Oligomerization of MLL-GPHN full and ex14. The 293T cells transiently expressing MLL(exon 5-8)–GPHN or its mutants were cross-linked in vivo and analyzed by Western blot after SDS-PAGE in reducing (R) or nonreducing conditions (NR) using anti-Flag antibody (B). The arrowheads indicate the cross-linked species. Cells expressing Flag-tagged TEL were used as a positive control for detecting oligomerization (A).