Página 5 dos resultados de 13330 itens digitais encontrados em 0.029 segundos

‣ Canonical P elements are transcriptionally active in the saltans group of Drosophila

De Castro, Juliana Polachini; Carareto, Cláudia Márcia A.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 31-40
Português
Relevância na Pesquisa
36.695742%
Up to now, investigations of expression and regulation of P transposable element have been almost exclusively carried out with the Drosophila melanogaster canonical P element. Analyzing eight species of the saltans group, we detected transposase mRNA in germline tissues of D. saltans and D. prosaltans and repressor mRNA in somatic tissues of D. saltans and D. sturtevanti. Sequencing analysis suggested that these transcripts might belong to the canonical subfamily and that they can be transpositionally active only in D. saltans. dN and dS values of Adh and the P element suggested that the sequences found in D. saltans and D. prosaltans might have been present in the ancestor of the saltans subgroup and that the sequence found in D. sturtevanti might have been horizontally transferred from D. saltans.

‣ Characterization and genome organization of a repetitive element associated with the nucleolus organizer region in leporinuselongatus (anostomidae: Characiformes)

Da Silva, E. L.; Busso, A. F.; Parise-Maltempi, P. P.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 22-28
Português
Relevância na Pesquisa
36.695742%
Chromosome mapping and studies of the genomic organization of repetitive DNA sequences provide valuable insights that enhance our evolutionary and structural understanding of these sequences, as well as identifying chromosomal rearrangements and sex determination. This study investigated the occurrence and organization of repetitive DNA sequences in Leporinus elongatus using restriction enzyme digestion and the mapping of sequences by chromosomal fluorescence in situ hybridization (FISH). A 378-bp fragment with a 54.2% GC content was isolated after digestion with the SmaI restriction enzyme. BLASTN search found no similarity with previously described sequences, so this repetitive sequence was named LeSmaI. FISH experiments were conducted using L. elongatus and other Anostomidae species, i.e. L. macrocephalus,L. obtusidens, L. striatus, L. lacustris, L. friderici, Schizodon borellii, S. isognathus, and Abramites hypselonotus which detected signals that were unique to male and female L. elongatus individuals. Double-FISH using LeSmaI and 18S rDNA showed that LeSmaI was located in a nucleolus organizer region (NOR) in the male and female metaphases of L. elongatus. This report also discusses the role of repetitive DNA associated with NORs in the diversification of Anostomidae species karyotypes. Copyright © 2012 S. Karger AG...

‣ Selected base sequence outside the target binding site of zinc finger protein Sp1

Nagaoka, Makoto; Shiraishi, Yasuhisa; Sugiura, Yukio
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artigo de Revista Científica
Publicado em 15/12/2001 Português
Relevância na Pesquisa
36.695742%
Human transcription factor Sp1 contains three contiguous repeats of the C2H2-type zinc finger motif and binds to the decanucleotide sequence 5′-(G/T)GGGCGG(G/A)(G/A)(C/T)-3′ (GC box). In order to determine whether the three-zinc finger peptide Sp1(530–623) has selectivity for sequence outside the GC box, we used a selection and amplification of binding experiment. The high affinity sequence generated from this selection is 5′-GGGTGGGCGTGGC-3′ (s-GC box), which is flanked by a novel conserved guanine triplet on the 5′-side of the core decanucleotide. Gel mobility shift assays reveal that Sp1(530–623) binds to the s-GC box with 2.3-fold higher affinity than to the wild-type GC box, 5′-GGGGCGGGGC-3′ (c-GC box). DNase I and hydroxyl radical footprinting analyses show that the area of the s-GC box protected by binding of Sp1(530–623) is wider by 1 nt than that of the c-GC box. On the other hand, alkylation interference analyses demonstrate that Sp1(530–623) forms only one special base contact at the guanine triplet. With respect to cleavage of the c-GC and s-GC boxes by the 1,10-phenanthroline–copper complex (OP-Cu), binding of Sp1(530–623) has no effect on the cleavage pattern of the s-GC box, whereas OP-Cu actually enhances cleavage of the c-GC box. Additionally...

‣ Inhibition of polyoma DNA synthesis by base pair substitutions at the replication origin.

Luthman, H; Osterlund, M; Magnusson, G
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 11/10/1984 Português
Relevância na Pesquisa
36.726797%
The effect of base pair substitutions on the function of the polyoma virus origin of DNA replication was studied. The mutations were all C-G to T-A transitions, induced by bisulfite treatment of recombinant DNA molecules. The mutagenesis was directed to short single-stranded gaps in duplex DNA, or to loops in heteroduplex molecules. Modification of a 34 base pair sequence of dyad symmetry led to cis-acting inhibition of viral DNA synthesis, ranging from slight defects to total inactivation. One of the mutants was temperature sensitive. Mutants with base changes in an adjacent DNA segment, including an 18 base pair long purine-pyrimidine tract, had similar, but less severe, deficiences. In contrast to the effect of mutations in the homologous region of the simian virus 40 genome, there was no strict relationship between mutation of the putative large T-antigen-binding base sequence GPuGGC and defective viral DNA synthesis.

‣ Purification of Mbo II methylase (GAAGmA) from Moraxella bovis: site specific cleavage of DNA at nine and ten base pair sequences.

McClelland, M; Nelson, M; Cantor, C R
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 25/10/1985 Português
Relevância na Pesquisa
36.695012%
The restriction modification methylase M. Mbo II has been purified using a sensitive oligonucleotide linker assay. The enzyme methylates the Mbo II recognition sequence* GAAGA at adenine to produce GAAGmA. M. Mbo II can be used in conjunction with the methylation dependent restriction endonuclease Dpn I (GmATC) to produce cleavage at the 10 base sequence GAAGATCTTC. When M. Mbo II is used in combination with M. Cla I (ATCGATCGAT), cleavage by Dpn I occurs at the four ten base sequences GAAGATCTTC, GAAGATCGAT, ATCGATCTTC and ATCGATCGAT, which is equivalent to a nine base recognition site. The use of combinations of adenine methylases and Dpn I to generate highly selective DNA cleavages at a variety of sequences up to fourteen base pairs is discussed.

‣ The primitive code and repeats of base oligomers as the primordial protein-encoding sequence.

Ohno, S; Epplen, J T
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /06/1983 Português
Relevância na Pesquisa
36.726797%
Even if the prebiotic self-replication of nucleic acids and the subsequent emergence of primitive, enzyme-independent tRNAs are accepted as plausible, the origin of life by spontaneous generation still appears improbable. This is because the just-emerged primitive translational machinery had to cope with base sequences that were not preselected for their coding potentials. Particularly if the primitive mitochondria-like code with four chain-terminating base triplets preceded the universal code, the translation of long, randomly generated, base sequences at this critical stage would have merely resulted in the production of short oligopeptides instead of long polypeptide chains. We present the base sequence of a mouse transcript containing tetranucleotide repeats conserved during evolution. Even if translated in accordance with the primitive mitochondria-like code, this transcript in its three reading frames can yield 245-, 246-, and 251-residue-long tetrapeptidic periodical polypeptides that are already acquiring longer periodicities. We contend that the first set of base sequences translated at the beginning of life were such oligonucleotide repeats. By quickly acquiring longer periodicities, their products must have soon gained characteristic secondary structures--alpha-helical or beta-sheet or both.

‣ Identical 3′-terminal octanucleotide sequence in 18S ribosomal ribonucleic acid from different eukaryotes. A proposed role for this sequence in the recognition of terminator codons

Shine, John; Dalgarno, Lynn
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /09/1974 Português
Relevância na Pesquisa
36.751748%
The 3′-terminal sequence of 18S ribosomal RNA from Drosophila melanogaster and Saccharomyces cerevisiae was determined by stepwise degradation from the 3′-terminus and labelling with [3H]isoniazid. The sequence G-A-U-C-A-U-U-AOH was found at the 3′-terminus of both 18S rRNA species. Less extensive data for 18S RNA from a number of other eukaryotes are consistent with the same 3′-terminal sequence, and an identical sequence has previously been reported for the 3′-end of rabbit reticulocyte 18S rRNA (Hunt, 1970). These results suggest that the base sequence in this region is strongly conserved and may be identical in all eukaryotes. As the 3′-terminal hexanucleotide is complementary to eukaryotic terminator codons we discuss the possibility that the 3′-end of 18S rRNA may have a direct base-pairing role in the termination of protein synthesis.

‣ Activation Energies for Dissociation of Double Strand Oligonucleotide Anions: Evidence for Watson–Crick Base Pairing in Vacuo

Schnier, Paul D.; Klassen, John S.; Strittmatter, Eric F.; Williams*, Evan R.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 23/09/1998 Português
Relevância na Pesquisa
36.726797%
The dissociation kinetics of a series of complementary and noncomplementary DNA duplexes, (TGCA)23−, (CCGG)23−, (AATTAAT)23−, (CCGGCCG)23−, A7·T73−, A7·A73−, T7·T73−, and A7·C73− were investigated using blackbody infrared radiative dissociation in a Fourier transform mass spectrometer. From the temperature dependence of the unimolecular dissociation rate constants, Arrhenius activation parameters in the zero-pressure limit are obtained. Activation energies range from 1.2 to 1.7 eV, and preexponential factors range from 1013 to 1019 s−1. Dissociation of the duplexes results in cleavage of the noncovalent bonds and/or cleavage of covalent bonds leading to loss of a neutral nucleobase followed by backbone cleavage producing sequence-specific (a – base) and w ions. Four pieces of evidence are presented which indicate that Watson–Crick (WC) base pairing is preserved in complementary DNA duplexes in the gas phase: i. the activation energy for dissociation of the complementary dimer, A7·T73−, to the single strands is significantly higher than that for the related noncomplementary A7·A73− and T7·T73− dimers, indicating a stronger interaction between strands with a specific base sequence, ii. extensive loss of neutral adenine occurs for A7·A73− and A7·C73− but not for A7·T73− consistent with this process being shut down by WC hydrogen bonding...

‣ Model-Free RNA Sequence and Structure Alignment Informed by SHAPE Probing Reveals a Conserved Alternate Secondary Structure for 16S rRNA

Lavender, Christopher A.; Lorenz, Ronny; Zhang, Ge; Tamayo, Rita; Hofacker, Ivo L.; Weeks, Kevin M.
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 20/05/2015 Português
Relevância na Pesquisa
36.727634%
Discovery and characterization of functional RNA structures remains challenging due to deficiencies in de novo secondary structure modeling. Here we describe a dynamic programming approach for model-free sequence comparison that incorporates high-throughput chemical probing data. Based on SHAPE probing data alone, ribosomal RNAs (rRNAs) from three diverse organisms – the eubacteria E. coli and C. difficile and the archeon H. volcanii – could be aligned with accuracies comparable to alignments based on actual sequence identity. When both base sequence identity and chemical probing reactivities were considered together, accuracies improved further. Derived sequence alignments and chemical probing data from protein-free RNAs were then used as pseudo-free energy constraints to model consensus secondary structures for the 16S and 23S rRNAs. There are critical differences between these experimentally-informed models and currently accepted models, including in the functionally important neck and decoding regions of the 16S rRNA. We infer that the 16S rRNA has evolved to undergo large-scale changes in base pairing as part of ribosome function. As high-quality RNA probing data become widely available, structurally-informed sequence alignment will become broadly useful for de novo motif and function discovery.

‣ Activities of Two Base Excision Repair Enzymes on Nucleosomal Substrates

Cole, Hope Abigail ; Hayes, Jeffrey J.
Fonte: Universidade de Rochester Publicador: Universidade de Rochester
Tipo: Tese de Doutorado
Português
Relevância na Pesquisa
36.726797%
Thesis (Ph.D.)--University of Rochester. School of Medicine and Dentistry. Dept. of Biochemistry and Biophysics, 2008.; In eukaryotic cells DNA is assembled into chromatin, the basic repeating unit of which is a nucleosome core particle (NCP), made up of approximately 147 base pairs (bp) of DNA wrapped around two copies each of histones H2A, H2B, H3, and H4. Any processes in the cell that use DNA as a substrate, such as DNA repair, replication, recombination, or transcription, must have ways of accessing the DNA present as chromatin. One such process is Base Excision Repair (BER) which repairs damage created by both exogenous and endogenous sources on DNA bases but that does cause major distortion of the DNA helix. If DNA damage is allowed to go uncorrected a variety of consequences could occur including cell death and cancer. Therefore it is important to understand how DNA repair occurs in the context of chromatin. In this thesis I explored the ability of two BER enzymes to carry out their activities on nucleosomal substrates. The first step of BER requires recognition of a damaged base by a DNA glycosylase, which is able to cleave the base from its sugar-phosphate backbone. I quantitatively examined the ability of a uracil DNA glycosylase (UDG) to cleave its substrate when this damage was present in a NCP and a nucleosome. This was done by creating either single site or random U for T substitutions on a DNA sequence that contained a nucleosome-positioning element (NPE) and then reconstituting nucleosomes in vitro. Assays on these substrates indicate that the nucleosome restricts but does not eliminate the activity of UDG when compared to its activity on free DNA substrates. The single site assays indicate that the activity of UDG is dependent on both rotational and translational position of the damage on the DNA within the nucleosome. I next examined what effects linker DNA and the linker histone H10 would have on UDG activity in a nucleosome. The activity of UDG on linker DNA appears to be the same as on free DNA while activity within the core region appears unaltered. Interestingly...

‣ Interpretação de dados de GPR com base na hierarquização de superfícies limitantes e na adaptação de critérios sismoestratigráficos

Andrade, Peryclys Raynyere de Oliveira
Fonte: Universidade Federal do Rio Grande do Norte; BR; UFRN; Programa de Pós-Graduação em Geodinâmica e Geofísica; Geodinâmica; Geofísica Publicador: Universidade Federal do Rio Grande do Norte; BR; UFRN; Programa de Pós-Graduação em Geodinâmica e Geofísica; Geodinâmica; Geofísica
Tipo: Dissertação Formato: application/pdf
Português
Relevância na Pesquisa
36.750828%
Due to its high resolution, Ground Penetrating Radar (GPR) has been used to image subsurface sedimentary deposits. Because GPR and Seismic methods share some principles of image construction, the classic seismostratigraphic interpretation method has been also applied as an attempt to interpret GPR data. Nonetheless some advances in few particular contexts, the adaptations from seismic to GPR of seismostratigraphic tools and concepts unsuitable because the meaning given to the termination criteria in seismic stratigraphy do not represent the adequate geologic record in the GPR scale. Essentially, the open question relies in proposing a interpretation method for GPR data which allow not only relating product and sedimentary process in the GPR scale but also identifying or proposing depositional environments and correlating these results with the well known Sequence Stratigraphy cornerstones. The goal of this dissertation is to propose an interpretation methodology of GPR data able to perform this task at least for siliciclastic deposits. In order to do so, the proposed GPR interpretation method is based both on seismostratigraphic concepts and on the bounding surface hierarchy tool from Miall (1988). As consequence of this joint use...

‣ High Resolution Melting Analysis of Almond SNPs derived from ESTs

Wu, S.; Wirthensohn, M.; Hunt, P.; Gibson, J.; Sedgley, M.
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica
Publicado em //2008 Português
Relevância na Pesquisa
36.695742%
High resolution melting curve (HRM) is a recent advance for the detection of SNPs. The technique measures temperature induced strand separation of short PCR amplicons, and is able to detect variation as small as one base difference between samples. It has been applied to the analysis and scan of mutations in the genes causing human diseases. In plant species, the use of this approach is limited. We applied HRM analysis to almond SNP discovery and genotyping based on the predicted SNP information derived from the almond and peach EST database. Putative SNPs were screened from almond and peach EST contigs by HRM analysis against 25 almond cultivars. All 4 classes of SNPs, INDELs and microsatellites were discriminated, and the HRM profiles of 17 amplicons were established. The PCR amplicons containing single, double and multiple SNPs produced distinctive HRM profiles. Additionally, different genotypes of INDEL and microsatellite variations were also characterised by HRM analysis. By sequencing the PCR products, 100 SNPs were validated/revealed in the HRM amplicons and their flanking regions. The results showed that the average frequency of SNPs was 1:114 bp in the genic regions, and transition to transversion ratio was 1.16:1. Rare allele frequencies of the SNPs varied from 0.02 to 0.5...

‣ Vergleichende Sequenzanalyse der Tegumentproteine UL24, UL32, UL48, UL128-131A bei humanen Cytomegalovirusvarianten mit unterschiedlichem Zelltropismus; Comparing sequence analyse of the tegument proteins UL24, UL32, UL48, UL128-131A of human cytomegalovirus variants with different cell tropism

Autenrieth, Susann Friedericke
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
Português
Relevância na Pesquisa
36.751748%
Stämme des menschlichen Cytomegalovirus (HCMV) zeigen genetisch determinierte Unterschiede im Zelltropismus. Auch Veränderungen im Zelltropismus im Rahmen der Zellkulturadaptation von HCMV-Stämmen sind mit Veränderungen der DNA assoziiert. Der entscheidende Schritt im Replikationszyklus ist hierbei, mit welcher Effizienz die Viruspartikel von HCMV-Stämmen nach der Penetration zum Zellkern transportiert werden. Der Phänotyp wird demnach durch Strukturproteine vermittelt, also Kapsidproteine, durch kapsidassoziierte Tegumentproteine oder Hüllproteine. In dieser Arbeit wurden Tegumentproteine, die durch die viralen Leserahmen UL24, UL32, UL48 und UL128-131A von HCMV-Stämmen mit unterschiedlichem Zelltropismus durch Sequenzierung verglichen, um so Informationen über ihre mögliche Bedeutung für den Zelltropismus von HCMV zu erhalten. Eine weitere wesentliche Aufgabe in dieser Arbeit war geeignete Stämme für den Sequenzvergleich auszuwählen. Es ist bekannt, dass ein direkter Sequenzvergleich zweier beliebiger HCMV-Stämme eine Vielzahl von Unterschieden in nahezu jedem untersuchten Gen aufweist, ohne dass diese für den Phänotyp bedeutsam wären. Daher wurden für diese Arbeit HCMV-Varianten gewählt, welche einen unterschiedlichen Phänotyp aufweisen und genetisch so eng verwandt sind...

‣ Behavior of the Fiber and the Base Points of Parametrizations Under Projections

Pérez Díaz, Sonia; Sendra Pons, Juan Rafael
Fonte: Springer Publicador: Springer
Tipo: info:eu-repo/semantics/article; info:eu-repo/semantics/submittedVersion Formato: application/pdf
Português
Relevância na Pesquisa
36.695012%
This is the author’s version of a work that was accepted for publication in Mathematics in Computer Science. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Mathematics in Computer Science Volume 7, Issue 2 (2013), Page 167-184 DOI 10.1007/s11786-013-0139-8; Given a rational parametrization P( t ), t = (t1, . . . , tr ), of an r-dimensional unirational variety, we analyze the behavior of the variety of the base points of P( t ) in connection to its generic fibre, when successively eliminating the parameters ti . For this purpose. we introduce a sequence of generalized resultants whose primitive and content parts contain the different components of the projected variety of the base points and the fibre. In addition, when the dimension of the base points is strictly smaller than 1 (as in the well known cases of curves and surfaces), we show that the last element in the sequence of resultants is the univariate polynomial in the corresponding Gröbner basis of the ideal associated to the fibre; assuming that the ideal is in t1-general position and radical.; This work has been partially supported by the Spanish Ministerio de Ciencia e Innovación under the project MTM2008-04699-C03-01 and by the Ministerio de Economía y Competitividad under the project MTM2011-25816-C02-01; both authors are members of the of the Research Group ASYNACS (Ref. CCEE2011/R34).

‣ Polymorphism of the yeast pyruvate carboxylase 2 gene and protein: Effects on biotinylation

Val, D.; Chapman-Smith, A.; Walker, M.; Cronan, J.; Wallace, J.
Fonte: The Biochemical Society, London Publicador: The Biochemical Society, London
Tipo: Artigo de Revista Científica
Publicado em //1995 Português
Relevância na Pesquisa
36.727634%
In Saccharomyces cerevisiae there are two isoenzymes of pyruvate carboxylase (Pyc) encoded by separate genes designated PYC1 and PYC2. We report the isolation and sequencing of a PYC2 gene, and the localization of both genes on the physical map of S. cerevisiae. Comparison with the previously reported sequence [Stucka, Dequin, Salmon and Gancedo (1991) Mol. Gen. Genet. 229, 307-315] revealed significant differences within the open reading frame. The most notable difference was near the 3' end, where we found a single base deletion reducing the open reading frame by 15 bases. We have confirmed the C-terminus of Pyc2 encoded by the gene isolated here by expressing and purifying an 86-amino-acid biotin-domain peptide. In addition, we investigated the effects of the two changes in the Pyc2 biotin domain (K1155R substitution and Q1178P/five-amino-acid extension) on the extent of biotinylation in vivo by Escherichia coli biotin ligase, and compared the biotinylation of peptides containing these changes with that of two different-length Pyc1 biotin-domain peptides. The K1155R substitution had very little effect on biotinylation, but the five-amino-acid C-terminal extension to Pyc2 and the N-terminal extension to Pycl both improved biotinylation in vivo.

‣ Base sequence determinants of amonafide stimulation of topoisomerase II DNA cleavage.

De Isabella, P; Zunino, F; Capranico, G
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 25/01/1995 Português
Relevância na Pesquisa
36.695742%
A number of antitumor drugs including naphthalimides, a new class of intercalating agents, interfere with the DNA breakage-reunion activity of mammalian DNA topoisomerase II resulting in DNA cleavage stimulation. In this work, the sequence specificity of a lead compound of this series, amonafide, in stimulating DNA cleavage by murine topoisomerase II has been studied. Amonafide-stimulated cleavage intensity patterns were markedly different from those of other antitumor drugs by using pBR322 and SV40 DNAs. This drug had an unusually high site selectivity since about 60% of DNA cleavage was observed at only one site in pBR322 DNA, and at two sites in SV40 DNA. A total of ninety-four drug-stimulated sites were collected, and a statistical analysis of their sequences showed that amonafide highly prefers a cytosine, and excludes guanines and thymines instead, at position -1. A lower preference for an adenine at position +1 was also noted. In agreement with the statistical analysis, the DNA sequences of the three sites stimulated by amonafide at exceptionally high levels showed that the drug requirements of a cytosine (-1) and adenine (+1) were present in both the two strands. In addition, a particular feature of these prominent cleavage sites was the presence of an inverted repeat from position -3 to +7. Comparison of amonafide stimulation of DNA cleavage in oligonucleotides bearing base mutations at positions -2...

‣ A highly conserved sequence in the 3'-untranslated region of the drosophila Adh gene plays a functional role in Adh expression.

Parsch, J; Stephan, W; Tanda, S
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /02/1999 Português
Relevância na Pesquisa
36.695742%
Phylogenetic analysis identified a highly conserved eight-base sequence (AAGGCTGA) within the 3'-untranslated region (UTR) of the Drosophila alcohol dehydrogenase gene, Adh. To examine the functional significance of this conserved motif, we performed in vitro deletion mutagenesis on the D. melanogaster Adh gene followed by P-element-mediated germline transformation. Deletion of all or part of the eight-base sequence leads to a twofold increase in in vivo ADH enzymatic activity. The increase in activity is temporally and spatially general and is the result of an underlying increase in Adh transcript. These results indicate that the conserved 3'-UTR motif plays a functional role in the negative regulation of Adh gene expression. The evolutionary significance of our results may be understood in the context of the amino acid change that produces the ADH-F allele and also leads to a twofold increase in ADH activity. While there is compelling evidence that the amino acid replacement has been a target of positive selection, the conservation of the 3'-UTR sequence suggests that it is under strong purifying selection. The selective difference between these two sequence changes, which have similar effects on ADH activity, may be explained by different metabolic costs associated with the increase in activity.

‣ The v-ski oncogene encodes a truncated set of c-ski coding exons with limited sequence and structural relatedness to v-myc.

Stavnezer, E; Brodeur, D; Brennan, L A
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /09/1989 Português
Relevância na Pesquisa
36.727634%
The nucleotide sequence of a biologically active v-ski gene from a cloned proviral segment shows that ski is a 1,312-base sequence embedded in the p19 region of the avian leukosis virus gag gene. The v-ski sequence contains a single open translational reading frame that encodes a polypeptide with a molecular mass of 49,000 daltons. The predicted amino acid sequence includes nuclear localization motifs that have been identified in other nuclear oncoproteins. It also contains a proline-rich region and a set of cysteine and histidine residues that could constitute a metal-binding domain. Two regions of the amino acid sequences of v-ski and v-myc are related, and the two proteins exhibit similar distributions of hydrophobic and hydrophilic amino acids. Cloned segments of the chicken c-ski proto-oncogene totaling 65 kilobases have been analyzed, and regions related to v-ski have been sequenced. The results indicate that v-ski is derived from at least five coding exons of c-ski, that it is correctly spliced, and that it is missing c-ski coding sequences at both its 5' and 3' ends. The c-ski and avian leukosis virus sequences that overlap the 5' virus/v-ski junction in Sloan-Kettering virus contain an 18-of-20-base sequence match that presumably played a role in the transduction of ski by facilitating virus/c-ski recombination.

‣ Sequence stratigraphy of the Nukumaruan Stratotype (Pliocene-Pleistocene, c. 2.08-1.63 Ma), Wanganui Basin, New Zealand

Abbott, Steve; Naish, Tim; Carter, R M; Pillans, Bradley
Fonte: CSLI Publications Publicador: CSLI Publications
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
36.751748%
Late Pliocene to Early Pleistocene (c. 2.08 - 1.63 Ma) strata exposed in coastal cliffs along Nukumaru and Ototoka beaches near Wanganui, between the top of the Nukumaru Limestone and the base of the Butlers Shell Conglomerate, comprise 11 depositional sequences of a total thickness of c. 86 m. The sequences consist predominantly of silicilclastic shoreline facies. Non-marine facies (including palaeosols), and a variety of shallow-marine shellbed facies, are also represented. Patterns in facies composition and sequence architecture reveal three sequence motifs (Marwell, Nukumaru, and Biragrove) that represent progressively increasing maximum palaeowater depths within a broadly basin-margin palaeogeographic setting. The sequence motif changes systematically up section and records a lower order tectonic influence on accommodation that has modulated the stacking patterns of individual sequences. Correlation of the sequences with oxygen isotope stages 77-57 is achieved using the basin-wide Ototoka tephra, and indicates that the sequences accumulated in response to obliquity driven (41 k.y. duration) glacio-eustatic sea-level oscillations. Correlation of the Nukumaru coast sequences with other sections along basin strike, and the global oxygen isotope record indicates that (i) 500 k.y. (δ11O stages MIS 56-34) is missing at the unconformity between the Nukumaruan and overlying Castlecliffian stratotypes on the Wanganui coast...

‣ Overcoming Proterozoic quartzite sand-body miscorrelations: integrated sequence stratigraphy and SHRIMP U-Pb dating of the Surprise Creek Formation, Torpedo Creek and Warrina Park Quartzites, Mt Isa Inlier

Jackson, M.; Southgate, P; Black, Lance; Blake, P; Domagala, J
Fonte: Blackwell Publishing Ltd Publicador: Blackwell Publishing Ltd
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
36.695742%
In the western part of the Mt Isa Inlier one of the most obvious lithostratigraphic correlations is the Torpedo Creek Quartzite (Lawn Hill Platform) and the Warrina Park Quartzite (Leichhardt River Fault Trough). These two sand bodies form the basal lithostratigraphic unit of their respective groups - McNamara and Mt Isa - and crop out as easily mappable, prominent ridges of white quartzite. Correlation of these sand bodies forms the linchpins for lithostratigraphic subdivision in the region. To test this correlation a 2000 m-thick stratigraphic interval around these two quartzite units was analysed using two modern techniques. A sequence stratigraphic analysis, which included detailed surface gammaray logging, was undertaken at 20 measured sections over an area of about 18 000 km2 to identify and correlate important stratal surfaces. Complementary high precision U-Pb SHRIMP dating of tuffaceous intervals was also done to provide independent control for the resulting new subdivisions of the section. The sequence analysis and SHRIMP dating of these units and the underlying Surprise Creek Formation demonstrate major miscorrelations in the current lithostratigraphy. SHRIMP dating helps to define a major unconformity with up to 20 million years of missing rock record: rocks above the surface are around 1670-1660 Ma...