(A) Comparative activity of the MBP P2 promoter in eosinophil (YJ-11, HL-60-C15), myelomonocytic (U937), lymphoid (Raji), and nonhematopoietic (HeLa) cell lines. Fifteen micrograms of the −117/MBP-luc promoter construct was transfected, along with 10 μg of pBluescript II KS(−) as carrier DNA, into each cell line. Promoter (luciferase) activities of the −117/MBP-luc construct were normalized based on the measurement of growth hormone expression from a control cotransfected CMV-hGH expression vector in the various cell lines. (B) Northern blot analysis for mRNA encoding eosinophil granule MBP in the various cell lines. Fifteen micrograms of total RNA isolated from the indicated human cell lines was hybridized to the MBP cDNA. Lane 1, YJ-11; lane 2, HL-60-C15; lane 3, HeLa; lane 4, Raji; and lane 5, U937. Hybridization of the same filter to a 18S rRNA probe is shown as control for amounts of RNA.