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Cell type-dependent transactivation or repression of mesoderm-restricted basic helix-loop-helix protein,
M Miyagishi1, M Hatta, T Ohshima
1Center for Institute of Applied Biochemistry, Institute of Applied Biochemistry, University of Tsukuba, Ibaraki, Japan.
Molecular and Cellular Biochemistry
|May 23, 2000
Summary
Basic helix-loop-helix (bHLH) proteins regulate cell growth. This study characterizes POD-1/Capsulin, revealing its dual transactivation and repression roles and identifying ITF-2 as a partner.
Area of Science:
- Molecular biology
- Genetics
- Cell biology
Background:
- Basic helix-loop-helix (bHLH) proteins are crucial transcription factors regulating cell growth and differentiation.
- POD-1/Capsulin is a mesoderm-specific bHLH protein with incompletely understood functions.
Purpose of the Study:
- To characterize the molecular properties of the bHLH protein POD-1/Capsulin.
- To investigate its transactivation and repression activities in mammalian cells.
- To identify potential interacting partners of POD-1/Capsulin.
Main Methods:
- Gal4 fusion system for transactivation assays in six mammalian cell lines.
- Domain mapping to identify regions responsible for transactivation and repression.
- Yeast two-hybrid screening using a human kidney cDNA library.
Main Results:
- POD-1/Capsulin exhibited transactivation in HT1080 and HeLa cells, but repression in HepG2 cells.
- The C-terminal domain is essential for transactivation, while both N-terminal and C-terminal domains contribute to repression.
- ITF-2, a class A bHLH protein, was identified as a potential heterodimeric partner.
Conclusions:
- POD-1/Capsulin possesses context-dependent regulatory functions (transactivation/repression).
- Specific domains of POD-1/Capsulin mediate its distinct activities.
- ITF-2 is a potential functional partner, suggesting heterodimerization in vivo.