Immunoglobulin (Ig) class switch DNA recombination (CSR) plays a critical role in the maturation of the immune response by diversifying the biological effector functions of antibodies. CSR is initiated by activation-induced cytidine deaminase (AID)-mediated deoxycytosine (dC) deamination, yielding deoxyuridine (dU), and dU glycosylation by uracil DNA glycosylase (Ung) in Ig switch (S) region DNA. Translesion DNA synthesis (TLS) polymerases, such as Rev1, play important roles in somatic hypermutation (SHM), but their role in CSR has not been defined. We found that Rev1 directly interacts with Ung to recruit it to S region DNA and enhance dU glycosylation for CSR. Rev1 targets S regions undergoing CSR in an AID-dependent and Ung-independent fashion. Ung recruitment to S regions, DNA-dU glycosylation and CSR are reduced in Rev1-/- B cells. Together with a mutation spectrum in S region DNA that is similar to that of Ung-/- B cells, our findings suggest that Rev1 operates in the same pathway as Ung during CSR, as emphasized by further decreased CSR in Rev1-/- Msh2-/- B cells. Rescue of CSR by a catalytically inactive Rev1 mutant in Rev1-/- B cells shows that the role of Rev1 in CSR is mediated by Rev1’s scaffolding function, not its enzymatic function. Thus, we describe a novel and important scaffolding function for Rev1 in CSR, which together with its known enzymatic function in SHM highlights a central role of this TLS polymerase in the maturation of the antibody response.
- Copyright © 2013 by The American Association of Immunologists, Inc.