Chromosomal aberrations that affect the Mixed-Lineage Leukemia gene (MLL, known also as HRX or ALL-1) located at 11q23 are associated with an aggressive type of acute leukemia. Frequent translocations create a diverse set of MLL fusion genes with acquired active transforming potential resulting in leukemic conversion of MLL transcription factor. The normal MLL protein is involved in epigenetic maintenance of homeotic (Hox) gene expression through several rounds of cell division during development and differentiation. Alterations of this process by oncogenic MLL chimeric transcription factors lead to leukemia. This review is intended to provide a coherent view on normal and malignant function of MLL proteins - mainly focusing on MLL-ENL - in our current knowledge. Our own contribution to the field is also summarized in this review.

        Key words: acute leukemia, MLL, translocation, chromatin, epigenetics, transcription