Search bioRxiv⌕ Search

Biology subjects

Hammani, K.

Publications and source records attributed to Hammani, K..

2 recordsLinked to original sources
bioRxiv2020

In vivo stabilization of endogenous chloroplast RNAs by customized artificial pentatricopeptide repeat proteins

Pentatricopeptide repeat (PPR) proteins are helical repeat-proteins that bind RNA in a modular fashion with a sequence-specificity that can be manipulated by the use of an amino acid code. As such, PPR repeats are promising scaffolds for the design of RNA binding proteins for synthetic biology applications. However, the in vivo functional capabilities of artificial PPR proteins built from consensus PPR motifs are just starting to be explored. Here, we report in vivo functions of an artificial PPR protein, dPPRrbcL, made of consensus PPR motifs that were designed to bind a sequence near the 5 end of rbcL transcripts in Arabidopsis chloroplasts. We used a functional complementation assay to demonstrate that this protein bound its intended RNA target with specificity in vivo and that it substituted for a natural PPR protein by stabilizing processed rbcL mRNA. We targeted a second protein of analogous design to the petL 5 UTR, where it substituted for the native stabilizing PPR protein PGR3, albeit inefficiently. These results showed that artificial PPRs can be engineered to functionally mimic the class of native PPR proteins that serve as physical barriers against exoribonucleases.

plant biology↗
bioRxiv2020

Arabidopsis mTERF9 protein promotes chloroplast ribosomal assembly and translation by establishing ribonucleoprotein interactions in vivo.

The mitochondrial transcription termination factor proteins are nuclear-encoded nucleic acid binders defined by degenerate tandem helical-repeats of ~30 amino acids. They are found in metazoans and plants where they localize to mitochondria or chloroplasts. In higher plants, the mTERF family comprises ~30 members and several of these have been linked to plant development and response to abiotic stress. However, knowledge of the molecular basis underlying these physiological effects is scarce. We show that the Arabidopsis mTERF9 protein promotes the accumulation of the 16S and 23S rRNAs in chloroplasts, and interacts predominantly with the 16S rRNA in vivo and in vitro. Furthermore, mTERF9 is found in large complexes containing ribosomes and polysomes in chloroplasts. The comprehensive analysis of mTERF9 in vivo protein interactome identified many subunits of the 70S ribosome whose assembly is compromised in the null mterf9 mutant, putative ribosome biogenesis factors and CPN60 chaperonins. Protein interaction assays in yeast revealed that mTERF9 directly interact with these proteins. Our data demonstrate that mTERF9 integrates protein-protein and protein-RNA interactions to promote chloroplast ribosomal assembly and translation. Besides extending our knowledge of mTERF functional repertoire in plants, these findings provide an important insight into the chloroplast ribosome biogenesis.

plant biology↗