van Dam, T. P. | bioRxiv Science

bioRxiv2026

AID Shapes Proliferation and Cell-of-Origin-associated Transcriptional Programs in Diffuse Large B-cell Lymphoma

Activation-induced cytidine deaminase (AID), which is essential for antibody diversification, exhibits elevated expression in the activated B-cell-like (ABC) subtype of diffuse large B-cell lymphoma (DLBCL). Here, we demonstrate that AID modulates transcriptional programs linked to cell cycle progression, proliferation, and DLBCL subtype identity. AID loss in ABC-type DLBCL cell lines negatively impacts MYC and E2F pathway activity, while AID re-expression restores activity, establishing a causal link. Consequently, loss of AID delays G1/S cell cycle transition and reduces proliferation. In addition, AID expression skews transcriptional programs towards ABC-type DLBCL in cell lines. In agreement, AID expression correlates with ABC-type gene expression in primary DLBCL patient samples. Moreover, AID overexpression resulted in increased IRF4 protein levels, and enhanced NF-{kappa}B activity, supporting AIDs role in reinforcing the ABC-type identity. Shared enrichment of the IRF4 co-factor BATF in AID-high tumors of both ABC- and GCB-subtypes points towards a common mechanism driving subtype skewing. These findings underscore a broader role for AID in DLBCL pathogenesis, establishing AID as a key regulator of transcriptional programs linked to cell cycle progression and DLBCL subtype.

cancer biology↗

bioRxiv2020

DNA polymerase β prevents AID-instigated mutagenic non-canonical mismatch DNA repair

In B cells, the error-prone repair of activation-induced cytidine deaminase (AID)-induced lesions in immunoglobulin variable genes cause somatic hypermutation (SHM) of antibody genes. Due to clonal selection in the germinal centers (GC) this active mutation process provides the molecular basis for antibody affinity maturation. AID deaminates cytosine (C) to create uracil (U) in DNA. Typically, the short patch base excision repair (spBER) effectively restores genomic U lesions. We here demonstrate that GC B cells actively degrade DNA polymerase {beta} (Pol{beta}), resulting in the inactivation of the gap-filling step of spBER. Consequently, lesions instigated by AID, and likely other base damages, are channeled towards mutagenic non-canonical mismatch repair (mncMMR), responsible for the vast majority of mutations at adenine and thymine (A:T) bases. Apparently, GC B cells prohibit faithful spBER, thereby favoring A:T mutagenesis during SHM. Lastly, our data suggest that the loss of Pol{beta} relates to hypoxia that characterizes the GC microenvironment.

immunology↗