Figure 6.

Model of strand-specific ribonucleotide excision repair in Escherichia coli cells. RNase HII is the major enzyme involved in RER with a particularly important role on the leading strand. In the absence of RNase HII, backup RER pathways are triggered: RER dependent on RNase HI, and under SOS activation conditions, NER. These pathways operate with higher efficiency on the lagging DNA strand. RNase HI can also remove primers synthesized by the primase, and its activity on the lagging strand can indirectly stimulate removal of single ribonucleotides by pol I on this strand.