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

2016 Fiscal Year Research-status Report

• Project/Area Number: 15K06834
• Research Institution: Kanazawa University
• Principal Investigator: Shamma A.A.Awad 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
• Keywords: ATM / RB / Reprogramming factors / Protein degradation / cellular reprogramming

Outline of Annual Research Achievements

The proteasome-mediated degradation of the core reprogramming factors determines the stem cell decision whether to proliferate or differentiate. Little is known about how the reprogramming proteins are identified and recruited for degradation. We discovered that the ataxia telangiectasia mutated (ATM) and the retinoblastoma (RB) proteins cooperatively regulate stem cell properties and cellular reprogramming. ATM and RB execute these functions through negative regulation of the histone deacetylase-5 (Hdac5) and provocation of acetylation-driven ubiquitination and subsequent proteasome-mediated degradation of the core reprogramming proteins Oct3/4, Sox2, KLF4, Nanog and c-Myc. Mouse embryonic fibroblasts (MEFs) or human adult fibroblasts simultaneously lacking ATM and RB exhibited stem cell-like morphology and growth properties under stem cell culture conditions. In addition, re-expression of ATM or pRB antagonized stem cell properties of cells simultaneously lacking ATM and RB. Importantly, proteasome inhibition antagonized these functions of ATM and RB, recued the overall protein abundance of the core reprogramming factors and restored the stem cell phenotype. These data indicate that ATM and RB functions regulate cellular reprogramming by controlling the proteasome-mediated degradation of the core reprogramming factors. Our findings have important implications in regenerative medicine, degenerative diseases and cancer.

Current Status of Research Progress

2: Research has progressed on the whole more than it was originally planned.

Reason

Although, we changed the research plan and focused on characterizing the functions of ATM and RB in global protein stability by screening several protein substrates known or predicted to be regulated by proteasomal degradation, we were lucky and could catch up because this short cut approach yielded lots of positive results including the novel cooperative functions of ATM and RB in controlling the proteasome-mediated degradation of the core reprogramming proteins and highly impact the autonomous cellular reprogramming.

Strategy for Future Research Activity

Currently, our priority is to finish the remaining experiments, processing the data into publication figures, finalizing the manuscript and hopefully we can submit this work for publication by the end of this summer.