The present invention relates to expression vectors for the
heterologous expression of a
nucleic acid sequence of interest in mammalian cells, the vectors comprising a chimeric
promoter regulatory sequence being operably linked to a
nucleic acid sequence to be expressed, wherein the chimeric
promoter regulatory sequence comprises a cytomegalovirus
promoter sequence derived from murine cytomegalovirus or from
human cytomegalovirus and being operably linked to the transcriptional
start site of the
nucleic acid sequence to be expressed; and a cytomegalovirus upstream region and / or
enhancer sequence derived from human and / or the simian cytomegalovirus, wherein the upstream region and / or
enhancer sequence is located 5′ of and operably linked to the murine or the human promoter sequence, and wherein the chimeric promoter
regulatory sequence comprises sequence elements being derived from at least two of the group consisting of murine cytomegalovirus,
human cytomegalovirus and simian cytomegalovirus. In particular embodiments, the chimeric promoter regulatory sequence comprises sequence elements derived from the murine or the
human cytomegalovirus IE1 promoter and from the human and / or the simian cytomegalovirus IE1 region. The invention also relates to mammalian host cells transfected with such expression vectors, a method for
heterologous expression of a
nucleic acid sequence in a mammalian host
cell by employing such expression vectors, and the use of such expression vectors for the
heterologous expression of a
nucleic acid sequence.