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PubMed2004

Gene expression profiles in primary ovarian serous papillary tumors and normal ovarian epithelium: identification of candidate molecular markers for ovarian cancer diagnosis and therapy.

With the goal of identifying genes with a differential pattern of expression between ovarian serous papillary carcinomas (OSPCs) and normal ovarian (NOVA) epithelium and using this knowledge for the development of novel diagnostic and therapeutic markers for ovarian cancer, we used oligonucleotide microarrays with probe sets complementary to 12,533 genes to analyze the gene expression profiles of 10 primary OSPC cell lines, 2 established OSPC cell lines (UCI-101, UCI-107) and 5 primary NOVA epithelial cultures. Unsupervised analysis of gene expression data identified 129 and 170 genes that exhibited >5-fold upregulation and downregulation, respectively, in primary OSPC compared to NOVA. Genes overexpressed in established OSPC cell lines had little correlation with those overexpressed in primary OSPC, highlighting the divergence of gene expression that occurs as a result of long-term in vitro growth. Hierarchical clustering of the expression data readily distinguished normal tissue from primary OSPC. Laminin, claudin 3, claudin 4, tumor-associated calcium signal transducers 1 and 2 (TROP-1/Ep-CAM, TROP-2), ladinin 1, S100A2, SERPIN2 (PAI-2), CD24, lipocalin 2, osteopontin, kallikrein 6 (protease M), kallikrein 10, matriptase (TADG-15) and stratifin were among the most highly overexpressed genes in OSPC compared to NOVA. Downregulated genes in OSPC included transforming growth factor-beta receptor III, platelet-derived growth factor receptor alpha, SEMACAP3, ras homolog gene family member I (ARHI), thrombospondin 2 and disabled-2/differentially expressed in ovarian carcinoma 2 (Dab2/DOC2). Differential expression of some of these genes, including claudin 3, claudin 4, TROP-1 and CD24, was validated by quantitative RT-PCR and flow cytometry on primary OSPC and NOVA. Immunohistochemical staining of formalin-fixed, paraffin-embedded tumor specimens from which primary OSPC cultures were derived further confirmed differential expression of CD24 and TROP-1/Ep-CAM markers on OSPC vs. NOVA. These results, obtained with highly purified primary cultures of ovarian cancer, highlight important molecular features of OSPC and may provide a foundation for the development of new type-specific therapies against this disease.

Adult↗
PubMed2006

Gene expression and glucosinolate accumulation in Arabidopsis thaliana in response to generalist and specialist herbivores of different feeding guilds and the role of defense signaling pathways.

Glucosinolate accumulation and expression of glucosinolate biosynthetic genes were studied in response to four herbivores in Arabidopsis thaliana (L.) wild-type (Columbia) and mutant lines affected in defense signaling. Herbivory on wild-type plants led to increased aliphatic glucosinolate content for three of four herbivores tested, the aphid generalist Myzus persicae (Sulzer), the aphid specialist Brevicoryne brassicae (L.), and the lepidopteran generalist Spodoptera exigua Hübner. The lepidopteran specialist Pieris rapae L. did not alter aliphatic glucosinolate content in the wild-type, but indole glucosinolates increased slightly. Gene expression associated with aliphatic glucosinolate biosynthesis increased after feeding by all species, indicating that glucosinolate accumulation is not always regulated at the level of these gene transcripts. A. thaliana lines with mutations in jasmonate (coi1), salicylate (npr1), and ethylene signaling (etr1) diverged in gene expression, glucosinolate content, and insect performance compared to wild-type suggesting the involvement of all three modes of signaling in responses to herbivores. The coi1 mutant had much lower constitutive levels of aliphatic glucosinolates than wild-type but content increased in response to herbivory. In contrast, npr1 had higher constitutive levels of aliphatic glucosinolates and levels did not increase after feeding. Glucosinolate content of the etr1 mutant was comparable to wild-type and did not change with herbivory, except for P. rapae feeding which elicited elevated indolyl glucosinolate levels. Unlike the wild-type response, gene transcripts of aliphatic glucosinolate biosynthesis did not generally increase in the mutants. Both glucosinolate content and gene expression data indicate that salicylate and ethylene signaling repress some jasmonate-mediated responses to herbivory.

Animals↗
PubMed2004

Divergent roles for C-type lectins expressed by cells of the innate immune system.

In recent years there has been increasing interest in the diversity and function of carbohydrates present on a range of endogenous mammalian glycoproteins and pathogen surfaces. It is clear that carbohydrate structures are not merely structural components of the molecules which bear them but are, in many instances, a source of information to be decoded by biological systems including the immune system. Macrophages and other antigen presenting cells express a variety of pattern recognition molecules which allow discrimination between self and non-self ligands and are well known for their ability to recognise and internalise foreign antigens. The role of carbohydrates as molecular determinants of self/non-self has been recognised for many years and a family of proteins known as the C-type lectins are implicated as the main players in carbohydrate recognition within the immune system. More recently, C-type lectin receptors which bind ligands other than carbohydrates have been identified, and there are additional receptors which bind both carbohydrate and non-carbohydrate ligands. In this review article we seek to shed light on the varied roles of this family of receptors, particularly those receptors expressed by antigen presenting cells and those with known ligands. We also review more recent data on several members of this family.

Animals↗
PubMed1997

Divergent and conserved features in the spatial expression of the Drosophila pseudoobscura esterase-5B gene and the esterase-6 gene of Drosophila melanogaster.

The regulatory regions of homologous genes encoding esterase 6 (Est-6) of Drosophila melanogaster and esterase 5B (Est-5B) of Drosophila pseudoobscura show very little similarity. We have undertaken a comparative study of the pattern of expression directed by the Est-5B and Est-6 5'-flanking DNA to attempt to reveal conserved elements regulating tissue-specific expression in adults. Esterase regulatory sequences were linked to a lacZ reporter gene and transformed into D. melanogaster embryos. Est-5B, 5' upstream elements, give rise to a beta-galactosidase expression pattern that coincides with the wild-type expression of Est-5B in D. pseudoobscura. The expression patterns of the Est-5B/lacZ construct are different from those of a fusion gene containing the upstream region of Est-6. Common sites of expression for both kinds of constructs are the third segment of antenna, the maxillary palps, and salivary glands. In vitro deletion mutagenesis has shown that the two genes have a different organization of regulatory elements controlling expression in both the third segment of antenna and maxillary palps. The results suggest that the conservation of the expression pattern in genes that evolved from a common ancestor may not be accompanied by preservation of the corresponding cis-regulatory elements.

Animals↗
PubMed2002

Divergent effects of retinoic acids on the expression of ERalpha and 17beta-hydroxysteroid dehydrogenase type 2 in endometrial carcinoma cells (RL 95-2).

The effects of E2 are dependent on ERs and local E2 concentration in target cells. Modulation of intracellular E2 concentration involves the action of 17beta-hydroxysteroid dehydrogenase (17HSD) type 2, the enzyme converting E2 to estrone. In the present study, the influence of RAs on the growth of endometrial cancer cell line RL 95-2 as well as the expression of ERs and 17HSD type 2 have been investigated. It was found that RAs repress the growth of RL 95-2 cells, which express all subtypes of RXR and RAR, as examined by RT-PCR. Also, quantitative RT-PCR analysis showed that both ERalpha and ERbeta are present in RL 95-2 cells, and Western blot assay further revealed that ERalpha expression was decreased by all trans-RA treatment. In contrast, RAs induced 17HSD type 2 mRNA expression in a dose- and time-dependent fashion. This stimulatory effect was also detected at the level of in vivo oxidative 17HSD activity in cultured cells. On the other hand, the abundance of 17HSD type 2 mRNA was not altered by RAs in cultured normal epithelial cells isolated from human early- and late-secretory endometrium. The data indicate that RAs have an inhibitory effect on the growth of RL 95-2 cells and a cross-talk with the estrogen pathway in estrogen-responsive endometrial cancer cells.

17-Hydroxysteroid Dehydrogenases↗
PubMed1992

Apolipoprotein B messenger RNA editing in rat liver: developmental and hormonal modulation is divergent from apolipoprotein A-IV gene expression despite increased hepatic lipogenesis.

Rat hepatic apolipoprotein B (apoB) mRNA editing is regulated developmentally as well as by hormonal and nutritional modulation of hepatic lipogenesis, changes previously associated with coordinate modulation of hepatic apoA-IV gene expression. We have examined the effects of dexamethasone administration on apoB mRNA editing and the expression of other apolipoprotein genes in both neonatal and adult rats. Administration of dexamethasone increased hepatic triglyceride content in neonatal rats and increased hepatic but not intestinal apoA-IV mRNA abundance. However, neither the developmental profile nor the extent of hepatic apoB mRNA editing was changed after hormone administration. Dexamethasone produced a dose-dependent increase in adult hepatic triglyceride content and a coordinate fourfold increase in hepatic but not intestinal apoA-IV mRNA abundance, and hepatic and serum apoA-IV protein concentrations. Immunocytochemical localization revealed apoA-IV to be expressed in hepatocytes around the central vein while dexamethasone treatment produced a dose-dependent appearance of fat-filled hepatocytes throughout the lobule that were immunoreactive for apoA-IV. Despite these changes in hepatic triglyceride accumulation there was no change in the extent of hepatic apoB mRNA editing at any dose of dexamethasone. The data suggest that hormonal and metabolic modulation of hepatic apoB mRNA editing may be independent of factors that modulate apoA-IV gene expression despite alterations in hepatic triglyceride content.

Animals↗
PubMed1990

[The antigenic divergence of tumor cells due to the expression of hetero-organic antigens as a manifestation of disordered differentiation in carcinogenesis].

The analysis has been made of the literary and the author's own experimental evidences on the antigenic diversion of tumor cells resulting from the expression of hetero-organic antigens, which is one of the most characteristic manifestations of disturbance of cytodifferentiation in carcinogenesis. Studies of hepatocellular tumors and liver of rats subject to single hepatocarcinogen injections being exemplified, the author considers some cases of detection of hetero-organic antigens of kidney origin in the cytosol, on the outer cell membranes and within the chromosomal non-histone proteins (NHP). Under discussion is the interrelation between the expression of hetero-organic antigens, attributed to the same tissue type in different cell structures, and a possible role of NHP as factors directing the disdifferentiation of neoplastically transformed cells.

Animals↗
PubMed1996

Structure and evolution of the actin gene family in Arabidopsis thaliana.

Higher plants contain families of actin-encoding genes that are divergent and differentially expressed. Progress in understanding the functions and evolution of plant actins has been hindered by the large size of the actin gene families. In this study, we characterized the structure and evolution of the actin gene family in Arabidopsis thaliana. DNA blot analyses with gene-specific probes suggested that all 10 of the Arabidopsis actin gene family members have been isolated and established that Arabidopsis has a much simpler actin gene family than other plants that have been examined. Phylogenetic analyses suggested that the Arabidopsis gene family contains at least two ancient classes of genes that diverged early in land plant evolution and may have separated vegetative from reproductive actins. Subsequent divergence produced a total of six distinct subclasses of actin, and five showed a distinct pattern of tissue specific expression. The concordance of expression patterns with the phylogenetic structure is discussed. These subclasses appear to be evolving independently, as no evidence of gene conversion was found. The Arabidopsis actin proteins have an unusually large number of nonconservative amino acid substitutions, which mapped to the surface of the actin molecule, and should effect protein-protein interactions.

Actins↗
PubMed2026

Integrative analysis of transcriptome and chromatin accessibility reveals promoter-proximal regulation and identifies candidate ABC transporters associated with cold stress responses in maize.

BACKGROUND: Low-temperature stress is a formidable environmental constraint that severely limits the growth and productivity of maize (Zea mays L.), particularly during the highly vulnerable early seedling stage. While cold tolerance is a critical agronomic objective, the integrated transcriptional and epigenetic regulatory mechanisms that govern this trait remain largely elusive. Characterizing these coordinated molecular networks is fundamental to the genetic enhancement of cold resilience in maize. METHODS: Using two maize inbred lines contrasting in chilling response (ZHB12 tolerant, B73 sensitive), we performed integrative time‑course RNA‑seq and ATAC‑seq to thoroughly and systematically characterize the precise dynamic interplay between gene expression and chromatin accessibility under cold stress conditions at the seedling stage. RESULTS: Physiological assessments confirmed that ZHB12 possesses superior cold tolerance, manifested by significantly attenuated electrolyte leakage and reduced foliar damage compared to B73. Transcriptomic profiling revealed a massive, time-dependent divergence in gene expression between the two genotypes, with a major regulatory transition identified at 24 h of cold exposure. Functional enrichment analysis demonstrated that ZHB12 preferentially activates a robust defense repertoire, including Photosystem II electron transport, diterpenoid biosynthesis, and ATP biosynthetic pathways. Notably, multiple ATP-binding cassette (ABC) transporter genes were coordinately upregulated under chilling, suggesting their potential involvement in cellular homeostasis. ATAC-seq analysis indicated that cold stress is associated with chromatin remodeling in ZHB12, with increased accessibility observed in proximal promoter regions. Integrative analysis identified a core set of dual-responsive genes, in which increased promoter accessibility coincided with transcriptional upregulation. These genes were predominantly enriched in transporter activity and transcriptional regulation, suggesting potential epigenetic link to the superior stress response of ZHB12. CONCLUSION: Our findings reveal extensive transcriptional and chromatin accessibility changes in ZHB12 under cold stress. The observed associations between promoter accessibility and gene activation, particularly in genes involved in transport processes, highlight candidate regulators potentially contributing to cold tolerance. This study provides a molecular framework and identifies high-value candidate genes that may inform future efforts in breeding cold-tolerant maize, pending functional validation.

Zea mays↗
PubMed1993

Homology cloning of rat 72 kDa type IV collagenase: cytokine and second-messenger inducibility in glomerular mesangial cells.

Glomerular mesangial cells (MC) play a central role in the synthesis and turnover of the glomerular extracellular matrix. Prior studies [Davies, Thomas, Martin and Lovett (1988) Biochem. J. 251, 419-425; Martin, Davies, Thomas and Lovett (1989) Kidney Int. 36, 790-801] have characterized at the protein level a 72 kDa type IV collagenase that is secreted by cultured human and rat MC. While exposure of most cell types to interleukin-1 beta (IL-1 beta), tumour necrosis factor-alpha (TNF-alpha) or phorbol ester has little or even an inhibitory effect on 72 kDa type IV collagenase secretion, these factors significantly increased the synthesis of this enzyme by rat MC. Given this divergent pattern of expression, a homology-based PCR cloning strategy using rat MC cDNA templates was employed to define at the molecular level the structure of the mesangial 72 kDa type IV collagenase. The nucleotide sequence within the open reading frame of the rat mesangial 72 kDa type IV collagenase cDNA diverges from the sequence of the human homologue by approx. 9%. The divergence in the 3' untranslated region was much more extensive. Steady-state levels of the 3.1 kb transcript of the 72 kDa type IV collagenase were low or undetectable in resting MC, but were greatly stimulated following incubation with IL-beta, TNF-alpha or phorbol ester. None of these factors induced synthesis by MC of the closely related 92 kDa type IV collagenase. Synthesis by MC of the 72 kDa type IV collagenase was also induced by second-messenger analogues, including 8-bromo-cyclic AMP and forskolin. It is concluded that MC regulate the expression of this enzyme in an unusual, tissue-specific fashion. Cytokine and second-messenger inducibility may contribute to the enhanced expression of the enzyme during glomerular inflammatory disorders.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1996

The tra region of the nopaline-type Ti plasmid is a chimera with elements related to the transfer systems of RSF1010, RP4, and F.

The Ti plasmids of Agrobacterium tumefaciens encode two transfer systems. One mediates the translocation of the T-DNA from the bacterium to a plant cell, while the other is responsible for the conjugal transfer of the entire Ti plasmid from one bacterium to another. The determinants responsible for conjugal transfer map to two regions, tra and trb, of the nopaline-type Ti plasmid pTiC58. By using transposon mutagenesis with Tn3HoHo1, we localized the tra determinants to an 8.5-kb region that also contains the oriT region. Fusions to lacZ formed by transposon insertions indicated that this region is expressed as two divergently transcribed units. We determined the complete nucleotide sequence of an 8,755-bp region of the Ti plasmid encompassing the transposon insertions defining tra. The region contains six identifiable genes organized as two units divergently transcribable from a 258-bp inter-genic region that contains the oriT site. One unit encodes traA, traF, and traB, while the second encodes traC, traD, and traG. Reporter insertions located downstream of both sets of genes did not affect conjugation but were expressed, suggesting that the two units encode additional genes that are not involved in transfer under the conditions tested. Proteins of the predicted sizes were expressible from traA, traC, traD, and traG. The products of several Ti plasmid tra genes are related to those of other conjugation systems. The 127-kDa protein expressed from traA contains domains related to MobA of RSF1O1O and to the helicase domain of TraI of plasmid F. The translation product of traF is related to TraF of RP4, and that of traG is related to TraG of RP4 and to VirD4 of the Ti plasmid T-DNA transfer system. Genetic analysis indicated that at least traG and traF are essential for conjugal transfer, while sequence analysis predicts that traA also encodes an essential function. traB, while not essential, is required for maximum frequency of transfer. Patterns of sequence relatedness indicate that the oriT and the predicted cognate site-specific endonuclease encoded by traA share lineage with those of the transfer systems of RSF1010 and plasmid F, while genes of the Ti plasmid encoding other essential tra functions share common ancestry with genes of the RP4 conjugation system.

Agrobacterium tumefaciens↗
PubMed1999

Phagotopes derived by antibody screening of phage-displayed random peptide libraries vary in immunoreactivity: studies using an exemplary monoclonal antibody, CII-C1, to type II collagen.

Antibody screening of phage-displayed random peptide libraries to identify mimotopes of conformational epitopes is promising. However, because interpretations can be difficult, an exemplary system has been used in the present study to investigate whether variation in the peptide sequences of selected phagotopes corresponded with variation in immunoreactivity. The phagotopes, derived using a well-characterized monoclonal antibody, CII-C1, to a known conformational epitope on type II collagen, C1, were tested by direct and inhibition ELISA for reactivity with CII-C1. A multiple sequence alignment algorithm, PILEUP, was used to sort the peptides expressed by the phagotopes into clusters. A model was prepared of the C1 epitope on type II collagen. The 12 selected phagotopes reacted with CII-C1 by both direct ELISA (titres from < 100-11 200) and inhibition ELISA (20-100% inhibition); the reactivity varied according to the peptide sequence and assay format. The differences in reactivity between the phagotopes were mostly in accord with the alignment, by PILEUP, of the peptide sequences. The finding that the phagotopes functionally mimicked the C1 epitope on collagen was validated in that amino acids RRL at the amino terminal of many of the peptides were topographically demonstrable on the model of the C1 epitope. Notably, one phagotope that expressed the widely divergent peptide C-IAPKRHNSA-C also mimicked the C1 epitope, as judged by reactivity in each of the assays used: these included cross-inhibition of CII-C1 reactivity with each of the other phagotopes and inhibition by a synthetic peptide corresponding to that expressed by the most frequently selected phagotope, RRLPFGSQM. Thus, it has been demonstrated that multiple phage-displayed peptides can mimic the same epitope and that observed immunoreactivity of selected phagotopes with the selecting mAb can depend on the primary sequence of the expressed peptide and also on the assay format used.

Amino Acid Sequence↗
PubMed2002

Genetic and phenotypic correlations between antibody responses to Escherichia coli, infectious bursa disease virus (IBDV), and Newcastle disease virus (NDV), in broiler lines selected on antibody response to Escherichia coli.

The genetic control of antibody (Ab) response to Escherichia coli (EC), infectious bursa disease virus, and Newcastle disease virus and the genetic and phenotypic correlation between these Ab responses, were evaluated under farm conditions in which chicks were simultaneously exposed to these antigens. The experimental population comprised five groups: two lines divergently selected for high (HH) or low (LL) Ab response to EC vaccination; a commercial broiler dam-line (CC), from which HH and LL had been derived; and the HH x CC and LL x CC hybrid groups (HC and LC, respectively). Lines LL and HH expressed similar symmetric divergence to all three antigens. The ranking of the LL, LC, CC, HC, and HH genetic groups according to their mean Ab responses and their very high linear correlation with the LL vs. HH genomic scale clearly indicate the additive nature of the genetic divergence between these lines. Several estimates of correlation were calculated between Ab responses of each pair of antigens and between BW and Ab to each antigen. The high correlation between group means, the near-zero within-group correlation, and the low phenotypic correlation indicate the strongly positive genetic correlation between Ab responses and no correlation with BW. The results of this study suggest that overall immunocompetence of commercial broilers can be improved by selection for high Ab response of young chicks to controlled immunization with a single antigen, without counteracting further selection for high BW.

Animals↗
PubMed2004

Characterization of a root-specific Arabidopsis terpene synthase responsible for the formation of the volatile monoterpene 1,8-cineole.

Arabidopsis is emerging as a model system to study the biochemistry, biological functions, and evolution of plant terpene secondary metabolism. It was previously shown that the Arabidopsis genome contains over 30 genes potentially encoding terpene synthases (TPSs). Here we report the characterization of a monoterpene synthase encoded by two identical, closely linked genes, At3g25820 and At3g25830. Transcripts of these genes were detected almost exclusively in roots. An At3g25820/At3g25830 cDNA was expressed in Escherichia coli, and the protein thus produced was shown to catalyze the formation of 10 volatile monoterpenes from geranyl diphosphate, with 1,8-cineole predominating. This protein was therefore designated AtTPS-Cin. The purified recombinant AtTPS-Cin displayed similar biochemical properties to other known monoterpene synthases, except for a relatively low K(m) value for geranyl diphosphate of 0.2 microm. At3g25820/At3g25830 promoter activity, measured with a beta-glucuronidase (GUS) reporter gene, was primarily found in the epidermis, cortex, and stele of mature primary and lateral roots, but not in the root meristem or the elongation zone. Although the products of AtTPS-Cin were not detected by direct extraction of plant tissue, the recent report of 1,8-cineole as an Arabidopsis root volatile (Steeghs M, Bais HP, de Gouw J, Goldan P, Kuster W, Northway M, Fall R, Vivanco JM [2004] Plant Physiol 135: 47-58) suggests that the enzyme products may be released into the rhizosphere rather than accumulated. Among Arabidopsis TPSs, AtTPS-Cin is most similar to the TPS encoded by At3g25810, a closely linked gene previously shown to be exclusively expressed in flowers. At3g25810 TPS catalyzes the formation of a set of monoterpenes that is very similar to those produced by AtTPS-Cin, but its major products are myrcene and (E)-beta-ocimene, and it does not form 1,8-cineole. These data demonstrate that divergence of organ expression pattern and product specificity are ongoing processes within the Arabidopsis TPS family.

Alkyl and Aryl Transferases↗
PubMed1999

Up-regulation of CCR2 chemokine receptor expression and increased susceptibility to the multitropic HIV strain 89.6 in monocytes exposed to glucocorticoid hormones.

Glucocorticoid hormones (GC) are potent antiinflammatory agents widely used in the treatment of diverse human diseases. The present study was aimed at assessing the effect of GC on chemokine receptor expression in human monocytes. Dexamethasone (Dex) up-regulated mRNA expression of the monocyte chemotactic protein (MCP-1, CCL2) chemokine receptor CCR2. The effect was selective in that other chemokine receptors were not substantially affected. Stimulation by Dex was observed after 4 h of exposure at concentrations of 10(-7) to 10(-5) M. Steroids devoid of GC activity were inactive, and the GC receptor antagonist, RU486, inhibited stimulation. Dex did not affect the rate of nuclear transcription, but augmented the CCR2 mRNA half-life. Augmentation of CCR2 expression by Dex was associated with increased chemotaxis. Finally, Dex treatment induced productive replication of the HIV strain 89.6, which utilizes CCR2 as entry coreceptor, in freshly isolated monocytes. Together with previous findings, these results indicate that at least certain pro- and antiinflammatory molecules have reciprocal and divergent effects on expression of a major monocyte chemoattractant, MCP-1, and of its receptor (CCR2). Augmentation of monocyte CCR2 expression may underlie unexplained in vivo effects of GC as well as some of their actions on HIV infection.

Cell Membrane↗
PubMed2000

Repression of the Escherichia coli melR promoter by MelR: evidence that efficient repression requires the formation of a repression loop.

The Escherichia coli MelR protein is a transcription activator that, in the presence of melibiose, activates expression of the melAB operon by binding to four sites located just upstream of the melAB promoter. MelR is encoded by the melR gene, which is expressed from a divergent transcript that starts 237 bp upstream of the melAB promoter transcript start point. In a recent study, we have identified a fifth DNA site for MelR that overlaps the melR promoter transcript start and -10 region. Here we show that MelR binding to this site can downregulate expression from the melR promoter; thus, MelR autoregulates its own expression. Optimal repression of the melR promoter is observed in the absence of melibiose and requires one of the four other DNA sites for MelR at the melAB promoter. The two MelR binding sites required for this optimal repression are separated by 177 bp. We suggest that, in the absence of melibiose, MelR forms a loop between these two sites. We argue that, in the presence of melibiose, this loop is broken as the melAB promoter is activated. However, in the presence of melibiose, the melR promoter can still be partially repressed by MelR binding to the site that overlaps the transcript start and -10 region. Parallels with the Escherichia coli araC-araBAD regulatory region are discussed.

Binding Sites↗
PubMed1994

The two duplicated insecticyanin genes, ins-a and ins-b are differentially expressed in the tobacco hornworm, Manduca sexta.

Two gene-specific probes were generated from the unique sequences in the 3' non-coding regions of the two insecticyanin genes, ins-a and ins-b to study the developmental expression of these genes in Manduca sexta. Both genes were initially transcribed in the freshly hatched first instar larvae and then expressed in the epidermis and to a lesser degree in the fat body during every larval feeding stage. In the epidermis of the 4th and 5th instar larvae, both mRNAs appeared shortly before ecdysis and accumulated to maximal levels within a day. As the larval epidermis became pupally committed on day 3 of the 5th (final) instar, INS-a mRNA quickly decreased, whereas INS-b mRNA showed a second peak of accumulation. In the fat body, both genes showed a similar expression pattern within the 4th instar to that of the epidermis except that levels were lower and ins-b mRNA dominated. In the final instar, only ins-b mRNA was present in significant amount. These findings not only reveal that the two duplicated insecticyanin genes have diverged in their expression pattern but also demonstrate, for the first time, that fat body also expresses insecticyanin genes.

Animals↗