RAPID DETECTION OF FUNCTIONAL EXPRESSION OF C-5-DNA METHYLTRANSFERASES IN YEAST

We have previously employed the cytosine-5-DNA methyltransferase (MTas e), M.SssI, as a probe for chromatin architecture in intact cells. Alt hough M.SssI offers the highest resolution of any currently available MTase, the difficulty in establishing stable, methylation-positive str ains poses a barrier to its general utility as a chromatin probe, We d escribe a simple screen for M.SssI-expressing strains that eliminates the purification of PCR products amplified from bisulfite-treated DNA, use of radioisotopes, polyacrylamide sequencing gel electrophoresis, and autoradiography, The high throughput of the method now makes it fe asible to introduce M.SssI into a variety of wild-type and mutant gene tic backgrounds.