UNG shapes the specificity of AID-induced somatic hypermutation.
Secondary diversification of antibodies through somatic hypermutation (SHM) and class switch recombination (CSR) is a critical component of the immune response. Activation-induced deaminase (AID) initiates both processes by deaminating cytosine residues in immunoglobulin genes. The resulting U:G mismatch can be processed by alternative pathways to give rise to a mutation (SHM) or a DNA double-strand break (CSR). Central to this processing is the activity of uracil-N-glycosylase (UNG), an enzyme normally involved in error-free base excision repair. We used next generation sequencing to analyze the contribution of UNG to the resolution of AID-induced lesions. Loss- and gain-of-function experiments showed that UNG activity can promote both error-prone and high fidelity repair of U:G lesions. Unexpectedly, the balance between these alternative outcomes was influenced by the sequence context of the deaminated cytosine, with individual hotspots exhibiting higher susceptibility to UNG-triggered error-free or error-prone resolution. These results reveal UNG as a new molecular layer that shapes the specificity of AID-induced mutations and may provide new insights into the role of AID in cancer development.
B Cell Biology Laboratory, Centro Nacional de Investigaciones Cardiovasculares (CNIC), 28029 Madrid, Spain.
Pablo
P
Pérez-Durán
Laura
L
Belver
Virginia G
VG
de Yébenes
Pilar
P
Delgado
David G
DG
Pisano
Almudena R
AR
Ramiro
D000818:Animals; D001402:B-Lymphocytes / Q000166:cytology / Q000378:metabolism; D002478:Cells, Cultured; D003564:Cytidine Deaminase / Q000235:genetics / Q000378:metabolism*; D053903:DNA Breaks, Double-Stranded; D004252:DNA Mutational Analysis / Q000379:methods; D004260:DNA Repair / Q000235:genetics; D005434:Flow Cytometry; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D009154:Mutation; D041681:NIH 3T3 Cells; D027041:Somatic Hypermutation, Immunoglobulin; D014162:Transfection; D051981:Uracil-DNA Glycosidase / Q000235:genetics / Q000378:metabolism*; D000098830:AICDA (Activation-Induced Cytidine Deaminase)
D008164:Luminescent Proteins; C413663:fluorescent protein 583; D049452:Green Fluorescent Proteins; D051981:Uracil-DNA Glycosidase; D000098830:AICDA (Activation-Induced Cytidine Deaminase); D003564:Cytidine Deaminase