Abstract 1562: Proteomic analysis of citrullinated targets regulated by the p53-PADI4 pathway

Abstract We recently reported that p53 regulates protein citrullination through the transcriptional regulation of PADI4 that converts an arginine residue in proteins to a citrulline residue. In response to DNA damage, p53-PADI4 pathway induces citrullination of NPM1, Histone H4, and Lamin C, and subsequently promotes apoptotic pathway. To verify the clinical significance of PADI4 in human carcinogenesis, we screened the mutation of PADI4 in hepatocellular carcinoma and found three non-synonymous mutations among 104 cancer tissues (2.9%). Then we evaluated these three mutations as well as 8 somatic mutations reported by ICGC or COMP projects. We found that 8 among 11 mutations remarkably inhibited the enzymatic activity of PADI4 protein. To identify novel PADI4 substrates, we conducted proteome analysis using HEK293T cells ectopically transfected with wild type or mutant PADI4 expressing plasmid. Among more than 10000 peptides identified by the liquid chromatography MS/MS analysis, 265 peptides (2.2%) were citrullinated in PADI4-introduced cells, while less than 0.4% of total peptides were citrullinated in control or mock transfected cells. Pathway analysis revealed that RNA binding proteins such as hnRNPs are dominantly citrullinated by PADI4, indicating that possible role of protein citrullination in RNA processing. Citation Format: Chizu Tanikawa, Koji Ueda, Hidewaki Nakagawa, Yusuke Nakamura, Koichi Matsuda. Proteomic analysis of citrullinated targets regulated by the p53-PADI4 pathway. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1562. doi:10.1158/1538-7445.AM2014-1562