pCSG-IBAwt1 is a large expression vector with universal features for transient expression as well as for generation of stable mammalian cell lines. The vector carries an ampicillin resistance cassette for selection of transformed E. coli cells and ColE1 origin for a high plasmid copy number. Extrachromosomal replication in mammalian cells could occur either by origin of replication from Epstein-Barr Virus (oriP) or by SV40 ori. For the former the vector provides the EBNA-1 gene and for the latter the cell line has to be latently infected with SV40 or express the SV40 large T antigen (e.g. HEK293T, COS-1, COS-7). Stable cell lines can be selected by the neomycin resistance gene (NeoR). In addition, the human cytomegalovirus (CMV) immediate-early promoter enables a high-level expression in a wide range of mammalian cells. Please note that cloning into pCSG-IBA acceptor vectors compulsorily requires the restriction enzyme Esp3I since no other MCS for the integration of a gene of interest is available. Besides to the direct cloning of the gene of interest into pCSG-IBA vectors with Esp3I, another option via a so-called entry vector is possible.