* 
Figure Southern blot analysis of NIH3T3 cells infected with the human LDL receptor 
retroviruses. Subconfluent plates of NIH3T3 cells were exposed to freshly prepared virus 
and total cellular DNA was isolated when the plates were confluent. DNA ( 1 0 p.g) was 
restricted with Kpn I, fractionated on an agarose gel, and transferred to a filter which was 
hybridized with a’human LDL receptor cDNA probe. 1 copy represents the addition of plasmid 
DNA to uninfected total cellular DNA at a level equal to a single copy per cell. The rest of the 
samples are DNAs from NIH3T3 cells infected with the indicated virus producers: BA- 1 6 
p-actin promoter no enhancer, 131 series p-actin promoter with the CMV enhancer in direct 
orientation, and the 132 series p-actin promoter with the CMV enhancer in reverse 
orientation. 
Recombinant DNA Research, Volume 15 
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