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Microphthalmia-associated transcription factor interacts with LEF-1, a mediator of Wnt signaling
Ken-ichi Yasumoto1, Kazuhisa Takeda, Hideo Saito
1Department of Molecular Biology and Applied Physiology, Tohoku University School of Medicine, Aoba-ku, Sendai, Miyagi 980-8575, Japan.
Abstract:
Wnt signals regulate differentiation of neural crest cells through the beta-catenin associated with a nuclear mediator of the lymphoid-enhancing factor 1 (LEF-1)/T-cell factors (TCFs) family. Here we show the interaction between the basic helix-loop-helix and leucine-zipper region of microphthalmia-associated transcription factor (MITF) and LEF-1. MITF is essential for melanocyte differentiation and its heterozygous mutations cause auditory-pigmentary syndromes. Functional cooperation of MITF with LEF-1 results in synergistic transactivation of the dopachrome tautomerase (DCT) gene promoter, an early melanoblast marker. This activation depends on the separate cis-acting elements, which are also responsible for the induction of the DCT promoter by lithium chloride that mimics Wnt signaling. beta-catenin is required for efficient transactivation, but dispensable for the interaction between MITF and LEF-1. The interaction with MITF is unique to LEF-1 and not detectable with TCF-1. LEF-1 also cooperates with the MITF-related proteins, such as TFE3, to transactivate the DCT promoter. This study therefore suggests that the MITF/TFE3 family is a new class of nuclear modulators for LEF-1, which may ensure efficient propagation of Wnt signals in many types of cells.
Insights
Microphthalmia-associated transcription factor (MITF) interacts with lymphoid-enhancing factor 1 (LEF-1) to regulate melanocyte differentiation. This interaction enhances Wnt signaling, impacting neural crest cell development.
Area of Science:
- Cell Biology
- Developmental Biology
- Genetics
Background:
- Wnt signaling pathways are crucial for neural crest cell differentiation.
- Lymphoid-enhancing factor 1 (LEF-1)/T-cell factors (TCFs) are key nuclear mediators in Wnt signaling.
- Microphthalmia-associated transcription factor (MITF) is vital for melanocyte development and linked to pigmentary syndromes.
Purpose of the Study:
- To investigate the interaction between MITF and LEF-1.
- To elucidate the functional cooperation between MITF and LEF-1 in gene transactivation.
- To determine the role of this interaction in Wnt signaling and melanocyte differentiation.
Main Methods:
- Co-immunoprecipitation to demonstrate protein-protein interactions.
- Reporter gene assays to measure synergistic transactivation of the dopachrome tautomerase (DCT) promoter.
- Analysis of cis-acting elements involved in DCT promoter regulation.
- Mutation analysis to assess the role of beta-catenin.
Main Results:
- MITF directly interacts with LEF-1 through its basic helix-loop-helix and leucine-zipper regions.
- MITF and LEF-1 synergistically transactivate the DCT gene promoter, an early melanoblast marker.
- This activation is dependent on specific cis-acting elements and mimicked by Wnt signaling activators like lithium chloride.
- Beta-catenin is required for efficient transactivation but not for the MITF-LEF-1 interaction.
- The interaction is specific to LEF-1 and not observed with TCF-1.
- MITF-related proteins, such as TFE3, also cooperate with LEF-1.
Conclusions:
- The MITF/TFE3 family represents a novel class of nuclear modulators for LEF-1.
- This interaction facilitates efficient Wnt signal propagation in various cell types.
- The findings provide new insights into the molecular mechanisms regulating melanocyte differentiation and Wnt signaling.