The structural flexibility of RNA interference (RNAi)-trig-gering nucleic acids suggests that the design of uncon-ventional RNAi trigger structures with novel features is possible. Here, we report a cross-shaped RNA duplex structure, termed quadruple interfering RNA (qiRNA), with multiple target gene silencing activity. qiRNA trig-gers the simultaneous down-regulation of four cellular target genes via an RNAi mechanism. In addition, qiRNA shows enhanced intracellular delivery and target gene silencing over conventional siRNA when complexed with jetPEI, a linear polyethyleneimine (PEI). We also show that the long antisense strand of qiRNA is incorporated intact into an RNA-induced silencing complex (RISC). This novel RNA scaffold further expands the repertoire of RNAi-triggering molecular structures and could be used in the development of therapeutics for various diseases including viral infections and cancer.

Keywords: polyethyleneimine (PEI), quadruple interfering RNA (qiRNA), RNA interference, small interfering RNA (siRNA)