Trypanosoma cruzi mitochondrial maxicircles display species- and strain-specific variation and a conserved element in the non-coding region.
BACKGROUND
The mitochondrial DNA of kinetoplastid flagellates is distinctive in the eukaryotic world due to its massive size, complex form and large sequence content. Comprised of catenated maxicircles that contain rRNA and protein-coding genes and thousands of heterogeneous minicircles encoding small guide RNAs, the kinetoplast network has evolved along with an extreme form of mRNA processing in the form of uridine insertion and deletion RNA editing. Many maxicircle-encoded mRNAs cannot be translated without this post-transcriptional sequence modification.


RESULTS
We present the complete sequence and annotation of the Trypanosoma cruzi maxicircles for the CL Brener and Esmeraldo strains. Gene order is syntenic with Trypanosoma brucei and Leishmania tarentolae maxicircles. The non-coding components have strain-specific repetitive regions and a variable region that is unique for each strain with the exception of a conserved sequence element that may serve as an origin of replication, but shows no sequence identity with L. tarentolae or T. brucei. Alternative assemblies of the variable region demonstrate intra-strain heterogeneity of the maxicircle population. The extent of mRNA editing required for particular genes approximates that seen in T. brucei. Extensively edited genes were more divergent among the genera than non-edited and rRNA genes. Esmeraldo contains a unique 236-bp deletion that removes the 5'-ends of ND4 and CR4 and the intergenic region. Esmeraldo shows additional insertions and deletions outside of areas edited in other species in ND5, MURF1, and MURF2, while CL Brener has a distinct insertion in MURF2.


CONCLUSIONS
The CL Brener and Esmeraldo maxicircles represent two of three previously defined maxicircle clades and promise utility as taxonomic markers. Restoration of the disrupted reading frames might be accomplished by strain-specific RNA editing. Elements in the non-coding region may be important for replication, transcription, and anchoring of the maxicircle within the kinetoplast network.
Westenberger
Scott J
SJ
Department of Microbiology, Immunology & Molecular Genetics, David Geffen School of Medicine, University of California at Los Angeles 90095, USA. swestenb@ucla.edu
Cerqueira
Gustavo C
GC
El-Sayed
Najib M
NM
Zingales
Bianca
B
Campbell
David A
DA
Sturm
Nancy R
NR
D000595:Amino Acid Sequence; D000818:Animals; D017849:Animals, Inbred Strains; D001482:Base Composition; D017124:Conserved Sequence / Q000235:genetics*; D018105:DNA, Kinetoplast / Q000235:genetics*; D018965:Frameshifting, Ribosomal / Q000235:genetics; D017353:Gene Deletion; D023061:Gene Order; D014644:Genetic Variation; D007891:Leishmania / Q000235:genetics; D008954:Models, Biological; D008969:Molecular Sequence Data; D009124:Muscle Proteins / Q000235:genetics; D009245:NADH Dehydrogenase / Q000235:genetics; D016366:Open Reading Frames / Q000235:genetics; D017393:RNA Editing / Q000235:genetics; D050436:Regulatory Elements, Transcriptional / Q000235:genetics*; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity; D000070584:Tripartite Motif Proteins; D014346:Trypanosoma brucei brucei / Q000235:genetics; D014349:Trypanosoma cruzi / Q000235:genetics*; D044767:Ubiquitin-Protein Ligases / Q000235:genetics; D020506:Untranslated Regions / Q000235:genetics*
D018105:DNA, Kinetoplast; D009124:Muscle Proteins; D000070584:Tripartite Motif Proteins; D020506:Untranslated Regions; C502755:muscle RING finger 2 protein, mouse; D009245:NADH Dehydrogenase; C499084:Trim63 protein, mouse; D044767:Ubiquitin-Protein Ligases