Phosphorylated CtIP functions as a co-factor of the MRE11-RAD50-NBS1 endonuclease in DNA end resection
To repair a DNA double-strand break (DSB) by homologous recombination (HR), the 5’-terminated strand of the DSB must be resected. The human MRE11-RAD50-NBS1 (MRN) and CtIP proteins were implicated in the initiation of DNA end resection, but the underlying mechanism remained undefined. Here we show that CtIP is a co-factor of the MRE11 endonuclease activity within the MRN complex. This function is absolutely dependent on CtIP phosphorylation that includes the key cyclin-dependent kinase target motif at Thr-847. Unlike in yeast where the Xrs2/NBS1 subunit is dispensable in vitro, NBS1 is absolutely required in the human system. The MRE11 endonuclease in conjunction with RAD50, NBS1 and phosphorylated CtIP preferentially cleaves 5’-terminated DNA strands near DSBs. Our results define the initial step of HR that is particularly relevant for the processing of DSBs bearing protein blocks or secondary DNA structures.
Date: 8 December 2016, 14:00 (Thursday, 9th week, Michaelmas 2016)
Venue: MRC Weatherall Institute of Molecular Medicine, Headington OX3 9DS
Venue Details: Seminar Room
Speaker: Professor Petr Cejka (Institute for Research in Biomedicine (IRB), Bellinzona, Switzerland)
Organising department: Department of Oncology
Organiser: Penny Berry (University of Oxford, Department of Oncology, Weatherall Institute of Molecular Medicine)
Organiser contact email address: penny.berry@oncology.ox.ac.uk
Host: Dr Wojciech Niedzwiedz (WIMM)
Part of: WIMM Occasional Seminars
Booking required?: Not required
Audience: Members of the University only
Editors: Penny Berry, Liz Rose