RNA is a biopolymer that is attractive for constructing nano-scale objects with complex structures. Three-dimensional (3D) structures of naturally occurring RNAs often have modular architectures. The 3D structure of a group I (GI) ribozyme from Tetrahymena has a typical modular architecture, which can be separated into two structural modules (ΔP5 and P5abc). The fully active ribozyme can be reconstructed by assembling the two separately prepared modules through highly specific and strong assembly between ΔP5 ribozyme and P5abc RNA. Such non-covalent assembly of the two modules allows the design of polygonal RNA nano-structures. Through rational redesign of the parent GI ribozyme, we constructed variant GI ribozymes as unit RNAs for polygonal-shaped (closed) oligomers with catalytic activity. Programmed trimerization and tetramerization of the unit RNAs afforded catalytically active nano-sized RNA triangles and squares, the structures of which were directly observed by atomic force microscopy (AFM).

Primary hepatic angiosarcoma is a rare tumor originating from endothelial cells in the liver and accounts for approximately 1% of all hepatic malignant tumors. It is difficult to diagnose due to the lack of specific symptoms or tumor markers. No effective treatment exists, but complete surgical resection may achieve a good outcome. Since most primary hepatic angiosarcomas are already at an advanced stage at diagnosis, few reports describe tumors smaller than 2 cm. We report a case of surgery for a 1.7-cm sized primary hepatic angiosarcoma. Further studies are required to improve the preoperative diagnosis of primary hepatic angiosarcoma.

Ribozymes with modular architecture constitute an attractive class of structural platforms for design and construction of nucleic acid nanostructures with biological functions. Through modular engineering of the Tetrahymena ribozyme, we have designed unit RNAs (L‐RNAs), assembly of which formed ribozyme‐based closed trimers and closed tetramers. Their catalytic activity was dependent on oligomer formation. In this study, the structural variety of L‐RNA oligomers was extended by tuning their structural elements, yielding closed pentamers and closed hexamers. Their assembly properties were analyzed by electrophoretic mobility shift assay (EMSA) and atomic force microscopy (AFM).

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