The histone methyltransferase KMT2B is required for RNA polymerase II association and protection from DNA methylation at the MagohB CpG island promoter.
KMT2B (MLL2/WBP7) is a member of the MLL subfamily of H3K4-specific histone lysine methyltransferases (KMT2) and is vital for normal embryonic development in the mouse. To gain insight into the molecular mechanism underlying KMT2B function, we focused on MagohB, which is controlled by a CpG island promoter. We show that in cells lacking Mll2-the gene encoding KMT2B-the MagohB promoter resides in inaccessible chromatin and is methylated. To dissect the molecular events leading to the establishment of silencing, we performed kinetic studies in Mll2-conditional-knockout embryonic stem cells. KMT2B depletion was followed by the loss of the active chromatin marks and progressive loss of RNA polymerase II binding with a concomitant downregulation of MagohB expression. Once the active chromatin marks were lost, the MagohB promoter was rapidly methylated. We demonstrate that in the presence of KMT2B, neither transcription elongation nor RNA polymerase II binding is required to maintain H3K4 trimethylation at the MagohB promoter and protect it from DNA methylation. Reexpression of KMT2B was sufficient to reinstate an active MagohB promoter. Our study provides a paradigm for the idea that KMT2 proteins are crucial components for establishing and maintaining the transcriptionally active and unmethylated state of CpG island promoters.
School of Cancer Sciences, Institute of Biomedical Research, College of Medical and Dental Sciences, University of Birmingham, Birmingham, United Kingdom.
Vasileios
V
Ladopoulos
Helmut
H
Hofemeister
Maarten
M
Hoogenkamp
Arthur D
AD
Riggs
A Francis
AF
Stewart
Constanze
C
Bonifer
D000818:Animals; D002460:Cell Line; D002843:Chromatin / Q000235:genetics / Q000378:metabolism; D018899:CpG Islands; D019175:DNA Methylation; D015536:Down-Regulation; D053595:Embryonic Stem Cells / Q000378:metabolism; D020868:Gene Silencing; D000076983:Histone Methyltransferases; D011495:Histone-Lysine N-Methyltransferase / Q000235:genetics* / Q000378:metabolism; D007700:Kinetics; D051379:Mice; D051788:Myeloid-Lymphoid Leukemia Protein / Q000235:genetics* / Q000378:metabolism; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism; D011401:Promoter Regions, Genetic; D012319:RNA Polymerase II / Q000235:genetics* / Q000378:metabolism
D002843:Chromatin; C491493:Magoh protein, mouse; D009687:Nuclear Proteins; D051788:Myeloid-Lymphoid Leukemia Protein; D000076983:Histone Methyltransferases; D011495:Histone-Lysine N-Methyltransferase; C510860:Kmt2d protein, mouse; D012319:RNA Polymerase II