The peptide corresponding to amino acids 3735 - 3973 of the MLL / HRX protein (accession number NP_001184033.1) was expressed in E. coli. The peptide contains the SET domain of MLL that is responsible for methyltransferase activity. Recombinant MLL / HRX - SET contains an N-terminal GST tag with a molecular weight of 53.7 kDa.
Myeloid/lymphoid or mixed-lineage leukemia (trithorax homolog, Drosophila), or MLL, also known as HRX, is a Trithorax-group protein that function collectively to promote gene expression. MLL is a transcriptional coactivator that plays an essential role in regulating gene expression during early development and hematopoiesis. The protein contains multiple conserved functional domains. In particular, the SET domain is a conserved C-terminal domain that characterizes proteins of the MLL (mixed-lineage leukemia) family. The SET domain is responsible for its histone H3 lysine 4 (H3K4) methyltransferase activity which mediates chromatin modifications associated with epigenetic transcriptional activation. This protein is processed by the enzyme Taspase 1 into two fragments, MLL-C and MLL-N. These fragments reassociate and further assemble into different multiprotein complexes that regulate the transcription of specific target genes, including many of the HOX genes. Multiple chromosomal translocations involving this gene are the cause of certain acute lymphoid leukemias and acute myeloid leukemias. Alternate splicing results in multiple transcript variants.