Mol. Cell. Biol. 
I (, »/v\_ -t *a 
140 McIVOR ET AL. 
LHM.PL i 
6 
t 
• 
4 
if 
-LTR — [ HPRT I 
-=^SOEE> 
— LTR- 
LHM i PL, - LTR — { HPRT } 
SB X* 
1 1 A 
-maflJ PNP 1 LTR - 
LHM.ALi 
■ -L- 
ADA t - 
Jf 
-LTR 
LHMj AL, 
S B 
_L L 
mma i ada 
FIG. 1. PNP and ADA recombinant retroviruses The large boxes contain the viral LTRs, the medium boxes contain the HPRT-. ADA-, 
or PNP-coding sequences, and the small boxes contain sequences derived from the promoter region of the mouse metallothionein I gene. 
Other viral sequences are located on the solid lines between the LTRs. Abbreviations for restriction sites: S, Sjfl; X. Xba 1; B, Bgl II. See text 
for details and sequence sources. 
Recombinant DNA Research, Volume 12 
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