Retrovirus integrations at 3′ side of the C/EBPβ gene were frequently found in Evi1-leukemia mice. (A) A flowchart of retrovirus infection and BMT. (B) Percentages of GFP/Ly-5.1 double-positive cells in PB. PB was obtained from the tail vein every month after transplantation. (C) Southern blot analysis of Evi1-leukemia mice. DNA samples were digested with EcoRI. Proviruses were probed with a GFP probe. Mice ID are shown at the top of the panel. (D-E) Integration site analysis in BM samples of Evi1-leukemia cells obtained by bubble PCR. Genomic DNAs were digested with EcoRI (D) or BamHI (E). White arrows indicate insertion sites near C/EBPβ. Black arrows indicate retroviral sequence. (F) Schema of integration sites near the C/EBPβ gene. Thick black arrows indicate integration sites. Thin black arrows indicate restriction sites. “B” indicate BamHI site. Black horizontal bars indicate the position of the probes for Southern blotting. (G) Schema of restriction sites on retroviral sequence near the junction of genomic DNA. (H) The leukemic clones with retroviral integration near the C/EBPβ gene were major clones. Black arrows indicate the endogenous band, and white arrows indicate the integrated band.