Trm11p and Trm112p Are both Required for the Formation of 2-Methylguanosine at Position 10 in Yeast tRNA

摘要

N²-Monomethylguanosine-10 (m²G10) and N²,N²-dimethylguanosine-26 (m²2G26) are the only two guanosine modifications that have been detected in tRNA from nearly all archaea and eukaryotes but not in bacteria. In Saccharomyces cerevisiae, formation of m²2G26 is catalyzed by Trm1p, and we report here the identification of the enzymatic activity that catalyzes the formation of m²G10 in yeast tRNA. It is composed of at least two subunits that are associated in vivo: Trm11p (Yol124c), which is the catalytic subunit, and Trm112p (Ynr046w), a putative zinc-binding protein. While deletion of TRM11 has no detectable phenotype under laboratory conditions, deletion of TRM112 leads to a severe growth defect, suggesting that it has additional functions in the cell. Indeed, Trm112p is associated with at least four proteins: two tRNA methyltransferases (Trm9p and Trm11p), one putative protein methyltransferase (Mtc6p/Ydr140w), and one protein with a Rossmann fold dehydrogenase domain (Lys9p/Ynr050c). In addition, TRM11 interacts genetically with TRM1, thus suggesting that the absence of m²G10 and m²2G26 affects tRNA metabolism or functioning.