MSH2–MSH6 stimulates DNA polymerase η, suggesting a role for A:T mutations in antibody genes

Wilson, Teresa; Vaisman, Alexandra; Martomo, Stella A.; SULLIVAN, P; Lan, Li; Hanaoka, Fumio; Yasui, Akira; Woodgate, Roger; Gearhart, Patricia J.

doi:10.1084/jem.20042066

Cited by 180 publications

(168 citation statements)

References 62 publications

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“…The increasing reductions of A,T mutations are slightly parallel with increasing proportions of known hotspots of the error-prone polymerase (WA, and its inverse TW) (34). This may suggest that pol is not the major polymerase interacting with MMR in SHM in the absence of Ung, although it has been reported that pol can interact with Msh2/Msh6 (35).…”

Section: Discussionmentioning

confidence: 76%

Somatic Hypermutation and Class Switch Recombination in Msh6−/−Ung−/− Double-Knockout Mice

Sui¹,

Tanaka²,

Bozek³

et al. 2006

The Journal of Immunology

116

123

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Somatic hypermutation (SHM) and class switch recombination (CSR) are initiated by activation-induced cytosine deaminase (AID). The uracil, and potentially neighboring bases, are processed by error-prone base excision repair and mismatch repair. Deficiencies in Ung, Msh2, or Msh6 affect SHM and CSR. To determine whether Msh2/Msh6 complexes which recognize single-base mismatches and loops were the only mismatch-recognition complexes required for SHM and CSR, we analyzed these processes in Msh6−/−Ung−/− mice. SHM and CSR were affected in the same degree and fashion as in Msh2−/−Ung−/− mice; mutations were mostly C,G transitions and CSR was greatly reduced, making Msh2/Msh3 contributions unlikely. Inactivating Ung alone reduced mutations from A and T, suggesting that, depending on the DNA sequence, varying proportions of A,T mutations arise by error-prone long-patch base excision repair. Further, in Msh6−/−Ung−/− mice the 5′ end and the 3′ region of Ig genes was spared from mutations as in wild-type mice, confirming that AID does not act in these regions. Finally, because in the absence of both Ung and Msh6, transition mutations from C and G likely are “footprints” of AID, the data show that the activity of AID is restricted drastically in vivo compared with AID in cell-free assays.

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Section: Discussionmentioning

confidence: 76%

Somatic Hypermutation and Class Switch Recombination in Msh6−/−Ung−/− Double-Knockout Mice

Sui¹,

Tanaka²,

Bozek³

et al. 2006

The Journal of Immunology

116

123

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“…The dA/dT-biased mutations in the transfected V H 1-DXP′ 1-J H 5 DNA suggest that Msh2, recruited by specific but yet identified features of V H 1-DXP′1-J H 5, triggers MMR in Phase 2. Translesion DNA polymerases, pol η in particular, would be recruited by Msh2 to insert mismatches mostly at dA/dT Indeed, pol η physically interacts with Msh2 (Wilson et al, 2005) and displays a preference in inserting transition at dA/dT (Rogozin et al, 2001;Zeng et al, 2001;Delbos et al, 2005;Martomo et al, 2005), consistent with the predominant dA/dT transitions in the V H 1-DXP′ 1-J H 5 DNA. In turn, the newly generated mismatches at dA/dT could trigger additional rounds of MMR, thereby introducing more mutations at dA/dT residues.…”

Section: Discussionmentioning

confidence: 91%

Biased dA/dT somatic hypermutation as regulated by the heavy chain intronic iEμ enhancer and 3′Eα enhancers in human lymphoblastoid B cells

Komori

et al. 2006

Molecular Immunology

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Somatic hypermutation (SHM) in immunoglobulin gene (Ig) variable (V) regions is critical for the maturation of the antibody response. It is dependent on the expression of activation-induced cytidine deaminase (AID) and translesion DNA polymerases in germinal center B cells as well as Ig V transcription, as regulated by the Ig heavy chain (H) intronic enhancer (iEµ) and the 3′ enhancer (3′Eα) region. We analyzed the role of these cis elements in SHM by stably transfecting Ramos human lymphoblastoid B cells with a rearranged human IgH chain VD (diversity) J (joining) DNA construct containing a V H promoter at the 5′ end and C H 1 and C H 2 exons of Cγ1 at the 3′ end. In this construct, mutations preferentially targeted dA/dT basepairs in the RGYW/ WRCY hotspot. Most of the dA/dT mutations and accompanying dC/dG mutations were transitions. Deletion of iEµ resulted in decreased SHM which could be partially restored by insertion of the IgH hs1,2 enhancer. Other two 3′Eα enhancers, hs3-hs4, did not significantly increase the mutation frequency, but further strengthened the dA/dT bias. The frequency and spectrum of the mutations were independent of the genomic integration of the transgene or V gene transcription level. Thus, we have established a novel in vitro system to analyze SHM and identify the role of multiple cis-regulatory elements in regulating dA/dT biased SHM. This model system will be useful to further address the role of other cis-regulating elements and recruited trans-acting factors in expressing the modalities of SHM.

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“…Second, U could be removed by uracil DNA glycosylase (UNG) to produce an abasic site, which when copied by low-fidelity DNA polymerases, would generate C:G transitions and transversions. Third, U could be recognized as a U:G mismatch by the MSH2-MSH6 mismatch repair (MMR) proteins, which would generate a gap that could be filled in by the low-fidelity DNA polymerase (pol) h to produce mutations of A:T base pairs (bp; Zeng et al 2001;Wilson et al 2005). The last two steps are also associated with strand breaks, which produce substrates for recombination during heavy-chain class switching.…”

Section: Aberrant Dna Repair Generates Antibody Diversitymentioning

confidence: 99%

Hijacked DNA repair proteins and unchained DNA polymerases

Saribasak

Rajagopal

Maul

et al. 2008

Phil. Trans. R. Soc. B

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Somatic hypermutation of immunoglobulin (Ig) genes occurs at a frequency that is a million times greater than the mutation in other genes. Mutations occur in variable genes to increase antibody affinity, and in switch regions before constant genes to cause switching from IgM to IgG. Hypermutation is initiated in activated B cells when the activation-induced deaminase protein deaminates cytosine in DNA to uracil. Uracils can be processed by either a mutagenic pathway to produce mutations or a non-mutagenic pathway to remove mutations. In the mutagenic pathway, we first studied the role of mismatch repair proteins, MSH2, MSH3, MSH6, PMS2 and MLH1, since they would recognize mismatches. The MSH2-MSH6 heterodimer is involved in hypermutation by binding to U:G and other mismatches generated during repair synthesis, but the other proteins are not necessary. Second, we analysed the role of low-fidelity DNA polymerases h, i and q in synthesizing mutations, and conclude that polymerase h is the dominant participant by generating mutations at A:T base pairs. In the non-mutagenic pathway, we examined the role of the Cockayne syndrome B protein that interacts with other repair proteins. Mice deficient in this protein had normal hypermutation and class switch recombination, showing that it is not involved.

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MSH2–MSH6 stimulates DNA polymerase η, suggesting a role for A:T mutations in antibody genes

Cited by 180 publications

References 62 publications

Somatic Hypermutation and Class Switch Recombination in Msh6−/−Ung−/− Double-Knockout Mice

Somatic Hypermutation and Class Switch Recombination in Msh6−/−Ung−/− Double-Knockout Mice

Biased dA/dT somatic hypermutation as regulated by the heavy chain intronic iEμ enhancer and 3′Eα enhancers in human lymphoblastoid B cells

Hijacked DNA repair proteins and unchained DNA polymerases

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