Campbell SJ, Edwards RA, Leung CC, Neculai D, Hodge CD, Dhe-Paganon S, Glover JN

The repair of DNA double strand breaks by Homologous Recombination (HR) relies on the unique topology of the chains formed by K63-ubiquitylation of chromatin to recruit repair factors such as BReast CAncer 1 (BRCA1) to sites of DNA damage. The human RING Finger (RNF) E3 ubiquitin ligases, RNF8 and RNF168, ...

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with the E2 ubiquitin conjugating complex Ubc13/Mms2, perform the majority of K63 ubiquitylation in HR. Here we show that RNF8 dimerizes and binds to Ubc13/Mms2, thereby stimulating formation of K63 ubiquitin chains, while the related RNF168 RING domain is a monomer and does not catalyze K63 poly-ubiquitylation. The crystal structure of the RNF8/Ubc13/Mms2 ternary complex reveals the structural basis for the interaction between Ubc13 and the RNF8 RING, and that an extended RNF8 coiled-coil is responsible for its dimerization. Mutations that disrupt the RNF8-Ubc13 binding surfaces, or that truncate the RNF8 coiled-coil, reduce RNF8-catalyzed ubiquitylation. These findings support the hypothesis that RNF8 is responsible for the initiation of K63-linked ubiquitylation in the DNA damage response, which is subsequently amplified by RNF168.

Date: May. 15, 2012

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