S1 nuclease protection analysis of spleen RNAs is isolated from hCG–PML-RARα transgenic mice. Molecular size markers are indicated on the left. The expected positions of probe fragments protected by hCG–PML-RARα, mCG, and mβ actin mRNAs are indicated by the arrows on the right. Founder line and transgene status for each RNA sample are indicated at the bottom. Increases in endogenous mCG mRNA levels are detected in founder lines 83, 72, 148, 137, and 135 (lanes 4, 6, 8, 10, and 11, respectively).