The present invention provides novel compounds, compositions, and methods for the delivery of biologically active RNA molecules to cells. Specifically, the invention provides novel nucleic acid molecules, polypeptides, and RNA-protein complexes useful for the delivery of biologically active RNAs to cells and polynucleotides encoding the same. The invention also provides vectors for expressing said polynucleotides. In addition, the invention provides cells and compositions comprising the novel compounds and vectors, which can be used as transfection reagents. The invention further provides methods for producing said compounds, vectors, cells, and compositions. Additionally, vectors and methods for delivering biologically active RNA molecules to cells and/or tissues are provided. The novel compounds, vectors, cells, and compositions are useful, for example, in delivering biologically active RNA molecules to cells to modulate target gene expression in the diagnosis, prevention, amelioration, and/or treatment of diseases, disorders, or conditions in a subject or organism.