To obtain a new DNA encoding γ-interferon signal peptide connected to an N end of mature mammalian protein except γ-interferon, increasing the expression of the protein, useful for a gene transportation system.

This new DNA encodes γ-interferon signal peptide connected to an N end of mature mammalian protein except γ-interferon, increases the expression of the protein from a mammalian cell and is useful for DNA recombinant technology for carrying out delivery of a protein such as a tumor necrosis factor and interleukin II to a cell, a protein providing a cell with multiple drug resistance, etc. The DNA is obtained by connecting a gene of γ-interferon signal peptide to a gene of tumor necrosis factor(TNF) being a mature mammalian protein except γ-interferon so as to encode a protein in which a signal peptide is connected to an N end of TNF as shown by the formula.