(A) Southern blot analysis of DNA digested with BamHI and probed with a 1.4-kb BamHI fragment of p300 cDNA probe. As a control, normal peripheral lymphocytes were used (lane 1). The patient exhibits rearranged bands (arrowhead), suggesting that a 1.4-kb BamHI fragment of p300 cDNA spans the translocation breakpoint (lane 2). (B) The same blot was rehybridized with the 0.9-kb BamHI fragment of MLL cDNA (probe x). The patient exhibits rearranged bands the same size as the bands detected with a BamHI fragment of p300 cDNA (arrowhead), suggesting that probe × also spans the breakpoint and that the p300 gene is translocated to the MLL gene. (C) Northern blot of RNAs using a 1.5-kb BamHI fragment of p300 cDNA probe. As a control, normal peripheral lymphocytes were used (lane 1). The patient showed an additional transcript (arrowhead) of approximately 11.5 kb (lane 2). (D) The same blot was rehybridized with the 0.9-kb BamHI fragment of MLL cDNA (probe x). The patient exhibits an aberrant band the same size as the band detected with a BamHI fragment of p300 cDNA (arrowhead). (E) Western blot analysis using p300-specific antibody against the C-terminal of p300. As a control, Namalwa, a Burkitt lymphoma cell line, was used (lane 1). The patient showed an additional polypeptide (arrowhead) of approximately 350 kD (lane 2).