Alkylating agents are a structurally diverse group of compounds that cause a wide range of biological effects, including cell death, mutation and cancer. DNA damaged by these agents contains widely different amounts of 12 alkylated purines/pyrimidines and two phosphotriester isomers. The biological effects appear to be mediated predominantly by attack at the O(6) position of guanine. DNA extrac...

A tRNA (guanine-2) methyltransferase has been purified to homogeneity from the protozoan Tetrahymena pyriformis. The enzyme methylates purified E. coli tRNAs which have a guanine residue at position 26 from the 5' end; it also methylates tRNA prepared from the m22G- yeast mutant trm 1. This methyltransferase is therefore equivalent to the guanine methyltransferase 2mGII found in mammalian extra...