Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Elements”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 847 records · Page 47Linked to original sources
PubMedDate not supplied

The effect of similarity between elemental stimuli and compounds in olfactory patterning discriminations.

We studied the ability of honeybees to discriminate between single odorants and binary olfactory mixtures. We analyzed the effect of the number of common elements between these two stimulus classes on olfactory discrimination. We used olfactory conditioning of the honeybees' proboscis extension reflex (PER), a paradigm in which odors can be associated with a reinforcement of sucrose solution. Bees were asked to discriminate reinforced from nonreinforced olfactory stimuli. They were trained with two elemental odors (A and B) versus a binary olfactory mixture. The mixture was either AB (group 2CE, two common elements), AC (group 1CE, one common element A), or CD (group 0CE, no common element). Three groups followed a positive patterning schedule (mixture reinforced and elements nonreinforced: groups 2CE+, 1CE+, and 0CE+) and three other groups a negative patterning schedule (mixture nonreinforced and elements reinforced: groups 2CE-, 1CE-, and 0CE-). We showed that a reduction of similarity (number of common elements) between elemental odors and compounds enhanced the ability to discriminate elements from compounds and that the kind of compound processing used by the bees supports theories that assume nonelemental compound processing (i.e., that exclude the mere summation of the elemental associative strengths upon compound presentation).

Animals↗
PubMed1975

Characterization of transmissible genetic elements from sucrose-fermenting Salmonella strains.

Two of seven sucrose-fermenting Salmonella strains obtained from clinical sources were found capable of conjugal transfer of the sucrose fermentation (Scr+) property to the Escherichia coli K-12 strain WR3026. The genetic elements conferring this Scr+ property, designated scr-53 and scr-94, were then conjugally transmissible from Escherichia coli WR3026 Scr+ exconjugants to other strains of Escherichia coli at frequences of 5 times 10- minus 6 to 5 times 10- minus 3 for the scr-53 element and 10- minus 6 to 10- minus 5 for the scr-94 element. In Escherichia coli hosts, both of these elements were compatible with F-lac and with each of six previously characterized transmissible lac elements. No antibiotic resistance characteristics or colicin production were discovered to be associated with either scr-53 or scr-94. Neither scr element generated a male host response to the female-specific phage phiII, but the scr-53 element rendered its Escherichia coli host sensitive to the male-specific phage R-17. Escherichia coli hosts containing scr-53 were susceptible to lysis by P1vir, and transduction of the scr-53 element was accomplished with this phage. The scr-53 element was isolated from Escherichia coli WR3026, Scr+ transductants, and Escherichia coli WR2036 Scr+ exconjugants as a covalently closed circular deoxyribonucleic acid molecule with a molecular weight (determined by electron microscopy) of approximately 52 times 10-6. Receipt of the scr-94 element rendered Escherichia coli hosts of this element unsusceptible to lysis by P1vir, although adsorption of the phage by an Escherichia coli WR3026 exconjugant containing scr-94 occurred as efficiently as it did on WR3026 itself. Repeated examination of Escherichia coli strains harboring scr-94, as well as of the Salmonella strain which initially contained it, did not reveal the presence of circular deoxyribonucleic acid. The synthesis of the sucrose cleaving enzyme was inducible in Escherichia coli exconjugants containing either scr-53 or scr-94.

Centrifugation, Density Gradient↗
PubMed1989

Excision of an 11-kilobase-pair DNA element from within the nifD gene in anabaena variabilis heterocysts.

The 3' region of the Anabaena variabilis nifD gene contains an 11-kilobase-pair element which is excised from the chromosome during heterocyst differentiation. We have sequenced the recombination sites which border the element in vegetative cells and the rearranged heterocyst sequences. In vegetative cells, the element was flanked by 11-base-pair direct repeats which were identical to the repeats present at the ends of the nifD element in Anabaena sp. strain PCC 7120 (Anabaena strain 7120). Although Anabaena strain 7120 and A. variabilis are quite distinct in many ways, the overall sequence similarity between the two strains for the regions sequenced was 96%. Like the Anabaena strain 7120 element, the A. variabilis element was excised in heterocysts to produce a functional nifD gene and a free circularized element which was neither amplified nor degraded. The Anabaena strain 7120 xisA gene is located at the nifK-proximal end of the nifD element and is required for excision of the element in heterocysts. The A. variabilis element also contained an xisA gene which could complement a defective Anabaena strain 7120 xisA gene. A. variabilis did not contain the equivalent of the Anabaena strain 7120 fdxN 55-kilobase-pair element.

Amino Acid Sequence↗
PubMed2000

Selective inhibition of splicing at the avian sarcoma virus src 3' splice site by direct-repeat posttranscriptional cis elements.

The direct-repeat elements (dr1) of avian sarcoma virus (ASV) and leukosis virus have the properties of constitutive transport elements (CTEs), which facilitate cytoplasmic accumulation of unspliced RNA. It is thought that these elements represent binding sites for cellular factors. Previous studies have indicated that in the context of the avian sarcoma virus genome, precise deletion of both ASV dr1 elements results in a very low level of virus replication. This is characterized by a decreased cytoplasmic accumulation of unspliced RNA and a selective increase in spliced src mRNA. Deletion of either the upstream or downstream dr1 results in a delayed-replication phenotype. To determine if the same regions of the dr1 mediate inhibition of src splicing and unspliced RNA transport, point mutations in the upstream and downstream elements were studied. In the context of viral genomes with single dr1 elements, the effects of the mutations on virus replication and increases in src splicing closely paralleled the effects of the mutations on CTE activity. For mutants strongly affecting CTE activity and splicing, unspliced RNA but not spliced RNA turned over in the nucleus more rapidly than wild-type RNA. In the context of wild-type virus containing two dr1 elements, mutations of either element that strongly affect CTE activity caused a marked delay of virus replication and a selective increase in src splicing. However, the turnover of the mutant unspliced RNA as well as the spliced mRNA species did not differ significantly from that of the wild type. These results suggest the dr1 elements in ASV act to selectively inhibit src splicing and that both elements contribute to the fitness of the wild-type virus. However, a single dr1 element is sufficient to stabilize unspliced RNA.

Animals↗
PubMed2002

The human papillomavirus type 31 late 3' untranslated region contains a complex bipartite negative regulatory element.

The papillomavirus life cycle is tightly linked to epithelial cell differentiation. Production of virus capsid proteins is restricted to the most terminally differentiated keratinocytes in the upper layers of the epithelium. However, mRNAs encoding the capsid proteins can be detected in less-differentiated cells, suggesting that late gene expression is controlled posttranscriptionally. Short sequence elements (less than 80 nucleotides in length) that inhibit gene expression in undifferentiated epithelial cells have been identified in the late 3' untranslated regions (UTRs) of several papillomaviruses, including the high-risk mucosal type human papillomavirus type 16 (HPV-16). Here we show that closely related high-risk mucosal type HPV-31 also contains elements that can act to repress gene expression in undifferentiated epithelial cells. However, the HPV-31 negative regulatory element is surprisingly complex, comprising a major inhibitory element of approximately 130 nucleotides upstream of the late polyadenylation site and a minor element of approximately 110 nucleotides mapping downstream. The first 60 nucleotides of the major element have 68% identity to the negative regulatory element of HPV-16, and these elements bind the same cellular proteins, CstF-64, U2AF(65), and HuR. The minor inhibitory element binds some cellular proteins in common with the major inhibitory element, though it also binds certain proteins that do not bind the upstream element.

3' Untranslated Regions↗
PubMed1994

Functional conservation of multiple elements in yeast chromosomal replicators.

Replicators that control the initiation of DNA replication in the chromosomes of Saccharomyces cerevisiae retain their function when cloned into plasmids, where they are commonly referred to as autonomously replicating sequences (ARSs). Previous studies of the structure of ARS1 in both plasmid and chromosome contexts have shown that it contains one essential DNA element, A, that includes a match to the ARS consensus sequence (ACS), and three additional elements, B1, B2, and B3, that are also important for ARS function. Elements A and B3 are bound by a candidate initiator protein called the origin recognition complex and ARS-binding factor 1, respectively. Although the A and B3 elements have been found in other ARSs, sequence comparisons among ARSs have failed to identify B1- and B2-like elements. To assess the generality of the modular nature of yeast replicators, linker substitution mutagenesis of another yeast chromosomal replicator, ARS307, was performed. Three DNA sequence elements were identified in ARS307, and they were demonstrated to be functionally equivalent to the A, B1, and B2 elements present in ARS1. Despite the lack of DNA sequence similarity, the B1 and B2 elements at each ARS were functionally conserved. Single-base substitutions in the core of the ARS1 B1 and B2 elements identified critical nucleotides required for the function of the B1 element. In contrast, no single-point mutations were found to affect B2 function. The results suggest that multiple DNA sequence elements might be a general and conserved feature of replicator sequences in S. cerevisiae.

Base Sequence↗
PubMed2001

Novel fluorescence-based screen to identify small synthetic internal ribosome entry site elements.

We report here a novel fluorescent protein-based screen to identify small, synthetic internal ribosome entry site (IRES) elements in vivo. A library of bicistronic plasmids encoding the enhanced blue and green fluorescent proteins (EBFP and EGFP) separated by randomized 50-nucleotide-long sequences was amplified in bacteria and delivered into mammalian cells via protoplast fusion. Cells that received functional IRES elements were isolated using the EBFP and EGFP reporters and fluorescence-activated cell sorting, and several small IRES elements were identified. Two of these elements were subsequently shown to possess IRES activity comparable to that of a variant of the encephalomyocarditis virus IRES element in a context-independent manner both in vitro and in vivo, and these elements functioned in multiple cell types. Although no sequence or structural homology was apparent between the synthetic IRES elements and known viral and cellular IRES elements, the two synthetic IRES elements specifically blocked poliovirus (PV) IRES-mediated translation in vitro. Competitive protein-binding experiments suggested that these IRES elements compete with PV IRES-mediated translation by utilizing some of the same factors as the PV IRES to direct translation. The utility of this fluorescent protein-based screen in identifying IRES elements with improved activity as well as in probing the mechanism of IRES-mediated translation is discussed.

Base Sequence↗
PubMed1999

Total arterial inertance as the fourth element of the windkessel model.

In earlier studies we found that the three-element windkessel, although an almost perfect load for isolated heart studies, does not lead to accurate estimates of total arterial compliance. To overcome this problem, we introduce an inertial term in parallel with the characteristic impedance. In seven dogs we found that ascending aortic pressure could be predicted better from aortic flow by using the four-element windkessel than by using the three-element windkessel: the root-mean-square errors and the Akaike information criterion and Schwarz criterion were smaller for the four-element windkessel. The three-element windkessel overestimated total arterial compliance compared with the values derived from the area and the pulse pressure method (P = 0.0047, paired t-test), whereas the four-element windkessel compliance estimates were not different (P = 0.81). The characteristic impedance was underestimated using the three-element windkessel, whereas the four-element windkessel estimation differed marginally from the averaged impedance modulus at high frequencies (P = 0.0017 and 0.031, respectively). When applied to the human, the four-element windkessel also was more accurate in these same aspects. Using a distributed model of the systemic arterial tree, we found that the inertial term results from the proper summation of all local inertial terms, and we call it total arterial inertance. We conclude that the fourelement windkessel, with all its elements having a hemodynamic meaning, is superior to the three-element windkessel as a lumped-parameter model of the entire systemic tree or as a model for parameter estimation of vascular properties.

Animals↗
PubMed1989

Multiple cis-acting DNA regulatory elements mediate hepatic angiotensinogen gene expression.

Angiotensinogen is the glycoprotein precursor of angiotensin II, an octapeptide hormone important for the regulation of blood pressure and volume homeostasis. The gene encoding angiotensinogen is expressed in liver and several other tissues, providing a model gene for understanding the role of cis-acting DNA control elements and trans-acting factors in tissue-type specific gene expression. To identify DNA control elements in the rat angiotensinogen gene we prepared an array of fusion genes consisting of either 5' or 3'-deleted sequences of the 5'-flanking region of the gene linked to a firefly luciferase reporter gene and analyzed the relative cellular specificity of expression of these genes after their introduction into hepato-carcinoma cells (Hep G2) that do express and placental cells (JEG-3) that do not express the endogenous angiotensinogen gene. Six transcriptionally active elements were found within 688 base pairs of 5'-flanking DNA. The interactions of DNA binding proteins with these elements was demonstrated by their specific protection to digestion with DNase I in the presence of liver cell extracts. The orientation and spatial requirements for transcription of two of the elements were analyzed further by the construction and expression of synthetic oligonucleotide cassettes incorporating the sequences of these elements when linked to a homologous (angiotensinogen) or a heterologous Simian virus 40 promoter and enhancer. One element located between 60 and 108 base pairs from the start of gene transcription functioned either as a silencer or an enhancer of transcription (SOAP box element), depending upon the distance from the angiotensinogen and viral gene promoters. Moreover, the SOAP box element demonstrated enhancer activity in JEG-3 cells when linked to the Simian virus 40 early promoter. An oligonucleotide mutation of the SOAP box element interfered with protein binding in a gel mobility shift assay and this mutant was transcriptionally inactive in both homologous and heterologous promoters. These observations indicate that expression of the angiotensinogen gene in liver cells is coordinately regulated by multiple cis-acting elements that interact with DNA binding proteins.

Angiotensinogen↗
PubMed1992

Differential capacity of wild type promoter elements for binding and trans-activation by retinoic acid and thyroid hormone receptors.

Retinoic acid receptor (RAR) and thyroid hormone receptor (T3R) are structurally similar and can bind as homodimers or T3R-RAR heterodimers to a single synthetic DNA response element. The interaction of these two types of receptors with wild type elements, however, has not been systematically investigated. Promoter elements from genes regulated by retinoic acid (RA) or thyroid hormone (T3) were tested for response to T3 and RA in transient transfections in both JEG and COS cells. The elements were classified as primarily responsive to RA or to T3 or responsive to both ligands. Binding of highly purified RAR alpha and T3R alpha to the various elements was assessed using the gel shift assay. Those elements predominantly responsive to one ligand showed preferential binding to the appropriate receptor. A series of point mutations were introduced into the rat GH T3 response element to further define sequence requirements for response to both RA and T3. Down-mutations in any of the three hexamers (previously demonstrated to be required for full response to T3 and full binding of T3R) also decreased RA induction and RAR binding. However, only one of two sets of up-mutations for T3 response also increased RA induction, demonstrating differences in hexamer preference between RAR and T3R. Variation in spacing of the three hexamers did not influence RA vs. T3 induction or RAR vs. T3R binding according to the predictions of a simple hexamer spacing model. There was a strong correlation between the extent of T3R dimer binding and strength of T3 induction for a subset of elements studied in JEG cells (r = 0.97, P < 0.01) and a weaker but significant correlation in COS cells (r = 0.65, P < 0.05)). In contrast, RAR dimer binding by the wild type elements did not quantitatively correlate with RA induction in either JEG (r = 0.13, P > 0.05) or COS cells (r = 0.21, P > 0.05). These results suggests that RAR interacts with a heterodimer partner(s) which influences binding site specificity, whereas T3R heterodimer partner(s) is less likely to alter binding site recognition. The observed difference in COS and JEG cells as well as the weak T3R binding-function relationship of the malic enzyme element, however, suggest that the influence of T3R heterodimer partner(s) on binding site specificity is likely to vary with cell type and the specific element tested.

Animals↗
PubMed1992

Estrogen response module of the mouse lactoferrin gene contains overlapping chicken ovalbumin upstream promoter transcription factor and estrogen receptor-binding elements.

Transcription of the lactoferrin gene is stimulated by estrogen in mouse uterus. To study direct estrogen regulation of this gene at the molecular level, we cloned and analyzed the 5'-flanking region of the mouse lactoferrin gene. Sequence analysis revealed a putative estrogen-responsive element (ERE) overlapping with a chicken ovalbumin up-stream promoter (COUP) element located at position -349 to -329 from the transcription initiation site. The ERE element differed from the consensus ERE sequence by one nucleotide at the second position of the 3' half of the element (G to A); the COUP element differed by one nucleotide from the chicken COUP element. Synthetic oligonucleotide containing the mouse lactoferrin COUP/ERE element was inserted into the reporter chloramphenicol acetyltransferase vector, then transiently transfected into human endometrium carcinoma RL95-2 cells to assess hormone responsiveness. We found that the COUP/ERE element confers estrogen action to both homologous and heterologous promoters. Nuclear proteins from diethylstilbestrol-treated mouse uteri and proteins from estrogen receptor expression vector-transfected RL95-2 whole cell extract bound in vitro to COUP/ERE element specifically, as assessed by band-shift assay. By using antibodies specific to the estrogen receptor and the COUP transcription factor, we demonstrated that both proteins were present in mouse uterine tissue and interacted specifically with the COUP/ERE element, as shown by the superband shift. Competition experiments with specific ERE or COUP oligonucleotides also confirmed the interaction between lactoferrin COUP/ERE element with the estrogen receptor and the COUP transcription factor. Therefore, we named this sequence mERM, the mouse lactoferrin estrogen response module.

Animals↗
PubMed1993

The constitution of a progesterone response element.

Progesterone receptors (PRs) recognize and bind to DNA in a sequence-specific manner. To define the sequence-specific determinants of PR binding to DNA, we employed a detailed series of target elements and analyzed both PR binding in vitro and PR-mediated activation of a reporter gene in vivo. These elements represent point substitution or insertion mutants of a progesterone response element derived from the mouse mammary tumor virus (MMTV). Substitution of a G for the first T in the 15-base pair (bp) MMTV progesterone response element core sequence, GTTACAAACTGTTCT, increases PR-DNA binding in vitro. All other tested mutations within this sequence either had no effect or decreased PR binding. From these analyses, we infer an optimal PR recognition sequence, -7RGNACANRNTGTNCY+7, composed of hexameric half-sites separated by precisely 3 bp and exhibiting dyad symmetry. Limited substitution of a suboptimal base for an optimal base, as in the wild type MMTV element, can be tolerated, but further suboptimal substitutions significantly decrease binding by PR. The identity of 1 bp within the hexameric half-site, position +/- 5, is unconstrained. Transition mutations, but not transversions, are permitted at position +/- 7. Here the hydrogen bond acceptor of the N-7 position of the purine ring may be involved in receptor recognition, since this feature is shared by the permitted substitutions. Insertion of a single base pair between the half-sites abolishes detectable binding, suggesting that the spatial orientation of the DNA binding domains of the monomeric receptor subunits are fixed by dimerization of the receptor. This pattern of sequence-specific recognition parallels that previously inferred for the glucocorticoid receptor, indicating that the two receptors may be unable to distinguish individual target sites. Each of the mutant response elements was also assessed for its ability to confer progestin responsiveness to a truncated MMTV promoter when introduced into a PR-containing cell line. Elements exhibiting strong receptor binding in vitro were fully inducible, whereas poorly inducible or uninducible elements displayed little or no recognition by receptor in vitro. However, some elements, though poorly bound in vitro, still activated transcription in vivo in response to hormone. In certain cases activation was as good as that seen with the wild type element. Further examination of in vitro receptor binding by this class of mutant elements using higher levels of baculovirus-expressed receptor revealed that many were indeed recognized by receptor, albeit with a lower affinity than the wild type sequence.(ABSTRACT TRUNCATED AT 400 WORDS)

Baculoviridae↗
PubMed2005

Bioinformatic identification of candidate cis-regulatory elements involved in human mRNA polyadenylation.

Polyadenylation is an essential step for the maturation of almost all cellular mRNAs in eukaryotes. In human cells, most poly(A) sites are flanked by the upstream AAUAAA hexamer or a close variant, and downstream U/GU-rich elements. In yeast and plants, additional cis elements have been found to be located upstream of the poly(A) site, including UGUA, UAUA, and U-rich elements. In this study, we have developed a computer program named PROBE (Polyadenylation-Related Oligonucleotide Bidimensional Enrichment) to identify cis elements that may play regulatory roles in mRNA polyadenylation. By comparing human genomic sequences surrounding frequently used poly(A) sites with those surrounding less frequently used ones, we found that cis elements occurring in yeast and plants also exist in human poly(A) regions, including the upstream U-rich elements, and UAUA and UGUA elements. In addition, several novel elements were found to be associated with human poly(A) sites, including several G-rich elements. Thus, we suggest that many cis elements are evolutionarily conserved among eukaryotes, and human poly(A) sites have an additional set of cis elements that may be involved in the regulation of mRNA polyadenylation.

Computational Biology↗
PubMed1991

Regulation of the human ApoA-II gene by the synergistic action of factors binding to the proximal and distal regulatory elements.

We have recently shown that the human apoA-II promoter contains a set of 11 distal regulatory elements between nucleotides -903 and -255 and three proximal regulatory elements between nucleotides -126 and -33 that are essential for hepatic and intestinal transcription of the apoA-II gene (Chambaz, J., Cardot, P., Pastier, D., Zannis, V. I., and Cladaras, C. (1991) J. Biol. Chem. 266, 11676-11685). Deletion or nucleotide substitution analysis has shown that alterations in elements L (nucleotides -803 to -773) and K (nucleotides -760 to -743) reduced hepatic transcription to 25 and 20% and intestinal transcription to 8 and 4% of control, respectively, as measured by chloramphenicol acetyltransferase assays, indicating that these elements play an important regulatory role. Nucleotide substitutions in element AB (nucleotides -65 to -33) reduced hepatic and intestinal transcription to 60 and 36% of control, respectively. The factors that recognize regulatory regions L, K, and AB were analyzed by DNA binding gel electrophoretic and competition assays. This analysis has shown that elements AB, K, and L bind with different affinities to a newly characterized heat-stable factor, CIIIB1, which is a transcriptional activator of the human apoC-III gene (Ogami, K., Kardassis, D., Cladaras, C., and Zannis, V. I. (1991) J. Biol. Chem. 266, 9640-9646). In addition, elements AB and K bind a heat-labile activity, designated AIIAB1, and element L binds to several CCAAT box binding activities. Mutations in domain L that prevented the binding of CCAAT box binding activities reduced both hepatic and intestinal transcription to 30% of control, indicating the importance of these factors in transcription. Simultaneous nucleotide substitutions that prevented the binding of CIIIB1 activity in elements AB, K, and L reduced hepatic and intestinal transcription to 7 and 6% of control, respectively, suggesting that the synergistic interaction of CIIIB1 (bound to the proximal and distal regulatory elements) with CCAAT box proteins (bound to element L) can modulate the level of transcription of the human apoA-II gene.

Animals↗
PubMed1985

Supernumerary chromosomal elements in lymphocytes cultured from phenotypically normal human adult males.

In a group of phenotypically normal men there were approximately 0.24% of metaphase lymphocytes with extra chromosomal elements along with the regular 46 chromosomes. They ranged in size from small acrocentric-acentric elements to elements longer than any chromosome arm. These elements have been referred to as supernumerary chromosomal elements. No significant effects due to donor's age, smoking history, season, storage of blood samples prior to culture, or culture medium, were found either in the frequency of supernumerary elements per cell or in the frequency of cells with supernumerary elements. Furthermore, the same subject did not consistently exhibit supernumerary elements. Furthermore, the same subject did not consistently exhibit supernumerary elements when sampled during four successive quarters of the year. Some of these elements in pairs were identified by G-banding technique as translocation chromosomes bearing long arms of chromosome number 2 and presumptive short arms of chromosome 8, acentric long arms of chromosome 4, and iso-acentric chromosomes for the long arms of chromosome 5. Presumably, more than one type of cytogenetic event occurred in their formation. Circumstantial evidence has been presented to show that the means of elimination of these supernumerary elements is a process of chromosomal disintegration.

Adult↗
PubMed1997

In situ dissection of the Fab-7 region of the bithorax complex into a chromatin domain boundary and a Polycomb-response element.

Parasegmental (PS)-specific expression of the homeotic genes of the bithorax-complex (BX-C) appears to depend upon the subdivision of the complex into a series of functionally independent cis-regulatory domains. Fab-7 is a regulatory element that lies between iab-6 and iab-7 (the PS11- and PS12-specific cis-regulatory domains, respectively). Deletion of Fab-7 causes ectopic expression of iab-7 in PS11 (where normally only iab-6 is active). Two models have been proposed to account for the dominant Fab-7 phenotype. The first considers that Fab-7 functions as a boundary element that insulates iab-6 and iab-7. The second model envisages that Fab-7 contains a silencer element that keeps iab-7 repressed in parasegments anterior to PS12. Using a P-element inserted in the middle of the Fab-7 region (the bit transposon), we have generated an extensive collection of new Fab-7 mutations that allow us to subdivide Fab-7 into a boundary element and a Polycomb-respond element (PRE). The boundary lies within 1 kb of DNA on the proximal side of the bit transposon (towards iab-6). Deletions removing this element alone cause a complex gain- and loss-of-function phenotype in PS11; in some groups of cells, both iab-6 and iab-7 are active, while in others both iab-6 and iab-7 are inactive. Thus, deletion of the boundary allows activating as well as repressing activities to travel between iab-6 and iab-7. We also provide evidences that the boundary region contains an enhancer blocker element. The Polycomb-response element lies within 0.5 kb of DNA immediately distal to the boundary (towards iab-7). Deletions removing the PRE alone do not typically cause any visible phenotype as homozygotes. Interestingly, weak ectopic activation of iab-7 is observed in hemizygous PRE deletions, suggesting that the mechanisms that keep iab-7 repressed in the absence of this element may depend upon chromosome pairing. These results help to reconcile the previously contradictory models on Fab-7 function and to shed light on how a chromatin domain boundary and a nearby PRE concur in the setting up of the appropriate PS-specific expression of the Abd-B gene of the BX-C.

Abdomen↗
PubMed2001

Multielement determination and speciation of major-to-trace elements in black tea leaves by ICP-AES and ICP-MS with the aid of size exclusion chromatography.

A multielement determination of major-to-trace elements in black tea leaves and their tea infusions was carried out by ICP-AES (inductively coupled plasma atomic emission spectrometry) and ICP-MS (inductively coupled plasma mass spectrometry). Tea infusions were prepared as usual tea beverage by brewing black tea leaves in boiling water for 5 min. About 40 elements in tea leaves and tea infusions could be determined over the wide concentration range in 8 orders of magnitude. The extraction efficiency of each element was estimated as the ratio of its concentration in tea infusions to that in tea leaves. From the experimental results for the extraction efficiencies, the elements in black tea leaves were classified into three characteristic groups: (i) highly-extractable elements (>55%): Na, K, Co, Ni, Rb, Cs and Tl, (ii) moderately-extractable elements (20-55%): Mg, Al, P, Mn and Zn, and (iii) poorly-extractable elements (<20%): Ca, Fe, Cu, Sr, Y, Zr, Mo, Sn, Ba and lanthanoid elements. Furthermore, speciation of major-to-trace elements in tea infusions was performed by using a combined system of size exclusion chromatography (SEC) and ICP-MS (or ICP-AES). As a result, many diverse elements were found to be present as complexes associated with large organic molecules in tea infusions.

Chromatography, Gel↗
PubMed1998

Recent B2 element insertions in the mouse genome.

B2 elements are a family of short interspersed repeats that have amplified within rodent genomes. Recent mobility of only two individual B2 elements has been reported to date. We identified an additional recent B2 insertion occurring within intron 4 of the murine beta-glucuronidase gene (Gus-s) of the BalbC strain of mouse by analyzing orthologous loci of a nonrandomly selected B2 element. The basis of selection for the B2 element was its high level of sequence identity to the B2 consensus. The selected B2 element was amplified by the polymerase chain reaction (PCR) using primers to the unique flanking sequences from genomic DNA of several species and laboratory strains of mice. Our results demonstrated the presence of the selected B2 element only in the genome of Mus musculus BalbC strain. Cloning and sequencing of a representative sample of the products obtained confirmed the absence of the B2 element within this intron in addition to other variations in the sequence. The detection of the B2 element only in the BalbC strain suggests that the element recently inserted within this mouse population when the initial laboratory colony was formed. Sequence comparison of the two previously identified recent B2 inserts also shows a low divergence in relation to the B2 type II consensus. The data presented confirms that recently inserted B2 elements closely match their consensus sequence, potentially allowing for their identification.

Animals↗