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. 1989 Sep;9(9):3777–3784. doi: 10.1128/mcb.9.9.3777

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

S Firek 1, C Read 1, D R Smith 1, T Moss 1
PMCID: PMC362439  PMID: 2779566

Abstract

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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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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