Xenopus borealis and Xenopus laevis 28 S ribosomal DNA and the complete 40 S ribosomal precursor RNA coding units of both species

1991 ◽  
Vol 245 (1312) ◽  
pp. 65-71 ◽  
Keyword(s):  
Xenopus Laevis ◽  
Ribosomal Dna ◽  
Precursor Rna ◽  
Ribosomal Precursor ◽  
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.

scholarly journals Organization of replication of ribosomal DNA in Saccharomyces cerevisiae.

1988 ◽  
Vol 8 (11) ◽  
pp. 4927-4935 ◽  
Author(s):  
M H Linskens ◽  
J A Huberman
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Ribosomal Dna ◽  
Repeat Unit ◽  
Replication Forks ◽  
Sequence Element ◽  
Autonomously Replicating Sequence ◽  
Nontranscribed Spacer ◽  
Precursor Rna ◽  
Mapping Techniques ◽  
Region Ii

Using recently developed replicon mapping techniques, we have analyzed the replication of the ribosomal DNA in Saccharomyces cerevisiae. The results show that (i) the functional origin of replication colocalizes with an autonomously replicating sequence element previously mapped to the nontranscribed spacer region, (ii) only a fraction of the potential origins are utilized in a single S phase, and (iii) the replication forks moving counter to the direction of transcription of the 37S precursor RNA stop at or near the termination site of transcription. Consequently, most ribosomal DNA is replicated unidirectionally by forks moving in the direction of transcription and most replicons are larger than the repeat unit. The significance of this finding for the replication of abundantly transcribed genes is discussed.

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