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5' to 3' exoribonucleolytic activity is a normal component of chloroplast mRNA decay pathways.
- Source :
-
The Plant journal : for cell and molecular biology [Plant J] 1999 Sep; Vol. 19 (5), pp. 521-31. - Publication Year :
- 1999
-
Abstract
- Molecular genetic studies have shown that determinants of chloroplast mRNA stability lie in both the 5' and 3' untranslated regions. While it is well-known that chloroplast mRNAs are unstable in the absence of certain nucleus-encoded factors, little is known of the decay mechanisms for chloroplast mRNA in wild-type cells. Here we used a poly(G)18 sequence, which impedes both 5'-->3' and 3'-->5' exoribonucleolytic RNA decay in vivo, to study the degradation pathway of petD mRNA in wild-type and mcd1 mutant chloroplasts of Chlamydomonas; the mcd1 mutant lacks a nucleus-encoded factor required for petD mRNA accumulation. Upon inserting poly(G) at positions -20, +25, +165 or +25/+165 relative to the mature petD 5' end, mRNAs accumulate with 5' ends corresponding to the poly(G) sequence, in addition to the normal RNA with its 5' end at +1. We interpret these results as evidence for continuous degradation of petD mRNA in wild-type cells by a 5'-->3' exoribonucleolytic activity. In the case of the -20 insertion, the accumulating RNA can be interpreted as a processing intermediate, suggesting that 5' end maturation may also involve this activity. When examined in the mcd1 mutant background, petD mRNAs with the poly(G) 5' ends, but not normal +1 ends, accumulated. However, no expression of SUIV, the petD gene product, was detected. Insertion of poly(G) at +165 in wild-type cells did not demonstrably affect SUIV accumulation, suggesting that ribosomal scanning does not occur upstream of this position. However, since neither poly(G) -20 nor +165 RNA could be translated in mcd1 cells, this raises the possibility that the MCD1 product is essential for translation.
- Subjects :
- Cell Cycle Proteins metabolism
Chromosomal Proteins, Non-Histone
Molecular Sequence Data
Nuclear Proteins
Phosphoproteins
Plant Proteins genetics
Plant Proteins metabolism
Poly G metabolism
Saccharomyces cerevisiae Proteins
Chloroplasts genetics
Exoribonucleases metabolism
RNA, Messenger metabolism
Subjects
Details
- Language :
- English
- ISSN :
- 0960-7412
- Volume :
- 19
- Issue :
- 5
- Database :
- MEDLINE
- Journal :
- The Plant journal : for cell and molecular biology
- Publication Type :
- Academic Journal
- Accession number :
- 10504574
- Full Text :
- https://doi.org/10.1046/j.1365-313x.1999.00546.x