ORIGIN  ACTIVATION

 

The DNA untwisting function in MCM is switched on upon ATP binding and the concomitant recruitment of helicase activators GINS/Cdc45 (together forming the CMG). We want to use cryo-EM to establish whether DNA untwisting involves impairing of nitrogenous bases and whether both strands remain trapped inside the MCM ring at this stage. Recruitment of firing factor Mcm10 is understood to cause an isomerization in the CMG helicase with opening of MCM and ejection of the lagging-strand template. At this stage CMG can start hydrolyzing ATP and translocate on the leading-strand template. We want to understand strand ejection and ATPase driven DNA translocation using time-resolved cryo-EM.

Relevant papers

Goswami P, Abid Ali F, Douglas M, Locke J, Purkiss A, Janska A, Eickhoff P, Early A, Nans A, Cheung A, Diffley JF, Costa A. CRYO-EM STRUCTURE OF DNA-CMG-POL EPSILON ELUCIDATES THE ROLES OF ESSENTIAL, NON-CATALYTIC POLYMERASE MODULES IN THE EUKARYOTIC REPLISOME. Nature Commun. In press.

Douglas ME, Abid Ali F, Costa A, Diffley JF. THE MECHANISM OF EUKARYOTIC CMG HELICASE ACTIVATION. Nature, 2018 Mar 8;555(7695):265-268 (rated ‘exceptional’ on f1000.com).

Abid Ali F, Costa A. THE MCM HELICASE MOTOR OF THE EUKARYOTIC REPLISOME. J Mol Biol. 2016 May 8;428(9 Pt B):1822-32.

Abid Ali F, Renault L, Gannon J, Gahlon HL, Kotecha A, Zhou JC, Rueda D, Costa A., CRYO-EM STRUCTURES OF THE EUKARYOTIC REPLICATIVE HELICASE BOUND TO A TRANSLOCATION SUBSTRATE. Nat. commun., 2016 Feb 18;7:10708.


Zhou JC, Costa A. PREPARING TO UNWIND. Elife. 2014 Apr 1;3:e02618.

Costa A*, Renault L, Swuec P, Petojevic T, Pesavento JJ, Ilves I, MacLellan-Gibson K, Fleck RA, Botchan MR*, Berger JM*. DNA BINDING POLARITY, DIMERIZATION, AND ATPASE RING REMODELING IN THE CMG HELICASE OF THE EUKARYOTIC REPLISOME. Elife. 2014 Aug 12;3:e03273. (*corresponding authors, three stars on f1000.com).

 

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