UMMS Affiliation

Program in Systems Biology; Department of Biochemistry and Molecular Pharmacology

Date

10-25-2016

Document Type

Article

Disciplines

Biochemistry | Computational Biology | Molecular Biology | Structural Biology | Systems Biology

Abstract

The transcription factor T-bet (Tbox protein expressed in T cells) is one of the master regulators of both the innate and adaptive immune responses. It plays a central role in T-cell lineage commitment, where it controls the TH1 response, and in gene regulation in plasma B-cells and dendritic cells. T-bet is a member of the Tbox family of transcription factors; however, T-bet coordinately regulates the expression of many more genes than other Tbox proteins. A central unresolved question is how T-bet is able to simultaneously recognize distant Tbox binding sites, which may be located thousands of base pairs away. We have determined the crystal structure of the Tbox DNA binding domain (DBD) of T-bet in complex with a palindromic DNA. The structure shows a quaternary structure in which the T-bet dimer has its DNA binding regions splayed far apart, making it impossible for a single dimer to bind both sites of the DNA palindrome. In contrast to most other Tbox proteins, a single T-bet DBD dimer binds simultaneously to identical half-sites on two independent DNA. A fluorescence-based assay confirms that T-bet dimers are able to bring two independent DNA molecules into close juxtaposition. Furthermore, chromosome conformation capture assays confirm that T-bet functions in the direct formation of chromatin loops in vitro and in vivo. The data are consistent with a looping/synapsing model for transcriptional regulation by T-bet in which a single dimer of the transcription factor can recognize and coalesce distinct genetic elements, either a promoter plus a distant regulatory element, or promoters on two different genes.

Rights and Permissions

Citation: Proc Natl Acad Sci U S A. 2016 Oct 25;113(43):E6572-E6581. Epub 2016 Oct 10. Link to article on publisher's site. Freely available online through the PNAS open access option.

Related Resources

Link to Article in PubMed

Keywords

DNA looping, T-bet, crystal structure, master regulator, transcriptional regulation

Journal Title

Proceedings of the National Academy of Sciences of the United States of America

PubMed ID

27791029

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