Cleavage of the MLL gene by activators of apoptosis is independent of topoisomerase II activity

C. J. Betti, M. J. Villalobos, Q. Jiang, E. Cline, M. O. Diaz, G. Loredo, Andrew T M Vaughan

Research output: Contribution to journalArticlepeer-review

29 Scopus citations


Exposure to topoisomerase II inhibitors is linked to the generation of leukemia involving translocations of the MLL gene, normally restricted to an 8.3kbp tract, the breakpoint cluster region (BCR). Using an in vitro assay, apoptotic activators, including radiation and anti-CD95 antibody, trigger site-specific cleavage adjacent to exon 12 within the MLL BCR and promote translocation of the MLL gene in cells that can survive. To explore the mechanism of cleavage and rearrangement in more detail, the entire MLL BCR was placed into the pREP4 episomal vector and transfected into human lymphoblastoid TK6 cells. Episomes containing either the MLL BCR, or deletion constructs of 367bp or larger, were cleaved at the same position as genomic MLL after exposure to apoptotic stimuli. Further analysis of sequence motifs surrounding the cleaved region of MLL showed the presence of both a predicted nuclear matrix attachment sequence and a potential strong binding site for topoisomerase II, flanking the site of cleavage. Inactivation of topoisomerase II by the catalytic inhibitor merbarone did not inhibit MLL cleavage, suggesting that the initial cleavage step for MLL rearrangement is not mediated by topoisomerase II.

Original languageEnglish (US)
Pages (from-to)2289-2295
Number of pages7
Issue number12
StatePublished - Dec 2005


  • Apoptosis
  • High molecular weight fragmentation
  • Merbarone
  • MLL (mixed lineage leukemia)
  • tATML (therapy related AML)
  • Topoisomerase II

ASJC Scopus subject areas

  • Hematology
  • Cancer Research


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