Expression pattern of dd4, a sole member of the d4 family of transcription factors in Drosophila melanogaster

Crystal structure of the Cys2His2-type zinc finger domain of human DPF2

DPF2 is an evolutionary highly conserved member of the d4-protein family characterized by an N-terminal 2/3 domain, a C2H2-type zinc finger (ZF), and a C-terminal tandem PHD zinc finger. DPF2 is identified as a transcription factor and may be related with some cancers in human. Here, we report the crystal structure of the C2H2-type zinc finger domain of human DPF2 with a canonical C2H2 fold, which contains two beta strands and one alpha helix. Several conserved residues, including Lys207, Lys216 and Arg217, constitute a positively charged surface in C2H2 domain, which implicates that it has the potential to bind DNA. The side chains of the residues Y209, C211, C214, K216, Y218, L224, H227 and H232 form the hydrophobic core of C2H2 domain, which indicates a potential-binding surface in the human DPF2.

Crosstalk between leukemia-associated proteins MOZ and MLL regulates HOX gene expression in human cord blood CD34+ cells

MOZ and MLL, encoding a histone acetyltransferase (HAT) and a histone methyltransferase, respectively, are targets for recurrent chromosomal translocations found in acute myeloblastic or lymphoblastic leukemia. In MOZ (MOnocytic leukemia Zinc-finger protein)/CBP- or mixed lineage leukemia (MLL)-rearranged leukemias, abnormal levels of HOX transcription factors have been found to be critical for leukemogenesis. We show that MOZ and MLL cooperate to regulate these key genes in human cord blood CD34+ cells. These chromatin-modifying enzymes interact, colocalize and functionally cooperate, and both are recruited to multiple HOX promoters. We also found that WDR5, an adaptor protein essential for lysine 4 trimethylation of histone H3 (H3K4me3) by MLL, colocalizes and interacts with MOZ. We detected the binding of the HAT MOZ to H3K4me3, thus linking histone methylation to acetylation. In CD34+ cells, depletion of MLL causes release of MOZ from HOX promoters, which is correlated to defective histone activation marks, leading to repression of HOX gene expression and alteration of commitment of CD34+ cells into myeloid progenitors. Thus, our results unveil the role of the interaction between MOZ and MLL in CD34+ cells in which both proteins have a critical role in hematopoietic cell-fate decision, suggesting a new molecular mechanism by which MOZ or MLL deregulation leads to leukemogenesis.

MOZ and MORF, two large MYSTic HATs in normal and cancer stem cells

Genes of the human monocytic leukemia zinc-finger protein MOZ (HUGO symbol, MYST3) and its paralog MORF (MYST4) are rearranged in chromosome translocations associated with acute myeloid leukemia and/or benign uterine leiomyomata. Both proteins have intrinsic histone acetyltransferase activity and are components of quartet complexes with noncatalytic subunits containing the bromodomain, plant homeodomain-linked (PHD) finger and proline-tryptophan-tryptophan-proline (PWWP)-containing domain, three types of structural modules characteristic of chromatin regulators. Although leukemia-derived fusion proteins such as MOZ-TIF2 promote self-renewal of leukemic stem cells, recent studies indicate that murine MOZ and MORF are important for proper development of hematopoietic and neurogenic progenitors, respectively, thereby highlighting the importance of epigenetic integrity in safeguarding stem cell identity.