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Site-specific binding of a PPR protein defines and stabilizes 5' and 3' mRNA termini in chloroplasts

Jeannette Pfalz1, Omer Ali Bayraktar, Jana Prikryl

  • 1Institute of Molecular Biology, University of Oregon, Eugene, OR 97403, USA.

The EMBO Journal
|May 9, 2009
PubMed

Insights

Pentatricopeptide repeat protein (PPR10) in maize chloroplasts defines mRNA segments by binding overlapping RNA regions. This protein acts as a protective cap, preventing RNA degradation and influencing mRNA stability.

Area of Science:

  • Plant molecular biology
  • Chloroplast gene expression
  • RNA processing and stability

Background:

  • Chloroplast mRNA populations originate from polycistronic precursors requiring processing.
  • The mechanisms and functional roles of these RNA processing events remain largely unknown.

Purpose of the Study:

  • To investigate the role of pentatricopeptide repeat (PPR) proteins in defining chloroplast mRNA segments.
  • To elucidate the mechanism by which PPR proteins contribute to chloroplast mRNA biogenesis and stability.

Main Methods:

  • In vivo and in vitro interaction studies of PPR protein PPR10 with specific RNA regions.
  • Mapping of PPR10 binding sites to overlapping intergenic RNA sequences.
  • Analysis of RNA accumulation in the presence and absence of functional PPR10.

Main Results:

  • PPR10 binds to two similar, overlapping intergenic RNA regions in maize chloroplasts.
  • PPR10 binding sites precisely overlap the processed 5' and 3' RNA termini.
  • PPR10 is essential for the accumulation of specific chloroplast RNAs with defined termini.

Conclusions:

  • PPR10 functions as a proteinaceous barrier, protecting RNA termini from degradation.
  • Protein binding, rather than RNA hairpins, can define mRNA termini in chloroplasts.
  • A unifying model for chloroplast mRNA biogenesis and stability is proposed, involving protein 'caps'.

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