Functional Roles of Phosphorylated DNA-PKcs and hNuPARP in Cell Cycle Progression

• Main Authors: Chou, Han-Yi E., 周涵怡
• Other Authors: Lee, Sheng-Chung
• Format: Others
• Language: en_US
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/27573822463847498840

博士 === 國立臺灣大學 === 分子醫學研究所 === 92 === Since its first description in 1990, DNA-PK catalytic subunit has been one of the most attractive and intriguing molecules in the research field. The bulk of studies has implicated its participation in a wide array of cellular functions, including DNA damage repair, V(D)J recombination, DNA replication, cell-cycle checkpoint and apoptosis. Nevertheless, the role and mode of action of DNA-PKcs in these pathways still remain obscure, mainly because of its difficulty in manipulation, as well as the lack of reagents for tracking the active molecule in vivo. We have raised several antibodies against different portions of DNA-PKcs, and most importantly, antibodies that can recognize specifically phosphorylated DNA-PKcs, which represents the active kinase in in vivo. These antibodies enable us to describe for the first time the behavior of activated DNA-PKcs in physiological conditions, as well as during cell cycle progression. Our clinicopathological survey revealed a strong correlation between loss of DNA-PKcs phosphorylation and malignant tumor progression. Furthermore, we detected the presence of phosphorylated DNA-PKcs on duplicated centrosomes, and described its positive role in microtubule nucleation. These intriguing observations could offer the key to unravel the role of DNA-PKcs in coordination of DNA replication, control of chromosome integrity, and tumor progression. In second part, we report the identification of a novel nucleolar protein hNuPARP that possesses intrinsic poly ADP-ribosylation activity. Our preliminary studies suggest that hNuPARP may be the major epitope for the P*N antibody, a putative substrate of the Cdk2/cyclinE kinase, that is suppressed in growth arrested cells and associates with the RNA polymerase I machinery.