Bogenhagen D F, Morvillo M V
Department of Pharmacological Sciences, State University of New York, Stony Brook 11794.
Nucleic Acids Res. 1990 Nov 11;18(21):6377-83. doi: 10.1093/nar/18.21.6377.
Transcription of the light strand of Xenopus laevis mitochondrial DNA initiates at two promoters located approximately 350 to 450 nucleotides upstream from the 5' ends of major D-loop DNA strands. Small RNAs within this region have been mapped by blot hybridization, primer extension and S1 nuclease protection methods. The results reveal that the large majority of RNAs within this region have 3' termini located at a sequence element, designated CSB 2, that is conserved in sequence and position in Xenopus, mouse, rat and human mtDNA. However, the X. laevis CSB 2 appears to be a site of RNA processing only, since RNA-to-DNA transitions are not detectable at this site. RNAs containing sequences downstream of CSB 2 are extremely rare. A significant fraction of these RNAs are processed by cleavage at a site just upstream of the most predominant 5' ends of D-loop DNAs. We suggest that RNA processing at this site may play a role in priming mtDNA replication.
非洲爪蟾线粒体DNA轻链的转录起始于两个启动子，它们位于主要D环DNA链5'端上游约350至450个核苷酸处。该区域内的小RNA已通过印迹杂交、引物延伸和S1核酸酶保护方法进行了定位。结果表明，该区域内的绝大多数RNA的3'末端位于一个序列元件处，该元件被命名为CSB 2，其在非洲爪蟾、小鼠、大鼠和人类线粒体DNA中的序列和位置是保守的。然而，非洲爪蟾的CSB 2似乎只是一个RNA加工位点，因为在该位点未检测到RNA到DNA的转变。含有CSB 2下游序列的RNA极其罕见。这些RNA中有很大一部分在D环DNA最主要的5'端上游的一个位点被切割加工。我们认为该位点的RNA加工可能在启动线粒体DNA复制中起作用。
