PT  - JOURNAL ARTICLE
AU  - Elisa Vilardo
AU  - Ursula Toth
AU  - Enxhi Hazisllari
AU  - Walter Rossmanith
TI  - Cleavage kinetics of human mitochondrial RNase P and contribution of its non-nuclease subunits
AID  - 10.1101/2023.03.27.534089
DP  - 2023 Jan 01
TA  - bioRxiv
PG  - 2023.03.27.534089
4099  - http://biorxiv.org/content/early/2023/03/27/2023.03.27.534089.short
4100  - http://biorxiv.org/content/early/2023/03/27/2023.03.27.534089.full
AB  - RNase P is the endonuclease responsible for the 5’-end processing of tRNA precursors (pre-tRNAs). Unlike the single-subunit protein-only RNase P (PRORP) found in plants or protists, human mitochondrial RNase P is a multi-enzyme assembly that in addition to the homologous PRORP subunit comprises a methyltransferase (TRMT10C) and a dehydrogenase (SDR5C1) subunit; these proteins, but not their enzymatic activities, are required for efficient pre-tRNA cleavage. Here we report a detailed kinetic analysis of the cleavage reaction by human PRORP and its interplay with TRMT10C-SDR5C1 using a comprehensive set of mitochondrial pre-tRNAs. Surprisingly, we found that PRORP alone binds pre-tRNAs with nanomolar affinity and can even cleave some of them at reduced efficiency without the other subunits. Thus, the ancient binding mode, involving the tRNA elbow and PRORP’s PPR domain, seems retained by human PRORP, and its metallonuclease domain is in principle correctly folded and functional. Our findings support a model according to which the main function of TRMT10C-SDR5C1 is to direct PRORP’s nuclease domain to the cleavage site, thereby increasing the rate and accuracy of cleavage. Human PRORP’s dependence on the extra tRNA binder appears to have evolved to secure specificity in the cleavage of the structurally degenerating mitochondrial tRNAs.Competing Interest StatementThe authors have declared no competing interest.