Table 4.

Effects of siRNA knockdown of Polλ on mutation frequencies and nucleotides inserted opposite a cis-syn TT dimer or a (6-4) TT photoproduct carried on the leading or lagging strand DNA template in nucleotide excision repair–defective XPA human fibroblasts.

DNA lesionLesion containing DNA strandsiRNANucleotide insertedMutation frequency %
# of Kan+ blue colonies sequencedAGCTOthera
cis-syn TT dimerLeadingNC334 (7)b3274 (3′ T)c2 (5′ T)2.1
1 (3′ T)
Polλ402 (3)3993 (3′ T)0.7
LaggingNC375 (10)3654 (5′ T)1 (5′ T)2.7
2 (3′ T)3 (3′ T)
Polλ318 (2)3162 (3′ T)0.6
(6-4) TT photoproductLeadingNC342 (8)3343 (5′ T)2 (3′ T)12.3
2 (3′ T)
Polλ347 (15)3321 (5′ T)6 (3′ T)4 (3′ T)24.3
2 (3′ T)
LaggingNC384 (7)3772 (5′ T)2 (3′ T)11.8
2 (3′ T)
Polλ320 (16)3044 (5′ T)4 (3′ T)3 (3′ T)25.0
3 (3′ T)
  • a Mutations at the flanking site.

  • b Numbers of colonies where TLS occurred by insertion of a nucleotide other than an A are shown in parenthesis.

  • c The site where mutation occurred, 3′T or 5′T of the UV lesion is indicated in parenthesis.