Identification of global epigenetic alterations indispensable for malignant transformation and mediated by the RB-ATM pathway

Research Project

Project/Area Number	15K06834
Research Category	Grant-in-Aid for Scientific Research (C)
Allocation Type	Multi-year Fund
Section	一般
Research Field	Tumor biology
Research Institution	Kanazawa University
Principal Investigator	Awad Shamma 金沢大学, がん進展制御研究所, 助教 (50402839)
Project Period (FY)	2015-04-01 – 2018-03-31
Project Status	Completed (Fiscal Year 2017)
Budget Amount *help	¥5,070,000 (Direct Cost: ¥3,900,000、Indirect Cost: ¥1,170,000) Fiscal Year 2017: ¥1,300,000 (Direct Cost: ¥1,000,000、Indirect Cost: ¥300,000) Fiscal Year 2016: ¥1,170,000 (Direct Cost: ¥900,000、Indirect Cost: ¥270,000) Fiscal Year 2015: ¥2,600,000 (Direct Cost: ¥2,000,000、Indirect Cost: ¥600,000)
Keywords	RB / ATM / KAT3B / HDAC5 / Proteasome / Reprogramming proteins / Reprogramming factors / Protein degradation / cellular reprogramming / DNA damage / Protein ubiquitination / Stem cell reprogramming / Cancer
Outline of Final Research Achievements	How the core reprogramming proteins are identified and recruited for degradation is unknown. Here, we demonstrate that functions of the retinoblastoma (RB) and the ataxia telangiectasia mutated (ATM) repress the pluripotency and self-renewal ability of the stem cell-like cells included in genetically modified mouse embryonic fibroblasts (MEFs) and A-T human adult fibroblasts (A-T HAFs) through acetylation-driven ubiquitination and subsequent proteasomal degradation of Oct3/4, Sox2, Klf4, Nanog and c-Myc (OSKNM) proteins. We discovered that RB recruits lysine acetyltransferase-3b (Kat3b) and inhibits the transcription of histone deacetylase-5 (Hdac5) whereas, ATM shuttles Hdac5 into the nucleus and serve as adaptor protein, which identify and assemble the acetylated-OSKNM proteins into ubiquitination complexes with the E3 ubiquitin ligase Uhrf1 or Fbxw7. These novel findings have important implications in regenerative medicine, neurodegenerative diseases and cancer.