The present invention relates to a novel system for the trans-membrane transport including the cellular uptake/delivery of nucleic acids, substances that contain a nucleic acid component, recombinant genetic material or substances that can be attached to a nucleic acid, in biological systems. In particular, the present invention relates to a nucleic acid comprising a first nucleotide sequence having a specific signal sequence, wherein said signal sequence increases or causes the uptake of the nucleic acid into a cell, and a pharmaceutical composition containing said nucleic acid.