FIG. 1.

Schematic representation of MLV-VL30m-lacZ monocistronic retroviral vectors. All MLV-VL30m vectors contain the 5′ LTR and the primer binding site of MLV. In vectors pVL30m-SJ E1 and pVL30m-SJ E2, different segments of the 5′ region of NLV-3 VL30 sequences were inserted upstream of the lacZ reporter cistron. The pMLV-LacZ+ vector, used as a positive control, contains the MLV Psi⁺ encapsidation sequence. pVL-SJE3, used as a negative control, contains no encapsidation sequence. Numbering is with respect to the VL30m RNA cap site (position +1).