Abstract
Transfer RNAs acquire a variety of naturally occurring chemical modifications during their maturation; these fine-tune their structure and decoding properties in a manner critical for protein synthesis. We recently reported that in the eukaryotic parasite, Trypanosoma brucei, a methylation and deamination event are unexpectedly interconnected, whereby the tRNA adenosine deaminase (TbADAT2/3) and the 3-methylcytosine methyltransferase (TbTrm140) strictly rely on each other for activity, leading to formation of m3C and m3U at position 32 in several tRNAs. Still however, it is not clear why these two enzymes, which work independently in other systems, are strictly codependent in T. brucei. Here, we show that these enzymes exhibit binding synergism, or a mutual increase in binding affinity, that is more than the sum of the parts, when added together in a reaction. Although these enzymes interact directly with each other, tRNA binding assays using enzyme variants mutated in critical binding and catalytic sites indicate that the observed binding synergy stems from contributions from tRNA-binding domains distal to their active sites. These results provide a rationale for the known interactions of these proteins, while also speaking to the modulation of substrate specificity between seemingly unrelated enzymes. This information should be of value in furthering our understanding of how tRNA modification enzymes act together to regulate gene expression at the post-transcriptional level and provide a basis for the interdependence of such activities.
Original language | English (US) |
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Pages (from-to) | 56-66 |
Number of pages | 11 |
Journal | RNA |
Volume | 24 |
Issue number | 1 |
DOIs | |
State | Published - Jan 2018 |
Externally published | Yes |
Bibliographical note
Funding Information:We thank Dr. Jane Jackman for the useful discussions and helpful advice. We are appreciative of all members of the Alfonzo laboratory for their support and suggestions. This work was partially supported by National Institutes of Health grant GM084065 to J.D.A. and a
Publisher Copyright:
© 2018 McKenney et al.
Keywords
- Modification
- RNA editing
- T. brucei
- TRNA