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Molecular and Cellular Biology, April 2001, p. 2359-2372, Vol. 21, No. 7
Department of Molecular Biology and Genetics,
Cornell University, Ithaca, New York
14853-2703,2 and Centre de
Génétique Moléculaire, Laboratoire propre du CNRS
associé à l'Université Pierre et Marie Curie,
91198 Gif-sur-Yvette Cedex, France1
Received 8 September 2000/Returned for modification 16 October
2000/Accepted 19 January 2001
The mitochondrial gene encoding yeast cytochrome oxidase subunit II
(Cox2p) specifies a precursor protein with a 15-amino-acid leader
peptide. Deletion of the entire leader peptide coding region is known
to block Cox2p accumulation posttranscriptionally. Here, we examined in
vivo the role of the pre-Cox2p leader peptide and the mRNA sequence
that encodes it in the expression of a mitochondrial reporter gene,
ARG8m, fused to the 91st codon of
COX2. We found within the coding sequence antagonistic
elements that control translation: the positive element includes
sequences in the first 14 codons specifying the leader peptide,
while the negative element appears to be within codons 15 to 91. Partial deletions, point mutations, and local frameshifts within the
leader peptide coding region were placed in both the
cox2::ARG8m reporter and in
COX2 itself. Surprisingly, the mRNA sequence of the
first six codons specifying the leader peptide plays an important
role in positively controlling translation, while the amino acid
sequence of the leader peptide itself is relatively unconstrained. Two
mutations that partially block translation can be suppressed by nearby
sequence substitutions that weaken a predicted stem structure
and by overproduction of either the COX2 mRNA-specific
translational activator Pet111p or the large-subunit mitochondrial
ribosomal protein MrpL36p. We propose that regulatory elements embedded
in the translated COX2 mRNA sequence could play a role,
together with trans-acting factors, in coupling regulated synthesis of nascent pre-Cox2p to its insertion in the mitochondrial inner membrane.
0270-7306/01/$04.00+0 DOI: 10.1128/MCB.21.7.2359-2372.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Mitochondrial Translation of Saccharomyces cerevisiae
COX2 mRNA Is Controlled by the Nucleotide Sequence
Specifying the Pre-Cox2p Leader Peptide
*
Corresponding author. Mailing address: Department of
Molecular Biology and Genetics, Cornell University, Ithaca, NY
14853-2703. Phone: (607) 254-4835. Fax: (607) 255-6249. E-mail:
tdf1{at}cornell.edu.
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