Regina Teresa M R, Lopez Loredana, Picardi Ernesto, Quagliariello Carla
Dipartimento di Biologia Cellulare, Università degli Studi della Calabria, 87030 Arcavacata di Rende, Italy.
Gene. 2002 Mar 6;286(1):33-41. doi: 10.1016/s0378-1119(01)00802-2.
The ribosomal protein S4 gene (rps4) has been identified as a single copy sequence in the mitochondrial genomes of two distant higher plants, Magnolia and Helianthus. Sequence analysis revealed that the rps4 genes present in the magnolia and sunflower mitochondrial genomes encode S4 polypeptides of 352 and 331 amino acids, respectively, longer than their counterparts in liverwort and bacteria. Expression of the rps4 genes in the investigated higher plant mitochondria was confirmed by Western blot analysis. In Helianthus, one of two short nucleotide insertions at the 3'-end introduces in the coding region a premature termination codon. Northern hybridizations and reverse transcription-polymerase chain reaction analysis demonstrated that the monocistronic RNA transcripts generated from the rps4 locus in Magnolia and Helianthus mitochondria are modified by RNA editing at 28 and 13 positions, respectively. Although evolutionarily conserved, RNA editing requirements of the rps4 appear more extensive in Magnolia than in Helianthus and in the other higher plants so far investigated. Furthermore, our analysis also suggests that selection of editing sites is RNA sequence-specific in a duplicated sequence context.
核糖体蛋白S4基因（rps4）已被鉴定为两种远缘高等植物木兰和向日葵线粒体基因组中的单拷贝序列。序列分析表明，木兰和向日葵线粒体基因组中存在的rps4基因分别编码352和331个氨基酸的S4多肽，比它们在苔类植物和细菌中的对应物更长。通过蛋白质免疫印迹分析证实了rps4基因在被研究的高等植物线粒体中的表达。在向日葵中，3'端两个短核苷酸插入之一在编码区引入了一个提前终止密码子。Northern杂交和逆转录-聚合酶链反应分析表明，木兰和向日葵线粒体中rps4基因座产生的单顺反子RNA转录本分别在28个和13个位置通过RNA编辑进行了修饰。尽管rps4在进化上是保守的，但与向日葵以及迄今为止研究的其他高等植物相比，木兰中rps4的RNA编辑需求似乎更为广泛。此外，我们的分析还表明，在重复序列背景下，编辑位点的选择具有RNA序列特异性。
