3'-5'exoribonuclease which is involved in the post-transcriptional processing, editing and degradation of mitochondrial RNAs, including mRNAs, rRNAs and guided RNAs (gRNA). As part of the mitochondrial 3' processome (MPsome), involved in the maturation of guided RNA (gRNA) precursors by catalyzing the processive 3'-5' degradation of uridylated gRNA precursors. Plays a role in the degradation of 12S rRNA processing intermediates and maturation by-products