I <«> « 
Construction of the amphotropic packaging vector. Restriction sites are indicated (E, EroRI; C. C/a I; S. Safi; H, Mind III; P, Pi/I). 
There were other Ball sites which are not shown. Splice donor (SO) and splice acceptor (SA) sites for generation of the env mRNA are 
indicated. The env gene and part of the pot region of MoMLV DNA clone pMLV-K (22) were replaced with a Jafl-to-C/al fragment Iron 
amphotropic virus clone 4070A (3) to make pAM. Packaging vector pPAM was derived from pAM by deletion of a Ball (MoMLV nucleotide 
position 214 (28]}-to-Pj/l (MoMLV nucleotide position 363 (28]) fragment spanning the packaging signal for the virus. A Pi/I linker was lipted 
to the Ball site and then joined to the 3' Pi/I site after partial digestion of a molecule containing both Pi/I sites present in pAM. p4070A is 
shown in its nonpermuted form, although the actual DNA done used was permuted and was cloned into pBR322 by using the unique EroRI 
she in env . The other viruses shown were inserted between the C/al and Piwll sites in pBR322 in place of the Tet r gene. kb. Kilobase. 
Fiq. 7. (Miller and Buttimore, 1985) 
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Recombinant DNA Research, Volume 12 
