Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.13.1 (exoribonuclease)
 732 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

As part of our genetic analysis of mRNA decay in Escherichia coli K-12, we examined the effect of the pcnB gene [encoding poly(A) polymerase I] on message stability. Eliminating poly(A) polymerase I (delta pcnB) dramatically stabilized the lpp, ompA, and trxA transcripts. The half-lives of individual mRNAs were increased in both a delta pcnB single mutant and a delta pcnB pnp-7 rnb-500 rne-1 multiple mutant. We also found mRNA decay intermediates in delta pcnB mutants that were not detected in control strains. By end-labeling total E. coli RNA with [32P]pCp and T4 RNA ligase and then digesting the RNA with RNase A and T1, we showed that many RNAs in a wild-type strain contained poly(A) tails ranging from 10 nt to > 50 nt long. When polynucleotide phosphorylase, RNase II, and RNase E were absent, the length (> 100 nt) and number (10- to 20-fold) of the poly(A) tails increased. After transcription initiation was stopped with rifampicin, polyadenylylation apparently continued. Deleting the structural gene for poly(A) polymerase I (pcnB) reduced the amount of 3'-terminal poly(A) sequences by > 90%. We propose a model for the role of polyadenylylation in mRNA decay.
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PMID:Polyadenylylation helps regulate mRNA decay in Escherichia coli. 789 80

We have examined the expression of pnp encoding the 3'-5'-exoribonuclease, polynucleotide phosphorylase, in Streptomyces antibioticus. We show that the rpsO-pnp operon is transcribed from at least two promoters, the first producing a readthrough transcript that includes both pnp and the gene for ribosomal protein S15 (rpsO) and a second, Ppnp, located in the rpsO-pnp intergenic region. Unlike the situation in Escherichia coli, where observation of the readthrough transcript requires mutants lacking RNase III, we detect readthrough transcripts in wild-type S. antibioticus mycelia. The Ppnp transcriptional start point was mapped by primer extension and confirmed by RNA ligase-mediated reverse transcription-PCR, a technique which discriminates between 5' ends created by transcription initiation and those produced by posttranscriptional processing. Promoter probe analysis demonstrated the presence of a functional promoter in the intergenic region. The Ppnp sequence is similar to a group of promoters recognized by the extracytoplasmic function sigma factors, sigma-R and sigma-E. We note a number of other differences in rspO-pnp structure and function between S. antibioticus and E. coli. In E. coli, pnp autoregulation and cold shock adaptation are dependent upon RNase III cleavage of an rpsO-pnp intergenic hairpin. Computer modeling of the secondary structure of the S. antibioticus readthrough transcript predicts a stem-loop structure analogous to that in E. coli. However, our analysis suggests that while the readthrough transcript observed in S. antibioticus may be processed by an RNase III-like activity, transcripts originating from Ppnp are not. Furthermore, the S. antibioticus rpsO-pnp intergenic region contains two open reading frames. The larger of these, orfA, may be a pseudogene. The smaller open reading frame, orfX, also observed in Streptomyces coelicolor and Streptomyces avermitilis, may be translationally coupled to pnp and the gene downstream from pnp, a putative protease.
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PMID:Organization and expression of the polynucleotide phosphorylase gene (pnp) of Streptomyces: Processing of pnp transcripts in Streptomyces antibioticus. 1512 78

Uridine insertion/deletion RNA editing in trypanosomatid mitochondria is a posttranscriptional RNA modification phenomenon required for translation of mitochondrial mRNAs. This process involves guide RNA-mediated cleavage at a specific site, insertion or deletion of Us from the 3' end of the 5' mRNA fragment, and ligation of the two mRNA fragments. The Leishmania major RNA ligase-containing complex protein 2 expressed in insect cells has a 3'-5' exoribonuclease activity and was therefore renamed RNA editing exonuclease 1 (REX1). Recombinant REX1 specifically trims 3' overhanging Us and stops at a duplex region. Evidence is presented that REX1 is responsible for deletion of the 3' overhanging Us from the bridged mRNA 5' cleavage fragment and that RNA editing ligase 1 is responsible for the ligation of the two mRNA cleavage fragments in U-deletion editing. The evidence involves both in vivo down-regulation of REX1 expression in Trypanosoma brucei by RNA interference and the reconstitution of precleaved U-deletion in vitro editing with only two recombinant enzymes: recombinant REX1 and recombinant RNA editing ligase 1.
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PMID:Reconstitution of uridine-deletion precleaved RNA editing with two recombinant enzymes. 1565 44

Mitochondrial pre-messenger RNAs (pre-mRNAs) in African trypanosomes require RNA editing in order to mature into functional transcripts. The process involves the addition and/or removal of U nucleotides and is mediated by a high-molecular-mass complex, the editosome. Editosomes catalyze the reaction through an enzyme-driven pathway that includes endo/exoribonuclease, terminal uridylate transferase and RNA ligase activities. Here we show that editing involves an additional reaction step, a 3' nucleotidyl phosphatase activity. The activity is associated with the editing complex and we demonstrate that the editosomal proteins TbMP99 and TbMP100 contribute to the activity. Both polypeptides contain endo-exonuclease-phosphatase domains and we show that gene ablation of either one of the two polypeptides is compensated by the other protein. However, simultaneous knockdown of both genes results in trypanosome cells with reduced 3' nucleotidyl phosphatase and reduced editing activity. The data provide a rationale for the exoUase activity of the editosomal protein TbMP42, which generates nonligatable 3' phosphate termini. Opposing phosphates at the two pre-mRNA cleavage fragments likely function as a roadblock to prevent premature ligation.
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PMID:Kinetoplastid RNA editing involves a 3' nucleotidyl phosphatase activity. 1919 92