24-23 
Figured. Northern 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 RNA was isolated when the plates were confluent. RNA ( 1 0 p.g unless 
otherwise noted) was fractionated on an agarose gel, and transferred to a filter which was 
hybridized with a human LDL receptor cDNA probe. 24-23 is RNA from a virus producer 
transfected with an LTR driven LDL receptor vector. The rest of the samples are RNAs from 
NIH3T3 cells infected with the indicated virus producers: BA- 16 is p-actin promoter no 
enhancer, 131-10 is p-actin promoter with' the CMV enhancer in direct orientation, and the 
132 series are vectors with the p-actin promoter the CMV enhancer in reverse orientation. 
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