PT  - JOURNAL ARTICLE
AU  - Giulia Fonti
AU  - Maria J. Marcaida
AU  - Louise C. Bryan
AU  - Sylvain Traeger
AU  - Alexandra S. Kalantzi
AU  - Pierre-Yves J.L. Helleboid
AU  - Davide Demurtas
AU  - Mark D. Tully
AU  - Sergei Grudinin
AU  - Didier Trono
AU  - Beat Fierz
AU  - Matteo Dal Peraro
TI  - KAP1 is an antiparallel dimer with a natively functional asymmetry
AID  - 10.1101/553511
DP  - 2019 Jan 01
TA  - bioRxiv
PG  - 553511
4099  - http://biorxiv.org/content/early/2019/02/19/553511.short
4100  - http://biorxiv.org/content/early/2019/02/19/553511.full
AB  - KAP1 (KRAB-domain associated protein 1) plays a fundamental role in regulating gene expression in mammalian cells by recruiting different transcription factors and altering the chromatin state. In doing so, KAP1 acts both as a platform for macromolecular interactions and as an E3 SUMO ligase. This work sheds light on the overall organization of the full-length protein combining solution scattering diffraction data, integrative modeling and single-molecule experiments. We show that KAP1 is an elongated antiparallel dimer with a native asymmetry at the C-terminal domain. This conformation supports our finding that the RING domain contributes to KAP1 auto-SUMOylation. Importantly, this intrinsic asymmetry has key functional implications for the KAP1 network of interactions, as the heterochromatin protein 1 (HP1) occupies only one of the two putative HP1 binding sites on the KAP1 dimer, resulting in an unexpected stoichiometry, even in the context of chromatin fibers.