Mdm2 Induces Mono-Ubiquitination of FOXO4

Background: The Forkhead box O (FOXO) class of transcription factors are involved in the regulation of several cellular responses including cell cycle progression and apoptosis. Furthermore, in model organisms FOXOs act as tumor suppressors and affect aging. Previously, we noted that FOXOs and p53 are remarkably similar within their spectrum of regulatory proteins [1]. For example, the de-ubiquitinating enzyme USP7 removes ubiquitin from both FOXO and p53. However, Skp2 has been identified as E3 ligase for FOXO1, whereas Mdm2 is the prime E3 ligase for p53. Principal Findings/Methodology: Here we provide evidence that Mdm2 acts as an E3 ligase for FOXO as well. In vitro incubation of Mdm2 and FOXO results in ATP-dependent (multi)mono-ubiquitination of FOXO similar to p53. Furthermore, in vivo co-expression of Mdm2 and FOXO induces FOXO mono-ubiquitination and consistent with this result, siRNAmediated depletion of Mdm2 inhibits mono-ubiquitination of FOXO induced by hydrogen peroxide. Regulation of FOXO ubiquitination by Mdm2 is likely to be direct since Mdm2 and FOXO co-immunoprecipitate. In addition, Mdm2-mediated ubiquitination regulates FOXO transcriptional activity. Conclusions/Significance: These data identify Mdm2 as a novel E3 ligase for FOXOs and extend the analogous mode o

Роль совершенствования бухгалтерского учета в управлении производственными запасами

Целью проведения исследования является обоснование направлений повышения эффективности использования материальных производственных запасов на предприятии в условиях рыночной экономики

Metabolic profiling of colorectal cancer organoids: A comparison between high-resolution magic angle spinning magnetic resonance spectroscopy and solution nuclear magnetic resonance spectroscopy of polar extracts

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FOXO transcription factor activation by oxidative stress mediated by the small GTPase Ral and JNK

Forkhead transcription factors of the FOXO class are negatively regulated by PKB/c-Akt in response to insulin/IGF signalling, and are involved in regulating cell cycle progression and cell death. Here we show that, in contrast to insulin signalling, low levels of oxidative stress generated by treatment with H 2 O 2 induce the activation of FOXO4. Upon treatment of cells with H 2 O 2 , the small GTPase Ral is activated and this results in a JNK-dependent phosphorylation of FOXO4 on threonine 447 and threonine 451. This Ral-mediated, JNK-dependent phosphorylation is involved in the nuclear translocation and transcriptional activation of FOXO4 after H 2 O 2 treatment. In addition, we show that this signalling pathway is also employed by tumor necrosis factor a to activate FOXO4 transcriptional activity. FOXO members have been implicated in cellular protection against oxidative stress via the transcriptional regulation of manganese superoxide dismutase and catalase gene expression. The results reported here, therefore, outline a homeostasis mechanism for sustaining cellular reactive oxygen species that is controlled by signalling pathways that can convey both negative (PI-3K/PKB) and positive (Ras/Ral) inputs

Chk1 and 14-3-3 proteins inhibit atypical E2Fs to prevent a permanent cell cycle arrest

The atypical E2Fs, E2F7 and E2F8, act as potent transcriptional repressors of DNA replication genes providing them with the ability to induce a permanent S-phase arrest and suppress tumorigenesis. Surprisingly in human cancer, transcript levels of atypical E2Fs are frequently elevated in proliferating cancer cells, suggesting that the tumor suppressor functions of atypical E2Fs might be inhibited through unknown post-translational mechanisms. Here, we show that atypical E2Fs can be directly phosphorylated by checkpoint kinase 1 (Chk1) to prevent a permanent cell cycle arrest. We found that 14-3-3 protein isoforms interact with both E2Fs in a Chk1-dependent manner. Strikingly, Chk1 phosphorylation and 14-3-3-binding did not relocate or degrade atypical E2Fs, but instead, 14-3-3 is recruited to E2F7/8 target gene promoters to possibly interfere with transcription. We observed that high levels of 14-3-3 strongly correlate with upregulated transcription of atypical E2F target genes in human cancer. Thus, we reveal that Chk1 and 14-3-3 proteins cooperate to inactivate the transcriptional repressor functions of atypical E2Fs. This mechanism might be of particular importance to cancer cells, since they are exposed frequently to DNA-damaging therapeutic reagents

Deciphering the mechanism of PSORI-CM02 in suppressing keratinocyte proliferation through the mTOR/HK2/glycolysis axis

Hyperplasia of epidermal keratinocytes that depend on glycolysis is a new hallmark of psoriasis pathogenesis. Our previous studies demonstrated that PSORI-CM02 could halt the pathological progression of psoriasis by targeting inflammatory response and angiogenesis, but its effect(s) and mechanism(s) on proliferating keratinocytes remained unclear. In this study, we aim to identify components of PSORI-CM02 that are absorbed into the blood and to determine the effect(s) of PSORI-CM02 on keratinocyte proliferation and its molecular mechanism(s). We used the immortalized human epidermal keratinocyte cell line, HaCaT, as an in vitro model of proliferating keratinocytes and the imiquimod-induced psoriasis mouse (IMQ) as an in vivo model. Metabolite profiles of vehicle pharmaceutic serum (VPS), PSORI-CM02 pharmaceutic serum (PPS), and water extraction (PWE) were compared, and 23 components of PSORI-CM02 were identified that were absorbed into the blood of mice. Both PPS and PWE inhibited the proliferation of HaCaT cells and consequently reduced the expression of the proliferation marker ki67. Additionally, PPS and PWE reduced phosphorylation levels of mTOR pathway kinases. Seahorse experiments demonstrated that PPS significantly inhibited glycolysis, glycolytic capacity, and mitochondrial respiration, thus reducing ATP production in HaCaT cells. Upon treatments of PPS or PWE, hexokinase 2 (HK2) expression was significantly decreased, as observed from the set of glycolytic genes we screened. Finally, in the IMQ model, we observed that treatment with PSORI-CM02 or BPTES, an inhibitor of mTOR signaling, reduced hyperproliferation of epidermal keratinocytes, inhibited the expression of p-S6 and reduced the number of proliferating cell nuclear antigen (PCNA)-positive cells in lesioned skin. Taken together, we demonstrate that PSORI-CM02 has an anti-proliferative effect on psoriatic keratinocytes, at least in part, by inhibiting the mTOR/HK2/glycolysis axis

Tdrd1 acts as a molecular scaffold for Piwi proteins and piRNA targets in zebrafish

Piwi proteins function in an RNAi-like pathway that silences transposons. Piwi-associated RNAs, also known as piRNAs, act as a guide to identify Piwi targets. The tudor domain-containing protein Tdrd1 has been linked to this pathway but its function has thus far remained unclear. We show that zebrafish Tdrd1 is required for efficient Piwi-pathway activity and proper nuage formation. Furthermore, we find that Tdrd1 binds both zebrafish Piwi proteins, Ziwi and Zili, and reveals sequence specificity in the interaction between Tdrd1 tudor domains and symmetrically dimethylated arginines (sDMAs) in Zili. Finally, we show that Tdrd1 complexes contain piRNAs and RNA molecules that are longer than piRNAs. We name these longer transcripts Tdrd1-associated transcripts (TATs). TATs likely represent cleaved Piwi pathway targets and may serve as piRNA biogenesis intermediates. Altogether, our data suggest that Tdrd1 acts as a molecular scaffold for Piwi proteins, bound through specific tudor domain–sDMA interactions, piRNAs and piRNA targets

The X Factor: Skewing X Inactivation towards Cancer

Increased expression of the epidermal growth factor receptor HER-2/ErbB2 is frequently observed in breast cancer and is targeted by the anticancer drug Herceptin. Now, Zuo et al. (2007) reveal that an X-linked gene encoding the transcription factor FOXP3 is a breast cancer tumor suppressor that represses expression of HER2/ErbB2