Mohanty Bijoy K, Petree Jessica R, Kushner Sidney R
Department of Genetics, University of Georgia, Athens, GA 30602, USA.
Department of Genetics, University of Georgia, Athens, GA 30602, USA
Nucleic Acids Res. 2016 Jul 27;44(13):6350-62. doi: 10.1093/nar/gkw517. Epub 2016 Jun 10.
We demonstrate here for the first time that proline tRNA 3' end maturation in Escherichia coli employs a one-step endonucleolytic pathway that does not involve any of the six 3' → 5' exonucleases (RNase T, RNase PH, RNase D, RNase BN, RNase II and polynucleotide phosphorylase [PNPase]) to generate the mature CCA terminus. Rather, RNase E is primarily responsible for the endonucleolytic removal of the entire Rho-independent transcription terminator associated with the proK, proL and proM primary transcripts by cleaving immediately downstream of the CCA determinant. In the absence of RNase E, RNase G and RNase Z are weakly able to process the proK and proM transcripts, while PNPase and RNase P are utilized in the processing of proL The terminator fragment derived from the endonucleolytic cleavage of proL transcript is degraded through a PNPase-dependent pathway. It is not clear which enzymes degrade the proK and proM terminator fragments. Our data also suggest that the mature 5' nucleotide of the proline tRNAs may be responsible for the cleavage specificity of RNase E at the 3' terminus.
我们首次在此证明，大肠杆菌中脯氨酸tRNA 3'末端成熟采用一步内切核酸酶途径，该途径不涉及六种3'→5'外切核酸酶（核糖核酸酶T、核糖核酸酶PH、核糖核酸酶D、核糖核酸酶BN、核糖核酸酶II和多核苷酸磷酸化酶[PNPase]）中的任何一种来生成成熟的CCA末端。相反，核糖核酸酶E主要负责通过在CCA决定簇下游立即切割，从与proK、proL和proM初级转录本相关的整个不依赖Rho的转录终止子上进行内切核酸酶切割。在没有核糖核酸酶E的情况下，核糖核酸酶G和核糖核酸酶Z能够微弱地加工proK和proM转录本，而PNPase和核糖核酸酶P则用于proL的加工。从proL转录本的内切核酸酶切割产生的终止子片段通过依赖PNPase的途径降解。目前尚不清楚哪些酶降解proK和proM终止子片段。我们的数据还表明，脯氨酸tRNA的成熟5'核苷酸可能负责核糖核酸酶E在3'末端的切割特异性。
