Under cellular stress, cytoplasmic mRNAs assemble and form stress granules (SGs). However, the fine structure of SGs has been unclear. We investigated the issue by stochastic optical reconstruction microscopy (STORM), which provided us super-resolution images with spatial resolution of several tens of nanometers. STORM imaging showed that endogenous mRNAs located in spherical compartments with a diameter of 200 nm. Furthermore, some SGs components showed distinct spatial patterns in SGs. These

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... esults suggested that STORM is a powerful tool to investigate the fine structure of granular architecture in cells and that SGs have highly organized composition that would be responsible for the physiological functions in cellular stress responses. 3P297 生細胞内における microRNA のイメージング MicroRNA (miRNA), a small noncoding RNA, takes part in translational regulations by targeting mRNA to trigger either cleavage or translational repression. It is known that miRNAs are closely related to certain disease; for instance, let-7 miRNA is depleted in cells of human lung cancer. Although the importance of miRNA activity is recognized, dynamics of miRNA in living cells are still unknown because no method has been available to capture them. Here, we show a new approach to chase the cellular dynamics of miRNA by introducing fluorescent precursors of miRNA into living cells followed by fluorescence imaging. This method allowed us to quantitatively image miRNA in living cells, which would be applicable to investigate functionality of miRNA in living cells. 3P298 大腸菌 RND 型異物排出トランスポーター AcrD の細胞内動 AcrD is an inner membrane transporter of the resistance-nodulation-cell division (RND) family for xenobiotic efflux. Upon induction by indole, AcrD forms a tripartite complex with the outer membrane channel TolC and the membrane fusion protein AcrA. In this study, we asked how newly expressed AcrD forms a tripartite complex in the cytoplasmic membrane and whether AcrA affects dynamics of AcrD as the effect of AcrA on AcrB dynamics has not been explored. When observed using TIRFM, most fluorescent foci of chromosome-encoded AcrD-GFP showed little lateral displacements, whereas they were moving incessantly in the tolC or acrAdeletion background. These results suggest that AcrA plays a critical role for assembly or stabilizaton of the tripartite complex. 3P299 大腸菌異物排出システム AcrAB-TolC の細胞内動態解析