Abstract
BackgroundThe myeloid translocation gene (MTG) proteins are non-DNA-binding transcriptional regulators capable of interacting with chromatin modifying proteins. As a consequence of leukemia-associated chromosomal translocations, two of the MTG proteins, MTG8 and MTG16, are fused to the DNA-binding domain of AML1, a transcriptional activator crucial for hematopoiesis. The AML1-MTG fusion proteins, as the wild type MTGs, display four conserved homology regions (NHR1-4) related to the Drosophila nervy protein. Structural protein analyses led us to test the hypothesis that specific MTG domains may mediate RNA binding.ResultsBy using an RNA-binding assay based on synthetic RNA homopolymers and a panel of MTG deletion mutants, here we show that all the MTG proteins can bind RNA. The RNA-binding properties can be traced to two regions: the Zinc finger domains in the NHR4, which mediate Zinc-dependent RNA binding, and a novel short basic region (SBR) upstream of the NHR2, which mediates Zinc-independent RNA binding. The two AML1-MTG fusion proteins, retaining both the Zinc fingers domains and the SBR, also display RNA-binding properties.ConclusionEvidence has been accumulating that RNA plays a role in transcriptional control. Both wild type MTGs and chimeric AML1-MTG proteins display in vitro RNA-binding properties, thus opening new perspectives on the possible involvement of an RNA component in MTG-mediated chromatin regulation.
Highlights
The myeloid translocation gene (MTG) proteins are non-DNA-binding transcriptional regulators capable of interacting with chromatin modifying proteins
The MTG proteins have RNA-binding properties We investigated the RNA-binding properties of MTG8, MTG16 and MTGR1 by analyzing their ability to interact with four synthetic RNA homopolymers, poly(A), poly(C), poly(G) and poly(U), coupled to Sepharose beads
Digestion with micrococcal nuclease of the Sepharose-conjugated poly(U) homopolymer apparently abolishes MTGs precipitation, demonstrating that the binding occurs via poly(U) RNA (Figure 1B)
Summary
The myeloid translocation gene (MTG) proteins are non-DNA-binding transcriptional regulators capable of interacting with chromatin modifying proteins. As a consequence of leukemia-associated chromosomal translocations, two of the MTG proteins, MTG8 and MTG16, are fused to the DNA-binding domain of AML1, a transcriptional activator crucial for hematopoiesis. The MTG proteins share four conserved domains that can be traced to the Drosophila protein nervy, and called nervy homology regions (NHR1-4) [6]. These domains carry information for distinct, but integrated, functional properties. The NHR2 domain is required for interaction with other MTG proteins and with the transcriptional co-repressor Sin3A [6,9,10,11]. The NHR4 domain, even if it contains two (page number not for citation purposes)
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