EDD Inhibits ATM-mediated Phosphorylation of p53

Abstract

The EDD (E3 identified by differential display) gene, first identified as a progestin-induced gene in T-47D breast cancer cells, encodes an E3 ubiquitin ligase with a HECT domain. It was reported that EDD is involved in the G 2 /M progression through ubiquitination of phospho-katanin p60. Previous study has also shown that EDD can act as a transcription cofactor independently of its E3 ligase activity. In this study, we uncover a new role for EDD during cell cycle progression in an E3 ligase-independent manner. We demonstrate that EDD can physically interact with p53 and that this interaction blocks the phosphorylation of p53 by ataxia telangiectasia mutated (ATM). Silencing of EDD induces phosphorylation of p53 at Ser 15 and activates p53 target genes in fibroblasts and some transformed cells without activation of DNA damage response. The G 1 /S arrest induced by EDD depletion depends on p53. On the other hand, overexpression of EDD inhibits p53-Ser 15 phosphorylation and suppresses the induction of p53 target genes during DNA damage, and this effect does not require its E3 ligase activity. Thus, through binding to p53, EDD actively inhibits p53 phosphorylation by ATM and plays a role in ensuring smooth G 1 /S progression.The tumor suppressor p53, one of the most important proteins in preventing human cancer, is a critical factor controlling cell cycle progression, particularly during the G 1 /S transition. Mutations of the p53 gene occur in at least half of all human cancers. Phosphorylation of p53 stabilizes p53 and hence induces both cell cycle arrest and apoptosis. Regulation of p53 phosphorylation is very complicated. There are three main kinases that are thought to be responsible for p53 phosphorylation at Ser 15 residue under genotoxic stresses: ataxia telangiectasia mutated (ATM), 3 ataxia telangiectasia and Rad3-related (ATR), and DNA-PK (DNA-dependent protein kinase) (1-3). ATM is a major player in phosphorylating p53 at Ser 15 in response to ionizing radiation, and ATR plays a central role in response to UV light. The group of proteins phosphorylated by DNA-PK, including p53, is mainly involved in the non-homologous end joining DNA double strand break repair. However, all these three kinases can phosphorylate p53 at Ser 15 , and there is a lot of cross-talk between these three pathways. Besides Ser 15 , ATM can also stimulate Chk2 to phosphorylate p53 at Ser 20 , a site that is critical for the stability of p53. In addition to phosphorylation, other post-translational modifications such as acetylation, methylation, ubiquitination, and sumoylation regulate p53 as well (4). The status of these post-translational modifications determines whether p53 is active or not. Even in the cycling cells, there exist spontaneous pulses of p53, but without sustained active modifications, these p53 fail to induce p21 or cell cycle arrest (5). Therefore, p53 is controlled actively by both inhibitors and activators in a delicate manner so that cellular proliferation can proceed in unstressed condition, but upon encount...

Expression of the Ubiquitin Proteasome System in Neonatal Rat Gonocytes and Spermatogonia: Role in Gonocyte Differentiation1

“…This is the case of Ubr5, which was reported to stabilize bcatenin via its ubiquitination, resulting in the upregulation of the Wnt signaling pathway [53]. Interestingly, both HUWE1 and Ubr5 are HECT-type E3 ligases recently shown to play a role in cell cycle progression by interacting with the tumor suppressor p53 [54][55][56]. Moreover, gonocytes and spermatogonia express high levels of Mdm2 transcript, an oncogenic ring finger E3 enzyme that targets p53 for proteosomal degradation [57].…”

The novel interaction between microspherule protein Msp58 and ubiquitin E3 ligase EDD regulates cell cycle progression

“…EDD is a nuclear protein that belongs to the family of HECT domain-containing ( h omologous to E 6-AP c arboxy- t erminus) ubiquitin ligases. Like Msp58, EDD plays a role in cell cycle regulation [13–15]. EDD also has important functions in the DNA damage response [13–18].…”

UBR5-mediated ubiquitination of ATMIN is required for ionizing radiation-induced ATM signaling and function

“…known as hyperplastic discs protein homolog (HYD) and E3 ligase identified by differential display (EDD) (14,18,19,21,22) (Fig. S1A).…”

“…UBR5 also has E3-independent roles as a transcriptional cofactor for the progesterone receptor (13) and interacts with other proteins such as p53 (14). UBR5 has been shown to mediate degradation of several proteins, including katanin p60, beta-catenin, TOPBP1, and TERT protein, the catalytic subunit of telomerase (15)(16)(17)(18).…”