Abstract
LRP130 (also known as LRPPRC) is an RNA-binding protein that is a constituent of postsplicing nuclear RNP complexes associated with mature mRNA. It belongs to a growing family of pentatricopeptide repeat (PPR) motif-containing proteins, several of which have been implicated in organellar RNA metabolism. We show here that only a fraction of LRP130 proteins are in nuclei and are directly bound in vivo to at least some of the same RNA molecules as the nucleocytoplasmic shuttle protein hnRNP A1. The majority of LRP130 proteins are located within mitochondria, where they are directly bound to polyadenylated RNAs in vivo. In vitro, LRP130 binds preferentially to polypyrimidines. This RNA-binding activity maps to a domain in its C-terminal region that does not contain any previously described RNA-binding motifs and that contains only 2 of the 11 predicted PPR motifs. Therefore, LRP130 is a novel type of RNA-binding protein that associates with both nuclear and mitochondrial mRNAs and as such is a potential candidate for coordinating nuclear and mitochondrial gene expression. These findings provide the first identification of a mammalian protein directly bound to mitochondrial RNA in vivo and provide a possible molecular explanation for the recently described association of mutations in LRP130 with cytochrome c oxidase deficiency in humans.