Translesion synthesis (TLS) allows the DNA replication machinery to bypass an unrepaired DNA damage site using special polymerases called TLS polymerases (Fischhaber and Friedberg, 2005). When compared with the replicative polymerases, TLS polymerases have comparatively large active sites to incorporate the base opposite the damaged DNA and low fidelity to ensure progression of synthesis using the damaged template (McCulloch and Kunkel, 2008). Though TLS rescues the cells from the collapse of the replication fork, the bypass of the lesions can be a potential cause for the mutation generation (Wang, 2001). Therefore, tight regulation of the TLS polymerases is extremely important. Recent research shows that Rev1 can act as a regulator and defines distinct mechanism for TLS when compared with PCNA (Edmunds et al., 2008; Hendel et al., 2011). In comparison to other TLS polymerases, the catalytic function of Rev1 is not required for the mutagenic DNA damage tolerance (Lawrence, 2004; Prakash et al., 2005). Instead the C-terminus of Rev1, which interacts with TLS polymerases κ, η, ι and ζ (consisting of Rev3 and Rev7) in eukaryotes (Murakumo et al., 2001; Guo et al., 2003; Ohashi et al., 2004), is reported to be required for the DNA damage tolerance (D'Souza et al., 2008). Therefore, the understanding of the molecular basis of the C-terminus of Rev1 and its related interactions with TLS polymerases is important in comprehending the mechanism of the TLS polymerases regulation. Here, we report the first structural studies on the TLS polymerase-interacting domain of human Rev11156–1251 [hRev1-polymerase-interacting domain (PID)] and its interactions with TLS polymerases κ, η, ι and ζ.