Cdc34-mediated Degradation of ATF5 Is Blocked by Cisplatin

Abstract

ATF5, a member of activating transcription factor (ATF)/ cAMP-response element-binding protein (CREB) family of b-ZIP transcription factors, contributes to neural cell differentiation and is involved in cell apoptosis in response to cisplatin and a number of environment factors. However, the mechanisms governing the regulation of ATF5 protein during apoptosis are largely unknown. In this study we reported that ATF5 protein was a substrate of the ubiquitin-proteasome pathway. Interestingly, the ubiquitin-dependent degradation of exogenous ATF5 protein was independent of lysine residues. Instead, the addition of a large N-terminal enhanced green fluorescence protein tag increased the stability of ATF5 protein, and the free amino acid group of the N-terminal methionine of ATF5 protein was a site for ubiquitinylation, indicating that exogenous ATF5 was degraded via the ubiquitin-proteasome system through N-terminal ubiquitinylation. Furthermore, cisplatin increased ATF5 protein expression via preventing its ubiquitin-dependent degradation, which might be associated with its promoting the nucleus-to-cytoplasm translocation of E2 ubiquitin-conjugating enzyme Cdc34 and reducing the interaction between ATF5 and Cdc34. In summary, a down-regulation of proteasome-mediated degradation of ATF5 might contribute to cisplatin-induced apoptosis, providing a new mechanism of cisplatin-induced apoptosis. ATF53 transcription factor, a member of ATF/cAMP-response element-binding protein (CREB) family of b-ZIP transcription factors (1), plays a critical role in regulating cAMP response element-dependent genes and functions as an essential role in neural cell differentiation (2-4).Accumulated data from our laboratory and other investigators indicated that ATF5 functions as an apoptosis-related protein in response to a number of environment factors and DNA damage (5, 6). Interference with the function or expression of ATF5 in glioma cells leads to their death in vitro and in vivo (7), indicating that ATF5 might be an attractive target for therapeutic intervention in glioblastoma. Consistent with this, ATF5 was widely expressed in carcinomas, and interference with its function caused apoptotic cell death of neoplastic breast cell lines (8). Furthermore, ATF5 functioned as an anti-apoptotic role in an interleukin 3-dependent cell line (9). And, we have showed that ATF5 was up-regulated by cisplatin, and its overexpression increased cisplatin-induced apoptosis in HeLa cells (5), indicating the pro-apoptotic role of ATF5 in DNA damageinduced apoptosis. Previously, Pati et al. (10) showed that ATF5 interacted with E2 ubiquitin-conjugating enzyme Cdc34. Cdc34 and RAD6 had been reported to be important components of the ubiquitin-proteasome system in the nucleus which was responsible for the degradation of some transcriptional factors (11). Although the progress in ATF5-interacting partners, function, and their relation to some diseases have been made in recent years, the precise molecular mechanisms of ATF5 protein regulation during apopto...

The 5′‐untranslated region regulates ATF5 mRNA stability via nonsense‐mediated mRNA decay in response to environmental stress

“…Cycloheximide, an inhibitor of translation, suppresses the glutamine limitation-induced increase in ATF5 mRNA [31], indicating that up-regulation of ATF5 mRNA depends on de novo protein synthesis. ATF5 is a target of ubiquitin-mediated [34,36,37,39,40] and caspase-mediated proteolysis [37,39], and its protein stability is up-regulated by stresses [36,37,39,40]. Recently, Liu et al found that the chaperone proteins HSP70 and nucleophosmin (NPM1) reciprocally regulate ATF5 protein stability [39].…”

“…Newman and Keating also reported that ATF5 acted as a C/EBPcbinding transcription factor in comprehensive protein array analysis [30]. ATF5 is a stress response transcription factor whose expression is regulated by posttranscriptional regulation [31], translational regulation [32,33] and post-translational regulation [34][35][36][37][38][39][40] in response to cellular stresses including endoplasmic reticulum (ER) stress [33,41], arsenite exposure [32,33,36] and amino acid limitation [31,32]. Limitation of a single amino acid (glutamine, methionine or leucine) in the cell culture medium increased ATF5 mRNA levels in HeLaS3 cells [31].…”

Nucleophosmin (NPM1/B23) Interacts with Activating Transcription Factor 5 (ATF5) Protein and Promotes Proteasome- and Caspase-dependent ATF5 Degradation in Hepatocellular Carcinoma Cells

“…diated proteolysis (9,24,25). We found recently that ATF5 interacts with chaperone protein HSP70, which protects ATF5 from otherwise extremely fast protein degradation in C6 glioma and MCF-7 breast cancer cells (12).…”

Stabilization of ATF5 by TAK1–Nemo-Like Kinase Critically Regulates the Interleukin-1β-Stimulated C/EBP Signaling Pathway

“…ATF5 was first identified as a partner of C/EBP␥ (26), and a recent study demonstrated that ATF5 associates with C/EBP␤ during 3T3-L1 differentiation (27). Several reports have suggested that ATF5 is inherently very unstable; however, it can be stabilized in response to a variety of stimuli, such as cisplatin (28), cadmium chloride (CdCl 2 ) (29), sodium arsenite (NaAsO 2 ) (30), and IL-1␤ (31).…”