Manipulation of SV40 Vectors
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SV40 is a small simian virus that has been extensively used as a viral vector in mammalian cells (1 –4 ). The viral genome is a double-stranded supercoiled DNA molecule of 5243 bp (Fig. 1A ) that is packaged into a capsid containing the viral structural proteins VP1,VP2, and VP3. SV40 induces a lytic infection cycle in permissive cells. The first step in the replication cycle is synthesis of early mRNA. This is followed by DNA replication and expression of late mRNAs that encode the structural proteins. New virus particles are formed, and the infection ultimately kills the cells.
Fig. 1. Schematic diagrams of the genome of SV40 and the SV40 expression vectors p14, pBABY, and pSVEpR4. The detailed maps and constructions of these vectors have been described elsewhere (8 ,(11 ,(12 ).
