Structure of KAP1 tripartite motif identifies molecular interfaces required for retroelement silencing.
Proceedings of the National Academy of Sciences of the United States of America
National Academy of Sciences
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Stoll, G. A., Oda, S., Chong, Z., Yu, M., McLaughlin, S. H., & Modis, Y. (2019). Structure of KAP1 tripartite motif identifies molecular interfaces required for retroelement silencing.. Proceedings of the National Academy of Sciences of the United States of America, 116 (30), 15042-15051. https://doi.org/10.1073/pnas.1901318116
Transcription of transposable elements is tightly regulated to prevent genome damage. KRAB domain-containing zinc finger proteins (KRAB-ZFPs) and KRAB-associated protein 1 (KAP1/TRIM28) play a key role in regulating retrotransposons. KRAB-ZFPs recognize specific retrotransposon sequences and recruit KAP1, inducing the assembly of an epigenetic silencing complex, with chromatin remodeling activities that repress transcription of the targeted retrotransposon and adjacent genes. Our biophysical and structural data show that the tripartite motif (TRIM) of KAP1 forms antiparallel dimers, which further assemble into tetramers and higher-order oligomers in a concentration-dependent manner. Structure-based mutations in the B-box 1 domain prevent higher-order oligomerization without significant loss of retrotransposon silencing activity, indicating that, in contrast to other TRIM-family proteins, self-assembly is not essential for KAP1 function. The crystal structure of the KAP1 TRIM dimer identifies the KRAB domain binding site, in the coiled-coil domain near the dyad. Mutations at this site abolished KRAB binding and transcriptional silencing activity of KAP1. This work identifies the interaction interfaces in the KAP1 TRIM responsible for self-association and KRAB binding and establishes their role in retrotransposon silencing.
Chromatin, Humans, Escherichia coli, Recombinant Proteins, Repressor Proteins, Retroelements, Crystallography, X-Ray, Cloning, Molecular, Sequence Alignment, Chromatin Assembly and Disassembly, Gene Expression, Transcription, Genetic, Epigenesis, Genetic, Gene Silencing, Binding Sites, Amino Acid Sequence, Protein Binding, Sequence Homology, Amino Acid, Genetic Vectors, Models, Molecular, Protein Interaction Domains and Motifs, Protein Multimerization, Protein Conformation, alpha-Helical, Protein Conformation, beta-Strand, Tripartite Motif-Containing Protein 28
This work was supported by Wellcome Trust through Senior Research Fellowship 101908/Z/13/Z and PhD Studentship 205833/Z/16/Z.
Wellcome Trust (101908/Z/13/Z)
External DOI: https://doi.org/10.1073/pnas.1901318116
This record's URL: https://www.repository.cam.ac.uk/handle/1810/293736
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