Figure 5

Breast tumor kinase mediates endogenous signal transducer and activator of transcription 5b transcriptional activity. (a) BT-549 cells were transfected with the Spi2.1 promoter luciferase construct along with pRc, breast tumor kinase (Brk), K219M, or Y447F expression vectors. Luciferase activity was measured and normalized to total protein. Values from four independent experiments carried out in triplicate were reported as average luciferase/protein ± standard error: pRc (1,859.37 ± 592.24); Brk (10,031.94 ± 1,359.68); K219M (3,109.82 ± 777.57), Y477F (12,878.57 ± 2,464.26). Student's t test was used to determine statistical significance between pRc and Brk, and between pRc and K219M. *P < 0.0001, • P = 0.0430. (b) BT-549 cells were transfected with the Spi2.1 promoter luciferase construct along with pRc, Brk, or K219M, and either pcDNA, c-Src, or K-Src expression vectors. Luciferase activity was measured and normalized to total protein. Values from four independent experiments carried out in triplicate were reported as the average fold induction over pcDNA, pRc ± SE: pcDNA, pRc (1.00 ± 0.00), Brk (2.92 ± 0.39), and K219M (1.36 ± 0.13); c-Src, pRc (1.10 ± 0.12), Brk (5.01 ± 0.38), and K219M (1.24 ± 0.18); K-Src, pRc (0.99 ± 0.19) and Brk (2.76 ± 0.89). Student's t test was used to determine statistical significance between pcDNA pRc and pcDNA Brk, between pcDNA pRc and pcDNA K219M, and between pRc Brk and c-Src Brk. *P = 0.0027, • P = 0.0322, ◆ P < 0.0086.