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PubMed1998

The mitochondrial ND8 gene from Crithidia oncopelti is not pan-edited.

RNA editing in trypanosomatid mitochondria is a process involving the insertion and deletion of uridine residues within the coding region of maxicircle messenger RNA transcripts. Twelve of the 17 known genes need editing to produce functional molecules. We have analyzed the predicted editing sites for the Crithidia oncopelti mitochondrial NADH-ubiquinone oxidoreductase subunit 8 (ND8) gene based on known mRNAs from other trypanosomatid species. All studied ND8 mRNAs undergo editing throughout the coding (and 3' noncoding) sequences (pan-editing). The 5' part of the C. oncopelti ND8 gene undergoes editing (like in Leishmania tarentolae and Trypanosoma brucei) while the 3' part of the pre-edited gene corresponds to the 3' part of edited ND8 mRNAs from other organisms. The organization of the ND8 gene in C. oncopelti mitochondrial DNA differs from all organisms investigated so far -- this gene is not pan-edited. We have also localized the guide RNA for cytochrome b between 9S rRNA and the ND8 gene. This RNA shows high homology to the gCYb-II gene of L. tarentolae and the gCyb gene of Crithidia fasciculata. A hypothetical editing pattern for the cytochrome b gene in C. oncopelti maxicircles is proposed.

Amino Acid Sequence↗
PubMed1995

The ins and outs of editing RNA in kinetoplastids.

Over 30 million people in tropical regions suffer from Chagas disease, African sleeping sickness or leishmaniasis. The causative agents of these diseases, flagellated protozoa collectively known as kinetoplastids, represent an ancient lineage of eukaryotes. These unusual organisms carry out a large number of unique biochemical processes, one striking example being the sequence editing of mitochondrial messenger RNAs. In this review, Scott Seiwert focuses on recent studies that examine the reaction mechanism, molecular machinery and evolutionary history of this unusual RNA processing reaction.

Journal Article↗
PubMed2005

The crystal structure of the Zbeta domain of the RNA-editing enzyme ADAR1 reveals distinct conserved surfaces among Z-domains.

The Zalpha domains represent a growing subfamily of the winged helix-turn-helix (HTH) domain family whose members share a remarkable ability to bind specifically to Z-DNA and/or Z-RNA. They have been found exclusively in proteins involved in interferon response and, while their importance in determining pox viral pathogenicity has been demonstrated, their actual target and biological role remain obscure. Cellular proteins containing Zalpha domains bear a second homologous domain termed Zbeta, which appears to lack the ability to bind left-handed nucleic acids. Here, we present the crystal structure of the Zbeta domain from the human double-stranded RNA adenosine deaminase ADAR1 at 0.97 A, determined by single isomorphous replacement including anomalous scattering. Zbeta maintains a winged-HTH fold with the addition of a C-terminal helix. Mapping of the Zbeta conservation profile on the Zbeta surface reveals a new conserved surface formed partly by the terminal helix 4, involved in metal binding and dimerization and absent from Zalpha domains. Our results show how two domains similar in fold may have evolved into different functional entities even in the context of the same protein.

Adenosine Deaminase↗
PubMed1991

RNA editing makes mistakes in plant mitochondria: editing loses sense in transcripts of a rps19 pseudogene and in creating stop codons in coxI and rps3 mRNAs of Oenothera.

An intact gene for the ribosomal protein S19 (rps19) is absent from Oenothera mitochondria. The conserved rps19 reading frame found in the mitochondrial genome is interrupted by a termination codon. This rps19 pseudogene is cotranscribed with the downstream rps3 gene and is edited on both sides of the translational stop. Editing, however, changes the amino acid sequence at positions that were well conserved before editing. Other strange editings create translational stops in open reading frames coding for functional proteins. In coxI and rps3 mRNAs CGA codons are edited to UGA stop codons only five and three codons, respectively, downstream to the initiation codon. These aberrant editings in essential open reading frames and in the rps19 pseudogene appear to have been shifted to these positions from other editing sites. These observations suggest a requirement for a continuous evolutionary constraint on the editing specificities in plant mitochondria.

Amino Acid Sequence↗
PubMed1990

Species-specific RNA editing patterns in the mitochondrial rps13 transcripts of Oenothera and Daucus.

Transcripts from the rps13 locus, which encodes ribosomal protein S13, in Oenothera and Daucus mitochondria are edited by several cytidine to uridine transitions in both plants. Analysis of individual cDNA clones and polymerase chain reaction (PCR)-amplified cDNA from the total mitochondrial mRNA population shows different editing patterns in the two species. Although the same genomic triplet is conserved, nucleotides altered in the mRNA of one species are not necessarily edited in the other. Individual editing sites appear to be modified to varying degrees in the mRNA populations in both plant species, indicating that completely edited transcripts constitute only a minor fraction of the rps13 mRNA molecules.

Amino Acid Sequence↗
PubMed1991

RNA editing of the transcript coding for subunit 4 of NADH dehydrogenase in wheat mitochondria: uneven distribution of the editing sites among the four exons.

The wheat mitochondrial (mt) NADH dehydrogenase subunit 4 gene (nad4) has been localized and sequenced. This gene, about 8 kb long, is composed of four exons separated by three class II introns. The nad4 gene exists as a single copy in the wheat mitochondrial genome and it is transcribed into one abundant mRNA of 1.8 kb, whose extremities have been mapped. The complete cDNA sequence corresponding to the nad4 transcript has been determined by combining the direct sequencing of uncloned cDNA and a method involving cDNA synthesis and PCR amplification using specific oligonucleotides as primers, followed by cloning and sequencing of the amplification product. Comparison of the genomic sequence with that of the cDNA shows that all nad4 transcripts are fully edited at 23 positions, with an uneven distribution of the editing sites between the different exons: While exon 1 and exon 4 are extensively edited (with a change of 11% of the amino acid sequence), exon 2 is not edited at all and exon 3 is 0.5% edited. This uneven distribution is discussed.

Amino Acid Sequence↗
PubMed1991

RNA editing of sorghum mitochondrial atp6 transcripts changes 15 amino acids and generates a carboxy-terminus identical to yeast.

Sequencing of sorghum mitochondrial atp6 cDNA clones revealed 19 C-to-U transcript editing events within a 756 bp-conserved core gene; three were silent and 16 resulted in 15 amino acid changes. Only one edit, which was silent, was found in the 381 bp amino-extension to the core gene. Eleven of the 15 changed amino acids were identical with or else represented conservative changes compared to yeast atp6. Editing of a CAA codon to TAA truncates the carboxy-terminus to a position identical to that of yeast. The frequency of editing at sites which change amino acids was very high in contrast to partial editing at silent, third base, sites.

Base Sequence↗
PubMed1991

A termination codon is created by RNA editing in the petunia atp9 transcript.

Analysis of the cDNA of the atp9-1 gene transcript from petunia mitochondria has revealed that ten C residues of the gene sequence are edited into U in the mRNA. Seven of these edits result in amino acid changes and one introduces a stop codon before the end of the open reading frame predicted from the gene sequence. The resulting protein is better conserved when compared to the same protein in other organisms. Comparison of the edited petunia sequence with other plant mitochondrial atp9 gene sequences idicates variation in the number and positions of edits required to obtain the same amino acids in ATP9 polypeptides of higher plants.

Amino Acid Sequence↗