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Special Issue: 8th International Symposium On Mass Spectrometry In The Life Sciences

Quantitative Proteomics Analysis of the Effects of Ionizing Radiation in Wild Type and p53^K317R Knock-in Mouse Thymocytes^*,S

Lisa M. Miller Jenkins, Sharlyn J. Mazur, Matteo Rossi, Olga Gaidarenko, Yang Xu and Ettore Appella^,¶

From the Laboratory of Cell Biology, NCI, National Institutes of Health, Bethesda, Maryland 20892 and Section of Molecular Biology, Division of Biological Sciences, University of California, San Diego, La Jolla, California 92093

The tumor suppressor protein p53 is a sequence-specific transcription factor that has crucial roles in apoptosis, cell cycle arrest, cellular senescence, and DNA repair. Following exposure to a variety of stresses, p53 becomes post-translationally modified with concomitant increases in activity and stability. To better understand the role of acetylation of Lys-317 in mouse p53, the effect of ionizing radiation (IR) on the thymocytes of p53^K317R knock-in mice was studied at the global level. Using cleavable ICAT quantitative mass spectrometry, the effect of IR on protein levels in either the wild type or p53^K317R thymocytes was determined. We found 102 proteins to be significantly affected by IR in the wild type thymocytes, including several whose expression has been shown to be directly regulated by p53. When the effects of IR in the wild type and p53^K317R samples were compared, 46 proteins were found to be differently affected (p < 0.05). The p53^K317R mutation has widespread effects on specific protein levels following IR, including the levels of proteins involved in apoptosis, transcription, and translation. Pathway analysis of the differently regulated proteins suggests an increase in p53 activity in the p53^K317R thymocytes as well as a decrease in tumor necrosis factor signaling. These results suggest that acetylation of Lys-317 modulates the functions of p53 and influences the cross-talk between the DNA damage response and other signaling pathways.