Published online 25 May 2004
Nucleic Acids Research, 2004, Vol. 32, No. 9 2957-2965
© 2004 Oxford University Press
Coupled amplification and degradation of exogenous RNA injected in amphibian oocytes
Laboratoire de Biologie du Développement, Université P. et M. Curie, CNRS, UMR 7622, 9 Quai St Bernard, 75251 Paris Cedex 05 France and 1 Laboratoire des régulations post-transcriptionnelles, Institut André Lwoff, CNRS, UPR 1983, 7 rue Guy Moquet, 94801 Villejuif Cedex France
*To whom correspondence should be addressed. Tel: +33 1 44 27 27 82; Fax: +33 1 44 27 35 78; Email: andeol@ccr.jussieu.fr
Received April 21, 2004; Revised and Accepted May 1, 2004
The early development of amphibians takes place in the absence of significant transcription and is controlled at the post-transcriptional level. We have reported that in vitro synthesized transcripts injected into axolotl fertilized eggs or oocytes were not continuously degraded as their abundance apparently fluctuated over time, with detected amounts sometimes higher than initial injected amounts. To further characterize this phenomenon, we have co-injected RNA chain terminators to prevent RNA synthesis. This led to the suppression of fluctuations and to a regular decrease in the amount of transcripts that appeared to be more stable in the presence of inhibitors. These observations indicate a coupling between RNA synthesis and an accelerated degradation. Throughout the time course, cRNA molecules could be detected, and their abundance increased in the early phase of the kinetics, supporting the implication of an RNA-dependent RNA polymerase in an asymmetric amplification process. Finally, when the fate of the injected transcripts was investigated in individual oocytes, we observed an absolute increase in abundance in some but not all oocytes, supporting the existence of a limiting step in the initiation of the RNA amplification stochastic process.