EDD ELISA Kit

Using proteomic approaches, we uncovered a DNA damage response (DDR) function for peroxisome proliferator activated receptor gamma (PPAR gamma) through its interaction with the DNA damage sensor MRE11-RAD50-NBS1 (MRN) and the E3 ubiquitin ligase UBR5. We show that PPAR gamma promotes ATM signaling and is essential for UBR5 activity targeting ATM interactor (ATMIN). PPAR gamma depletion increases ATMIN protein independent of transcription and suppresses DDR-induced ATM signaling. Blocking ATMIN in this context restores ATM activation and DNA repair. We illustrate the physiological relevance of PPAR gamma DDR functions by using pulmonary arterial hypertension (PAH) as a model that has impaired PPAR gamma signaling related to endothelial cell (EC) dysfunction and unresolved DNA damage. In pulmonary arterial ECs (PAECs) from PAH patients, we observed disrupted PPAR gamma-UBR5 interaction, heightened ATMIN expression, and DNA lesions. Blocking ATMIN in PAH PAEC restores ATM activation. Thus, impaired PPAR gamma DDR functions may explain the genomic instability and loss of endothelial homeostasis in PAH.

MLLE (previously known as PABC) is a peptide-binding domain that is found in poly(A)-binding protein (PABP) and EDD (E3 isolated by differential display), a HECT E3 ubiquitin ligase also known as HYD (hyperplastic discs tumor suppressor) or UBR5. The MLLE domain from PABP recruits various regulatory proteins and translation factors to poly(A) mRNAs through binding of a conserved 12 amino acid peptide motif called PAM2 (for PABP-interacting motif 2). Here, we determined crystal structures of the MLLE domain from PABP alone and in complex with PAM2 peptides from PABP-interacting protein 2. The structures provide a detailed view of hydrophobic determinants of the MLLE binding coded by PAM2 positions 3, 5, 7, 10, and 12 and reveal novel intermolecular polar contacts. In particular, the side chain of the invariant MLLE residue K580 forms hydrogen bonds with the backbone of PAM2 residues 5 and 7. The structures also show that peptide residues outside of the conserved PAM2 motif contribute to binding. Altogether, the structures provide a significant advance in understanding the molecular basis for the binding of PABP by PAM2-containing proteins involved in translational control, mRNA deadenylation, and other cellular processes. (C) 2010 Elsevier Ltd. All rights reserved.