ANALYSIS OF PEPTIDYLARGININE DEIMINASE 4 AND HISTONE CITRULLINATION IN TRANSCRIPTIONAL REGULATION AND INNATE IMMUNITY

Open Access
Author:
Li, Pingxin
Graduate Program:
Genetics
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
April 30, 2010
Committee Members:
  • Yanming Wang, Dissertation Advisor
  • Yanming Wang, Committee Member
  • David Scott Gilmour, Committee Chair
  • Zhi Chun Lai, Committee Member
  • Joseph C. Reese, Committee Member
  • Robert Paulson, Committee Member
Keywords:
  • Peptidylarginine Deiminase 4
  • Histone Citrullination
  • p53
  • p21
  • Histone Deacetylase 2
  • Neutrophil Extracellular Traps
Abstract:
Peptidylarginine deiminase 4 is an enzyme capable of converting both histone arginine and monomethyl-arginine residues into citrulline through reactions termed deimination/citrullination or demethylimination to regulate histone arginine methylation. This histone posttranslational modification has been related to transcriptional regulation. This dissertation first investigated the role of PAD4 and PAD4 catalyzed histone citrullination in the transcriptional repression of p53-target genes, such as p21/CIP1/WAF1. PAD4 is recruited to the p53-target gene promoter in a p53-dependent manner. Paused RNA Pol II and PAD4 are detected at the p21 promoter before UV irradiation, while RNA Pol II activity and PAD4 association at the p21 promoter are dynamically regulated after UV irradiation. We also detected that PAD4 and histone citrullination coordinate with HDAC2 that mediates histone lysine deacetylation in repressing tumor suppressor gene expression. PAD4 and HDAC2 associated with p21 promoter simultaneously, and both dissociated from several p53-target gene promoters after DNA damage. Our data further revealed that PAD4 promoter association and histone citrullination level are dependent on both p53 and HDAC activity, but HDAC2 promoter association and histone Lys acetylation level are only slightly affected by p53 and PAD4 activity. PAD4 inhibitor Cl-amidine and HDAC inhibitor SAHA induced p53-target gene expression and inhibited cancer cell growth additively in a p53-dependent manner. Using knockout PAD4 mice as a genetic model, we found that PAD4 knockout mice cannot form neutrophil extracellular traps, which are highly decondensed chromatin structures that are important in fighting against invading pathogens after stimulated with chemokines and bacteria. These PAD4 knockout mice are more susceptible to bacterial infection due to the lack of NET-mediated anti-bacterial ability, suggesting an essential role of PAD4 and histone citrullination in innate immunity.