Shamma A, Suzuki M, Hayashi N, Kobayashi M, Sasaki N, Nishiuchi T, Doki Y, Okamoto T, Kohno S, Muranaka H, Kitajima S, Yamamoto KI, Takahashi C

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 of chromatin modifiers. However, the biological and clinical significance of this activity was not well elucidated. To address this, we performed genetic and epigenetic analyses ...

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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 promoter of at least Ink4a, Shc2, FoxO6 and Noggin genes. Further, we demonstrate that inactivation of pRB promotes the 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 pRB pathway in coordination with aberration in DNA damage response deregulates DNMT1 stability leading to abnormal DNA methylation pattern and malignant progression.

Date: Jun. 10, 2013

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