scholarly journals Patterns of major divergence between the internal transcribed spacers of ribosomal DNA in Xenopus borealis and Xenopus laevis, and of minimal divergence within ribosomal coding regions.

1983 ◽  
Vol 2 (3) ◽  
pp. 443-448 ◽  
Author(s):  
J.C. Furlong ◽  
B.E. Maden
Keyword(s):  
Xenopus Laevis ◽  
Ribosomal Dna ◽  
Internal Transcribed Spacers ◽  
Coding Regions ◽  
Xenopus Borealis

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

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.

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