3'-to-5'exoribonuclease that preferentially degrades DNA and RNA oligonucleotides composed of only two nucleotides (By similarity). Binds and degrades longer oligonucleotides with a lower affinity (By similarity). 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 (By similarity). Essential for correct initiation of mitochondrial transcription, degrading mitochondrial RNA dinucleotides to prevent RNA-primed transcription at non-canonical sites in the mitochondrial genome (By similarity). Essential for embryonic development (By similarity). Homodimer (By similarity). Homotetramer (By similarity). Belongs to the oligoribonuclease family.