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Eukaryotic Cell, August 2004, p. 862-869, Vol. 3, No. 4
1535-9778/04/$08.00+0     DOI: 10.1128/EC.3.4.862-869.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.

An Intragenic Guide RNA Location Suggests a Complex Mechanism for Mitochondrial Gene Expression in Trypanosoma brucei

Sandra L. Clement,1 Melissa K. Mingler,2 and Donna J. Koslowsky1*

Department of Microbiology and Molecular Genetics,1 Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan 488242

Received 2 April 2004/ Accepted 4 June 2004

In Trypanosoma brucei, two classes of transcripts are produced from two distinct mitochondrial genome components. Guide RNAs (gRNAs) are usually minicircle encoded and exist as primary transcripts, while the maxicircle-encoded rRNAs and mRNAs are processed from a polycistronic precursor. The genes for the gRNAs gMURF2-II and gCYb(560) each have uncommon kinetoplast DNA (kDNA) locations that are not typically associated with transcription initiation events. We demonstrate that the conserved maxicircle gRNA gMURF2-II has an unusual location within the ND4 gene. This is the first report of a completely intragenic gene in kDNA. In addition, the gMURF2-II and ND4 transcripts are generated by distinctly different events; the ND4 mRNA is processed from a polycistronic precursor, while transcription of the gRNA initiates downstream of the 5' end of the ND4 gene. The gCYb(560) gene has an atypical minicircle location in that it is not flanked by the inverted repeat sequences that surround the majority of minicircle gRNA genes. Our data indicate that the mature gCYb(560) gRNA is also a primary transcript and that the 5'-end heterogeneity previously observed for this gRNA is a result of multiple transcription initiation sites and not of imprecise 5'-end processing. Together, these data indicate that gRNA genes represent individual transcription units, regardless of their genomic context, and suggest a complex mechanism for mitochondrial gene expression in T. brucei.

* Corresponding author. Mailing address: 2209 Biomedical Physical Sciences Building, Michigan State University, East Lansing, MI 48824. Phone: (517) 355-6463, ext. 1564. Fax: (517) 353-8957. E-mail: koslowsk{at}msu.edu.

Eukaryotic Cell, August 2004, p. 862-869, Vol. 3, No. 4
1535-9778/04/$08.00+0     DOI: 10.1128/EC.3.4.862-869.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

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