Drosophila myeloid leukemia factor acts with DREF to activate the JNK signaling pathway

Abstract

Drosophila myelodysplasia/myeloid leukemia factor (dMLF), a homolog of human MLF1, oncogene was first identified by yeast two-hybrid screen using the DNA replication-related element-binding factor (DREF) as bait. DREF is a transcription factor that regulates proliferation-related genes in Drosophila. It is known that overexpression of dMLF in the wing imaginal discs through the engrailed-GAL4 driver causes an atrophied wing phenotype associated with the induction of apoptosis. However, the precise mechanisms involved have yet to be clarified. Here, we found the atrophied phenotype to be suppressed by loss-of-function mutation of Drosophila Jun N-terminal kinase (JNK), basket (bsk). Overexpression of dMLF induced ectopic JNK activation in the wing disc monitored with the puckered-lacZ reporter line, resulting in induction of apoptosis. The DREF-binding consensus DRE sequence could be shown to exist in the bsk promoter. Chromatin immunoprecipitation assays in S2 cells with anti-dMLF IgG and quantitative real-time PCR revealed that dMLF binds specifically to the bsk promoter region containing the DRE sequence. Furthermore, using a transient luciferase expression assay, we provide evidence that knockdown of dMLF reduced bsk gene promoter activity in S2 cells. Finally, we show that dMLF interacts with DREF in vivo. Altogether, these data indicate that dMLF acts with DREF to stimulate the bsk promoter and consequently activates the JNK pathway to promote apoptosis.

Control of RUNX-induced repression of Notch signaling by MLF and its partner DnaJ-1 during Drosophila hematopoiesis

“…Whereas vertebrates have two closely related MLF paralogs, Drosophila has a single mlf gene encoding a protein that displays around 50% identity with human MLF in the central conserved domain [ 16 , 17 ]. In the fly, MLF was identified as a partner of the transcription factor DREF (DNA replication-related element-binding factor) [ 16 ], for which it acts a co-activator to stimulate the JNK pathway and cell death in the wing disc [ 18 ]. MLF has been shown to bind chromatin [ 18 – 20 ], as does its mouse homolog [ 21 ], and it can either activate or repress gene expression by a still unknown mechanism [ 18 , 20 ].…”

“…In the fly, MLF was identified as a partner of the transcription factor DREF (DNA replication-related element-binding factor) [ 16 ], for which it acts a co-activator to stimulate the JNK pathway and cell death in the wing disc [ 18 ]. MLF has been shown to bind chromatin [ 18 – 20 ], as does its mouse homolog [ 21 ], and it can either activate or repress gene expression by a still unknown mechanism [ 18 , 20 ]. MLF also interacts with Suppressor of Fused, a negative regulator of the Hedgehog signaling pathway [ 19 ], and, like its mammalian counterpart [ 13 ], with Csn3, a component of the COP9 signalosome [ 22 ], but the functional consequences of these interactions remain elusive.…”

ZBED1/DREF: A transcription factor that regulates cell proliferation (Review)

“…These findings confirm the association between DRE/DREF and the Hippo pathway. Furthermore, in addition to Hippo pathway-associated genes, DREF also associates with Drosophila myeloid leukemia factor in thorax development to positively regulate the basket gene and thereby activate the JNK signaling pathway ( 61 , 62 ), which induces apoptosis and protects the genome.…”

The cell survival pathways of the primordial RNA-DNA complex remain conserved in the extant genomes and may function as proto-oncogenes

“…The drosophila myelodysplasia/myeloid leukemia factor (dMLF, so-called even though drosophila does not have bone marrow, or granulocyte colony stimulating factor GCSF/CSF ligand and/or receptor, and produces no myelocytes/granulocytes) is a homolog of the human myeloid leukemia factor, hMLF1, a nucleophosmin fusion oncogene/oncoprotein at t (3,5) (q25.1,q34). The dMLF exerts its action through the Hh, RUNX (runt-related), and JNK pathways within the crystal cells [86]. In the human bone marrow, JAK-STAT mutations are the major causative factors for myelofi brosis and myelodysplasia with GCSF/CSF as their promoter, and small molecular JAK-inhibitor ruxolitinib as their suppressor [87,88].…”