Mundel C, Schuster W
Institut für Genbiologische Forschung Berlin GmbH, Ihnestrasse 63, D-14195 Berlin, Germany.
Curr Genet. 1996 Nov;30(5):455-60. doi: 10.1007/s002940050156.
We have analysed a region downstream from the atp9 gene in Oenothera mitochondrial DNA which contains an open reading frame of 224 codons. This open reading frame, designated orf224, is co-transcribed with the atp9 gene. In wheat mitochondria, a homologous reading frame (orf174) has been described which is considerably shorter at the N-terminus compared to the putative Oenothera gene. The deduced polypeptides from both species show high similarity to the N-terminal third of ribosomal protein S1 of bacteria. Transcripts of orf174 are edited in wheat mitochondria whereas the similarly conserved cytidine positions in orf224 mRNAs of Oenothera are silent. On the other hand, atp9 sequences, which are located upstream on the same co-transcript, are fully edited. Because of this, we conclude that editing sites are selected independently for mRNA sections. Our results suggest that orf224 represents a transcribed pseudogene in Oenothera. The active gene for a functional ribosomal protein S1 for mitochondria is therefore expected to be present in the nucleus. A nuclear localization for this gene is likewise suggested for Arabidopsis due to the fact that rps1 sequences are absent from the mitochondrial genome.
我们分析了月见草属线粒体DNA中atp9基因下游的一个区域，该区域包含一个有224个密码子的开放阅读框。这个开放阅读框被命名为orf224，它与atp9基因共同转录。在小麦线粒体中，已经描述了一个同源阅读框（orf174），与推测的月见草属基因相比，其N端要短得多。这两个物种推导的多肽与细菌核糖体蛋白S1的N端三分之一高度相似。orf174的转录本在小麦线粒体中发生编辑，而月见草属orf224 mRNA中类似保守的胞嘧啶位置未发生编辑。另一方面，位于同一共转录本上游的atp9序列被完全编辑。因此，我们得出结论，mRNA片段的编辑位点是独立选择的。我们的结果表明，orf224在月见草属中代表一个转录假基因。因此，线粒体功能性核糖体蛋白S1的活性基因预计存在于细胞核中。由于线粒体基因组中不存在rps1序列，拟南芥的该基因同样被认为定位于细胞核。
