NSun2 Promotes Cell Growth via Elevating Cyclin-Dependent Kinase 1 Translation

The tRNA methytransferase NSun2 promotes cell proliferation, but the molecular mechanism has not been elucidated. Here, we report that NSun2 regulates cyclin-dependent kinase 1 (CDK1) expression in a cell cycle-dependent manner. Knockdown of NSun2 decreased the CDK1 protein level, while overexpression of NSun2 elevated it without altering CDK1 mRNA levels. Further studies revealed that NSun2 methylated CDK1 mRNA in vitro and in cells and that methylation by NSun2 enhanced CDK1 translation. Importantly, NSun2-mediated regulation of CDK1 expression had an impact on the cell division cycle. These results provide new insight into the regulation of CDK1 during the cell division cycle.     

Computational Identification of Protein Pupylation Sites by Using Profile-Based Composition of k-Spaced Amino Acid Pairs

Prokaryotic proteins are regulated by pupylation, a type of post-translational modification that contributes to cellular function in bacterial organisms. In pupylation process, the prokaryotic ubiquitin-like protein (Pup) tagging is functionally analogous to ubiquitination in order to tag target proteins for proteasomal degradation. To date, several experimental methods have been developed to identify pupylated proteins and their pupylation sites, but these experimental methods are generally laborious and costly. Therefore, computational methods that can accurately predict potential pupylation sites based on protein sequence information are highly desirable. In this paper, a novel predictor termed as pbPUP has been developed for accurate prediction of pupylation sites. In particular, a sophisticated sequence encoding scheme [i.e. the profile-based composition of k-spaced amino acid pairs (pbCKSAAP)] is used to represent the sequence patterns and evolutionary information of the sequence fragments surrounding pupylation sites. Then, a Support Vector Machine (SVM) classifier is trained using the pbCKSAAP encoding scheme. The final pbPUP predictor achieves an AUC value of 0.849 in10-fold cross-validation tests and outperforms other existing predictors on a comprehensive independent test dataset. The proposed method is anticipated to be a helpful computational resource for the prediction of pupylation sites. The web server and curated datasets in this study are freely available at http://protein.cau.edu.cn/pbPUP/.     

Expression of Semaphorin 4A and its potential role in rheumatoid arthritis

IntroductionSemaphorin 4A (Sema4A) plays critical roles in many physiological and pathological processes including neuronal development, angiogenesis, immune response regulation, autoimmunity, and infectious diseases. The present study aimed to investigate its expression and biological activity in rheumatoid arthritis (RA).MethodsRNA and protein were isolated from synovial tissues in RA and osteoarthritis (OA) patients. Treatment with recombinant human Sema4A (rhSema4A) or small interfering RNA (siRNA) was applied to examine its effect on the biological activity of synovial fibroblasts of RA (RASFs). Expression of Sema4A and NF-κB were measured by quantitative RT-PCR (qRT-PCR) and Western blot after lipopolysaccharide (LPS) stimulation. Chromatin immunoprecipitation (ChIP) and siRNA targeting p50 and p60 were applied to detect the regulation of Nuclear factor kappa (NF-κB) on Sema4A. Sema4A, interleukin 1β (IL-1β), interleukin 6 (IL-6), and tumor necrosis factor-α (TNF-α) secretion were measured by ELISA-based assays.ResultsIncreased levels of Sema4A were detected in the synovial tissue and fluid of patients with RA compared with those with OA. Furthermore, synovial fluid level of Sema4A correlated with Disease Activity Score (DAS) in RA. Treatment with rhSema4A promoted invasion of RASFs by upregulating the expression of Matrix metallopeptidase3 (MMP3), MMP9, alpha-smooth muscle actin(α-SMA), and Vimentin, and exacerbated inflammation by promoting the production of IL-6 in RASFs, as well as IL-1β and TNF-α in THP-1 cells. The induction of IL-6 and TNF-α by Sema4A was confirmed at the protein level in fluid samples from patients with RA. Knock-down experiments showed the participation of Plexin B1 towards rhSema4A in the induction of cytokines. In addition, LPS stimulation induced Sema4A expression in RASFs in an NF-κB-dependent manner, and rhSema4A treatment could also activate NF-κB signaling.ConclusionsThese findings suggest an NF-κB-dependent modulation of Sema4A in the immune response. Further, increased expression of Sema4A is required to promote inflammation of RA.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-015-0734-y) contains supplementary material, which is available to authorized users.     

Oncostatin M (OSM) protects against cardiac ischaemia/reperfusion injury in diabetic mice by regulating apoptosis,mitochondrial biogenesis and insulin sensitivity

Oncostatin M (OSM) exhibits many unique biological activities by activating Oβ receptor. However, its role in myocardial I/R injury in diabetic mice remains unknown. The involvement of OSM was assessed in diabetic mice which underwent myocardial I/R injury by OSM treatment or genetic deficiency of OSM receptor Oβ. Its mechanism on cardiomyocyte apoptosis, mitochondrial biogenesis and insulin sensitivity were further studied. OSM alleviated cardiac I/R injury by inhibiting cardiomyocyte apoptosis through inhibition of inositol pyrophosphate 7 (IP7) production, thus activating PI3K/Akt/BAD pathway, decreasing Bax expression while up‐regulating Bcl‐2 expression and decreasing the ratio of Bax to Bcl‐2 in db/db mice. OSM enhanced mitochondrial biogenesis and mitochondrial function in db/db mice subjected to cardiac I/R injury. On the contrary, OSM receptor Oβ knockout exacerbated cardiac I/R injury, increased IP7 production, enhanced cardiomyocyte apoptosis, impaired mitochondrial biogenesis, glucose homoeostasis and insulin sensitivity in cardiac I/R injured diabetic mice. Inhibition of IP7 production by TNP (IP6K inhibitor) exerted similar effects of OSM. The mechanism of OSM on cardiac I/R injury in diabetic mice is partly associated with IP7/Akt and adenine mononucleotide protein kinase/PGC‐1α pathway. OSM protects against cardiac I/R Injury by regulating apoptosis, insulin sensitivity and mitochondrial biogenesis in diabetic mice through inhibition of IP7 production.     

Solution structure of BmP08, a novel short-chain scorpion toxin from Buthus martensi Karsch

A novel short-chain scorpion toxin BmP08 was purified from the venom of the Chinese scorpion Buthus martensi Karsch by a combination of gel-filtration, ion exchange, and reversed-phase chromatography. The primary sequence of BmP08 was determined using the tandem MS/MS technique and Edman degradation, as well as results of NMR sequential assignments. It is composed of 31 amino acid residues including six cysteine residues and shares less than 25% sequence identity with the known alpha-KTx toxins. BmP08 shows no inhibitory activity on all tested voltage-dependent and Ca(2+)-activated potassium channels. The 3D-structure of BmP08 has been determined by 2D-NMR spectroscopy and molecular modeling techniques. This toxin adopts a common alpha/beta-motif, but shows a distinctive local conformation and features a 3(10)-helix and a shorter beta-sheet. The unique structure is closely related to the distinct primary sequence of the toxin, especially to the novel arrangement of S-S linkages in the molecule, in which two disulfide bridges (C(i)-C(j) and C(i+3)-C(j+3)) link covalently the 3(10)-helix with one strand of the beta-sheet structure. The electrostatic potential surface analysis of the toxin reveals salt bridges and hydrogen bonds between the basic residues and negatively charged residues nearby in BmP08, which may be unfavorable for its binding with the known voltage-dependent and Ca(2+)-activated potassium channels. Thus, finding the target for this toxin should be an interesting task in the future.     

陆源人类活动对近海生态系统的影响

随着海岸带快速城市化和经济发展,人类活动对近海生态系统的影响日益增加。通过对国内外大量相关文献的分析和与国际专家的研讨,分别从海洋资源开发、海岸带城市化和环境变化等几个方面概述了陆源人类活动对近海生态系统的影响。目前陆源人类活动导致近海生态系统出现的主要问题有:海洋生物资源过度捕捞、海岸带富营养化、海洋酸化、珊瑚礁退化、海洋垃圾、以及海岸带矿产开采等高强度开发活动引发的重金属和持久性有机污染物污染等。这些问题会直接导致海洋生物群落结构变化、影响水质、降低海洋生物多样性,最终影响海洋生态系统服务功能,威胁海洋生态系统健康。这些问题的根源多来自陆地,必须将海洋和陆地作为一个有机整体,整合海陆系统相互作用的科学计划,推进海洋资源和近海生态系统的可持续管理。