A calcium ionophore-inducible cellular promoter is highly active and has enhancerlike properties

Effect of tributyltin chloride (TBT-Cl) exposure on expression of HSP90β1 in the river pufferfish (Takifugu obscurus): Evidences for its immunologic function involving in exploring process

HSP90β1 (known as glyco-protein 96, GP96) is a vital endoplasmic reticulum (ER) depended chaperonin among the HSPs (heat shock proteins) family. Furthermore, it always processes and presents antigen of the tumor and keeps balance for the intracellular environment. In the present study, we explored the effect of tributyltin chloride (TBT-Cl) exposure on HSP90β1 expression in river pufferfish, Takifugu obscurus. The full length of To-HSP90β1 was gained with 2775 bp in length, with an ORF (open reading frame) encoding an 803 aa polypeptide. A phylogenetic tree was constructed and showed the close relationship to other fish species. The HSP90β1 mRNA transcript was expressed in all tissues investigated with higher level in the gill and liver. After the acute and chronic exposure of TBT-Cl, the To-HSP90β1 mRNA transcript significantly was up-regulated in gills. Moreover, the histology study indicated the different injury degree of TBT-Cl in liver and gill. Immunohistochemistry (IHC) staining results implied the cytoplasm reorganization after TBT-Cl stress and the function of immunoregulation for To-HSP90β1 to TBT-Cl exposure. All the results indicated that HSP90β1 may be involved in the resistance to the invasion of TBT-Cl for keeping autoimmune homeostasis.

Modification of plant cell wall structure accompanied by enhancement of saccharification efficiency using a chemical, lasalocid sodium

The cell wall is one major determinant of plant cell morphology, and is an attractive bioresource. Here, we report a novel strategy to modify plant cell wall property by small molecules. Lasalocid sodium (LS) was isolated by chemical screening to identify molecules that affect the cell morphology of tobacco BY-2 cells. LS treatment led to an increase in cell wall thickness, whilst the quantity and sugar composition of the cell wall remained unchanged in BY-2 cells. The chemical also disordered the cellular arrangement of hypocotyls of Arabidopsis plants, resulting in a decrease in hypocotyl length. LS treatment enhanced enzymatic saccharification efficiency in both BY-2 cells and Arabidopsis plants. Microarray analysis on Arabidopsis showed that exposure to LS upregulated type III peroxidase genes, of which some are involved in lignin biogenesis, and jasmonic acid response genes, and phloroglucinol staining supported the activation of lignification by the LS treatment. As jasmonic acid-mediated lignification is a typical reaction to cell wall damage, it is possible that LS induces cell wall loosening, which can trigger cell wall damage response. Thus, LS is a unique chemical for modification of cell wall and morphology through changes in cell wall architecture.

Mouse hepatitis virus nucleocapsid protein as a translational effector of viral mRNAs

The mouse hepatitis virus (MHV) nucleocapsid protein stimulated translation of a chimeric reporter mRNA containing an intact MHV 5'-untranslated region and the chloramphenicol acetyltransferase (CAT) coding region. The nucleocapsid protein binds specifically the tandemly repeated-UCYAA- of the MHV leader. This RNA sequence is the same as the intergenic motif found in the genome RNA. Preferential translation of viral mRNA in MHV infected cells is stimulated in part by this interaction and represents a specific, positive translational control mechanism employed by coronaviruses.

Biological activity and modular structure of RE-1-silencing transcription factor (REST), a repressor of neuronal genes

The zinc finger protein RE-1-silencing transcription factor (REST)1 is a transcriptional repressor that represses neuronal genes in nonneuronal tissues. Transfection experiments of neuroblastoma cells using a REST expression vector revealed that synapsin I promoter activity is controlled by REST. The biological activity of REST was further investigated using a battery of model promoters containing strong promoters/enhancers and REST binding sites. REST functioned as a transcriptional repressor when REST binding motifs derived from the genes encoding synapsin I, SCG10, alpha1-glycine receptor, the beta2-subunit of the neuronal nicotinic acetylcholine receptor, and the m4-subunit of the muscarinic acetylcholine receptor were present in the promoter region. No differences in the biological activity of these REST binding motifs tested were detected. Moreover, we found that REST functioned very effectively as a transcriptional repressor at a distance. Thus, REST represents a general transcriptional repressor that blocks transcription regardless of the location or orientation of its binding site relative to the enhancer and promoter. This biological activity could also be attributed to isolated domains of REST. Both repressor domains identified at the N and C termini of REST were transferable to a heterologous DNA binding domain and functioned from proximal and distal positions, similar to the REST protein.

Calcium-sensitive transcriptional activation of the proximal CCAAT regulatory element of the grp78/BiP promoter by the human nuclear factor CBF/NF-Y

Transcription of the gene encoding GRP78/BiP, a calcium-binding molecular chaperone localized in the endoplasmic reticulum, is induced in mammalian cells through gradual depletion of the intracellular calcium stores. The multimeric CCAAT binding factor, CBF/NF-Y, binds to the most proximal CCAAT regulatory element (C1) of the grp78 promoter required for both basal level expression and stress response. Using an in vitro transcription system, we show through factor competition and immunodepletion that the grp78 C1-mediated enhancement of transcription requires primarily CBF. Correlating with the previous observation that CBF binding to the 78C1 site is enhanced by EGTA and EDTA, these divalent cation chelators specifically stimulate 78C1-directed transcription. In contrast, increasing amounts of calcium ions are inhibitory. These results provide evidence that CBF is functionally important in transactivating the grp78 C1 transcriptional activity, and suggest a possible mechanism by which grp78 transcription is stimulated by calcium depletion. We further discovered that in addition to binding CBF, both the 78C1 element and the CBF binding site of the alpha2(I) collagen promoter interact weakly with the multifunctional transcription factor YY1. Our studies show that the binding sites for CBF and YY1 are distinct for the two promoter sites, suggesting that YY1 and other interacting factors could exert differential effects on individual promoters bearing the same CBF site.

Structure and regulation of the mouse GRP78 (BiP) promoter by glucose and calcium ionophore

Dietary calorie restriction, also termed energy restriction, increases mean and maximum life span, reduces the incidence of tumors and increases the mean age of onset of diseases and tumors in every animal tested. Because life-span is genetically determined, we are studying the mechanisms by which energy restriction regulates the expression of genes. We found that energy restriction reduces hepatic glucose-regulated protein-78 (GRP78) and protein-94 mRNA levels by 2-3-fold in mice [Spindler et al., J. Nutr. 20 (1990) 1412-1417]. To investigate this down-regulation, we have cloned the mouse GRP78 promoter (pGRP78) and studied its regulation by glucose. The mouse pGRP78 and the previously cloned rat promoter mediate responsiveness to glucose deprivation, as well as to the calcium ionophore A23187. These studies are the first demonstration that cis-elements in the pGRP78 mediate responsiveness to glucose deprivation.

Expression of the glucose-regulated proteins (GRP94 and GRP78) in differentiated and undifferentiated mouse embryonic cells and the use of the GRP78 promoter as an expression system in embryonic cells

We examined the expression of GRP94 and GRP78 in embryonal carcinoma (EC) cells and during early mouse development. The GRP78 protein is constitutively expressed in the undifferentiated F9 cells whereas the level of GRP94 is below detection limit. These cells, like adult differentiated cells, exhibit enhancement of the GRP94 and GRP78 transcript levels in response to the calcium ionophore A23187, resulting in an increase of GRP94 and GRP78 proteins after 8 h of treatment. The GRP78 promoter has been identified as containing a strong enhancer. To test whether the GRP78 promoter is effective in directing expression of a heterologous gene in F9 cells, CAT fusion genes containing the GRP78 promoter were transfected into F9 cells. In non-induced F9 cells the activity of the GRP78 promoter was about 5- and 10-fold higher than the RSV promoter and the SV40 early promoter, respectively. Treatment of the cells with A23187 further increased the GRP78 promoter activity 3-fold. Since GRP78 is expressed during mouse embryogenesis and the promoter is also active in F9 cells treated with retinoic acid, the GRP78 promoter may be useful for the efficient expression of heterologous genes in undifferentiated and differentiated mouse embryonal cells.

Characterization of the hsp70 multigene family of Caenorhabditis elegans

Our laboratory has been characterizing the hsp70 multigene family from the nematode Caenorhabditis elegans as the first step to the genetic characterization of the heat shock response in a relatively simple multicellular eukaryote. Two gene members, hsp-1 and hsp-2ps have already been characterized (Snutch et al., 1988; Heschl and Baillie, 1989). The third gene member, hsp-3, is expressed constitutively and is non-heat inducible; its mRNA is most abundant at the L1 larval stage. The hsp-3 protein (hsp70C) shares a high degree of identity with the rat grp78 protein and has a long, hydrophobic leader sequence. The carboxyl terminus of hsp70C has the putative ER-retention signal, KDEL. The fourth gene member, hsp-6 is expressed constitutively and moderately heat inducible. A partial hsp-6 protein (hsp70F) sequence shares a higher degree of identity with the Escherichia coli dnaK protein than with eukaryotic hsp70 proteins. The predicted amino-terminal half of the hsp70F polypeptide also contains a long, amphiphilic leader sequence similar to mitochondrial import leader sequences. These two genes encode proteins that potentially cross intracellular membranes. We compared the 5'-flanking DNA from the C. elegans hsp-3 gene to fragment containing enhancer activity from the rat grp78 gene regulatory region (Lin et al., 1986). A 23-nucleotide sequence was conserved between the two promoter regions. This sequence shares approximately 80% identity between these two evolutionary distant organisms. A comparison to other hsp70 genes did not reveal any conservation of this 23-nucleotide sequence. We propose that this sequence may be involved in a unique aspect of the regulation of the C. elegans' grp78-like gene and the rat grp78 gene.

Cooperative interactions between the GRP78 enhancer and promoter elements in hamster fibroblasts

A non-tissue-specific enhancer derived from the promoter of the rat 78-kDa glucose-regulated protein (GRP78)-coding gene was tested for its ability to stimulate the activity of its homologous promoter and two heterologous promoters (simian virus 40 and mouse mammary tumor virus). Single and double copies of the enhancer were inserted at positions 5' and 3' of the cat-expression vectors under the direction of the above promoters. The recombinant plasmids were transfected into hamster fibroblast K12 cells and assayed for chloramphenicol acetyl transferase activity under induced and non-induced conditions. We report that the GRP78 enhancer (i) exhibits strong cooperative interactions with its homologous promoter; (ii) can activate and confer a calcium ionophore (A23187) inducibility to heterologous promoters in an orientation-independent manner; (iii) prefers the 5' over the 3' location and; (iv) is dosage dependent in that two copies are twice as active as a single unit.

Human gene encoding the 78,000-dalton glucose-regulated protein and its pseudogene: structure, conservation, and regulation

The isolation and characterization of a human functional GRP78 gene and a processed pseudogene are described. We present the complete primary structure of the human GRP78 gene, which spans over 5 kb and consists of eight exons. Sequence comparisons reveal that the GRP78 gene shares unusual homology among the human, rat, and hamster in the protein-coding and 3' untranslated regions. In addition, short domains highly conserved with HSP70 isolated from human, Drosophila, Xenopus, yeast, and E. coli DNA are identified within the hydrophobic regions of GRP78. The intronless pseudogene resembles that of a processed gene. It is flanked by a short direct repeat and is embedded within an AT-rich genomic region. The highly active promoter from the functional human GRP78 gene contains a TATA box, five CCAAT sequences, and two potential binding sites for the transcriptional factor Sp1. It consists of a distal domain that enhances basal level expression and a proximal domain essential for responses to calcium ionophore and for a temperature-sensitive mutation which induce the GRP78 gene. Both domains are highly conserved between the rat and the human GRP78 promoters.

Regulation of the glucose-regulated protein genes by beta-mercaptoethanol requires de novo protein synthesis and correlates with inhibition of protein glycosylation

Treatment of hamster fibroblasts with the sulfhydryl-reducing agent beta-mercaptoethanol (beta-ME) results in increased synthesis of the glucose-regulated proteins (GRPs). The most abundant protein species being induced is the GRP78, with a minor increase also observed for GRP94. The enhanced synthesis of the GRP94 and GRP78 is primarily due to an increase in the steady state levels of the two GRP transcripts. Although beta-ME has a general inhibitive affect on amino acid uptake and protein synthesis, compared to other protein synthesis inhibitors such as cycloheximide, puromycin, and amino acid analogue canavanine, beta-ME is a more potent inducer of GRP gene expression. In addition, the induction by low dosage of beta-ME requires de novo protein synthesis and is preceded by a drop in the rate of protein glycosylation. Our results support the hypothesis that denatured proteins can induce the GRP genes; however, a blockage of some post-translocational processing step in the endoplasmic reticulum, as a result of beta-ME or other stress treatments, may provide the additional stimulation which transcriptionally activates the GRP genes to high levels.

Enhanced synthesis of the glucose/calcium-regulated proteins in a hamster cell mutant deficient in transfer of oligosaccharide core to polypeptides

The properties of two Chinese hamster temperature-sensitive mutants, K12 and H3.5, were examined. Both mutants originated from the same parental cell line, Wg1A, and were isolated as cell cycle mutants arrested in G1. Previously, we had been shown that the H3.5 ts mutation affected the transfer of the oligosaccharide from the lipid carrier to the nascent polypeptide and that the K12 ts mutation regulated the transcription of two glucose/calcium-regulated genes. We report here that these two mutants exhibit almost identical phenotypes at the biochemical level. Furthermore, a genetic complementation test demonstrates that the two ts lesions must be closely related, or even identical. Our results suggest that a specific defect in glycosylation may result in the overproduction of the glucose/calcium-regulated proteins and is capable of activating the promoter of the major glucose-regulated gene.

Promotor and enhancer like activity at the 5'-end of normal and T24 Ha-ras1 genes

We have used a short-term transfection technique, in which we monitor the ability of DNA fragments to induce the expression of the chloramphenicol acetyltransferase (CAT) gene in rat 208F fibroblast cells. Using appropriate vectors we have assayed for promoter or enhancer activity of the 0.8 kb SstI fragment located within the 5'-flanking sequences of the first coding exon of the human T24 and normal Ha-ras1 genes. We find that this fragment contains promoter and enhancer activities in both the normal and the T24 Ha-ras1 gene.