ATM Mediates pRB Function To Control DNMT1 Protein Stability and DNA Methylation

Abstract

The retinoblastoma tumor suppressor gene (RB) product has been implicated in epigenetic control of gene expression owing to its ability to physically bind to many chromatin modifiers. However, the biological and clinical significance of this activity was not well elucidated. To address this, we performed genetic and epigenetic analyses in an Rb-deficient mouse thyroid C cell tumor model. Here we report that the genetic interaction of Rb and ATM regulates DNMT1 protein stability and hence controls the DNA methylation status in the promoters of at least the Ink4a, Shc2, FoxO6, and Noggin genes. Furthermore, we demonstrate that inactivation of pRB promotes Tip60 (acetyltransferase)-dependent ATM activation; allows activated ATM to physically bind to DNMT1, forming a complex with Tip60 and UHRF1 (E3 ligase); and consequently accelerates DNMT1 ubiquitination driven by Tip60-dependent acetylation. Our results indicate that inactivation of the pRB pathway in coordination with aberration in the DNA damage response deregulates DNMT1 stability, leading to an abnormal DNA methylation pattern and malignant progression.

SUPPLEMENTAL MATERIAL

Supplemental material for this article may be found at http://dx.doi.org/10.1128/MCB.01597-12.

ACKNOWLEDGMENTS

We thank J. McKinnon, A. Hirao, T. Jacks, N. Sharpless, D. Chen, E. Hara, and T. Ikura for providing materials; M. Asano and E. Kamimura for support in animal experiments; M. Ewen, D. Peeper, and M. Monden for encouragement; Y. Kido for technical and N. Nagatani for secretarial assistance; and all the colleagues in the Takahashi laboratory for valuable discussion.

This work was supported by the Funding Program for Next Generation World-Leading Researchers (NEXT) to C.T., a grant-in-aid for scientific research (MEXT) to C.T. and A.S., the Astellas Foundation for Research on Metabolic Disorders, the Takeda Science Foundation, the Naito Foundation, the Daiichi-Sankyo Foundation for Life Science, the NOVARTIS Foundation (Japan) for the Promotion of Science, and the Hokkoku Foundation for Cancer Research to C.T.

We declare that we have no conflicts of interest.