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Molecular and Cellular Biology, January 2001, p. 189-195, Vol. 21, No. 1
Service de Biochimie et Génétique
Moléculaire, CEA-Saclay, F-91191 Gif Sur Yvette Cedex, France
Received 5 July 2000/Returned for modification 3 August
2000/Accepted 9 October 2000
Temperature-sensitive RNA polymerase III (rpc160-112
and rpc160-270) mutants were analyzed for the synthesis of
tRNAs and rRNAs in vivo, using a double-isotopic-labeling technique in
which cells are pulse-labeled with [33P]orthophosphate
and coextracted with [3H]uracil-labeled wild-type cells.
Individual RNA species were monitored by Northern blot hybridization or
amplified by reverse transcription. These mutants impaired the
synthesis of RNA polymerase III transcripts with little or no influence
on mRNA synthesis but also largely turned off the formation of the 25S,
18S, and 5.8S mature rRNA species derived from the common 35S
transcript produced by RNA polymerase I. In the rpc160-270
mutant, this parallel inhibition of tRNA and rRNA synthesis also
occurred at the permissive temperature (25°C) and correlated with an
accumulation of 20S pre-rRNA. In the rpc160-112 mutant,
inhibition of rRNA synthesis and the accumulation of 20S pre-rRNA were
found only at 37°C. The steady-state rRNA/tRNA ratio of these mutants
reflected their tRNA and rRNA synthesis pattern: the
rpc160-112 mutant had the threefold shortage in tRNA
expected from its preferential defect in tRNA synthesis at 25°C,
whereas rpc160-270 cells completely adjusted their
rRNA/tRNA ratio down to a wild-type level, consistent with the tight
coupling of tRNA and rRNA synthesis in vivo. Finally, an RNA polymerase
I (rpa190-2) mutant grown at the permissive temperature had
an enhanced level of pre-tRNA, suggesting the existence of a
physiological coupling between rRNA synthesis and pre-tRNA processing.
0270-7306/01/$04.00+0 DOI: 10.1128/MCB.21.1.189-195.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Cross Talk between tRNA and rRNA Synthesis in
Saccharomyces cerevisiae
*
Corresponding author. Mailing address: Service de
Biochimie et Génétique Moléculaire, CEA-Saclay,
F-91191 Gif Sur Yvette Cedex, France. Phone: 33 1 69 08 35 86. Fax: 33 1 69 08 47 12. E-mail:
thuriaux{at}matthieu.saclay.cea.fr.
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