Polyadenylation and Degradation of mRNA in the Chloroplast1

Schuster, Gadi; Lisitsky, Irena; Klaff, Petra

doi:10.1104/pp.120.4.937

Cited by 81 publications

(76 citation statements)

References 34 publications

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“…Thus, in chloroplasts RNA unwinding may be uncoupled from PNPase activity. In vivo, however, RNAs that terminate in stem-loops are poorly polyadenylated, most likely for steric reasons (36), which affords another level of protection for correctly matured transcripts.…”

Section: Discussionmentioning

confidence: 99%

Evidence for in vivo modulation of chloroplast RNA stability by 3′-UTR homopolymeric tails in Chlamydomonas reinhardtii

Komine

Kikis

Schuster

et al. 2002

Proc. Natl. Acad. Sci. U.S.A.

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Polyadenylation of synthetic RNAs stimulates rapid degradation in vitro by using either Chlamydomonas or spinach chloroplast extracts. Here, we used Chlamydomonas chloroplast transformation to test the effects of mRNA homopolymer tails in vivo, with either the endogenous atpB gene or a version of green fluorescent protein developed for chloroplast expression as reporters. Strains were created in which, after transcription of atpB or gfp, RNase P cleavage occurred upstream of an ectopic tRNA Glu moiety, thereby exposing A28, U25A3, [A؉U]26, or A3 tails. Analysis of these strains showed that, as expected, polyadenylated transcripts failed to accumulate, with RNA being undetectable either by filter hybridization or reverse transcriptase-PCR. In accordance, neither the ATPase ␤-subunit nor green fluorescent protein could be detected. However, a U25A3 tail also strongly reduced RNA accumulation relative to a control, whereas the [A؉U] tail did not, which is suggestive of a degradation mechanism that does not specifically recognize poly(A), or that multiple mechanisms exist. With an A 3 tail, RNA levels decreased relative to a control with no added tail, but some RNA and protein accumulation was observed. We took advantage of the fact that the strain carrying a modified atpB gene producing an A28 tail is an obligate heterotroph to obtain photoautotrophic revertants. Each revertant exhibited restored atpB mRNA accumulation and translation, and seemed to act by preventing poly(A) tail exposure. This suggests that the poly(A) tail is only recognized as an instability determinant when exposed at the 3 end of a message.

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Section: Discussionmentioning

confidence: 99%

Evidence for in vivo modulation of chloroplast RNA stability by 3′-UTR homopolymeric tails in Chlamydomonas reinhardtii

Komine

Kikis

Schuster

et al. 2002

Proc. Natl. Acad. Sci. U.S.A.

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“…Polyadenylation is required for stabilizing virtually all nuclear-encoded mRNAs in all eukaryotes. In contrast, polyadenylation targets mRNAs for degradation in eubacteria (1,2), chloroplasts (3)(4)(5)(6), plant mitochondria (7)(8)(9), and trypanosome mitochondria (10). In eubacteria and chloroplasts, degradation of mRNAs is initiated by endonucleolytic cleavages.…”

mentioning

confidence: 99%

“…In both systems, polyadenylation targets endonucleolytic cleavage products for rapid degradation. In chloroplasts, structured mature 3Ј ends are poor substrates for polyadenylation as compared with the internal RNA fragments generated by endonuclease(s) (5,6).…”

mentioning

confidence: 99%

Plant Mitochondrial Polyadenylated mRNAs Are Degraded by a 3′- to 5′-Exoribonuclease Activity, Which Proceeds Unimpeded by Stable Secondary Structures

Gagliardi¹,

Perrin²,

Maréchal-Drouard³

et al. 2001

Journal of Biological Chemistry

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Recently, we and others have reported that mRNAs may be polyadenylated in plant mitochondria, and that polyadenylation accelerates the degradation rate of mRNAs. To further characterize the molecular mechanisms involved in plant mitochondrial mRNA degradation, we have analyzed the polyadenylation and degradation processes of potato atp9 mRNAs. The overall majority of polyadenylation sites of potato atp9 mRNAs is located at or in the vicinity of their mature 3-extremities. We show that a 3-to 5-exoribonuclease activity is responsible for the preferential degradation of polyadenylated mRNAs as compared with non-polyadenylated mRNAs, and that 20 -30 adenosine residues constitute the optimal poly(A) tail size for inducing degradation of RNA substrates in vitro. The addition of as few as seven non-adenosine nucleotides 3 to the poly(A) tail is sufficient to almost completely inhibit the in vitro degradation of the RNA substrate. Interestingly, the exoribonuclease activity proceeds unimpeded by stable secondary structures present in RNA substrates. From these results, we propose that in plant mitochondria, poly(A) tails added at the 3 ends of mRNAs promote an efficient 3-to 5-degradation process.The control of mRNA stability constitutes an important aspect of the regulation of gene expression in all organisms. Polyadenylation of mRNAs is involved in the control of mRNA stability, however, with two significantly different roles depending on the organism or subcellular compartment concerned. Polyadenylation is required for stabilizing virtually all nuclear-encoded mRNAs in all eukaryotes. In contrast, polyadenylation targets mRNAs for degradation in eubacteria (1, 2), chloroplasts (3-6), plant mitochondria (7-9), and trypanosome mitochondria (10). In eubacteria and chloroplasts, degradation of mRNAs is initiated by endonucleolytic cleavages. The resulting fragments are then degraded by 3Ј-to 5Ј-exonuclease activities (1, 5). In both systems, polyadenylation targets endonucleolytic cleavage products for rapid degradation. In chloroplasts, structured mature 3Ј ends are poor substrates for polyadenylation as compared with the internal RNA fragments generated by endonuclease(s) (5, 6).In plant mitochondria, molecular mechanisms involved in mRNA stability or degradation are still poorly understood (11). For instance, no proteins involved in these processes have been formally identified, although several candidate genes have now been identified since the completion of the nuclear genome sequence of Arabidopsis thaliana. Stable secondary structures can be predicted at the 3Ј-extremities of some but not all plant mitochondrial mRNAs (12). When present, these structures appear to be involved in stabilizing the transcripts (13-15) and in the correct processing of 3Ј-extremities rather than being signals for transcription termination (15). Mature 3Ј termini of plant mitochondria mRNAs are generated by 3Ј-processing of longer pre-mRNA molecules (15), and stable mature mRNAs are not constitutively polyadenylated at their 3Ј-extremit...

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“…Removal of the stemloop structure, for instance by internal endonucleolytic cuts, results in rapid degradation of the investigated RNAs, both in vitro and in vivo. Interestingly, similar to the situation in bacteria, polyadenylation of the resulting cleavage products at their 3¢ ends targets them for degradation (Hayes et al 1999;Schuster et al 1999). In E. coli, polyadenylation of RNAs and their subsequent degradation are performed by a poly(A)polymerase and the exoribonuclease poynucleotide phosphorylase (PNPase), respectively.…”

Section: Rbps Involved In 3¢ End Formation Of Chloroplast Rnasmentioning

confidence: 94%

Chloroplast RNA-binding proteins

Nickelsen

2003

Current Genetics

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Chloroplast gene expression is regulated by nucleus-encoded factors, which mainly act at the posttranscriptional level. Plastid RNA-binding proteins (RBPs) represent good candidates for mediating these functions. The picture emerging from recent analyses is that of a great number of differentially regulated RBPs, which are organized in distinct, spatially separated supramolecular complexes. This reflects the complexity of the regulatory network that underlies the intracellular communication system between the nucleus and the chloroplast.

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Polyadenylation and Degradation of mRNA in the Chloroplast1

Cited by 81 publications

References 34 publications

Evidence for in vivo modulation of chloroplast RNA stability by 3′-UTR homopolymeric tails in Chlamydomonas reinhardtii

Evidence for in vivo modulation of chloroplast RNA stability by 3′-UTR homopolymeric tails in Chlamydomonas reinhardtii

Plant Mitochondrial Polyadenylated mRNAs Are Degraded by a 3′- to 5′-Exoribonuclease Activity, Which Proceeds Unimpeded by Stable Secondary Structures

Chloroplast RNA-binding proteins

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