Figure 4.

Expression of PGK–Neo in wild-type (WT), granzyme B −/−, cathepsin G −/−, and HS-3 −/− mice. RNA (15 μg) derived from resting spleen, MLR, and bone marrow from each animal was analyzed using S1 nuclease protection assays; each mRNA sample was cohybridized with probes for granzyme B, cathepsin G, PGK–Neo, and β₂-microglobulin. Note that abundant, correctly initiated PGK–Neo mRNA is detected in MLR lymphocytes (or LAK cells, data not shown) only when the cassette is located within the granzyme B gene (lane 5 versus lanes 8 and 11). PGK–Neo is detected in the spleen and bone marrow of mice containing the cassette in the murine β-globin LCR (lanes 10 and 12); both of these organs contain erythroid precursors in adult mice. PGK–Neo mRNA is not detected in the marrow of the mice containing the cathepsin G −/− mutation. The granzyme B mutation does not affect expression of cathepsin G in marrow (lane 6), as reported (24). These experiments were repeated four times with identical results.