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MNDA binds NPM/B23 and the NPM-MLF1 chimera generated by the t(3;5) associated with myelodysplastic syndrome and
J Xie1, J A Briggs, S W Morris
1Department of Pathology, Vanderbilt University School of Medicine, Nashville, TN 37232-5310, USA.
Abstract:
The myeloid cell nuclear differentiation antigen (MNDA) is a nuclear protein expressed specifically in developing cells of the human myelomonocytic lineage, including the end-stage monocytes/macrophages and granulocytes. Nuclear localization, lineage- and stage-specific expression, association with chromatin, and regulation by interferon alpha indicate that this protein is involved in regulating gene expression uniquely associated with the differentiation process and/or function of the monocyte/macrophage. MNDA does not bind specific DNA sequences, but rather a set of nuclear proteins that includes nucleolin (C23). Both in vitro binding assays and co-immunoprecipitation were used to demonstrate that MNDA also binds protein B23 (nucleophosmin/NPM). Three reciprocal chromosome translocations found in certain cases of leukemia/lymphoma involve fusions with the NPM/B23 gene, t(5;17) NPM-RARalpha, t(2;5) NPM-ALK, and the t(3;5) NPM-MLF1. In the current study, MNDA was not able to bind the NPM-ALK chimera originating from the t(2;5) and containing residues 1-117 of NPM. However, MNDA did bind the NPM-MLF1 product of the t(3;5) that contains the N-terminal 175 residues of NPM. The additional 58 amino acids (amino acids 117-175) of the NPM sequence that are contained in the product of the NPM-MLF1 fusion gene relative to the product of the NPM-ALK fusion appear responsible for MNDA binding. This additional NPM sequence contains a nuclear localization signal and clusters of acidic residues believed to bind nuclear localization signals of other proteins. Whereas NPM and nucleolin are primarily localized within the nucleolus, MNDA is distributed throughout the nucleus including the nucleolus, suggesting that additional interactions define overall MNDA localization.
Insights
Myeloid cell nuclear differentiation antigen (MNDA) binds nucleophosmin (NPM) in specific leukemia-associated fusion proteins. This interaction is mediated by an additional 58 amino acids in the NPM-MLF1 fusion, influencing MNDA
Area of Science:
- Molecular Biology
- Cell Biology
- Hematology
Background:
- Myeloid cell nuclear differentiation antigen (MNDA) is a nuclear protein specific to the human myelomonocytic lineage.
- MNDA's nuclear localization and chromatin association suggest a role in regulating gene expression during monocyte/macrophage differentiation.
- MNDA interacts with nuclear proteins like nucleolin (C23) and nucleophosmin (NPM/B23).
Purpose of the Study:
- To investigate the interaction between MNDA and NPM in the context of leukemia-associated chromosomal translocations.
- To identify the specific region of NPM responsible for MNDA binding in NPM fusion proteins.
Main Methods:
- In vitro binding assays were employed to test MNDA interactions with NPM and its fusion proteins.
- Co-immunoprecipitation was used to confirm MNDA-NPM binding.
- Analysis of NPM-ALK and NPM-MLF1 fusion proteins derived from specific translocations.
Main Results:
- MNDA did not bind the NPM-ALK fusion protein (t(2;5)) containing NPM residues 1-117.
- MNDA bound the NPM-MLF1 fusion protein (t(3;5)) containing NPM residues 1-175.
- An additional 58 amino acids (residues 117-175) in NPM are crucial for MNDA binding, containing a nuclear localization signal.
Conclusions:
- The N-terminal region of NPM, specifically residues 117-175, mediates MNDA binding in NPM fusion proteins.
- This interaction is relevant to understanding the molecular mechanisms in certain leukemias involving NPM translocations.
- Differential MNDA binding to NPM fusion proteins may influence cellular localization and function.