PT Unknown
AU Becker, M
TI Characterization of the Dnmt2 homolog Pmt1 in Schizosaccharomyces pombe
PD 09
PY 2013
LA en
AB DNA nucleotide methyltransferases (Dnmts) are the enzymes responsible for the conversion of cytosine to 5-methylcytosine in eukaryotes. The fission yeast Schizosaccharomyces pombe contains a putative DNA methyltransferase, termed pombe methyltransferase1 (Pmt1) that belongs to the Dnmt2 family of cytosine methyltransferases, but intriguingly has no DNA methylation. Dnmt2 family members from several organisms have been demonstrated to methylate tRNAAsp at position
C38 rather than cytosines in DNA, but the biological function of this tRNA
modification has remained largely unknown. In this study, we found that Pmt1 is able to methylate position C38 of tRNAAsp and to a lesser extent tRNAGlu in vitro using methylation of tRNA transcripts by recombinant
Pmt1. RNA bisulfite sequencing of tRNAs showed that Pmt1 is also active in vivo. These results show that mt1 in principle has methyltransferase activity, although it was previously thought to be inactive due to a deviation in catalytic motif IV from other Dnmt2 enzymes. Furthermore, in vivo Pmt1 activity was strongly influenced by a nutritional factor in the growth medium. Induction of Pmt1 methyltransferase activity was observed upon the addition of peptone to S. pombe growth medium.
Furthermore, the induction of Pmt1 activity required the serine/threonine kinase Sck2 and was independent of the kinases Sck1, Pka1 and Tor1. Significantly, cells with full tRNA methylation displayed a shortened chronological lifespan, whereas the deletion of pmt1+ lead to an elongated lifespan in fission yeast. In summary, out data show that Pmt1 is an active tRNA methyltransferase. Furthermore, Pmt1 function is regulated in a nutrient-dependent manner by the serine/threonine kinase Sck2, and it is involved in the regulation of chronological
aging in the fission yeast Schizosaccharomyces pombe.
ER