Nucleic Acids Research Advance Access originally published online on November 2, 2007
Nucleic Acids Research 2007 35(22):7614-7625; doi:10.1093/nar/gkm917
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Nucleic Acids Research, 2007, Vol. 35, No. 22 7614-7625
© 2007 The Author(s)
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Nucleic Acid Enzymes |
Ribonuclease P processes polycistronic tRNA transcripts in Escherichia coli independent of ribonuclease E
Department of Genetics, University of Georgia, Athens, GA 30602, USA
*To whom correspondence should be addressed. Tel: +1 706 542 8000; Fax: +1 706 542 3910;Email: skushner{at}uga.edu
Received August 6, 2007. Revised October 3, 2007. Accepted October 9, 2007.
The first step in the current model for the processing and maturation of mono- and polycistronic tRNA precursors in Escherichia coli involves initial cleavages by RNase E 1–3 nt downstream of each chromosomally encoded CCA determinant. Subsequently, each mature 5' terminus is generated by single RNase P cleavage, while the 3' terminus undergoes exonucleolytic processing by a combination of 3'
5' exonucleases. Here we describe for the first time a previously unidentified pathway for the maturation of tRNAs in polycistronic operons (valV valW and leuQ leuP leuV) where the processing of the primary transcripts is independent of RNase E. Rather, RNase P cleavages separate the individual tRNA precursors with the concomitant formation of their mature 5' termini. Furthermore, both polynucleotide phosphorylase (PNPase) and RNase II are required for the removal of the 3' Rho-dependent terminator sequences. Our data indicate that RNase P substrate recognition is more complex than previously envisioned.