Figure 4 : Simplified overviews of non-homologous end joining (NHEJ) and
homologous recombination (HR) repair
(modified Illustration of [30]).

(A) In HR repair, the MRN complex consisting of the proteins Mre11, Rad50 and Nbs1, binds to
both ends of the break which are subsequently processed into 3’ ssDNA. The ssDNA end is
coated with DNA replication protein A (RPA), after which RAD51 nucleoprotein filament is
assembled, which replaces the RPA-coated ssDNA ends, performs homology sequence searching,
mediates strand invasion and promotes DNA strand exchange. The recombining partner strands
are seperated by the enzyme Resolvase.
(B) During NHEJ the first proteins to bind to the break is the Ku-heterodimer, serving as a docking
station for additional proteins. The Artemis/DNA-PKcs complex excises any damaged bases on
either end of the break. Polymerases μ and λ then synthesize new DNA and XLF, XRCC4 and Ligase
IV seal the seams.

Peters et al.Oncology Discovery  2014 2:3DOI : 10.7243/2052-6199-2-3