Arginine methylation is a critical post-translational modification that plays multifaceted biological functions. However, the manipulation of protein arginine methylation largely depends on genetic or pharmaceutic inhibition of the regulatory enzymes, protein arginine methyltransferases (PRMTs), or non-methylation substitution of corresponding arginine residue to lysine or alanine of protein of interest (POI), which inevitably affects other substrates, or disrupts the structure of POI. Thus, it urges an approach to specifically modulate the arginine methylation of a POI under physiological conditions. To this end, we report the discovery of a methylation tagging system (MeTAG), that enables targeted modification of protein arginine methylation. Through bridging the methyltransferase PRMT5 proximity to a POI, MeTAG facilitates the arginine methylation of POIs, including known arginine methylated proteins, androgen receptor (AR) and protein kinase B (AKT), as well as a neo-substrate E1A binding protein (p300), in a reversible and PRMT5-dependent manner. Moreover, MeTAG can regulate downstream signaling in a methylation dependent manner, leading to downregulation of PSMA mRNA level and activation of AKT. Therefore, MeTAG represents a feasible approach to modulate protein methylation and thereby perturbs protein function in biological and therapeutic contexts.

Objective:To discuss the synergistic inhibitory effect of apatinib mesylate(apatinib)combined with radiotherapy(RT)on the hepatocellular carcinoma(HepG2)cells in vitro,and to clarify its related antitumor mechanism.Methods:The HepG2 cells were cultured in vitro and treated with different concentrations of apatinib and/or varying doses of X-rays.MTT method was used to detect the survival rates of the cells in various groups;the inhibitory rates of cell proliferation and the 20％inhibitory concentration(IC20)of apatinib were calculated;the X-ray irradiation dose for subsequent experiments was detected.The HepG2 cells were divided into apatinib group,RT group,and apatinib+RT group(combined group).Flow cytometry was used to detect the apoptotic rates of the cells in various groups;wound healing assay was used to detect the migration rates of the cells in various groups;ELISA method was used to detect the levels of vascular endothelial growth factor(VEGF)in the cell culture supernatant in various groups.Results:The MTT results showed that the IC20 of apatinib was 1.32 μmol·L-1,and this concentration was used for subsequent experiments,and the X-ray irradiation dose for the follow-up experiments was 2 Gy.Compared with control group,the apoptotic rates of the cells in apatinib group and RT group had no significant differences(P＞0.05),while the apoptotic rate of the cells in combined group was increased(P＜0.05).Compared with control group,the migration rates of the cells in apatinib group,RT group,and combined group were decreased(P＜0.05);compared with apatinib group and RT group,the migration rate of the cells in combined group was decreased(P＜0.05).Compared with control group,the levels of VEGF in the cell culture supernatant in apatinib group and combined group were decreased(P＜0.05);compared with apatinib and RT group,the level of VEGF in the cell culture supernatant in combined group was decreased(P＜0.05).Conclusion:Apatinib combined with radiotherapy significantly inhibits the proliferation and migration of the HepG2 cells in vitro and induces the apoptosis;its effect may be related to the inhibition of VEGF secretion by cells.

To discuss the conformational change and the recognition mechanism of hydroxy isoindol ketone derivatives with HIV-1 integrase, fifty-eight hydroxy isoindol ketone derivatives were docked to the integrase using AutoDock program. Molecular dynamics simulation with 16 ns was carried out for the two complex modes, respectively, in which the corresponding small molecules exhibited strong inhibition ability. Main force acting on the association of small molecules with integrase was explored based on the docking complex model. After analyzing the hydrogen-bond and conformational changes, it was found that the hydrogen-bond between N155 and D64 was the key factor maintaining the DDE motif stability. Furthermore, the hydrophobic interactions between the loop region where Y143 located and the hydroxy isoindol ketone derivatives were found to play an important role for their recognition.