Proper patterns of genome-wide DNA methylation, mediated by DNA methyltransferases DNMT1, -3A and -3B, are essential for embryonic development and genomic stability in mammalian cells. The de novo DNA methyltransferase DNMT3B is of particular interest because it is frequently over-expressed in tumor cells and is mutated in immuno-deficiency, centromere instability and facial anomalies (ICF) syndrome. In order to gain a better understanding of DNMT3B, in terms of the targeting of its methylation activity and its role in genome stability, we biochemically purified endogenous DNMT3B from HeLa cells. DNMT3B co-purifies and interacts, both in vivo and in vitro, with several components of the condensin complex (hCAP-C, hCAP-E and hCAP-G) and KIF4A. Condensin mediates genome-wide chromosome condensation at the onset of mitosis and is critical for proper segregation of sister chromatids. KIF4A is proposed to be a motor protein carrying DNA as cargo. DNMT3B also interacts with histone deacetylase 1 (HDAC1), the co-repressor SIN3A and the ATP-dependent chromatin remodeling enzyme hSNF2H. Furthermore, DNMT3B co-localizes with condensin and KIF4A on condensed chromosomes throughout mitosis. These studies therefore reveal the first direct link between the machineries regulating DNA methylation and mitotic chromosome condensation in mammalian cells.
Bibliographical noteFunding Information:
We thank En Li for providing the DNMT3B cDNA. This work was supported by intramural funds from the National Cancer Institute, National Institutes of Health (NIH). K.D.R. is a National Cancer Institute Scholar. T.M.G. was supported by the Pharmacology Research Associate Training Fellowship Program (National Institute of General Medical Sciences, NIH). K.Y. is a Scholar of the Leukemia and Lymphoma Society and is supported by NIH grant GM59150. Y.Z. is supported by the Robert A. Welch Foundation (I-1550) and NIH grant CA85146.