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Published on: August 20, 2019
TBX3 and its splice variant TBX3 + exon 2a are functionally similar
Willem M H Hoogaars1, Phil Barnett, Mercedes Rodriguez
1Center for Heart Failure Research, Academic Medical Centre, Amsterdam, The Netherlands.
Pigment Cell & Melanoma Research
|May 1, 2008
Summary
Tbx3 and its splice variant Tbx3+2a are functionally equivalent transcriptional repressors. Both bind DNA and regulate genes involved in heart development and cancer, suggesting Tbx3 also acts as an anti-senescence factor in melanoma.
Area of Science:
- Developmental biology
- Molecular oncology
- Gene regulation
Background:
- Tbx3 is a T-box transcription factor crucial for heart development, specifically sinoatrial node formation.
- Both TBX3 and TBX2 genes are implicated in cancer, potentially due to their anti-senescence properties by suppressing p14(Arf) and p21(CIP) expression.
- The Tbx3+2a splice variant, with an insertion in the DNA-binding domain, was previously thought to lack DNA-binding ability.
Purpose of the Study:
- To investigate the DNA-binding ability and functional equivalence of Tbx3 and its splice variant Tbx3+2a.
- To determine if Tbx3+2a acts as a functional antagonist to Tbx3.
- To explore the roles of Tbx3 and Tbx3+2a in gene regulation relevant to cardiac development and cancer.
Main Methods:
- Electrophoretic mobility shift assays (EMSAs) to assess DNA-binding.
- Reporter gene assays to evaluate promoter activity regulation.
- Co-immunoprecipitation to study protein interactions.
- In vivo studies using ectopic expression in mouse embryonic hearts.
Main Results:
- Both Tbx3 and Tbx3+2a bind the T-element, p21(CIP1) promoter, and Nppa cardiac gene promoter.
- Both isoforms function as repressors of p21(CIP1) and Nppa promoter activity.
- Tbx3 and Tbx3+2a interact with the homeobox factor Nkx2-5.
- Ectopic expression of both isoforms in mouse embryos suppressed cardiac chamber formation and key cardiac marker genes (Nppa, Cx40).
Conclusions:
- Tbx3 and Tbx3+2a are functionally equivalent in the studied assays.
- Tbx3+2a possesses DNA-binding ability and acts as a repressor, contrary to previous reports.
- Tbx3, similar to Tbx2, may function as an anti-senescence factor in melanoma.
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