DNMT1 but not its interaction with the replication machinery is required for maintenance of DNA methylation in human cells.
DNA methylation plays a central role in the epigenetic regulation of gene expression in vertebrates. Genetic and biochemical data indicated that DNA methyltransferase 1 (Dnmt1) is indispensable for the maintenance of DNA methylation patterns in mice, but targeting of the DNMT1 locus in human HCT116 tumor cells had only minor effects on genomic methylation and cell viability. In this study, we identified an alternative splicing in these cells that bypasses the disrupting selective marker and results in a catalytically active DNMT1 protein lacking the proliferating cell nuclear antigen-binding domain required for association with the replication machinery. Using a mechanism-based trapping assay, we show that this truncated DNMT1 protein displays only twofold reduced postreplicative DNA methylation maintenance activity in vivo. RNA interference-mediated knockdown of this truncated DNMT1 results in global genomic hypomethylation and cell death. These results indicate that DNMT1 is essential in mouse and human cells, but direct coupling of the replication of genetic and epigenetic information is not strictly required.
Spada
Fabio
F
Department of Biology II and 2Department of Chemistry, Ludwig Maximilians University Munich, 82152 Planegg-Martinsried, Germany.
Haemmer
Andrea
A
Kuch
David
D
Rothbauer
Ulrich
U
Schermelleh
Lothar
L
Kremmer
Elisabeth
E
Carell
Thomas
T
Längst
Gernot
G
Leonhardt
Heinrich
H
D017398:Alternative Splicing; D045744:Cell Line, Tumor; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000502:physiology*; D019175:DNA Methylation; D004261:DNA Replication / Q000502:physiology; D044127:Epigenesis, Genetic; D006801:Humans; D009154:Mutation; D018809:Proliferating Cell Nuclear Antigen / Q000378:metabolism; D034622:RNA Interference
D018809:Proliferating Cell Nuclear Antigen; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases; C000619380:DNMT1 protein, human; C000619381:Dnmt1 protein, mouse