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Molecular and Cellular Biology, December 2003, p. 9061-9072, Vol. 23, No. 24
0270-7306/03/$08.00+0 DOI: 10.1128/MCB.23.24.9061-9072.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.
Audra E. Yermovsky-Kammerer, and Stephen L. Hajduk*
Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, Alabama 35294
Received 4 June 2003/ Returned for modification 9 July 2003/ Accepted 5 September 2003
Trypanosoma brucei lacks mitochondrial genes encoding tRNAs and must import nuclearly encoded tRNAs from the cytosol. The mechanism and specificity of this process remain unclear. We have identified a unique sequence motif, YGG(C/A)RRC, upstream of the genes encoding mitochondrially localized tRNAs in T. brucei. Both in vitro import studies and in vivo transfection studies indicate that deletion of the YGG(C/A)RRC sequence alters mitochondrial localization of tRNALeu, and in vivo studies also show a decrease in the cellular abundance of tRNALeu. These studies provide direct evidence for cis-acting RNA motifs within precursor tRNAs that facilitate the selection of tRNAs for mitochondrial import in trypanosomes. Furthermore, we found that mutations to the YGG(C/A)RRC sequence also altered the intracellular distribution of other endogenous tRNAs, suggesting a general role for this sequence in tRNA trafficking in trypanosomes.
Present address: Global Infectious Disease Program, Marine Biological Laboratory, Woods Hole, MA 02543.
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