SAMHD1 enhances immunoglobulin hypermutation by promoting transversion mutation.
basic_science · Level V
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- Record sourced from PubMed, PMID 29669924.
- Also identified by DOI 10.1073/pnas.1719771115 and PMC identifier 5948975.
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Abstract
Activation-induced deaminase (AID) initiates hypermutation of <i>Ig</i> genes in activated B cells by converting C:G into U:G base pairs. G<sub>1</sub>-phase variants of uracil base excision repair (BER) and mismatch repair (MMR) then deploy translesion polymerases including REV1 and Pol η, which exacerbates mutation. dNTP paucity may contribute to hypermutation, because dNTP levels are reduced in G<sub>1</sub> phase to inhibit viral replication. To derestrict G<sub>1</sub>-phase dNTP supply, we CRISPR-inactivated SAMHD1 (which degrades dNTPs) in germinal center B cells. <i>Samhd1</i> inactivation increased B cell virus susceptibility, increased transition mutations at C:G base pairs, and substantially decreased transversion mutations at A:T and C:G base pairs in both strands. We conclude that SAMHD1's restriction of dNTP supply enhances AID's mutagenicity and that the evolution of <i>Ig</i> hypermutation included the repurposing of antiviral mechanisms based on dNTP starvation.
Medical subject headings
- B-Lymphocytes
- G1 Phase
- Lymphocyte Activation
- Mutation
- SAM Domain and HD Domain-Containing Protein 1
- Somatic Hypermutation, Immunoglobulin