Exoribonuclease R in Mycoplasma genitalium can carry out both RNA processing and degradative functions and is sensitive to RNA ribose methylation
Abstract
Mycoplasma genitalium, a small bacterium having minimal genome size, has only one identified exoribonuclease, RNase R (MgR). We have purified MgR to homogeneity, and compared its RNA degradative properties to those of its Escherichia coli homologs RNase R (EcR) and RNase II (EcII). MgR is active on a number of substrates including oligoribonucleotides, poly(A), rRNA, and precursors to tRNA. Unlike EcR, which degrades rRNA and pre-tRNA without formation of intermediate products, MgR appears sensitive to certain RNA structural features and forms specific products from these stable RNA substrates. The 3′-ends of two MgR degradation products of 23S rRNA were mapped by RT-PCR to positions 2499 and 2553, each being 1 nucleotide downstream of a 2′-O-methylation site. The sensitivity of MgR to ribose methylation is further demonstrated by the degradation patterns of 16S rRNA and a synthetic methylated oligoribonucleotide. Remarkably, MgR removes the 3′-trailer sequence from a pre-tRNA, generating product with the mature 3′-end more efficiently than EcII does. In contrast, EcR degrades this pre-tRNA without the formation of specific products. Our results suggest that MgR shares some properties of both EcR and EcII and can carry out a broad range of RNA processing and degradative functions.
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Footnotes
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↵3 Present addresses: Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520-8114, USA;
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↵4 Center for Disease Control of Liaoning Province, Shenyang, People's Republic of China.
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Reprint requests to: Zhongwei Li, Department of Biomedical Science, Florida Atlantic University, Boca Raton, FL 33431, USA; e-mail: zli{at}fau.edu; fax: (561) 297-0819.
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Article published online ahead of print. Article and publication date are at http://www.rnajournal.org/cgi/doi/10.1261/rna.706207.
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- Received June 27, 2007.
- Accepted August 10, 2007.
- Copyright © 2007 RNA Society