The kinesin KIF1C transports APC-dependent mRNAs to cell protrusions.

RNA localization and local translation are important for numerous cellular functions. In mammals, a class of mRNAs localize to cytoplasmic protrusions in an APC-dependent manner, with roles during cell migration. Here, we investigated this localization mechanism. We found that the KIF1C motor interacts with APC-dependent mRNAs and is required for their localization. Live cell imaging revealed rapid, active transport of single mRNAs over long distances that requires both microtubules and KIF1C. Two-color imaging directly revealed single mRNAs transported by single KIF1C motors, with the 3'UTR being sufficient to trigger KIF1C-dependent RNA transport and localization. Moreover, KIF1C remained associated with peripheral, multimeric RNA clusters and was required for their formation. These results reveal a widespread RNA transport pathway in mammalian cells, in which the KIF1C motor has a dual role in transporting RNAs and clustering them within cytoplasmic protrusions. Interestingly, KIF1C also transports its own mRNA, suggesting a possible feedback loop acting at the level of mRNA transport.

Anticancer Activity of Thymoquinone Cubic Phase Nanoparticles Against Human Breast Cancer: Formulation, Cytotoxicity and Subcellular Localization.

INTRODUCTION: Triple negative breast cancer is an aggressive disorder which accounts for at least 15% of breast cancer diagnosis and a high percentage of breast cancer morbidity, hence intensive research efforts are focused on the development of effective therapies to overcome the disease. Thymoquinone (TQ), the bioactive constituent of Nigella sativa, exhibits anticancer activity, yet its translation to the clinic is hindered by its poor bioavailability and lack of quantification method in blood and tissues. To overcome these limitations, cubosomes were utilized for the encapsulation and delivery of this anticancer molecule. METHODS: Thymoquinone loaded cubosomes were prepared through the emulsification homogenization method. The physicochemical characteristics, including particle size, zeta potential, morphology and entrapment efficiency, were studied. Moreover, the in vitro antitumor activity was tested on breast cancer cell lines (MCF-7 and MDA-MB-231) and compared to non-tumorigenic cell line (MCF-10A). Subcellular localization, cellular uptake and apoptotic effects of the formulations were assessed. RESULTS: The results revealed that the TQ loaded cubosomal formulation exhibited a mean particle size of 98.0 ± 4.10 nm with narrow unimodal distribution. The high entrapment efficiency (96.60 ± 3.58%) and zeta potential (31.50 ±4.20 mV) conceived the effectiveness of this nanosystem for TQ encapsulation. Cell viability in both breast cancer cell lines demonstrated a dose-dependent decrease in response to treatment with free TQ or TQ-loaded cubosomes, with enhanced antitumor activity upon treating with the latter formulation. A significant increase in apoptotic bodies and cleaved caspase 3 was observed upon treatment of MDA-MB-231 cells with either TQ or TQ-loaded cubosomes. Localization and trafficking studies unveiled that cubosomes accumulate in the cytoplasm of the studied breast cancer cell lines. DISCUSSION: Our results show that thymoquinone encapsulation in cubosomal nanoparticles provides a promising anticancer drug delivery system with the ability to label, detect and subsequently trace it within the human cells.

A Dual Protein-mRNA Localization Screen Reveals Compartmentalized Translation and Widespread Co-translational RNA Targeting.

Local translation allows spatial control of gene expression. Here, we performed a dual protein-mRNA localization screen, using smFISH on 523 human cell lines expressing GFP-tagged genes. 32 mRNAs displayed specific cytoplasmic localizations with local translation at unexpected locations, including cytoplasmic protrusions, cell edges, endosomes, Golgi, the nuclear envelope, and centrosomes, the latter being cell-cycle-dependent. Automated classification of mRNA localization patterns revealed a high degree of intercellular heterogeneity. Surprisingly, mRNA localization frequently required ongoing translation, indicating widespread co-translational RNA targeting. Interestingly, while P-body accumulation was frequent (15 mRNAs), four mRNAs accumulated in foci that were distinct structures. These foci lacked the mature protein, but nascent polypeptide imaging showed that they were specialized translation factories. For ß-catenin, foci formation was regulated by Wnt, relied on APC-dependent polysome aggregation, and led to nascent protein degradation. Thus, translation factories uniquely regulate nascent protein metabolism and create a fine granular compartmentalization of translation.