Using Drosophila and mouse knock out models, we demonstrate that upon loss of DmANGEL or ANGEL2, transcripts that undergo non-canonical processing, accumulate 3’ phosphates, preventing their polyadenylation, causing a respiratory chain deficiency. Here, we identify that ANGEL2 and its Drosophila homologue, DmAngel, are mitochondrial proteins that are essential during non-canonical processing. But whether additional deadenylases function within mitochondria is unknown.
In mitochondria only the carbon catabolite repression 4 (Ccr4) family member, 2’,5’-phosphodiesterase, PDE12, has been proposed to have deadenylation function 48, 49, 50, capable of removing spurious poly(A) additions on selected mitochondrial tRNAs 50.
#Angel wings 3d model full#
Previous studies revealed that polyadenylation occurs prior to full partitioning of the primary transcripts 10, 47, necessitating a deadenylase to remove such tails from immature tRNAs prior to maturation, and although a PNPase/SUV3 complex has been shown to degrade mRNAs 38, 39, 40, 41, 42, their role in deadenylation is not clear. The role of the poly(A) tail in translation is not clear, but we previously demonstrated that transcripts lacking a poly(A) signal can still be translated but lose their 3′ integrity 21. While several mitochondrial transcripts require polyadenylation to complete their translational stop codons, mt:Nd6 is the only mRNA not polyadenylated in humans or mouse for yet unknown reasons 20. Furthermore, the leucine rich pentatricopeptide repeat containing protein, LRPPRC, stabilises mitochondrial mRNAs and stimulates MTPAP activity 41, 45, 46. For instance, the polynucleotide phosphorylase, PNPase, and the ATP-dependent RNA helicase SUV3 have been shown to inversely regulate poly(A) tail length via MTPAP 38, 39, 40, 41, 42, 43, 44. Several factors have been shown to directly affect MTPAP activity and polyadenylation. While the mechanisms of transcription, processing, and translation are increasingly understood 36, 37, the role of polyadenylation inside mitochondria is less clear, and has been proposed to act as both degradation and stabilisation signal 20. Specifically, FASTKD4 and FASTKD5 have been implicated in the maturation of transcripts lacking flanking tRNAs, but the mechanism is unclear 18.Īfter excision, the individual transcripts are further modified by polyadenylation of most mRNAs by the mitochondrial polynucleotide adenylyltransferase MTPAP 19, 20, 21, 22, and methylation and pseudouridylation of mitochondrial tRNAs and rRNAs 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35. Several members of the FAST kinase domain containing protein family have been associated with cleavage of such junctions 14, 15, 16, 17. However, in mammals at least two gene junctions do not follow this canonical pattern, and the mechanism of their processing has remained mainly unknown. Mammalian mtDNA encodes for 2 rRNA, 22 tRNAs and 11 mRNAs, and this model explains processing of most transcripts in metazoan mitochondria 7, 9, 10, 11, 12, 13. Since then, the responsible ribonucleases RNase P and ELAC2 and their mechanistic and structural basis have been described 3, 4, 5, 6, 7, 8, 9. The mitochondrial tRNA punctuation model, proposed 40 years ago, defines that tRNAs intersperse the mitochondrial genome and act as excision sites to release the individual transcripts prior to maturation 2. Transcription of the mammalian mitochondrial genome (mtDNA) is initiated from two designated promoter regions, which generate long, primary polycistronic transcripts that cover almost the entire length of the mtDNA molecule 1. Nature Communications volume 13, Article number: 5750 ( 2022) ANGEL2 phosphatase activity is required for non-canonical mitochondrial RNA processing
0 kommentar(er)
