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Cardiovascular basic helix loop helix factor 1, a novel transcriptional repressor expressed preferentially in the
M T Chin1, K Maemura, S Fukumoto
1Program of Developmental Cardiovascular Biology, Cardiovascular Program of Developmental Cardiovascular Biology, Cardiology Division, Brigham and Women's Hospital, Department of Medicine, Harvard Medical School, Boston, MA 02115, USA.
Insights
Cardiovascular helix-loop-helix factor 1 (CHF1) acts as a transcriptional repressor, inhibiting ARNT/EPAS1 activity. This novel factor is crucial for cardiovascular development, with expression patterns in the heart and vasculature.
Area of Science:
- Cardiovascular Biology
- Molecular Biology
- Developmental Biology
Background:
- Basic helix-loop-helix (bHLH) factors regulate diverse cellular processes.
- Arylhydrocarbon receptor nuclear translocator (ARNT) is a key transcription factor involved in cellular responses.
- Understanding novel cardiovascular regulators is essential for developmental biology.
Purpose of the Study:
- To identify and characterize novel cardiovascular-restricted transcription factors.
- To investigate the role of Cardiovascular helix-loop-helix factor 1 (CHF1) in cardiovascular development.
- To elucidate the interaction between CHF1 and ARNT/EPAS1.
Main Methods:
- Yeast two-hybrid screening for protein interactions.
- Expression pattern analysis during mouse embryonic development.
- In vitro studies of smooth muscle cell differentiation.
- Transfection and electrophoretic mobility shift assays.
Main Results:
- CHF1, a novel bHLH factor, was identified and cloned.
- CHF1 expression is detected early in the developing heart and vasculature.
- CHF1 functions as a transcriptional repressor, inhibiting ARNT/EPAS1-dependent transcription.
- CHF1 expression is induced during smooth muscle cell differentiation.
Conclusions:
- CHF1 is a cardiovascular-restricted transcriptional repressor.
- CHF1 plays a significant role in cardiovascular development.
- CHF1 interacts with and inhibits ARNT/EPAS1 activity.
Abstract:
We have cloned a cardiovascular-restricted basic helix-loop-helix factor that interacts with arylhydrocarbon receptor nuclear translocator (ARNT) in a yeast two-hybrid screen. Cardiovascular helix-loop-helix factor 1 (CHF1) is distantly related to the hairy family of transcriptional repressors. We analyzed its expression pattern during mouse embryo development. At day 8.5, the expression of CHF1 is first detected in the primitive ventricle of the primordial heart tube and persists throughout gestation. In rat hearts, this expression is down-regulated after birth, concurrent with terminal differentiation of cardiomyocytes. In the developing vasculature, CHF1 first appears in the dorsal aorta at day 9.0, which precedes the reported expression of smooth muscle cell markers, and persists into adulthood. In an in vitro system of smooth muscle cell differentiation, CHF1 mRNA was barely detectable in undifferentiated cells but was induced highly in differentiated smooth muscle cells. To determine whether CHF1 might affect the function of ARNT, we performed transfection studies. Co-transfection of CHF1 inhibited ARNT/EPAS1-dependent transcription by 85%, and this inhibition is dose-dependent. In electrophoretic mobility studies, CHF1 inhibited the binding of the ARNT/EPAS1 heterodimer to its target site. Our data suggest that CHF1 functions as a transcriptional repressor and may play an important role in cardiovascular development.