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Molecular and Cellular Biology, February 2001, p. 731-742, Vol. 21, No. 3
Molekulare Botanik, Universität Ulm,
89069 Ulm, Germany
Received 29 August 2000/Returned for modification 26 September
2000/Accepted 24 October 2000
To determine the influence of posttranscriptional modifications on
3' end processing and RNA stability in plant mitochondria, pea
atp9 and Oenothera atp1 transcripts were
investigated for the presence and function of 3' nonencoded
nucleotides. A 3' rapid amplification of cDNA ends approach initiated
at oligo(dT)-adapter primers finds the expected poly(A) tails
predominantly attached within the second stem or downstream of the
double stem-loop structures at sites of previously mapped 3' ends.
Functional studies in a pea mitochondrial in vitro processing system
reveal a rapid removal of the poly(A) tails up to termini at the
stem-loop structure but little if any influence on further degradation
of the RNA. In contrast 3' poly(A) tracts at RNAs without such
stem-loop structures significantly promote total degradation in vitro.
To determine the in vivo identity of 3' nonencoded nucleotides more
accurately, pea atp9 transcripts were analyzed by a direct
anchor primer ligation-reverse transcriptase PCR approach. This
analysis identified maximally 3-nucleotide-long nonencoded extensions
most frequently of adenosines combined with cytidines. Processing
assays with substrates containing homopolymer stretches of different
lengths showed that 10 or more adenosines accelerate RNA processivity,
while 3 adenosines have no impact on RNA life span. Thus
polyadenylation can generally stimulate the decay of RNAs, but
processivity of degradation is almost annihilated by the stabilizing
effect of the stem-loop structures. These antagonistic actions thus
result in the efficient formation of 3' processed and stable transcripts.
0270-7306/01/$04.00+0 DOI: 10.1128/MCB.21.3.731-742.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Transcript Lifetime Is Balanced between Stabilizing
Stem-Loop Structures and Degradation-Promoting Polyadenylation in
Plant Mitochondria
*
Corresponding author. Mailing address: Abt. Molekulare
Botanik, Universität Ulm, Albert-Einstein-Allee, D-89069 Ulm,
Germany. Phone: 49 731 502 2625. Fax: 49 731 502 2626. E-mail:
stefan.binder{at}biologie.uni-ulm.de.
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