Expression of the intron VII–spliced and –unspliced mRNAs for EPOR in various leukemia cell lines and leukemia cells. Total cellular RNA (A, B, and C) or polyA(+) RNA (C) was reverse-transcribed and subjected to PCR using the primer sets of sense-2 and antisense-2. (A) Lane a, BV-173 (lymphoid); b, NALM-16 (lymphoid); c, NALM-24 (lymphoid); d, K562 (erythroid); e, MEG-01 (megakaryocytic); f, HEL (erythroid); g, JOSK-1 (monocytic); h, SU-DHL-4 (lymphoid); and i, CCRF-CEM (lymphoid). (B) Lane a, KOPT-K1 (lymphoid); b, PEER (lymphoid); c, F-36E (erythroid); d, F-36P (erythroid); e, UT-7 (megakaryocytic); and f, TF-1 (erythroid). (C) One microgram total RNA prepared from U-937 cells, 0.5 μg polyA(+) RNA therefrom, and 0.5 μg polyA(+) RNA prepared from peripheral blood leukemia cells from a patient with CML in blast crisis9 was reverse-transcribed and subjected to the PCR protocol with the indicated number of cycles. Total RNA was used in lanes a to c and polyA(+) RNA in d to i. The number of cycles was 30 (lanes a, d, and g), 35 (b, e, and h), and 40 (c, f, and i). The sizes of intron VII–spliced and –unspliced mRNAs are 236 bp and 331 bp, respectively. (D) RNase protection assay shows expression of EPOR-F and EPOR-T mRNAs in U-937 and leukemia cells obtained from the same patient as described in C. A 420-bp [³²P]-labeled riboprobe was hybridized with 10 μg polyA(+) RNA samples, digested with the mixture of RNase A and RNase T1, and analyzed in 5% polyacrylamide/8 mol/L urea gel. Lane a, undigested probe; b, yeast RNA; c, U-937; d, CML blast crisis.