The human tRNA m⁵C methyltransferase Misu is multisite-specific

Abstract

The human tRNA m⁵C methyltransferase Misu is a novel downstream target of the proto-oncogene Myc that participates in controlling cell division and proliferation. Misu catalyzes the transfer of a methyl group from S-adenosyl-L-methionine to carbon 5 of cytosines in tRNAs. It was previously shown to catalyze in vitro the intron-dependent formation of m⁵C at the first position of the anticodon (position 34) within the human pre-tRNA^Leu_(CAA). In addition, it was recently reported that C48 and C49 are methylated in vivo by Misu. We report here the expression of hMisu in Escherichia coli and its purification to homogeneity. We show that this enzyme methylates position 48 in tRNA^Leu_(CAA) with or without intron and positions 48, 49 and 50 in tRNA^Gly2_(GCC) in vitro. Therefore, hMisu is the enzyme responsible for the methylation of at least four cytosines in human tRNAs. By comparison, the orthologous yeast enzyme Trm4 catalyzes the methylation of carbon 5 of cytosine at positions 34, 40, 48 or 49 depending on the tRNAs.

Keywords: :

• tRNA modification enzyme
• RNA methyltransferase
• 5-methylcytosine
• m⁵C
• Misu
• NSun2
• Trm4

Disclosure of Potential Conflicts of Interest

No potential conflicts of interest were disclosed.

Acknowledgments

Funding was provided by the Association pour la Recherche sur le Cancer (to B.G.P.) and the CNRS. We acknowledge the use of the Imagif cloning and proteins expression Platform and thank Laetitia Cormier for performing the cloning experiments and expression tests and David Touboul for critical reading of the manuscript.

Supplemental Material

Supplemental material may be found here: 
www.landesbioscience.com/journals/rnabiology/article/22180