Affiliation:
1. Centre de Génétique Moléculaire, Laboratoire propre du CNRS associé à l'Université Pierre et Marie Curie, 91198 Gif-sur-Yvette Cedex, France1
2. Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York 14853-2703, 2 and
Abstract
ABSTRACT
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,
ARG8
m
, 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
::
ARG8
m
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.
Publisher
American Society for Microbiology
Subject
Cell Biology,Molecular Biology
Cited by
61 articles.
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