DNA methylation in wheat: purification and properties of DNA methyltransferase

摘要: The origin and function of the large amount 5-methylcytosine in plant DNA is not well understood. As a tool for vitro studies methylcytosine formation plants we have isolated characterized methyltransferase present germinating wheat embryo. An enzyme fraction enriched 300-fold over tissue homogenate was obtained by salt extraction nuclei, chromatography on DEAE-cellulose, Sephadex G-75, blue Sepharose immobilized cellulose. It catalyzes methylation cytosine residues double-stranded DNAs from wheat, maize, calf thymus or bacteria using S-adenosylmethionine as methyl donor. efficient both an unmethylated plasmid its hemimethylated derivative indicate that methylase can de novo maintenance methylation. A relative molecular mass 50,000-55,000 estimated gel permeation sucrose density gradient centrifugation. Polyacrylamide electrophoresis showed presence protein Mr = 50,000 one other component (Mr 35,000). preference endogenous, substrate lower distinguish methylases mammalian sources. properties resemble, however, those alga Chlamydomonas reinhardii, suggesting cells possess their own type biosynthesis high content DNA.