該基因編碼一個轉錄輔激活子，在早期發育和造血過程中起到調節基因表達的重要作用。編碼蛋白包含多個保守功能域。其中一個域，即集合域，負責其組蛋白H3賴氨酸4（H3K4）甲基轉移酶活性，介導與表觀遺傳轉錄激活相關的染色質修飾。這種蛋白由酶Taspase 1加工成兩個片段，MLL-C和MLL-N。這些片段重新結合并進一步組裝成不同的多蛋白復合物，調節特定靶基因的轉錄，包括許多HOX基因。涉及該基因的多個染色體易位是導致某些急性淋巴細胞性白血病和急性髓性白血病的原因。交替剪接導致多個轉錄變體。
This gene encodes a transcriptional coactivator that plays an essential role in regulating gene expression during early development and hematopoiesis. The encoded protein contains multiple conserved functional domains. One of these domains, 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.