Fig. 2.

Consequences of cytosine deaminations at the replication fork. Deamination of three cytosines and the consequences of processing of the resulting uracils through replication or repair pathways are shown. Copying of the LGST is discontinuous, and two Okazaki fragments are shown. The open arrowhead represents the helicase DnaB and is pointed in the overall direction of replication. Class 1 and class 2 refer to two classes of uracils generated through cytosine deamination and have different biochemical consequences. The class 2 uracils are likely to be replaced with cytosines through BER, whereas the class 1 uracils lead to C:G to T:A mutations or double-strand (DS) breaks. The latter may be repaired through recombinational repair or result in the collapse of the replication fork.