This invention provides messenger RNA (mRNA) molecules comprising an open reading frame that encodes a protein of interest, wherein said modified RNA comprises a modified nucleoside selected from the group consisting of: (I), (II), and (III), gene therapy vectors comprising same, methods of synthesizing same, and methods for gene replacement, gene therapy, gene transcription silencing, and the delivery of therapeutic proteins to tissue in vivo, comprising the molecules. The present invention also provides methods of reducing the immunogenicity of mRNA molecules.