Expression of BRCA1 mRNA and Western blot analysis. (A) Relative expression of BRCA1 mRNA in UT-7 cell clones expressing different levels of BCR-ABL. Mean levels of expression of the BRCA1 gene, normalized to β-2 microglobulin gene, are displayed logarithmically on the y-axis. For clarity, only positive error bars (SD) are shown. For all categories, n = 3. (B) Western blot analysis showing the effects of proteasome inhibitor in UT-7 cell clones. Parental UT-7/P and BCR-ABL–expressing UT-7/9 cells were grown in recombinant human granulocyte macrophage colony-stimulating factor (rhGM-CSF) and exposed to proteasome inhibitor lactacystin 5 μM diluted in DMSO; similar volume of DMSO was added for 8 hours as a control. Whole-cell extracts were subjected to Western blot analysis using anti-BRCA1, anti–c-ABL (lane 1, UT-7/P + DMSO; lane 2, UT-7/P + lactacystin; lane 3, UT-7/9 + DMSO; lane 4, UT-7/9 + lactacystin).