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Murine Tbx2 contains domains that activate and repress gene transcription
Christian Paxton1, Honghua Zhao, Yvette Chin
1Department of Animal Science, Iowa State University, Ames, IA 50011, USA.
Abstract:
T-box (Tbx) genes represent a phylogenetically conserved family of transcription factors that play important roles during embryonic development. Tbx family members have been shown to either activate or inhibit gene expression. However, little is known about the domains within Tbx proteins responsible for mediating gene transcription. While Tbx2 is known to repress gene expression, the domain(s) within Tbx2 remains poorly defined. Deletion of the carboxy-terminus of Tbx2, which contains a domain that is highly conserved with Tbx3 and ET, which has been demonstrated to contain a repression domain, only minimally diminishes the ability of Tbx2 to repress gene expression. However, in combination with the carboxy-terminal truncation, deletion of the amino acids located amino-terminal to the T-box abolished the ability of Tbx2 to repress gene expression. Both of these domains were capable of repressing gene expression when linked to the GAL4 DNA binding domain. In contrast to these two repression domains, the T-box was capable of weakly activating gene expression depending on the promoter context. Deletion analysis of the T-box suggests that this activation domain is located in the amino-terminal end of the T-box. These results reveal a novel transcription repression domain, confirm the presence of a previously implicated domain, and suggest a novel role for the T-box. Taken together, these results provide the basis for understanding the molecular mechanism whereby Tbx2 regulates gene expression and subsequently controls embryonic development.
Insights
T-box (Tbx) genes regulate embryonic development. Researchers identified novel repression domains in Tbx2, revealing its molecular mechanism for controlling gene expression during development.
Area of Science:
- Developmental Biology
- Molecular Biology
- Genetics
Background:
- T-box (Tbx) genes are crucial transcription factors in embryonic development.
- Tbx proteins can activate or repress gene expression, but the specific domains involved are often unclear.
- Tbx2 is known to repress gene expression, yet its functional domains remain poorly defined.
Purpose of the Study:
- To identify and characterize the specific domains within Tbx2 responsible for mediating gene transcription.
- To elucidate the molecular mechanisms underlying Tbx2's role in regulating gene expression.
- To understand how Tbx2 controls embryonic development.
Main Methods:
- Deletion analysis of Tbx2 protein domains.
- Assays using the GAL4 DNA binding domain to test repression and activation functions.
- Investigating the role of carboxy-terminal and amino-terminal regions, as well as the T-box domain.
Main Results:
- Deletion of the carboxy-terminus of Tbx2 minimally affected its gene repression ability.
- Combining carboxy-terminal truncation with deletion of amino acids N-terminal to the T-box abolished Tbx2's repression.
- Both the carboxy-terminal and the N-terminal regions (outside the T-box) function as repression domains when linked to GAL4.
- The T-box domain itself can weakly activate gene expression, with the activation domain located at its N-terminus.
Conclusions:
- Tbx2 possesses at least two distinct transcription repression domains.
- A novel transcription repression domain was identified in Tbx2.
- The T-box domain has a previously unrecognized role in gene activation.
- These findings provide a molecular basis for Tbx2's function in embryonic development.