Direct interaction between DNMT1 and G9a coordinates DNA and histone methylation during replication

  1. Pierre-Olivier Estève1,
  2. Hang Gyeong Chin1,
  3. Andrea Smallwood2,
  4. George R. Feehery1,
  5. Omkaram Gangisetty3,
  6. Adam R. Karpf3,
  7. Michael F. Carey2, and
  8. Sriharsa Pradhan1,4
  1. 1 New England Biolabs, Ipswich, Massachusetts 01938, USA;
  2. 2 Department of Biological Chemistry, Gene Regulation Program, Jonsson Cancer Center, University of California at Los Angeles School of Medicine, Los Angeles, California 90095, USA;
  3. 3 Department of Pharmacology and Therapeutics, Roswell Park Cancer Institute, Buffalo, New York 14263, USA

Abstract

Chromatin methylation is necessary for stable repression of gene expression during mammalian development. During cell division, DNMT1 maintains the DNA methylation pattern of the newly synthesized daughter strand, while G9a methylates H3K9. Here, DNMT1 is shown to directly bind G9a both in vivo and in vitro and to colocalize in the nucleus during DNA replication. The complex of DNMT1 and G9a colocalizes with dimethylated H3K9 (H3K9me2) at replication foci. Similarly, another H3K9 histone methyltransferase, SUV39H1, colocalizes with DNMT1 on heterochromatic regions of the nucleoli exclusively before cell division. Both DNMT1 and G9a are loaded onto the chromatin simultaneously in a ternary complex with loading factor PCNA during chromatin replication. Small interfering RNA (siRNA) knockdown of DNMT1 impairs DNA methylation, G9a loading, and H3K9 methylation on chromatin and rDNA repeats, confirming DNMT1 as the primary loading factor. Additionally, the complex of DNMT1 and G9a led to enhanced DNA and histone methylation of in vitro assembled chromatin substrates. Thus, direct cooperation between DNMT1 and G9a provides a mechanism of coordinated DNA and H3K9 methylation during cell division.

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  1. Published in Advance November 3, 2006, doi: 10.1101/gad.1463706 Genes & Dev. 20: 3089-3103 Copyright © 2006, Cold Spring Harbor Laboratory Press

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