DNMT3L and the formation of heterotetramers restores processivity to R882H DNMT3A.
A, the EMSA shows that DNMT3L binds to DNMT3A tetramers to form heterotetramers. R882H binds to DNMT3L; all other mutants at the dimer interface become heterodimers. B, DNMT3L (1:1 ratio) activates DNMT3A tetramers at ∼5-fold. Dimer interface mutants show a 2–4-fold activation other than R882H, which show an 8.8-fold stimulation. DNMT3A heterotetramers (C, WT; D, R882H) are processive, and heterodimers (E, H873A) are non-processive as demonstrated by the processive chase assay. ●, only substrate (20 μm bp RASSF1A); ■, substrate and then 400 μm bp chase (pCpGL at 20 min; ▴, substrate and pCpGL at the start of the reaction.