rRNA N6-methyltransferase that specifically methylates the adenine in position 4220 of 28S rRNA. N6-methylation of adenine(4220) in 28S rRNA is required for translation. adenosine(4220) in 28S rRNA + S-adenosyl-L-methionine = H(+) + N(6)-methyladenosine(4220) in 28S rRNA + S-adenosyl-L-homocysteine Interacts with components of the ASC-1 complex TRIP4, ASCC1, ASCC2 and ASCC3. Interact with AHCYL1 and AHCYL2. Interact with YTHDC2. Accumulates in the nucleolus, where ribosome biogenesis takes place. The regulatory loop blocks the catalytic center by bridging the methyltransferase domain and the C-terminal CCHC-type zinc finger, resulting in an autoinhibitory conformation. Belongs to the ZCCHC4 family.