Fig. 8. Two step Rev1/Polζ-dependent TLS. After PCNA monoubiquitination by Rad6/Rad18, an inserter Y-family TLS polymerase replaces a replicative polymerase, Polδ or Polε, and inserts nucleotides across the DNA lesion. The extender TLS polymerase Polζ continues replication past the site of DNA damage.