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Translation of the chloroplast psbA mRNA requires the nuclear-encoded poly(A)-binding protein, RB47
1Department of Cell Biology, and The Skaggs Institute of Chemical Biology, The Scripps Research Institute, La Jolla, California 92037, USA.
Abstract:
A set of nuclear mutants of C. reinhardtii were identified that specifically lack translation of the chloroplast-encoded psbA mRNA, which encodes the photosystem II reaction center polypeptide D1. Two of these mutants are deficient in the 47-kD member (RB47) of the psbA RNA-binding complex, which has previously been identified both genetically and biochemically as a putative translational activator of the chloroplast psbA mRNA. RB47 is a member of the poly(A)-binding protein family, and binds with high affinity and specificity to the 5' untranslated region of the psbA mRNA. The results presented here confirm RB47's role as a message-specific translational activator in the chloroplast, and bring together genetic and biochemical data to form a cohesive model for light- activated translational regulation in the chloroplast.
Insights
Researchers identified nuclear mutants in Chlamydomonas reinhardtii lacking translation of psbA mRNA. These mutants confirm RB47
Area of Science:
- Chloroplast biology
- Molecular genetics
- Photosynthesis research
Background:
- The psbA mRNA encodes the D1 polypeptide, a crucial component of photosystem II.
- Chloroplast gene expression is regulated post-transcriptionally.
- RB47, a 47-kD protein, is part of the psbA RNA-binding complex and is a putative translational activator.
Purpose of the Study:
- To investigate the role of RB47 in the translation of chloroplast-encoded psbA mRNA.
- To elucidate the mechanism of light-activated translational regulation in chloroplasts.
- To confirm RB47's function as a message-specific translational activator.
Main Methods:
- Analysis of nuclear mutants of Chlamydomonas reinhardtii lacking psbA mRNA translation.
- Biochemical characterization of the psbA RNA-binding complex.
- Genetic analysis of RB47 function.
Main Results:
- Two nuclear mutants deficient in RB47 were identified.
- RB47 binds with high affinity and specificity to the 5' untranslated region of psbA mRNA.
- These findings confirm RB47's role in activating psbA mRNA translation.
Conclusions:
- RB47 is essential for the translation of psbA mRNA in Chlamydomonas reinhardtii chloroplasts.
- A cohesive model for light-activated translational regulation in chloroplasts is proposed.
- Genetic and biochemical data support RB47's function as a message-specific translational activator.