Scaffold functions of 14-3-3 adaptors in B cell immunoglobulin class switch DNA recombination (IRC3P.472)

Abstract

Abstract Immunoglobulin (Ig) class switch DNA recombination (CSR) crucially diversifies antibody biological effector functions. CSR involves the induction of activation-induced cytidine deaminase (AID) expression and targeting to switch (S) regions by 14-3-3 adaptors. We hypothesized that 14-3-3 adaptors function as scaffolds to stabilize CSR elements on S regions. Here, we demonstrate that all seven 14-3-3 adaptors (β, ε, γ, η, σ, τ and ζ), directly interacted with AID, PKA-Cα (catalytic subunit) and PKA-RIα (regulatory inhibitory subunit) and uracil DNA glycosylase (Ung). 14-3-3 adaptors, however, did not interact with AIDΔ(180-198) C-terminal truncation-mutant or AIDF193A and AIDL196A point-mutants (which have been shown not to bind to S region DNA and fail to mediate CSR). 14-3-3 adaptors colocalized with AID and replication protein A (RPA) in B cells undergoing CSR. 14-3-3 and AID binding to S region DNA was disrupted by HIV-1 viral protein R (Vpr), which inhibited CSR without altering AID expression. Accordingly, we demonstrate that 14-3-3 directly interacted with Vpr, which in turn, also interact with AID, PKA-Cα and Ung. Thus, we describe that 14-3-3 adaptors play important scaffold functions and nucleate the assembly of CSR factors on S regions. Such assembly can be disrupted by a viral protein, thereby allowing us to hypothesize that small molecule compounds that specifically block 14-3-3 interactions with AID, PKA and/or Ung can be used to inhibit unwanted CSR.