Yuanyuan Zhao

Ubiquitin specific protease 4 (USP4) is a deubiquitinating enzyme with key roles in the regulation of p53 and TGFβ signaling, suggesting its importance in tumorigenesis. However, the mechanisms and regulatory roles of USP4 in cancer, including colorectal cancer, remain largely elusive. Here, we present the first evidence that USP4 regulates the growth, invasion, and metastasis of colorectal cancer. USP4 expression was significantly elevated in colorectal cancer tissues and was significantly associated with tumor size, differentiation, distant metastasis, and poor survival. Knockdown of USP4 diminished colorectal cancer cell growth, colony formation, migration, and invasion in vitro and metastasis in vivo. Importantly, we found that phosphatase of regenerating liver-3 (PRL-3) is indispensable for USP4-mediated oncogenic activity in colorectal cancer. Mechanistically, we observed that USP4 interacted with and stabilized PRL-3 via deubiquitination. This resulted in activation of Akt and reduction of E-cadherin, critical regulators of cancer cell growth and metastasis. Examination of clinical samples confirmed that USP4 expression positively correlates with PRL-3 protein expression, but not mRNA transcript levels. Taken together, our results demonstrate that aberrant expression of USP4 contributes to the development and progression of colorectal cancer and reveal a critical mechanism underlying USP4-mediated oncogenic activity. These observations suggest that the potential of harnessing proteolytic degradation processes for therapeutic manipulation may offer a much-needed new approach for improving colorectal cancer treatment strategies. Cancer Res; 76(1); 83–95. ©2015 AACR.

The SETD3 enzyme has been identified as the methyltransferase for the His73 methylation in β-actin, and such methylation plays an important role in regulating the actin’s biochemical properties and fine­tuning the protein’s cellular roles. Further studies have demonstrated that SETD3 may be able to methylase some other residues, including lysine and methionine, that substitute His73 in the β-actin peptide. The activity of SETD3 on the Met73 peptide is low without turnover. Interestingly, it has been shown that the N255V and N255A mutations of SETD3 can increase the activity by about 3-fold for the methionine methylation, while such mutations lead to a significant reduction of k_cat for the His73 methylation. The detailed mechanism that leads to such increase of the activity for the Met73 methylation as a result of the mutations has not been understood. In this work, QM/MM molecular dynamics (MD) and potential of mean force (PMF) free energy simulations are undertaken for investigating structural, dynamic, and energetic properties involving the complex of SETD3 and Met73 peptide and to study the SETD3-catalyzed methionine methylation and the effects of the N255V mutation. It is demonstrated that the free energy barrier in the case of the methionine methylation in SETD3 is about 10 kcal/mol higher than that for the histidine methylation. Moreover, the free energy barrier for the methionine methylation in the N255V mutant is about 1 kcal/mol lower than that in the wild-type enzyme. These results agree with previous experimental observation. The origin of the free-energy barrier changes as a result of the H to M substitution on the β-actin peptide and the N255V mutation of SETD3 is discussed based on the data obtained from the simulations. Graphical abstract

Diacylglycerol kinase ζ (DGKZ) is a diacylglycerol kinase that metabolizes diacylglycerol to yield phosphatidic acid, and its function in breast cancer progression remains unclear. In this study, via screening of a CRISPR-Cas9 knockout library containing lipid metabolic genes, DGKZ was identified as a potential prometastatic gene. We first confirmed that high DGKZ expression correlated with tumor progression and poor prognosis in patients. Next, knockout of DGKZ in triple-negative breast cancer cell lines were found to significantly inhibit metastatic behaviors in vitro and in vivo, whereas its overexpression increased the metastatic potential of cell lines. Mechanistic studies based on RNA sequencing and bioinformatic analysis indicated that DGKZ might regulate cell metastasis by promoting epithelial–mesenchymal transition via the transforming growth factor β (TGFβ) signaling pathway. Furthermore, we found that overexpression of DGKZ activated the TGFβ/TGFβR2/Smad3 signaling pathway by inhibiting the degradation of TGFβR2 through suppression of caveolin/lipid raft-dependent endocytosis. Moreover, the caveolin/lipid raft-dependent endocytosis of TGFβR2 was regulated by the metabolite phosphatidic acid, which might alter TGFβR2 partitioning in lipid rafts and nonlipid rafts by affecting the fluidity of the plasma membrane. These findings suggested that DGKZ is a novel promoter of metastasis and that it could be a potential prognostic indicator in patients with triple-negative breast cancer.

This work numerically investigates the detailed combustion kinetics of partially premixed combustion (PPC) in a diesel engine under three different premixed ratio fuel conditions. A reduced Primary Reference Fuel (PRF) chemical kinetics mechanism was coupled with CONVERGE-SAGE CFD model to predict PPC combustion under various operating conditions. The experimental results showed that the increase of premixed ratio (PR) fuel resulted in advanced combustion phasing. To provide insight into the effects of PR on ignition delay time and key reaction pathways, a post-process tool was used. The ignition delay time is related to the formation of hydroxyl (OH). Thus, the validated Converge CFD code with the PRF chemistry and the post-process tool was applied to investigate how PR change the formation of OH during the low-to high-temperature reaction transition. The reaction pathway analyses of the formations of OH before ignition time were investigated. It was found that in the case of PR0%, the second isomerization from C₇H₁₄OOH₂-4O₂ to NC7KET24 and the decomposition of NC7KET24 contributed 27.6% and 46.46% of OH formation respectively. The contribution of AC₈H₁₆OOH-B to the formation of OH was just 12.13%. It can be concluded that the low temperature oxidation reactions of n-heptane were key steps in producing OH. While in the cases of PR30% and PR50%, because of the higher in-cylinder temperature, most of OH derived from the decomposition reaction of H₂O₂ that contributed 54.47% and 54.63% of OH formation respectively. Besides, in the PR30% and PR50%, the oxidation reactions of IC₄H₇ contributed 31.95% and 33.84% of OH formation respectively, and the oxidation reaction of IC₄H₆OH contributed 19.08% and 22.22% of OH formation respectively, which indicated that the oxidation of iso-octane also contributed to the production of OH. In addition, the distributions of mass fraction, production rate and representative creation reaction (RCR) of OH showed that in the case of PR30% and PR50%, the formation of OH outside the spray periphery were dominated by the reactions R394 (H2O2 (+ M) <=> 2 OH (+ M)), while that in the spray periphery were predominantly controlled by the reaction R21 (NC7KET24 => NC3H7CHO + CH3COCH2 + OH) and R125 (IC₄H₆OH + HO₂ <=> CH₂CCH₂OH + CH₂O + OH). Premixed fuel from port injection changed the formation pathway of OH during the oxidation of direct injection fuel through the reaction R125.

In the present study we investigated the developmental expression patterns of Lbx1 gene in skeletal muscle of different genetic profile pigs after birth. A total of 28 Mashen pigs and 28 Large White pigs from seven development stages of 1, 30, 60, 90, 120, 150, 180 d were used and the expression patterns in longissimus dorsi were studied by quantitative real time-polymerase chain reaction and western blot in this study. The results showed that the breed, age, and the interaction of breed and age significantly affected the Lbx1 mRNA and protein expressions in longissimus dorsi (P<0.05). In Large White, the amount of Lbx1 protein was increased from new birth to 30 d, and decreased after 30 d to the lowest level at 180 d. In Mashen pig, Lbx1 protein level showed an increase trend with the age increase before 90 d, then decreased to the lowest level at 120 d, and then gradually increased upwards to the expression peak at 180 d. Before 120 d, the Lbx1 protein content in Large White was higher than that in Mashen pig, except for at 60 d. Afterwards, the protein level in Mashen was higher than that in Large White. The Lbx1 expression pattern was related to the age and genetic profiles of Mashen and Large White pigs, which indicates that Lbx1 could participate in the muscle development through activating the satellite cells of skeletal muscle after birth.