Study On The Interaction Of PPR Protein Ppr10 And Mpa1 In Schizosaccharomyces Pombe

The PPR proteins characterized by tandem repeats of a degenerate 35-amino-acid motif function in all aspects of organellar RNA metabolism, many of which are essential for organellar gene expression. The majority of PPR proteins are involved in expression of genes encoded by the organellal genome, including intron splicing, RNA editing, RNA stabilization and translational activation. In humans, PPR proteins play an important role in many physiological and pathological processes. In plants, most of the PPR proteins are involved in chloroplast RNA processing, translation and RNA editing.Recently, a genome-wide analysis of PPR proteins in S. pombe revealed that Pprl-9 (In S. pombe, PPR proteins were numbered sequentially from 1) modulate mitochondrial RNA expression. Here we characterized a fission yeast Schizosaccharomyces pombe PPR protein, Ppr10. The growth of the ppr10 deletion mutant is dramatically impaired for during the late-stationary phase. Deletion of ppr10 does not affect the processing and stability of RNAs encoded by the mitochondrial genome. RNA immunoprecipitation assays demonstrate an association of Ppr10 with mitochondrial mRNAs.We found a new protein named Mpal that interacts with Ppr10 through the tandem affinity purification (TAP) of Ppr10-TAP. We confirmed their interaction by co-immunoprecipitation. The interaction between Ppr10 and Mpal is independent on RNA. One of Mpal’s functions is to maintain the normal protein levels of Ppr10 by preventing it from degradation by mitochondrial matrix metalloproteinase Lonl.There are two mitochondrial translation initiation factors Mti2 and Mti3 in S. pombe. We showed that Ppr10 can interact Mti2. These results suggest that Ppr10 is a general mitochondrial translation activator that is likely to function through interaction with the mitochondrial translation initiation factor Mti2 Our results also suggest that Ppr10 requires Mpal association for stability and function.