Chloroplast ribonucleoproteins function as a stabilizing factor of ribosome-free mRNAs in the stroma

Citation
T. Nakamura et al., Chloroplast ribonucleoproteins function as a stabilizing factor of ribosome-free mRNAs in the stroma, J BIOL CHEM, 276(1), 2001, pp. 147-152
Citations number
54
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Biochemistry & Biophysics
Journal title
JOURNAL OF BIOLOGICAL CHEMISTRY
ISSN journal
0021-9258 → ACNP
Volume
276
Issue
1
Year of publication
2001
Pages
147 - 152
Database
ISI
SICI code
0021-9258(20010105)276:1<147:CRFAAS>2.0.ZU;2-H
Abstract
Post-transcriptional RNA processing is an important step in the regulation of chloroplast gene expression, and a number of chloroplast ribonucleoprote ins (cpRNPs) are likely to be involved in this process, The major tobacco c pRNPs are composed of five species: cp28, cp29A, cp29B, cp31, and cp33 and these are divided into three groups (I, II, and III). By immunoprecipitatio n, gel filtration, and Western blot analysis, we demonstrated that these cp RNPs are abundant stromal proteins that exist as complexes with ribosome-fr ee mRNAs. Many ribosome-free psbA mRNAs coprecipitate with cpRNPs, indicati ng that the majority of stromal psbA mRNAs are associated with cpRNPs, In a ddition, an In vitro mRNA degradation assay indicated that exogenous psbA m RNA is more rapidly degraded in cpRNP-depleted extracts than in nondepleted extracts. When the depleted extract was reconstituted with recombinant cpR NPs, the psbA mRNA in the extract was protected from degradation to a simil ar extent as the psbA mRNA in the nondepleted extract. Moreover, restoratio n of the stabilizing activity varied following addition of individual group -specific cpRNPs alone or in combination, When the five cpRNPs were supplem ented in the depleted extract, full activity was restored. We propose that these cpRNPs act as stabilizing factors for nonribosome-bound mRNAs in the stroma.