PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Essential elements”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

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

At least 37 records · Page 2Linked to original sources
PubMed1986

Tripartite upstream promoter element essential for expression of Saccharomyces cerevisiae ribosomal protein genes.

To initiate a genetic analysis of yeast ribosomal protein gene promoters, we have constructed a gene fusion between the yeast ribosomal protein gene RP39A and the Escherichia coli lacZ gene. This gene fusion contains approximately 1,030 nucleotides of the 5' flanking region and the first 49 1/3 codons of RP39A fused in frame to a large 3' end fragment of lacZ. Whether it is introduced into yeast cells on a moderately high-copy-number plasmid, or integrated into the yeast genome at the RP39A locus, this RP39A-lacZ gene directs the synthesis of a hybrid transcript which encodes beta-galactosidase activity. Deletions in the 5' flanking region of RP39A-lacZ were constructed by linker insertion and BAL 31 mutagenesis. The expression of the mutant genes in yeast cells was assayed by measuring RP39A-lacZ mRNA and beta-galactosidase levels. By these means we have shown that the sequences between nucleotides -256 and -170 upstream of RP39A are essential for expression of this gene. Three sequence motifs, HOMOL1, RPG, and a T-rich region, which were found in that order 5'----3' upstream of most yeast ribosomal protein genes, were present within this interval. We found that substitution of the CYC1-lacZ upstream activation site with the fragment from nucleotides -298 to -172 upstream of RP39A, containing the HOMOL1-RPG-T-rich motif in that 5'----3' orientation, fully restored expression of the CYC1-lacZ gene. The essentially of HOMOL1, the RPG sequence, and the T-rich region for wild-type levels of expression of RP39A, the conserved location and order of these sequence motifs in yeast ribosomal protein genes, and the ability of a DNA fragment carrying these three sequence elements to substitute for the upstream activation site regions of CYC1 indicate that these three oligonucleotides may be essential to the transcription of yeast ribosomal protein genes.

Base Sequence↗
PubMed1990

Interactions between lead and essential elements: a review.

Young children are especially susceptible to the toxic effects of lead. Although the effects of overt lead intoxication have been well studied, critical information on the long-term effects of low level lead exposure is lacking. The results of recent clinical studies indicate that "chronic" low level lead exposure during development can result in behavioral alterations in the absence of overt neurotoxicity. The perturbation of central nervous system functioning may be the result of essential mineral deficiencies resulting from lead-induced impairment of mineral availability and/or an increased sensitivity to lead in the absence of adequate levels of essential minerals. This article reviews research undertaken to examine the interactions between calcium, iron, zinc, copper and lead with reference to how this may impact central nervous system functioning.

Animals↗
PubMed1990

A myosin-like dimerization helix and an extra-large homeodomain are essential elements of the tripartite DNA binding structure of LFB1.

The transcription activator LFB1 is a major determinant of hepatocyte-specific expression of many genes. To study the mechanisms underlying LFB1 transcriptional selectivity, we have initiated its biochemical characterization. By in vitro complementation assays we have defined two distinct regions required for high levels of transcription, which resemble previously described activation domains. In contrast, the region of LFB1 necessary for DNA binding displays several novel features. The DNA binding domain is tripartite, including a homeodomain of unusual length (81 amino acids) and an N-terminal helix similar to part of myosin. This helical region mediates dimerization, which is shown to be essential for DNA binding.

Amino Acid Sequence↗
PubMed1990

Identification of essential elements in U14 RNA of Saccharomyces cerevisiae.

The U14 RNA of Saccharomyces cerevisiae is a small nucleolar RNA (snoRNA) required for normal production of 18S rRNA. Depletion of U14 results in impaired processing of pre-rRNA, deficiency in 18S-containing intermediates and marked under-accumulation of mature 18S RNA. The present report describes results of functional mapping of U14, by a variety of mutagenic approaches. Special attention was directed at assessing the importance of sequence elements conserved between yeast and mouse U14 as well as other snoRNA species. Functionality was assessed in a test strain containing a galactose dependent U14 gene. The results show portions of three U14 conserved regions to be required for U14 accumulation or function. These regions include bases in: (i) the 5'-proximal box C region, (ii) the 3'-distal box D region, and (iii) a 13 base domain complementary to 18S rRNA. Point and multi-base substitution mutations in the snoRNA conserved box C and box D regions prevent U14 accumulation. Mutations in the essential 18S related domain do not effect U14 levels, but do disrupt synthesis of 18S RNA, indicating that this region is required for function. Taken together, the results suggest that the box C and box D regions influence U14 expression or stability and that U14 function might involve direct interaction with 18S RNA.

Animals↗
PubMed1985

The conserved CAAGAAAGA spacer sequence is an essential element for the formation of 3' termini of the sea urchin H3 histone mRNA by RNA processing.

Analysis of cDNA sequences obtained from the small nuclear RNA U7 has previously suggested specific contacts, by base pairing, between the conserved stem-loop structure and CAAGAAAGA sequence of the histone pre-mRNA and the 5'-terminal sequence of the U7 RNA during RNA processing. In order to test some aspects of the model we have created a series of linker scan, deletion and insertion mutants of the 3' terminus of a sea urchin H3 histone gene and have injected mutant DNAs or in vitro synthesized precursors into frog oocyte nuclei for interpretation. We find that, in addition to the stem-loop structure of the mRNA, the CAAGAAAGA spacer transcript within the histone pre-mRNA is required absolutely for RNA processing, as predicted from our model. Spacer sequences immediately downstream of the CAAGAAAGA motif are not complementary to U7 RNA. Nevertheless, they are necessary for obtaining a maximal rate of RNA processing, as is the ACCA sequence coding for the 3' terminus of the mature mRNA. An increase of distance between the mRNA palindrome and the CAAGAAAGA by as little as six nucleotides abolishes all processing. It may, therefore, be useful to regard both these sequence motifs as part of one and the same RNA processing signal with narrowly defined topologies. Interestingly, U7 RNA-dependent 3' processing of histone pre-mRNA can occur in RNA injection experiments only when the in vitro synthesized pre-mRNA contains sequence extensions well beyond the region of sequence complementarities to the U7 RNA. In addition to directing 3' processing the terminal mRNA sequences may have a role in histone mRNA stabilization in the cytoplasmic compartment.

Animals↗
PubMed1989

Injury biomechanics research: an essential element in the prevention of trauma.

The central aspects of injury biomechanics research are defined and research approaches described. These aspects include the identification and definition of impact injury mechanisms, the quantification of biomechanical response to impact, the determination of impact tolerance levels, and the development and use of injury assessment devices and techniques for evaluating injury prevention systems. The current status of knowledge and technology is then reviewed for the head, cervical spine, thorax, abdomen, and lower extremity. Important gaps are identified, and research priorities emphasizing functional impairment are proposed.

Abdominal Injuries↗
PubMedDate not supplied

Yeast calmodulin: structural and functional elements essential for the cell cycle.

The budding yeast Saccharomyces cerevisiae is a suitable organism for studying calmodulin function in cell proliferation. Genetic studies in yeast demonstrate that vertebrate calmodulin can functionally replace yeast calmodulin. In addition, expression of half of the yeast calmodulin molecule is found to be sufficient for cell growth. Characterization of conditional-lethal mutants of yeast calmodulin as well as the intracellular distribution of calmodulin have suggested that at least two cell cycle steps require calmodulin function. One is nuclear division and the other is the maintenance of cell polarity. A current focus is to understand which kinds of target proteins are involved in mediating the essential functions of yeast calmodulin in these processes. Thus far, three yeast enzymes whose activity is regulated by calmodulin have been identified.

Calmodulin↗
PubMed1978

Iron, an essential element for biosynthesis of aromatic compounds.

Homogeneous preparations of 3-deoxy-D-arabino-heptulosonate-7-phosphate synthase [7-phospho-2-keto-3-deoxy-D-arabino-heptonate D-erythrose-4-phosphate lyase (pyruvate phosphorylating), EC 4.1.2.15] isolated as the enzyme-phosphoenolpyruvate complex from Escherichia coli are shown by atomic absorption analysis to contain approximately one mole of iron per mole of native enzyme. No cobalt was found, in contrast to suggestions of earlier workers. Pure enzyme preparations show a unique absorption maximum around 350 nm with an epsilon value of about 3500 M-1cm-1. The 350-nm band as well as the enzyme activity is lost when the enzyme is denatured with guanidine-hydrochloride, or when phosphoenolpyruvate, the first substrate to bind to the enzyme, is totally removed from the enzyme by incubation with an excess of erythrose 4-phosphate, the second substrate to bind to the enzyme. The iron remains bound to the enzyme when phosphoenolpyruvate is removed from the enzyme-phosphoenolpyruvate complex.

3-Deoxy-7-Phosphoheptulonate Synthase↗
PubMed1992

Coping: an essential element of nursing.

How well a person copes is central in determining his or her well-being, no matter how ill he or she is. Without an accurate appreciation of what coping is and how it may be facilitated, attempts to help patients may be both ineffective and harmful. But the subject is multifaceted and poses many problems for clinicians and researchers alike. This paper attempts to synthesize available knowledge on coping from various disciplines and apply it to life as nurses know it.

Adaptation, Psychological↗
PubMed1985

Point mutations implicate repeated sequences as essential elements of the CYC7 negative upstream site in Saccharomyces cerevisiae.

The transcription of the CYC7 gene of Saccharomyces cerevisiae, encoding the iso-2-cytochrome c protein, is controlled by two upstream regulatory elements, a positive element and a negative element. The nature of the DNA sequences in the negative element were investigated in a two-part approach. The first involved the construction of a CYC7-galK fusion gene which placed the coding sequence of the Escherichia coli galactokinase gene under the regulation of the CYC7 upstream sequences. This fusion allowed the quantitation by galactokinase enzyme assays of the effects on gene expression of a variety of previously isolated deletion mutations within the negative site. The results suggested that the negative site contained three related sequences. This hypothesis was tested in the second part of these studies, the selection of point mutations within the region of the negative site which led to increased CYC7 expression. Point mutations were introduced by a technique which induced mutations within a localized region at high efficiency. All but one of the mutations involved more than a single base-pair change. The mutations followed the pattern that multiple base-pair changes occurred in one repeat or single base-pair changes occurred in two repeats, with the exception of one mutant, which had a single base-pair change in one repeat. This pattern of mutations and the base pairs that were altered strongly supported the hypothesis that the repeats are integral elements of the negative site.

Base Sequence↗
PubMed1988

Three sequence-specific DNA-protein complexes are formed with the same promoter element essential for expression of the rat somatostatin gene.

We identified three sequence-specific DNA-protein complexes which are formed after in vitro binding of nuclear extracts, derived from neuronal (CA-77, rat brain) or non-neuronal (HeLa) cells, to positions -70 to -29 of the rat somatostatin promoter. The protein(s) responsible for the formation of the three sequence-specific complexes was fractionated from rat brain whole cell extracts by DEAE-Sepharose chromatography. The critical contact residues of the factor(s) in each complex, as determined by methylation interference analyses, are located within positions -59 to -35, which is protected from DNase I digestion; these include the G residues of a TGACGTCA consensus also found in the cAMP-responsive human enkephalin (positions -105 to -76) and E1A-inducible adenovirus type 5 E3 (positions -72 to -42) promoters. Competition assays with these heterologous promoters reveal that the factor(s) of each complex displays approximately 50-fold greater affinity for the somatostatin promoter-binding site. Synthetic oligonucleotides spanning positions -70 to -29 of the somatostatin promoter and containing single-base substitutions of the G residues in the TGACGTCA consensus were utilized in competition assays. The G residues located in the center of the module are the most critical determinants in the formation of the three sequence-specific complexes. Deletions disrupting the TGACGTCA consensus abolish not only formation of the three complexes in vitro but also expression of the somatostatin promoter in vivo, suggesting that formation of one or more of these complexes is essential for transcription of the rat somatostatin gene.

Adenoviridae↗