Structure of the Arabidopsis TOPLESS corepressor provides insight into the evolution of transcriptional repression

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Martin-Arevalillo, Raquel | Nanao, Max H. | Larrieu, Antoine | Vinos-Poyo, Thomas | Mast, David | Galvan-Ampudia, Carlos | Brunoud, Geraldine | Vernoux, Teva | Dumas, Renaud | Parcy, François

Edité par CCSD ; National Academy of Sciences -

Transcriptional repression involves a class of proteins called corepressors that link transcription factors to chromatin remodeling complexes. In plants such as Arabidopsis thaliana, the most prominent corepressor is TOPLESS (TPL), which plays a key role in hormone signaling and development. Here we present the crystallographic structure of the Arabidopsis TPL N-terminal region comprising the LisH and CTLH (C-terminal to LisH) domains and a newly identified third region, which corresponds to a CRA domain. Comparing the structure of TPL with the mammalian TBL1, which shares a similar domain structure and performs a parallel corepressor function, revealed that the plant TPLs have evolved a new tetramerization interface and unique and highly conserved surface for interaction with repressors. Using site-directed mutagenesis, we validated those surfaces in vitro and in vivo and showed that TPL tetramerization and repressor binding are interdependent. Our results illustrate how evolution used a common set of protein domains to create a diversity of corepressors, achieving similar properties with different molecular solutions.

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