Error-Prone Translesion DNA Synthesis by Escherichia coli DNA Polymerase IV (DinB) on Templates Containing 1,2-dihydro-2-oxoadenine

Table 3

Frequencies of mutations to Lac⁺ in E. coli CC101~CC106 strains with overexpressed dinB gene after incubation with hydrogen peroxide.

Strain	Base substitution	Plasmid	Mutants/10^8 viable cells		Increase in mutation frequency (b−a)	Fold increase in mutation frequency (b/a)
			No H2O^a2	10 mM H2O^b2
CC101	A:T→C:G	pDinB	1.9	4.2	2.3	2.2
		pDinB003	1.5	1.8	0.3	1.2
CC105	A:T→T:A	pDinB	3.6	4.4	0.8	1.2
		pDinB003	1.5	3.4	1.9	2.3
CC106	A:T→G:C	pDinB	1.1	11.6	10.5	10.5
		pDinB003	0.8	1.8	1.0	2.3

E. coli CC101, CC105, and CC106 transformed with a plasmid wild-type plasmid (pDinB) and a mutant Pol IV (pDinB003) in stationary phase were incubated at 37^∘C with 1 mM of IPTG for 5 hr, followed by the treatment 10 mM H₂O₂ for 1 hr. The mutant Pol IV (DinB003) was generated by site-specific mutagenesis replacing aspartic acid in position 103 with aspargine [4]. The mutation frequency was expressed as number of mutants/10⁸ viable cells.