Oncogene RNA helicase DDX6 promotes the process of c-Myc expression in gastric cancer cells.

Human DEAD-box RNA helicase gene DDX6 was cloned from B-cell lymphoma cell line RC-K8. Previously, we reported that DDX6 acts as oncogene in several cancers such as colorectal cancer and hepatocellular carcinoma. However, the detailed mechanism of DDX6 action in carcinogenesis is largely unknown. In this study, we examined the functions of DDX6 in clinical gastric cancer (GC) samples and GC cells. DDX6 protein expression levels of cancer samples were higher than those of the adjacent normal tissues in 25 clinical GC samples (median value: 1.4 times higher). Also, the results of an RNA immunoprecipitation-assay (RIP-assay) showed that DDX6 associated with c-Myc mRNA. Moreover, enforced overexpression of DDX6 promoted both mRNA and protein expression of c-Myc in GC cells. On the other hand, the gene silencing of DDX6 induced growth suppression through down-regulation of c-Myc in GC cells grown in either two or three dimensions. Furthermore, c-Myc mRNA expression levels of cancer samples were higher than those of the adjacent normal tissues in DDX6 up-regulated-GC clinical samples. Our findings in this study suggested that DDX6 acted as oncogene in GC cells through promotion of c-Myc expression by association with the mRNA of c-Myc.

Targeted delivery of fluorogenic peptide aptamers into live microalgae by femtosecond laser photoporation at single-cell resolution.

Microalgae-based metabolic engineering has been proven effective for producing valuable substances such as food supplements, pharmaceutical drugs, biodegradable plastics, and biofuels in the past decade. The ability to accurately visualize and quantify intracellular metabolites in live microalgae is essential for efficient metabolic engineering, but remains a major challenge due to the lack of characterization methods. Here we demonstrate it by synthesizing fluorogenic peptide aptamers with specific binding affinity to a target metabolite and delivering them into live microalgae by femtosecond laser photoporation at single-cell resolution. As a proof-of-principle demonstration of our method, we use it to characterize Euglena gracilis, a photosynthetic unicellular motile microalgal species, which is capable of producing paramylon (a carbohydrate granule similar to starch). Specifically, we synthesize a peptide aptamer containing a paramylon-binding fluorescent probe, 7-nitrobenzofurazan, and introduce it into E. gracilis cells one-by-one by suppressing their mobility with mannitol and transiently perforating them with femtosecond laser pulses at 800 nm for photoporation. To demonstrate the method's practical utility in metabolic engineering, we perform spatially and temporally resolved fluorescence microscopy of single live photoporated E. gracilis cells under different culture conditions. Our method holds great promise for highly efficient microalgae-based metabolic engineering.