biostudies-literatureTaglini FCancer Research UKDarwin Trust of EdinburghUniversity of EdinburghMedical Research CouncilWellcome TrustUKRI | Medical Research CouncilA. G. Leventis FoundationERASMUS+ scholarship1130-1155https://www.ebi.ac.uk/biostudies/studies/S-EPMC7615734biostudies-literatureUnknown25(3)The correct establishment of DNA methylation patterns is vital for mammalian development and is achieved by the de novo DNA methyltransferases DNMT3A and DNMT3B. DNMT3B localises to H3K36me3 at actively transcribing gene bodies via its PWWP domain. It also functions at heterochromatin through an unknown recruitment mechanism. Here, we find that knockout of DNMT3B causes loss of methylation predominantly at H3K9me3-marked heterochromatin and that DNMT3B PWWP domain mutations or deletion result in striking increases of methylation in H3K9me3-marked heterochromatin. Removal of the N-terminal region of DNMT3B affects its ability to methylate H3K9me3-marked regions. This region of DNMT3B directly interacts with HP1α and facilitates the bridging of DNMT3B with H3K9me3-marked nucleosomes in vitroEMBO reportsDNMT3B PWWP mutations cause hypermethylation of heterochromatin.PMC7615734T029471/1C157/A25186210493228154/Z/23/ZC47648/A2083720837MC_UU_00009/2MRC_UU_00009218736203149Rolls WGautier PSproul DWills JWheeler AKerr LMusialik KILee HYDavidson-Smith HKumar DMarenda MMurphy LCWilson MDTaglini FZhang YRubio-Ramon CKafetzopoulos IFinan HWapenaar HfalseDNMT3B PWWP mutations cause hypermethylation of heterochromatin.The correct establishment of DNA methylation patterns is vital for mammalian development and is achieved by the de novo DNA methyltransferases DNMT3A and DNMT3B. DNMT3B localises to H3K36me3 at actively transcribing gene bodies via its PWWP domain. It also functions at heterochromatin through an unknown recruitment mechanism. Here, we find that knockout of DNMT3B causes loss of methylation predominantly at H3K9me3-marked heterochromatin and that DNMT3B PWWP domain mutations or deletion result in striking increases of methylation in H3K9me3-marked heterochromatin. Removal of the N-terminal region of DNMT3B affects its ability to methylate H3K9me3-marked regions. This region of DNMT3B directly interacts with HP1α and facilitates the bridging of DNMT3B with H3K9me3-marked nucleosomes in vitro2024-01-01T00:00:00Z2024 Mar2026-07-16T12:04:09.689Z2025-04-04T09:35:36.798ZS-EPMC76157343829133710.1038/s44319-024-00061-5