Description: N 2 -methylguanosine is one of the most universal modified nucleosides required for proper function in transfer RNA (tRNA) molecules. In archaeal tRNA species, a specific S -adenosyl-L-methionine (SAM)-dependent tRNA methyltransferase (MTase), aTrm11, catalyzes formation of N 2 -methylguanosine and N 2 , N 2 -dimethylguanosine at position 10. Here, we report the first X-ray crystal structures of aTrm11 from Thermococcus kodakarensis ( Tko ), of the apo-form, and of its complex with SAM. The structures show that Tko Trm11 consists of three domains: an N-terminal ferredoxinlike domain (NFLD), THUMP domain and Rossmann-fold MTase (RFM) domain. A linker region connects the THUMP-NFLD and RFM domains. One SAM molecule is bound in the pocket of the RFM domain, suggesting that Tko Trm11 uses a catalytic mechanism similar to that of other tRNA MTases containing an RFM domain. Furthermore, the conformation of NFLD and THUMP domains in Tko Trm11 resembles that of other tRNA-modifying enzymes specifically recognizing the tRNA acceptor stem. Our docking model of Tko Trm11-SAM in complex with tRNA, combined with biochemical analyses and pre-existing evidence, provides insights into the substrate tRNA recognition mechanism: The THUMP domain recognizes a 3'-ACCA end, and the linker region and RFM domain recognize the T-stem, acceptor stem and V-loop of tRNA, thereby causing Tko Trm11 to specifically identify its methylation site.

Description: Non-alcoholic fatty liver disease (NAFLD), the hepatic manifestation of obesity, is an emerging risk factor for hepatocellular carcinoma (HCC). Accumulating evidence has shown that chronic inflammation represents a plausible link between obesity and HCC and that the pro-inflammatory cytokine interleukin (IL)-6 contributes to the development of obesity-related HCC. In the present study, we aimed to examine the therapeutic potential of the omega-3 polyunsaturated fatty acid, eicosapentaenoic acid (EPA), which exerts anti-inflammatory effects. The results showed that the development of carcinogen-induced HCC was significantly less in mice fed a high-fat diet (HFD) supplemented with EPA than in those fed HFD only, suggesting that EPA attenuates the development of obesity-related HCC. Although EPA did not appear to affect obesity-linked inflammation, it suppressed the activation of the pro-tumorigenic IL-6 effector STAT3, contributing to the inhibition of tumor growth. These findings suggest a clinical implication of EPA as a treatment for obesity-related HCC.

Description: Aims  Controlling vascular integrity is expected to be a novel therapeutic target of cancers as well as cardiovascular diseases. Adrenomedullin (AM) and its receptor-modulating protein, RAMP2, have been identified as essential mediators of cardiovascular homeostasis. In this study, we used inducible vascular endothelial cell-specific RAMP2 knockout (DI-E-RAMP2 –/– ) mice to clarify the contribution made by the endogenous AM-RAMP2 system to angiogenesis and metastasis. Methods and results  Subcutaneously transplanted sarcoma or melanoma cells showed less growth and angiogenesis in DI-E-RAMP2 –/– than in control mice. On the other hand, after the transplantation of B16BL6 melanoma cells into hindlimb footpads, spontaneous metastasis to the lung was enhanced in DI-E-RAMP2 –/– mice. Early after RAMP2 gene deletion, DI-E-RAMP2 –/– mice showed enhanced vascular permeability, endothelial–mesenchymal transition (EndMT)-like change, and systemic oedema. Within the lungs of DI-E-RAMP2 –/– mice, pulmonary endothelial cells were deformed, and inflammatory cells infiltrated the vessel walls and expressed the chemotactic factors S100A8/9 and SAA3, which attract tumour cells and mediate the formation of a pre-metastatic niche. Conversely, the overexpression of RAMP2 suppressed tumour cell adhesion to endothelial cells, tumour metastasis, and improved survival. Conclusion  These findings indicate that the AM-RAMP2 system regulates vascular integrity, whereas RAMP2 deletion promotes vascular permeability and EndMT-like change within primary lesions and formation of pre-metastatic niches in distant organs by destabilizing the vascular structure and inducing inflammation. Vascular integrity regulated by the AM-RAMP2 system could thus be a hopeful therapeutic target for suppressing tumour metastasis.