Figure 3.

RNase protection assay to detect the p27^kip1 mRNA expression in the human breast cancer cell lines as in Fig. 2. The marker is ³²P-labeled MspI-digested pBR322 DNA. The 350-bp p27^kip1 RNA probe and the β-actin probe from Ambion are labeled as probe. The loading order of protected p27^kip1 mRNA from the 12 breast cancer cell lines are the following. Lanes 1–12 are ZR75-1, SKBR5, SKBR7, MCF-7, MDAMB453, BT20, GI-101, T47D, CAMA, CAL51, ZR75-30, and 734B, respectively. Lane 13 is the protected p27^kip1 mRNA from a T lymphoid tumor cell line Jurkat, and the negative control yeast RNA is labeled as indicated. (Lower) The protected β-actin mRNA from the same RNase protection assay is used as a RNA loading control.