Oligoribonuclease, mitochondrial

3'-to-5'exoribonuclease that preferentially degrades DNA and RNA oligonucleotides composed of only two nucleotides. Binds and degrades longer oligonucleotides with a lower affinity. Plays dual roles in mitochondria, scavenging nanoRNAs (small RNA oligonucleotides of <5 nucleotides) that are produced by the degradosome and clearing short RNAs that are generated by RNA processing. Essential for correct initiation of mitochondrial transcription, degrading mitochondrial RNA dinucleotides to prevent RNA-primed transcription at non-canonical sites in the mitochondrial genome. Essential for embryonic development (By similarity).; [Isoform 3]: 3'-to-5'exoribonuclease that preferentially degrades DNA and RNA oligonucleotides composed of only two nucleotides.