Assembly of 5S ribosomal RNA is required at a specific step of the pre-rRNA processing pathway. |
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Authors: | A M Dechampesme O Koroleva I Leger-Silvestre N Gas S Camier |
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Institution: | Service de Biochimie et de Génétique Moléculaire, Commissariat á L'Energie Atomique (CEA)/Saclay, F-91191 Gif-sur-Yvette Cedex, France. |
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Abstract: | A collection of yeast strains surviving with mutant 5S RNA has been constructed. The mutant strains presented alterations of the nucleolar structure, with less granular component, and a delocalization of the 25S rRNA throughout the nucleoplasm. The 5S RNA mutations affected helix I and resulted in decreased amounts of stable 5S RNA and of the ribosomal 60S subunits. The shortage of 60S subunits was due to a specific defect in the processing of the 27SB precursor RNA that gives rise to the mature 25S and 5.8S rRNA. The processing rate of the 27SB pre-rRNA was specifically delayed, whereas the 27SA and 20S pre-rRNA were processed at a normal rate. The defect was partially corrected by increasing the amount of mutant 5S RNA. We propose that the 5S RNA is recruited by the pre-60S particle and that its recruitment is necessary for the efficient processing of the 27SB RNA precursor. Such a mechanism could ensure that all newly formed mature 60S subunits contain stoichiometric amounts of the three rRNA components. |
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