27 did not affect sensitivity to oxidative stress. These results suggested that constitutively high expression of HSP27 in KMST-6 cells make them susceptible to oxidative stress resulting in growth arrest, and this mechanism could involve the phosphorylation of HSP27.

The juvenile hormone analogue, methoprene, inhibits ecdysterone induction of small heat shock protein gene expression

The small heat shock protein (hsp) genes of Drosophila are expressed in cultured cells in response to the moulting hormone, ecdysterone. We show here that juvenile hormone (JHIII) and the juvenile hormone analogue, methoprene, inhibit that induction in a dose-dependent manner. Heat shock induction is not inhibited. In transient expression studies using S3 line cells transfected with EcRE-CAT constructs, methoprene inhibition was found to require a 2-hr pretreatment (before ecdysterone addition), and methoprene's continued presence was essential. Farnesol, farnesyl acetate, and retinoic acid did not cause inhibition. Several models of methoprene inhibition are discussed.

Temporal and spatial expression patterns of the small heat shock (hsp16) genes in transgenic Caenorhabditis elegans

The expression of the hsp16 gene family in Caenorhabditis elegans has been examined by introducing hsp16-lacZ fusions into the nematode by transformation. Transcription of the hsp16-lacZ transgenes was totally heat-shock dependent and resulted in the rapid synthesis of detectable levels of beta-galactosidase. Although the two hsp16 gene pairs of C. elegans are highly similar within both their coding and noncoding sequences, quantitative and qualitative differences in the spatial pattern of expression between gene pairs were observed. The hsp16-48 promoter was shown to direct greater expression of beta-galactosidase in muscle and hypodermis, whereas the hsp16-41 promoter was more efficient in intestine and pharyngeal tissue. Transgenes that eliminated one promoter from a gene pair were expressed at reduced levels, particularly in postembryonic stages, suggesting that the heat shock elements in the intergenic region of an hsp16 gene pair may act cooperatively to achieve high levels of expression of both genes. Although the hsp16 gene pairs are never constitutively expressed, their heat inducibility is developmentally restricted; they are not heat inducible during gametogenesis or early embryogenesis. The hsp16 genes represent the first fully inducible system in C. elegans to be characterized in detail at the molecular level, and the promoters of these genes should find wide applicability in studies of tissue- and developmentally regulated genes in this experimental organism.

Genes for Drosophila small heat shock proteins are regulated differently by ecdysterone

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. This regulation has been simulated in cultured Drosophila cells in which the genes are activated by the addition of ecdysterone. Sequence elements (HERE) involved in ecdysterone regulation of the hsp27 and hsp23 genes have been defined by transfection studies and have recently been identified as binding sites for ecdysterone receptor. We report here that the hsp27 and hsp23 genes are regulated differently by ecdysterone. The hsp27 gene is activated rapidly by ecdysterone, even in the absence of protein synthesis. In contrast, high-level expression of the hsp23 gene begins only after a lag of about 6 h, is dependent on the continuous presence of ecdysterone, and is sensitive to low concentrations of protein synthesis inhibitors. Transfection experiments with reporter constructs show that this difference in regulation is at the transcriptional level. Synthetic hsp27 or hsp23 HERE sequences confer hsp27- or hsp23-type ecdysterone regulation on a basal promoter. These findings indicate that the hsp27 gene is a primary, and the hsp23 gene is mainly a secondary, hormone-responsive gene. Ecdysterone receptor is implied to play a role in the regulation of both genes.

Genes for Drosophila small heat shock proteins are regulated differently by ecdysterone

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. This regulation has been simulated in cultured Drosophila cells in which the genes are activated by the addition of ecdysterone. Sequence elements (HERE) involved in ecdysterone regulation of the hsp27 and hsp23 genes have been defined by transfection studies and have recently been identified as binding sites for ecdysterone receptor. We report here that the hsp27 and hsp23 genes are regulated differently by ecdysterone. The hsp27 gene is activated rapidly by ecdysterone, even in the absence of protein synthesis. In contrast, high-level expression of the hsp23 gene begins only after a lag of about 6 h, is dependent on the continuous presence of ecdysterone, and is sensitive to low concentrations of protein synthesis inhibitors. Transfection experiments with reporter constructs show that this difference in regulation is at the transcriptional level. Synthetic hsp27 or hsp23 HERE sequences confer hsp27- or hsp23-type ecdysterone regulation on a basal promoter. These findings indicate that the hsp27 gene is a primary, and the hsp23 gene is mainly a secondary, hormone-responsive gene. Ecdysterone receptor is implied to play a role in the regulation of both genes.

Heat-shock response of rat hepatoma variant cells

The effect of mild heat shock on protein synthesis was examined in differentiated and dedifferentiated, glucocorticoid-sensitive and resistant clones of H4IIEC3 rat hepatoma cells by one- and two-dimensional gel electrophoresis of [35S]methionine-labeled proteins. Among the major heat-shock proteins, five were induced in all hepatoma clones. Certain members of the HSP70 family and the corresponding mRNAs were only slightly inducible in the glucocorticoid-resistant variants, but were strongly inducible in the sensitive ones. Three other proteins lacked heat inducibility in the dedifferentiated clones. The constitutive level of one major heat-shock protein was elevated in all dedifferentiated variants. These results show that the stage of differentiation influences the expression of heat-shock genes of hepatoma cells. We found no correlation between the elevated constitutive or induced level of heat-shock proteins and heat resistance.

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

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.

Ecdysterone regulatory elements function as both transcriptional activators and repressors

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). Hybrid constructs were transfected into Drosophila S3 cells and assayed for ecdysterone-inducible CAT expression. In the absence of ecdysterone a tandem pair of EcREs repressed the high constitutive level of CAT activity found after transfection with the parent reporter plasmid alone. After hormone addition very high levels of CAT activity were observed. Insertion of the EcRE pair 3' of the CAT gene also led to high levels of ecdysterone-induced CAT expression, but the repression of high constitutive levels of CAT activity failed to occur. The EcRE-CAT construct was cotransfected with plasmids containing tandem 10-mers or 40-mers of the EcRE but lacking a reporter gene. These additional EcREs led to a reduced level of ecdysterone-induced CAT activity and to an elevation of basal CAT activity in the absence of hormone. The data suggest that the receptor binds to the EcRE in the absence of hormone, blocking basal transcription from a constitutive promoter. In the presence of ecdysterone, receptor-hormone binding to the EcRE leads to greatly enhanced transcription.

Ecdysterone regulatory elements function as both transcriptional activators and repressors

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). Hybrid constructs were transfected into Drosophila S3 cells and assayed for ecdysterone-inducible CAT expression. In the absence of ecdysterone a tandem pair of EcREs repressed the high constitutive level of CAT activity found after transfection with the parent reporter plasmid alone. After hormone addition very high levels of CAT activity were observed. Insertion of the EcRE pair 3' of the CAT gene also led to high levels of ecdysterone-induced CAT expression, but the repression of high constitutive levels of CAT activity failed to occur. The EcRE-CAT construct was cotransfected with plasmids containing tandem 10-mers or 40-mers of the EcRE but lacking a reporter gene. These additional EcREs led to a reduced level of ecdysterone-induced CAT activity and to an elevation of basal CAT activity in the absence of hormone. The data suggest that the receptor binds to the EcRE in the absence of hormone, blocking basal transcription from a constitutive promoter. In the presence of ecdysterone, receptor-hormone binding to the EcRE leads to greatly enhanced transcription.

Expression of heat shock proteins during development in Drosophila

Studies on the expression of heat shock proteins during development in Drosophila clearly show that individual Hsps accumulate in a tissue- and developmental stage-specific manner. This is in contrast to their coordinate expression in response to stress. Therefore, the Hsps may play at least two roles, one as housekeeping proteins during development and/or differentiation and the second one in restoring cellular functions after environmental stress. Research in the first two decades following the discovery of the heat shock response have focused on a search for functions in stressed cells. The next few years should bring us further understanding on the role of these fascinating proteins during development in Drosophila as well as in other eukaryotes.

Tissue-specific expression of the heat shock protein HSP27 during Drosophila melanogaster development

The alpha-crystallin-related heat shock (stress) protein hsp27 is expressed in absence of heat shock during Drosophila melanogaster development. Here, we describe the tissue distribution of this protein using an immunoaffinity-purified antibody. In embryos, hsp27 translated from maternal RNA is uniformly distributed, except in the yolk. During the first, second, and early third larval stages, hsp27 expression is restricted to the brain and the gonads. These tissues are characterized by a high level of proliferating cells. In late third instar larvae and early pupae, in addition to the central nervous system and the gonads, all the imaginal discs synthesize hsp27. The disc expression seems restricted to the beginning of their differentiation since it disappears during the second half of the pupal stage: no more hsp27 is observed in the disc-derived adult organs. In adults, hsp27 is still present in some regions of the central nervous system, and is also expressed in the male and female germ lines where it accumulates in mature sperm and oocytes. The transcript and the protein accumulate in oocytes since the onset of vitellogenesis with a uniform distribution similar to that found in embryos. The adult germ lines transcribe hsp27 gene while no transcript is detected in the late pupal and adult brain. These results suggest multiple roles of hsp27 during Drosophila development which may be related to both the proliferative and differentiated states of the tissues.

The differentially expressed 16-kD heat shock genes of Caenorhabditis elegans exhibit differential changes in chromatin structure during heat shock

The 16-kD heat shock genes of Caenorhabditis elegans are encoded by four highly similar genes, arranged as divergently transcribed pairs. In spite of the high level of identity that exists between the HSP16 genes, after 2 hr of heat shock the mRNA from one locus accumulates at 7-14 times the level of that from the other locus. To determine if differential HSP16 gene transcriptional activity contributes to these differences, we examined the chromatin structure of the HSP16 genes in nonshocked embryos and in embryos undergoing both the initial phases of heat shock and after 2 hr of heat shock. To carry out these studies, we developed a nuclei isolation procedure that has allowed us to prepare large amounts of nuclei from C. elegans embryos, larvae, and adults that are essentially free of endogenous nuclease and protease activities and appear to be an excellent substrate for investigating chromatin structure in C. elegans. This procedure has enabled us to report the first observations of C. elegans basic chromatin structure, as well as characterize HSP16 chromatin structure in detail. The data suggest that differential HSP16 RNA accumulation following 2 hr of heat shock appears to be correlated with a change in the chromatin structure of one of the HSP16 loci to a preinduction, transcriptionally inactive configuration.

Differential regulation of closely related members of the hsp16 gene family in Caenorhabditis elegans

The heat-inducible genes encoding 16-kD heat shock polypeptides in Caenorhabditis elegans are found at two separate loci, one containing the 16-1 and 16-48 genes (locus A), and the other, the 16-2 and 16-41 genes (locus B). Despite the highly conserved structures of these genes and their promoters, the B locus produces up to sevenfold more mRNA during heat induction than does the A locus. Since there are two copies of the 16-1 and 16-48 genes at the A locus, the discrepancy in mRNA production is actually as high as 14:1 on a per gene basis. Measurements of the rate of hsp16 mRNA decay during recovery from a heat shock suggest that this difference is not caused by differential mRNA stability; furthermore, nuclear runon experiments yield rates of transcription for the 16-1/48 locus that are approximately threefold higher than those from the 16-2/41 locus. The higher levels of mRNA from the 16-2/41 locus, particularly at longer induction times, seem to be due to a marked difference in the temporal pattern of mRNA production from the two loci. While both loci are transiently activated by a heat shock, the 16-1 and 16-48 genes of the A locus are down-regulated to a lower transcription rate sooner than the genes from the B locus.

Ecdysteroid regulation of glucose dehydrogenase and alcohol dehydrogenase gene expression in Drosophila melanogaster

The temporal patterns of glucose dehydrogenase (Gld) and alcohol dehydrogenase (Adh) expression in Drosophila are correlated positively and negatively, respectively, with ecdysterone titers during the late third instar. In mutant l(3)ecdysone-1ts (ecd-1) larvae, the normal peak of Gld mRNA late in the third instar is not expressed. Conversely, the normal decrease in Adh mRNA at this stage fails to occur in ecd-1. These two abnormal patterns can be reversed by treatment with exogenous ecdysterone. Premature exposure of wild type mid-third instar larvae to ecdysterone also results in the rapid accumulation of Gld mRNA and signals the repression of Adh mRNA. The observed decrease in Adh mRNA expression is accompanied by a transient switch in promoter usage from proximal to distal transcription start sites, which normally occurs later in the third instar.

Perturbation of chromatin architecture on ecdysterone induction of Drosophila melanogaster small heat shock protein genes

Alterations in the pattern of DNase I hypersensitivity were observed on ecdysterone-stimulated transcription of Drosophila melanogaster small heat shock protein genes. Perturbations were induced near hsp27 and hsp22, coupled with an extensive domain of chromatin unfolding in the intergenic region between hsp23 and the developmentally regulated gene 1. These regions represent candidates for ecdysterone regulatory interactions.

Perturbation of chromatin architecture on ecdysterone induction of Drosophila melanogaster small heat shock protein genes

Alterations in the pattern of DNase I hypersensitivity were observed on ecdysterone-stimulated transcription of Drosophila melanogaster small heat shock protein genes. Perturbations were induced near hsp27 and hsp22, coupled with an extensive domain of chromatin unfolding in the intergenic region between hsp23 and the developmentally regulated gene 1. These regions represent candidates for ecdysterone regulatory interactions.

Absence of mutation in the beta-amyloid cDNAs cloned from the brains of three patients with sporadic Alzheimer's disease

Using an oligonucleotide probe, we isolated cDNA clones corresponding to the precursor of the beta-amyloid peptide (BAP) from brain libraries of 3 patients with sporadic Alzheimer's disease (AD). DNA sequencing showed that the largest cDNA clone encompasses 83% of the open reading frame proposed by Kang et al. to encode the BAP precursor (APP). cDNA clones from each of the 3 AD brain libraries were identical to the sequence of the APP-cDNAs cloned from normal adult human and fetal brain. An antisense-radiolabeled RNA copy of one of the AD clones detected a pattern of 3 gene transcripts measuring 3.5, 3.2 and 1.6 kilobases (kb) in both normal and AD brain RNAs. These data suggest that there are no mutations in or about the 42 amino acid (aa) sequence of BAP and that the accumulation of amyloid consistently found in AD may result from altered post-translational processing of APP.

Characterization of HSP27 and three immunologically related polypeptides during Drosophila development

The low-molecular-weight heat-shock protein HSP27 is made in the absence of heat shock during Drosophila melanogaster development. An analysis of the accumulation of HSP27 during specific stages of development is presented using an antiserum recognizing this protein. Whereas HSP27 is abundant during embryogenesis, the level of this protein begins to decrease in the 20-h old embryo and is no longer detectable in second instar larvae. A high level of HSP27 is again observed in third instar larvae and reaches a maximal level in late pupae. While still abundant in young adult flies of both sexes, a greater amount of HSP27 is found in females with the protein being highly concentrated within the ovaries. Following lysis of whole pupae, about 60% of HSP27 is found in the soluble lysate fraction in a form which sediments between 5 and 20 S. Anti-HSP27 serum also recognizes three other developmentally regulated polypeptides with apparent MW of 33, 85 and 120 kDa. The 33 kDa protein accumulates in pupae while those of 85 and 120 kDa are more abundant in third instar larvae. Unlike HSP27, these proteins are not detected in embryos or ovaries. Immunoblot analysis of V8 proteolytic fragments suggests that HSP 27 and 33 kDa are related polypeptides. Exposure of the developing insect to heat-shock treatment results in increased level of HSP27. In larvae, a small amount of the 33 kDa protein accumulates following heat shock, while in pupae and adult flies a decrease in the concentration of this protein is observed after heat shock. Finally, different cellular localizations and distributions within the pupal body have been found for these developmentally regulated polypeptides.

Cellular localization of HSP23 during Drosophila development and following subsequent heat shock

The low-molecular-weight heat-shock protein HSP23 is synthesized in the absence of heat shock during Drosophila development. Here, I present a quantitative analysis of this phenomenon and describe the cellular localization of this protein during normal development and after a subsequent heat shock. HSP23 is first detected in the late third instar larvae and continues to accumulate reaching a maximum level in late pupae. In a 1-week-old adult, HSP23 can no longer be detected. Following lysis of whole pupae, HSP23 is found in the soluble lysate fraction in a form which sediments between 10 and 20 S. Exposure of larvae, pupae, and the adult fly to heat stress (37 degrees C) results in an increased amount of HSP23 which, however, is recovered in an insoluble particulate form following insect lysis. During recovery from heat shock, HSP23 is again found in the soluble 10- to 20-S lysate fraction. In pupae which are exposed to a severe heat stress (41 degrees C) HSP23 remains in the pellet fraction after the heat stress and no pupae are able to emerge as adult flies. However, when pupae are first exposed to a mild heat-shock treatment prior to the 41 degrees C stress, the thermotolerance process is induced and HSP23 is again rapidly found in the soluble lysate fraction during the recovery from heat shock. These observations suggest a possible correlation between the survival of pupae after heat shock and the recovery of HSP23 in the soluble lysate fraction as 10- to 20-S structures after the heat shock.

Heat-shock proteins and development

At the simplest level there is little doubt that the heat shock response is homeostatic, to protect the cell against the ravages of the environmental insult and ensure that the cell can continue its normal life after the crisis has passed.

Sequence requirement for expression of the Drosophila melanogaster heat shock protein hsp22 gene during heat shock and normal development

A 14-base-pair sequence element present in almost all Drosophila melanogaster heat shock genes has been implicated in the heat inducibility of transcription. The D. melanogaster gene encoding the smallest heat shock protein, hsp22, contains within its 5' flanking sequences three such repeats, two close to the transcription start site and a distally located third one 101 base pairs further upstream. Deletion analyses reveal that the 5' flanking sequences required for full expression of the hsp22 gene extend beyond the distal repeat. Deletion of the furthest upstream repeat results in a five to sixfold reduction of gene expression. The small heat shock genes are transiently expressed in the late third instar larval and early pupal stages without external stimulation. A deletion of 5' flanking sequences to position -194, which includes two nucleotides of the distal heat shock element, has no effect on the developmental expression, whereas removal of an additional 18 nucleotides, including 12 nucleotides of the distal heat shock element, severely reduces developmental expression.

Molecular cloning of a steroid-regulated 108K heat shock protein gene from hen oviduct

The natural gene for a steroid inducible 108K heat shock protein has been isolated from a lambda genomic library prepared from hen oviduct tissue. Genomic DNA blots indicate that it exists as a single copy gene in the chick oviduct haploid genome. The 9.9 kilobase gene codes for a messenger RNA of 2733bp (21) and is split into 18 exons as established by sequence comparison of cDNA and genomic clones. The 3' end of the gene contains a repetitive element which shares homology with the CR1 family of repeats. The first exon contains both the untranslated leader and coding regions of the gene. The promoter region is rich in G + C residues (70%) and the dinucleotide CG. This 5' flanking segment contains bases similar both in sequence and location to the Goldberg-Hogness TATA homology and consensus sequence CCAAT. A consensus sequence located upstream of steroid hormone responsive chicken genes is found at -267 and on a reverse orientation at -593. The structure of this gene is of interest since the presence of introns in heat shock genes is rare in any species examined to date. Furthermore, this gene lacks the previously described heat shock promoter consensus sequence (C-GAA-TTC-G) present in other species.

Efficient transcription of a Caenorhabditis elegans heat shock gene pair in mouse fibroblasts is dependent on multiple promoter elements which can function bidirectionally

A divergently transcribed pair of Caenorhabditis elegans hsp16 genes was introduced into mouse fibroblasts by stable transfection with vectors containing bovine papillomavirus plasmid maintenance sequences and a selectable gene. The hsp16 genes were transcriptionally inactive in the mouse cells under normal growth conditions and were strongly induced by heat shock or arsenite. In a cell line with 12 copies of the gene pair, there were estimated to be more than 10,000 hsp16 transcripts in each cell after 2 h of heat shock treatment. The hsp16 transcript levels were more than 100 times higher than those of a gene with a herpes simplex virus thymidine kinase gene promoter carried on the same vector. A single heat shock promoter element (HSE) could activate bidirectional transcription of the two hsp16 genes when placed between the two TATA elements, but the transcriptional efficiency was reduced 10-fold relative to that of the wild-type gene pair. Four overlapping HSEs positioned between the two TATA elements resulted in inducible bidirectional transcription at greater than wild-type levels. The number of HSEs can therefore be a major determinant of the promoter strength of heat-inducible genes in mammalian cells. Partial disruption of an alternating purine-pyrimidine sequence between the two hsp16 genes had no significant effect on their transcriptional activity.

HSP 26 and 27 are phosphorylated in response to heat shock and ecdysterone in Drosophila melanogaster cells

Protein phosphorylation has been studied in Drosophila melanogaster 8.9 K cells following heat shock. By in vivo double labelling with [35S]-methionine and [32P]-orthophosphate, we observed that two proteins are newly phosphorylated among the 26,000-27,000 dalton heat-shock proteins group. These two proteins are also phosphorylated after ecdysterone treatment, albeit at a lower level. That this phosphorylation event is induced by two different treatments, i.e. ecdysterone, a key steroid hormone of development, and heat-shock, a cellular stress suggests a possible common pathway for those two events and an important function for the phosphorylated heat-shock proteins.

Characterization of rabbit genes for synovial cell collagenase

To provide tools for understanding collagenase gene expression in rheumatoid arthritis, we have isolated and characterized genomic clones for rabbit synovial cell collagenase. These clones represent 2 types of collagenase gene, at least 1 of which is transcribed in synovial fibroblasts. By examining the rabbit genome in situ, we provide evidence that there are only 2 different synovial cell collagenase genes found in a haploid genome. Amplification of these genes is not a mechanism for collagenase messenger RNA induction by phorbol esters.

Amino acid sequence of a chicken heat shock protein derived from the complementary DNA nucleotide sequence

The complete nucleotide sequence for a chicken heat shock protein (hsp108) was determined from cDNA clones isolated from hen oviduct and bursal lymphoma recombinant DNA libraries. This protein has certain biochemical similarities to the progesterone receptor, but it is clearly distinct from it. The initial cDNA clone, isolated from a chicken oviduct cDNA library, was detected by antibody screening and hybrid-selected translation [Zarucki-Schulz, T., Kulomaa, M. S., Headon, D. R., Weigel, N. L., Baez, M., Edwards, D. P., McGuire, W. L., Schrader, W. T., & O'Malley, B. W. (1984) Proc. Natl. Acad. Sci. U.S.A. 81, 6358-6362]. The earlier clones were used to screen for additional cDNAs, and cDNAs that define the entire mRNA sequence of hsp108 have been obtained. The nucleotide sequence codes for peptides present in hsp108 as determined by protein microsequencing. The 5' end of the mRNA was determined by primer extension studies. The mRNA contains a noncoding region of 101 nucleotides upstream from the predicted initiation codon. The 3' untranslated region contains 244 nucleotides beyond the termination codon, and it contains a predicted polyadenylation signal 26 nucleotides from the end of the complete cDNA. The coding region of 2385 nucleotides corresponds to a polypeptide chain of 795 amino acids, giving a molecular weight of 91,555 for the hsp108 protein. In another paper, evidence is presented that hsp108 shows a high degree of amino acid sequence homology with two heat shock proteins, hsp90 (yeast) and hsp83 (Drosophila), and is indeed inducible by heat shock [Sargan, D. R., Tsai, M.-J., & O'Malley, B. W. (1986) Biochemistry (following paper in this issue)].

hsp108,,,,,, a novel heat shock inducible protein of chicken

cDNA clones encoding a protein that copurifies with the progesterone receptor B subunit but does not bind progesterone have been described [Kulomaa, M. S., Weigel, N. L., Kleinsek, D. A., Beattie, W. G., Conneely, O. M., March, C., Zarucki-Schulz, T., Schrader, W. T., & O'Malley, B. W. (1986) Biochemistry (preceding paper in this issue)]. A full-length sequence for these clones was derived and was found to encode a protein that is structurally unrelated to the progesterone receptor but that contains significant homologies to the previously described heat shock proteins hsp90 of yeast and hsp83a of Drosophila melanogaster. In this paper it is shown that this protein is indeed a heat shock protein. Though the apparent molecular weight of the protein is 108,000 on sodium dodecyl sulfate-polyacrylamide gels, the molecular weight of the polypeptide backbone is 92,000. The steady-state level of gene transcripts as well as the level of protein is inducible by heat shock, but the gene is constitutively expressed in a number of tissues. A previously undescribed heat shock protein of molecular weight 78,000 in these preparations is also reported.

Efficient transcription of a Caenorhabditis elegans heat shock gene pair in mouse fibroblasts is dependent on multiple promoter elements which can function bidirectionally

A divergently transcribed pair of Caenorhabditis elegans hsp16 genes was introduced into mouse fibroblasts by stable transfection with vectors containing bovine papillomavirus plasmid maintenance sequences and a selectable gene. The hsp16 genes were transcriptionally inactive in the mouse cells under normal growth conditions and were strongly induced by heat shock or arsenite. In a cell line with 12 copies of the gene pair, there were estimated to be more than 10,000 hsp16 transcripts in each cell after 2 h of heat shock treatment. The hsp16 transcript levels were more than 100 times higher than those of a gene with a herpes simplex virus thymidine kinase gene promoter carried on the same vector. A single heat shock promoter element (HSE) could activate bidirectional transcription of the two hsp16 genes when placed between the two TATA elements, but the transcriptional efficiency was reduced 10-fold relative to that of the wild-type gene pair. Four overlapping HSEs positioned between the two TATA elements resulted in inducible bidirectional transcription at greater than wild-type levels. The number of HSEs can therefore be a major determinant of the promoter strength of heat-inducible genes in mammalian cells. Partial disruption of an alternating purine-pyrimidine sequence between the two hsp16 genes had no significant effect on their transcriptional activity.

Cellular localization of steroid hormone-regulated proteins during sexual development in Achlya

In the fungus Achlya ambisexualis sexual development in the male strain E87 is controlled by the steroid hormone antheridiol. To investigate the effects of antheridiol on the synthesis and/or accumulation of specific cellular proteins we have analysed [35S]methionine-labeled proteins from control and hormone-treated cells using both one-dimensional (1D) and two-dimensional (2D) PAGE. Since in a total cell extract, hormone-induced changes in specific proteins might not be apparent against a background of more abundant proteins, cells were fractionated prior to protein isolation. It was also necessary to establish a concentration of hormone carrier, in this case methanol, which by itself did not alter the pattern of protein synthesis. Using these approaches the addition of the hormone antheridiol to vegetatively growing cells of Achlya E87 was found to result in changes in the synthesis and/or accumulation of at least 16 specific proteins, which could be localized to the cytoplasmic, nuclear or cell wall/cell membrane fractions. The most prominent changes observed in the hormone-treated cells included the appearance in the cytoplasmic fraction of labeled proteins at 28.4 and 24.3 kD which were not detectable in control cells, and a significant enrichment in the labeling of a 24.3 kD protein in the cell wall/cell membrane fraction. A marked increase in the labeling of 85, 63 and 47 kD proteins in the nuclear fraction from hormone-treated cells was also noted. The molecular weight (MW) and the behavior on 2D gels of the 85 kD hormone-induced protein appeared very similar to that of the 85 kD heat-shock protein reported in Achlya. Quantitive changes in the [35S]methionine labeling of several other proteins were noted in all three cell fractions.

Sequence requirement for expression of the Drosophila melanogaster heat shock protein hsp22 gene during heat shock and normal development

A 14-base-pair sequence element present in almost all Drosophila melanogaster heat shock genes has been implicated in the heat inducibility of transcription. The D. melanogaster gene encoding the smallest heat shock protein, hsp22, contains within its 5' flanking sequences three such repeats, two close to the transcription start site and a distally located third one 101 base pairs further upstream. Deletion analyses reveal that the 5' flanking sequences required for full expression of the hsp22 gene extend beyond the distal repeat. Deletion of the furthest upstream repeat results in a five to sixfold reduction of gene expression. The small heat shock genes are transiently expressed in the late third instar larval and early pupal stages without external stimulation. A deletion of 5' flanking sequences to position -194, which includes two nucleotides of the distal heat shock element, has no effect on the developmental expression, whereas removal of an additional 18 nucleotides, including 12 nucleotides of the distal heat shock element, severely reduces developmental expression.

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.

Transcript length heterogeneity at the small heat shock protein genes of Drosophila

Expression of the small heat shock protein (hsp) genes can be induced in cultured Drosophila cells by high temperature shock and by exposure to physiological doses of the insect molting hormone ecdysterone. Northern blot analysis was performed in order to compare the size of small hsp transcripts synthesized in response to these two stimuli. Transcripts from several other genes were also examined. Two types of length heterogeneity were observed for the small hsp gene transcripts. One involved the synthesis of what are designated as long form transcripts during heat shock; small hsp messenger RNAs extended at the 3' end by some 1.5 X 10(3) base-pairs. The second type of size heterogeneity observed is based on differences in the length of the poly(A) tail. The results of S1 nuclease protection analysis provided evidence that different initiation sites are not used for hsp 22 mRNA transcription in response to the two stimuli.

Expression of Drosophila hsp 70-CAT hybrid gene in Aedes cells induced by heat shock

DNA-mediated transfer of a Drosophila hsp 70-CAT hybrid gene into Drosophila S3 cells leads to the appearance of heat shock (37 degrees C)-inducible chloramphenicol acetyltransferase (CAT) activity. When this hybrid gene construction was transfected into cultured Aedes, Plodia, or Manduca cells, only trace levels of heat-inducible CAT activity were observed. Induction could be somewhat improved by using Schneider's Drosophila medium for transfection. In the case of Aedes cells, levels of CAT induction comparable to that seen using Drosophila cells could be achieved by raising the heat-shock temperature to 41 degrees C, a treatment which is lethal to Drosophila.