scholarly journals DNA sequences for typical ribosomal gene spacers from Xenopus laevis and Xenopus borealis

1987 ◽  
Vol 15 (8) ◽  
pp. 3623-3623 ◽  
Author(s):  
Paul Labhart ◽  
Ronald H. Reeder
Keyword(s):  
Xenopus Laevis ◽  
Dna Sequences ◽  
Ribosomal Gene ◽  
Xenopus Borealis

scholarly journals Human 18 S ribosomal RNA sequence inferred from DNA sequence. Variations in 18 S sequences and secondary modification patterns between vertebrates

1985 ◽  
Vol 232 (3) ◽  
pp. 725-733 ◽  
Author(s):  
F S McCallum ◽  
B E H Maden
Keyword(s):  
Xenopus Laevis ◽  
Ribosomal Rna ◽  
Dna Sequences ◽  
Methyl Groups ◽  
Methyl Group ◽  
Human Sequence ◽  
Sequence Variations ◽  
Group Distribution ◽  
18 S Ribosomal Rna ◽  
Xenopus Borealis

We have determined the DNA sequences encoding 18 S ribosomal RNA in man and in the frog, Xenopus borealis. We have also corrected the Xenopus laevis 18 S sequence: an A residue follows G-684 in the sequence. These and other available data provide a number of representative examples of variation in primary structure and secondary modification of 18 S ribosomal RNA between different groups of vertebrates. First, Xenopus laevis and Xenopus borealis 18 S ribosomal genes differ from each other by only two base substitutions, and we have found no evidence of intraspecies heterogeneity within the 18 S ribosomal DNA of Xenopus (in contrast to the Xenopus transcribed spacers). Second, the human 18 S sequence differs from that of Xenopus by approx. 6.5%. About 4% of the differences are single base changes; the remainder comprise insertions in the human sequence and other changes affecting several nucleotides. Most of these more extensive changes are clustered in a relatively short region between nucleotides 190 and 280 in the human sequence. Third, the human 18 S sequence differs from non-primate mammalian sequences by only about 1%. Fourth, nearly all of the 47 methyl groups in mammalian 18 S ribosomal RNA can be located in the sequence. The methyl group distribution corresponds closely to that in Xenopus, but there are several extra methyl groups in mammalian 18 S ribosomal RNA. Finally, minor revisions are made to the estimated numbers of pseudouridines in human and Xenopus 18 S ribosomal RNA.

A comparison of host-defense peptides in skin secretions of female Xenopus laevis×Xenopus borealis and X. borealis×X. laevis F1 hybrids

Peptides ◽  
2013 ◽  
Vol 45 ◽  
pp. 1-8 ◽  
Author(s):  
Milena Mechkarska ◽  
Manju Prajeep ◽  
Jérôme Leprince ◽  
Hubert Vaudry ◽  
Mohammed A. Meetani ◽  
...  
Keyword(s):  
Xenopus Laevis ◽  
Host Defense ◽  
F1 Hybrids ◽  
Host Defense Peptides ◽  
Skin Secretions ◽  
Defense Peptides ◽  
Xenopus Borealis

Distribution, expression and germ line transmission of exogenous DNA sequences following microinjection into Xenopus laevis eggs

Development ◽  
1987 ◽  
Vol 99 (1) ◽  
pp. 15-23
Author(s):  
L.D. Etkin ◽  
B. Pearman
Keyword(s):  
Xenopus Laevis ◽  
Dna Sequences ◽  
Copy Number ◽  
Germ Line ◽  
Gene Promoter ◽  
Early Gene ◽  
Mosaic Pattern ◽  
Exogenous Dna ◽  
Gene Coding ◽  
Germ Line Transmission

We analysed the fate, expression and germ line transmission of exogenous DNA which was microinjected into fertilized eggs of Xenopus laevis. DNA was injected into fertilized eggs within 1 h following fertilization. The injected DNA was dispersed around the site of injection and became localized to cleavage nuclei by stage 6. Injected DNA persisted in the tissues of 6- to 8-month-old frogs and exhibited a mosaic pattern of distribution with regard to the presence or absence and copy number between different tissues. We detected the exogenous DNA sequences in 60% of injected frogs. Restriction digestion analysis of this DNA suggested that it is not rearranged and was organized as head-to-tail multimers. The copy number varied from 2 to 30 copies/cell in various tissues of the same frog. Plasmid pSV2CAT which contains the prokaryotic gene coding for chloramphenicol acetyl transferase (CAT) enzyme linked to the SV40 early gene promoter was expressed in 50% of the animals containing the gene. The pattern of expression, however, varied between different animals and could not be correlated with copy number. We also showed that the exogenous DNA sequences were transmitted through the male germ line and that each offspring contained the gene integrated into a different region of the genome.

Molecular phylogenetic position of Haplometroides intercaecalis (Digenea, Plagiorchiidae)

2018 ◽  
Vol 63 (3) ◽  
pp. 522-526 ◽  
Author(s):  
Maria Isabel Müller ◽  
Drausio Honorio Morais ◽  
Reinaldo José da Silva
Keyword(s):  
Dna Sequences ◽  
Additional Data ◽  
Ribosomal Gene ◽  
Valid Species ◽  
Phylogenetic Position ◽  
Systematic Analysis ◽  
Future Studies ◽  
New Family ◽  
Molecular Phylogenetic ◽  
Morphological Differences

Abstract Three valid species of Haplometroides Odhner, 1910 parasitise snakes and amphisbaenians from South America. This study provides additional data on morphometric and molecular phylogenetic position inferred from the nuclear ribosomal gene 28S (partial). DNA sequences were isolated from Haplometroides intercaecalis Silva, Ferreira and Strüssmann, 2007 found in one specimen of Phalotris matogrossensis Lema, D’Agostini and Cappellari, 2005. Five digenean specimens were recovered from the esophagus of this snake, and four specimens were used for morphometrical studies and one specimen for molecular analysis. Phylogenetic analysis using maximum likelihood and Bayesian methods was conducted with sequences available for the order Plagiorchiida and its phylogenetic position places H. intercaecalis among the brachycoeliids Brachycoelium (Dujardin, 1845) Stiles and Hassall, 1898 and Parabrachycoelium Pérez-Ponce de León, Mendoza-Garfias, Razo-Mendivil and Parra-Olea, 2011, and the mesocoeliid Mesocoelium Odhner, 1910, not closely related to plagiorchids as expected. Due to morphological differences among these families, it may be necessary to create a new family to accommodate Haplometroides spp. However, more genera/taxa as well as other molecular markers should be added in future studies to confirm our results and resolve this matter. This is the first phylogenetic positioning of digeneans of the genus Haplometroides, contributing to the systematic analysis of the helminthological biodiversity of Neotropical snakes.

The Xenopus laevis ribosomal gene terminator contains sequences that both enhance and repress ribosomal transcription

1989 ◽  
Vol 9 (9) ◽  
pp. 3777-3784
Author(s):  
S Firek ◽  
C Read ◽  
D R Smith ◽  
T Moss
Keyword(s):  
Xenopus Laevis ◽  
Point Mutation ◽  
Ribosomal Dna ◽  
Ribosomal Gene ◽  
Promoter Element ◽  
Base Pairs ◽  
Transcription Terminator ◽  
Upstream Promoter

A DNA segment approximately 200 base pairs upstream of the Xenopus laevis ribosomal promoter acts both as an upstream promoter element that augments transcription and as a transcription terminator. It is, however, unclear to what extent these two activities are related. A segment of the X. laevis ribosomal DNA, containing the terminator and the upstream promoter element, was subjected to point mutation, and the effects of the resulting mutations were investigated by oocyte microinjection. Analysis of 26 point mutants revealed not only sequences that augment 40S transcription but also those that repress it. The sequences that augmented transcription lay within the T3 homology box and also near the site of 3'-end formation. These sequences also played a role in termination. The sequences that repressed transcription lay within the G+C-rich DNA flanking the T3 box. It can be concluded that termination is probably essential but may not be sufficient for the activity of the upstream promoter element.

scholarly journals Upstream domains of the Xenopus laevis rDNA promoter are revealed in microinjected oocytes.

1986 ◽  
Vol 6 (4) ◽  
pp. 1228-1234 ◽  
Author(s):  
J Windle ◽  
B Sollner-Webb
Keyword(s):  
Xenopus Laevis ◽  
Dna Sequences ◽  
Promoter Region ◽  
Core Promoter ◽  
Rrna Genes ◽  
Deletion Mutants ◽  
Low Concentrations ◽  
Upstream Promoter ◽  
Polymerase I ◽  
Vector Dna

The DNA sequences involved in promoting transcription of the Xenopus laevis rRNA genes were determined by microinjecting a series of deletion mutants into oocyte nuclei. A very small promoter region is sufficient to direct efficient transcription when templates are microinjected at high rDNA concentration, since 5'delta- 9 and 3'delta +6 templates are fully active. However, as the concentration of injected template is decreased, an increasing requirement for upstream domains, extending to nucleotide approximately -170, is observed. The major downstream border of the required region does not change. This apparently expanding 5' promoter border results from the fact that, as the rDNA concentration is decreased, transcription from templates lacking the upstream promoter domain falls off much more sharply than does transcription from a complete promoter. In fact, the deleted promoters are virtually inactive below a threshold rDNA concentration. It is indeed the rDNA concentration that is important, for coinjected vector DNA does not increase the level of transcription obtained from low concentrations of the 5' deletions. From these data we conclude that polymerase I transcription factors can recognize and initiate transcription from a small core promoter domain, but that sequences extending upstream to nucleotide approximately -170 increase the efficiency of initiation. A model is presented that could account for these results.

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