Ko Jae-hyeong, Han Kook, Kim Yool, Sim Soyeong, Kim Kwang-sun, Lee Sang-Joon, Cho Bongrae, Lee Kangryul, Lee Younghoon
Department of Chemistry and Center for Molecular Design and Synthesis, Korea Advanced Institute of Science and Technology, Daejeon 305-701, Korea.
Biochemistry. 2008 Jan 15;47(2):762-70. doi: 10.1021/bi701528j. Epub 2007 Dec 20.
M1 RNA, the gene product of rnpB, is the catalytic subunit of RNase P in Escherichia coli. M1 RNA is transcribed from a proximal promoter as pM1 RNA, a precursor M1 RNA, and then is processed at its 3' end by RNase E. In addition to pM1 RNA, large rnpB-containing transcripts are produced from unknown upstream promoters. However, it is not known yet how these large transcripts contribute to M1 RNA biosynthesis. To examine their biological relevance to M1 RNA biosynthesis, we constructed a model upstream transcript, upRNA, and analyzed its cellular metabolism. We found that upRNA was primarily degraded rather than processed to M1 RNA in the cell and that this degradation occurred in RNase E-dependent manner. The in vitro cleavage assay with the N-terminal catalytic fraction of RNase E showed that the M1 RNA structural sequence in upRNA was much more vulnerable to the enzyme than the sequence in pM1 RNA. Considering that RNase E is a processing enzyme involved in 3' end formation of M1 RNA, our results imply that this enzyme plays a dual role in processing and degradation to achieve tight control of M1 RNA biosynthesis.
M1 RNA是rnpB的基因产物，是大肠杆菌中核糖核酸酶P的催化亚基。M1 RNA从近端启动子转录为前体M1 RNA即pM1 RNA，然后在其3'端由核糖核酸酶E进行加工。除了pM1 RNA外，还从未知的上游启动子产生含rnpB的大转录本。然而，这些大转录本如何促进M1 RNA生物合成尚不清楚。为了研究它们与M1 RNA生物合成的生物学相关性，我们构建了一个模型上游转录本upRNA，并分析了其细胞代谢。我们发现upRNA在细胞中主要被降解而不是加工成M1 RNA，并且这种降解以核糖核酸酶E依赖的方式发生。用核糖核酸酶E的N端催化片段进行的体外切割试验表明，upRNA中的M1 RNA结构序列比pM1 RNA中的序列更容易受到该酶的作用。鉴于核糖核酸酶E是参与M1 RNA 3'端形成的加工酶，我们的结果表明该酶在加工和降解中起双重作用，以实现对M1 RNA生物合成的严格控制。
