Exoribonuclease R in Mycoplasma genitalium can carry out both RNA processing and degradative functions and is sensitive to RNA ribose methylation.
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.
Lalonde
Maureen S
MS
Department of Biomedical Science, Florida Atlantic University, Boca Raton, FL 33431, USA.
Zuo
Yuhong
Y
Zhang
Jianwei
J
Gong
Xin
X
Wu
Shaohui
S
Malhotra
Arun
A
Li
Zhongwei
Z
D000241:Adenosine / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D001483:Base Sequence; D029968:Escherichia coli Proteins / Q000378:metabolism; D005095:Exoribonucleases / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D008745:Methylation; D008780:Methyltransferases / Q000378:metabolism; D008969:Molecular Sequence Data; D045704:Mycoplasma genitalium / Q000201:enzymology*; D009690:Nucleic Acid Conformation; D011108:Polymers / Q000378:metabolism; D012322:RNA Precursors / Q000378:metabolism*; D012323:RNA Processing, Post-Transcriptional / Q000502:physiology*; D012329:RNA, Bacterial / Q000378:metabolism*; D012335:RNA, Ribosomal / Q000378:metabolism
D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D011108:Polymers; D012322:RNA Precursors; D012329:RNA, Bacterial; D012335:RNA, Ribosomal; C489683:rnr protein, E coli; C069424:polyadenosine; D008780:Methyltransferases; D005095:Exoribonucleases; C022535:exoribonuclease II; C080868:ribonuclease R; D000241:Adenosine