Characterization of the Dnmt2 metyltransferase homolog pmt1 from Schizosaccharomyces pombe

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DNA methylation on cytosine residues is a modification used by many organisms to regulate gene expression. The fission yeast Schizosaccharomyces pombe carries a homolog of the Dnmt2 family of methyltransferases called Pmt1, but possesses no detectable DNA methylation. Our work has shown that Pmt1 has tRNA methylation activity, both in vitro and in vivo. Surprisingly, its in vivo activity is strongly regulated by nutritional conditions, and this regulation requires the serine/ threonine kinase Sck2 and has an impact on chronological aging in S. pombe.In this project, we will expand on this work and will further define the nutritional requirements and dynamics of Pmt1-dependent tRNA methylation, and we will seek to identify other conditions for Pmt1 induction. We will evaluate Sck2 as well as other kinase signaling pathways for their role in Pmt1 activation and will ask whether it occurs via a direct or indirect phosphorylation of Pmt1 or by interaction of Pmt1 with other proteins. Furthermore, we will place the effect of Pmt1 on aging in the context of known aging pathways. Based on the knowledge gained in the first grant period, we will search for genes that show a synthetic lethal interaction with pmt1Δ, which will give indications as to functional roles of Pmt1. Finally, we will reevaluate the role of Pmt1 on epigenetic gene silencing, taking into consideration the nutritional circumstances of Pmt1 activation.