SETDB1 activity is globally directed by H3K14 acetylation via its Triple Tudor Domain

SETDB1 is a major H3K9 methyltransferase. It contains a unique Triple Tudor Domain (3TD) which specifically bind the dual modification of H3K14ac in the presence of H3K9me1/2/3. In this study, we explored the role of the 3TD H3K14ac interaction in the H3K9 methylation activity by SETDB1. We generated the 3TD binding reduced F332A mutant and demonstrate in biochemical methylation assays on recombinant nucleosomes containing H3K14ac analogs, that H3K14 acetylation is crucial for the 3TD mediated recruitment of SETDB1. We also see this effect in the cells where SETDB1 binding and activity was globally correlated with H3K14ac, and knock-out (KO) of the H3K14 acetyltransferase HBO1 caused a drastic reduction in the H3K9me3 levels at SETDB1 dependent sites. Further analyses revealed that 3TD was not required for SETDB1 recruitment for regions targeted by KAP1, but at specific target regions, SETDB1 KO could not be efficiently reconstituted by a 3TD mutant of SETDB1 as shown by the finding that H3K9 methylation of L1M repeat elements is highly dependent on an intact 3TD. In summary, our data demonstrate an important role of the 3TD interaction with H3 tails containing K14ac and K9 methylation in the recruitment of SETDB1 to chromatin which is particularly relevant at L1M repeats.