Effect of L-ethionine on macromolecular synthesis in mitogen-stimulated lymphocytes.

2--4 mM L-ethionine completely inhibits DNA synthesis in phytohaemagglutinin- or concanavalin A-stimulated lymphocytes even though it does not prevent the morphological changes characteristic of blast formation. Evidence is presented which indicates that complete commitment to DNA synthesis as well as a substantial increase in the rates of RNA and protein synthesis can occur in the presence of ethionine. Ethionine, however, does inhibit methylation of tRNA and prevents mitogen-induced increase in the activity of histone-modifying enzymes.