A gamma subtype methylase that recognizes the double-stranded sequence 5'-TCGA-3' and methylates A-4 on both strands. a 2'-deoxyadenosine in DNA + S-adenosyl-L-methionine = an N(6)-methyl-2'-deoxyadenosine in DNA + H(+) + S-adenosyl-L-homocysteine Not essential for viral replication it can be deleted. Belongs to the N(4)/N(6)-methyltransferase family.