The Crithidia fasciculata RNH1 gene encodes both nuclear and mitochondrial isoforms of RNase H.
The Crithidia fasciculata RNH1 gene encodes both nuclear and mitochondrial isoforms of RNase H.
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Crithidia fasciculata RNH1 基因编码 RNase H 的核亚型和线粒体亚型。
DOI：
10.1093/nar/29.3.725
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发表时间：
2001
影响因子：
14.9
通讯作者：
Ray,DS
中科院分区：
文献类型：
--
作者：
Engel,ML;Hines,JC;Ray,DS
束状棘球蚴arnh11基因编码一种RNA酶H，一种特异性降解RNA - dna杂交体RNA链的酶。thernh1基因包含在一个开放阅读框（ORF）中，预计编码53.7 kDa的蛋白质。先前的研究表明，rnh11表达两种蛋白质：一种是38 kDa的蛋白质，另一种是45 kDa的蛋白质，这两种蛋白质富集于着丝体提取物中。thernh1基因c端表位标记导致该蛋白定位于着丝体和细胞核。从第二帧内蛋氨酸密码子开始的ORF的翻译预测一个38 kDa的蛋白质。在ORF的第一个ATG密码子和第二个帧内ATG密码子之间插入两个串联停止密码子，导致仅表达38 kDa蛋白，该蛋白特异性定位于细胞核。第二个蛋氨酸密码子突变为缬氨酸密码子，阻止了38 kDa蛋白的表达，导致45 kDa蛋白的排他性产生，并且该蛋白仅在着丝体中定位。这些结果表明，着丝体酶是由全长53.7 kDa蛋白加工产生的。核酶似乎是由第二帧内ATG密码子的翻译起始引起的。这是锥虫体内第一个由单个基因产生核和线粒体同种异构体蛋白的例子，也是RNase HI基因家族中唯一一个编码线粒体RNase H的真核基因。
TheCrithidia fasciculataRNH1gene encodes an RNase H, an enzyme that specifically degrades the RNA strand of RNA–DNA hybrids. TheRNH1gene is contained within an open reading frame (ORF) predicted to encode a protein of 53.7 kDa. Previous work has shown thatRNH1expresses two proteins: a 38 kDa protein and a 45 kDa protein which is enriched in kinetoplast extracts. Epitope tagging of the C-terminus of theRNH1gene results in localization of the protein to both the kinetoplast and the nucleus. Translation of the ORF beginning at the second in-frame methionine codon predicts a protein of 38 kDa. Insertion of two tandem stop codons between the first ATG codon and the second in-frame ATG codon of the ORF results in expression of only the 38 kDa protein and the protein localizes specifically to the nucleus. Mutation of the second methionine codon to a valine codon prevents expression of the 38 kDa protein and results in exclusive production of the 45 kDa protein and localization of the protein only in the kinetoplast. These results suggest that the kinetoplast enzyme results from processing of the full-length 53.7 kDa protein. The nuclear enzyme appears to result from translation initiation at the second in-frame ATG codon. This is the first example in trypanosomatids of the production of nuclear and mitochondrial isoforms of a protein from a single gene and is the only eukaryotic gene in the RNase HI gene family shown to encode a mitochondrial RNase H.