Phi29 pRNA vector for efficient escort of hammerhead ribozyme targeting survivin in multiple cancer cells

Abstract

Ribozymes are potential therapeutic agents which suppress specific genes in disease-affected cells. Ribozymes have high substrate cleavage efficiency, yet their medical application has been hindered by RNA degradation, aberrant cell trafficking, or misfolding when fused to a carrier. In this study, we constructed a chimeric ribozyme carried by the motor pRNA of bacteriophage phi29 to achieve proper folding and enhanced stability. A pRNA molecule contains an interlocking loop domain and a 5´/3´ helical domain, which fold independently of one another. When a ribozyme is connected to the helical domain, the chimeric pRNA/ribozyme reorganize into a circularly permuted form, in which the 5´/3´ ends are relocated and buried in the original 71′/75′ positions. Effective silencing of an anti-apoptotic gene survivin by an appropriately designed chimeric ribozyme, as demonstrated at mRNA and protein levels, led to programmed cell death in various human cancer cell lines, including breast, prostate, cervical, nasopharyngeal, and lung, without causing significant non-specific cytotoxicity. Through the interlocking interaction of right and left loops, monomer pRNA/ribozyme chimeras can be incorporated into multi-functional dimer, trimer and hexamer complexes for specific gene delivery. Using the phi29 motor pRNA as an escort may revive the ribozyme's strength in medical application again.