Human Argonaute2 and Argonaute3 are catalytically activated by different lengths of guide RNA

RNA interfering is a eukaryote-specific gene silencing by 20∼23-nucleotide (nt) microRNAs and small interfering RNAs that recruit Argonaute proteins to complementary RNAs for degradation. In humans, Argonaute2 (AGO2) has been known as the only slicer while Argonaute3 (AGO3) barely cleaves RNAs. Therefore, the intrinsic slicing activity of AGO3 remains controversial and a long-standing question. Here, we report 14-nt 3′ end-shortened variants of let-7a, miR-27a, and specific miR-17–92 families that make AGO3 an extremely competent slicer, increasing target cleavage up to ∼82-fold in some instances. These RNAs, named cleavage-inducing tiny guide RNAs (cityRNAs), conversely lower the activity of AGO2, demonstrating that AGO2 and AGO3 have different optimum guide lengths for target cleavage. Our study sheds light on the role of tiny guide RNAs.

The Synthesis of Ascorbic Acid in Rice Roots Plays an Important Role in the Salt Tolerance of Rice by Scavenging ROS

The root plays an important role in the responses of plants to stresses, but the detailed mechanisms of roots in stress responses are still obscure. The GDP-mannose pyrophosphate synthetase (GMPase) OsVTC1-3 is a key factor of ascorbic acid (AsA) synthesis in rice roots. The present study showed that the transcript of OsVTC1-3 was induced by salt stress in roots, but not in leaves. Inhibiting the expression of OsVTC1-3 by RNA interfering (RI) technology significantly impaired the tolerance of rice to salt stress. The roots of OsVTC1-3 RI plants rapidly produced more O2−, and later accumulated amounts of H2O2 under salt stress, indicating the impaired tolerance of OsVTC1-3 RI plants to salt stress due to the decreasing ability of scavenging reactive oxygen species (ROS). Moreover, exogenous AsA restored the salt tolerance of OsVTC1-3 RI plants, indicating that the AsA synthesis in rice roots is an important factor for the response of rice to salt stress. Further studies showed that the salt-induced AsA synthesis was limited in the roots of OsVTC1-3 RI plants. The above results showed that specifically regulating AsA synthesis to scavenge ROS in rice roots was one of important factors in enhancing the tolerance of rice to salt stress.

Delivery of miRNA Using Fe2O3 Nanoparticles Capped Polyethyleneimine as a Nonviral Carrier

An efficient and safe delivery system of RNA interfering is required for clinical application of gene therapy. The study aimed to develop Fe2O3-based nanoparticles for gene delivery to overcome the disadvantages of polyethyleneimine (PEI) or cationic liposome as gene carrier including the cytotoxicity caused by positive charge and aggregation in the cells surface. PEI-capped Fe2O3 nanoparticles are successfully manufactured utilizing Fe2O3 as core, PEI as carapace, which bind miRNA at an appropriate weight ratio by electrostatic interaction and result in well-dispersed nanoparticles. The synthesized GFP tag with miR-26a expression plasmid was used for monitoring transfection efficiency in HepG2 cells. The nanocomplex exhibited higher transfection efficiency and lower cytotoxicity in HepG2 cells than the PEI/DNA complex and commercially available liposome. The delivery resulted in a significantly upregulation of miR-26a in HepG2 cells. Our results offer an alternate delivery system for RNA interfering that can be used on any gene of interest.