Several lines of evidence demonstrate that the DNA of the iridovirus frog virus 3 (FV3) is methylated in all 5*-CG-3* sequences both in virion DNA and in the intracellular viral DNA at late times after infection. The 5-methyldeoxycytidine residues in this viral DNA occur exclusively in 5*-CG-3* dinucleotide positions. We have cloned and determined the nucleotide sequence of the L1140 gene and i...