Finally, SEC may be recruited to its target promoters through tissue-specific and sequence-specific DNA binding partners, such as the HIV Tat protein in HIV-infected cells, MLL-fusion proteins in leukemia cells (He and Zhou, 2011; Smith et al., 2011) or retinoic acid receptor in differentiating mouse embryonic stem cells (Lin et al., 2011). This evidence concerns the gene KMT2A and leukemia.