Emerging evidence indicates that gene expression in higher organisms is regulated by RNA polymerase II stalling during early transcription elongation. To probe the mechanisms responsible for this regulation, we developed methods to isolate and characterize short RNAs derived from stalled RNA polymerase II in Drosophila cells. Significant levels of these short RNAs were generated from over one third of all genes, indicating that promoter-proximal stalling is a general feature of early polymerase elongation. Nucleotide composition of the initially transcribed sequence played an important role in promoting transcriptional stalling by rendering polymerase elongation complexes highly susceptible to backtracking and arrest. These results indicate that the intrinsic efficiency of early elongation can greatly affect gene expression.

As an emerging applied material, graphene has shown tremendous application potential in many fields, including biomedicine. However, the biological behavior of these nanosheets, especially their interactions with cells, is not well understood. Here, we report our findings about the cell surface adhesion, subcellular locations, and size-dependent uptake mechanisms of protein-coated graphene oxide nanosheets (PCGO). Small nanosheets enter cells mainly through clathrin-mediated endocytosis, and the increase of graphene size enhances phagocytotic uptake of the nanosheets. These findings will facilitate biomedical and toxicologic studies of graphenes and provide fundamental understanding of interactions at the interface of two-dimensional nanostructures and biological systems.

Background The long non-coding RNA PVT1 (lncRNA PVT1) has been reported to act as an oncogenic regulator of several cancers. However, its expression and function in gallbladder cancer (GBC) remain largely unknown. Methods In situ hybridization (ISH) and quantitative real-time PCR (qPCR) were performed to detect the expression of PVT1 and miR-143 in GBC tissues and cell lines. Immunohistochemistry (IHC) assays were performed to assess the expression of the hexokinase 2 (HK2) protein. The relationships among PVT1, miR-143 and HK2 were evaluated using dual-luciferase reporter, RNA immunoprecipitation (RIP) and biotin pull-down assays. The biological functions of PVT1, miR-143 and HK2 in GBC cells were explored with cell counting kit 8 (CCK-8), 5-ethynyl-20-deoxyuridine (EdU), colony formation, transwell, wound healing and glucose metabolism assays in vitro. For in vivo experiments, a xenograft model was used to investigate the effects of PVT1 and HK2 on GBC. Results PVT1 was upregulated in GBC tissues and cells and was positively associated with malignancies and worse overall survival. PVT1 knockdown inhibited cell proliferation, migration, and invasion in vitro and restrained tumor growth in vivo. Further studies demonstrated that PVT1 positively regulated HK2 expression via its competing endogenous RNA (ceRNA) activity on miR-143. Additionally, HK2 expression and function were positively correlated with PVT1. Furthermore, we observed that the PVT1/miR-143/HK2 axis promoted cell proliferation and metastasis by regulating aerobic glucose metabolism in GBC cells. Conclusions The results of our study reveal a potential ceRNA regulatory pathway in which PVT1 modulates HK2 expression by competitively binding to endogenous miR-143 in GBC cells, which may provide new insights into novel molecular therapeutic targets for GBC. Electronic supplementary material The online version of this article (10.1186/s12943-019-0947-9) contains supplementary material, which is available to authorized users.