Studies on Ac/Ds methylation
--Lihua Wang, Manfred Heinlein and Peter Starlinger

In vitro, the DNA-binding affinity of the Ac transposase is enhanced if its hexameric target motif AAACGG is hemimethylated. This observation by Reinhard Kunze seems to fit to the earlier finding by geneticists that transposition is often linked to replication. In order to test the in vivo significance of this correlation, we have begun genomic sequencing of the subterminal sequences of Ac by a PCR-based method developed by Frommer et al. (PNAS 89:1827-1831, 1992). We make use of the fact that the mutagen bisulfite is able to distinguish between methylated cytosin residues, which are stable, and non-methylated cytosin residues, which are oxidatively desaminated to yield uracil.
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