scholarly journals Partial mapping of methylated sequences in Xenopus laevis ribosomal RNA by preparative hybridization to cloned fragments of ribosomal DNA

1979 ◽  
Vol 6 (3) ◽  
pp. 817-830 ◽  
Author(s):  
B.Edward H. Maden ◽  
Ronald H. Reeder
Keyword(s):  
Xenopus Laevis ◽  
Ribosomal Rna ◽  
Ribosomal Dna

scholarly journals DIFFERENTIATION OF DROSOPHILA CELLS LACKING RIBOSOMAL DNA, IN VITRO

Genetics ◽  
1973 ◽  
Vol 73 (3) ◽  
pp. 429-434
Author(s):  
J James Donady ◽  
R L Seecof ◽  
M A Fox
Keyword(s):  
Drosophila Melanogaster ◽  
Ribosomal Rna ◽  
Ribosomal Dna ◽  
Rna Synthesis ◽  
Wild Type ◽  
Drosophila Cells

ABSTRACT Drosophila melanogaster embryos that lacked ribosomal DNA were obtained from appropriate crosses. Cells were taken from such embryos before overt differentiation took place and were cultured in vitro. These cells differentiated into neurons and myocytes with the same success as did wild-type controls. Therefore, ribosomal RNA synthesis is not necessary for the differentiation of neurons and myocytes in vitro.

Synthesis of RNA in oocytes of Xenopus laevis during culture in vitro

Development ◽  
1974 ◽  
Vol 32 (2) ◽  
pp. 515-532
Author(s):  
A. Colman
Keyword(s):  
Xenopus Laevis ◽  
In Vitro Culture ◽  
Ribosomal Rna ◽  
Rna Synthesis ◽  
Culture Medium ◽  
Salt Medium ◽  
Complex Media ◽  
18S Ribosomal Rna ◽  
Rna Precursor

RNA synthesis can be maintained in large oocytes of Xenopus laevis during periods of in vitro culture of at least 10 days. A simple salt medium, modified Barth's solution, is found to be as effective a culture medium for these oocytes as several other complex media. The newly synthesized RNA is characterized electrophoretically and shown to consist predominantly of ribosomal RNA precursor, 28S and 18S ribosomal RNA, and 4S RNA. The distribution of this RNA within the oocyte is detected autoradiographically, where it is found to be greatly concentrated over the nucleoli. No qualitative alterations in either of these parameters are found during culture, within the limits of sensitivity of the assay procedures.

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.

Properties and Composition of the Isolated Ribosomal DNA Satellite of Xenopus laevis

Nature ◽  
1968 ◽  
Vol 219 (5153) ◽  
pp. 454-463 ◽  
Author(s):  
M. BIRNSTIEL ◽  
J. SPEIRS ◽  
I. PURDOM ◽  
K. JONES ◽  
U. E. LOENING
Keyword(s):  
Xenopus Laevis ◽  
Ribosomal Dna
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