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DNA polymerase eta is involved in hypermutation occurring during immunoglobulin class switch recombination.

Faili A, Aoufouchi S, Weller S, Vuillier F, Stary A, Sarasin A, Reynaud CA, Weill JC - J. Exp. Med. (2004)

Bottom Line: Base substitutions, deletions, and duplications are observed at the immunoglobulin locus in DNA sequences involved in class switch recombination (CSR).These mutations are dependent upon activation-induced cytidine deaminase (AID) and present all the characteristics of the ones observed during V gene somatic hypermutation, implying that they could be generated by the same mutational complex.Here we show, by analyzing switched memory B cells from two XP-V patients, that pol eta is also an A/T mutator during CSR, in both the switch region of tandem repeats as well as upstream of it, thus suggesting that the same error-prone translesional polymerases are involved, together with AID, in both processes.

View Article: PubMed Central - PubMed

Affiliation: INSERM U373, Faculté de Médecine Necker-Enfants Malades, Université Paris V, France.

ABSTRACT
Base substitutions, deletions, and duplications are observed at the immunoglobulin locus in DNA sequences involved in class switch recombination (CSR). These mutations are dependent upon activation-induced cytidine deaminase (AID) and present all the characteristics of the ones observed during V gene somatic hypermutation, implying that they could be generated by the same mutational complex. It has been proposed, based on the V gene mutation pattern of patients with the cancer-prone xeroderma pigmentosum variant (XP-V) syndrome who are deficient in DNA polymerase eta (pol eta), that this enzyme could be responsible for a large part of the mutations occurring on A/T bases. Here we show, by analyzing switched memory B cells from two XP-V patients, that pol eta is also an A/T mutator during CSR, in both the switch region of tandem repeats as well as upstream of it, thus suggesting that the same error-prone translesional polymerases are involved, together with AID, in both processes.

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Mutation pattern of JH4 intronic sequences and Sμ core upstream regions in normal controls and XP-V patients. (a) Distribution and nucleotide substitution preference of mutations in JH4 intronic sequences. The distribution of mutations is represented along the 283 bp of intronic JH4 sequence, with the proportion of mutated clones in ordinates. Mutations from normal controls are represented above the nucleotide position, and those from XP-V patients are below. Nucleotide substitution preferences are corrected for base composition. A, 18.0%; G, 31.1%; C, 32.2%; T, 18.7%. (b) Distribution and nucleotide substitution preference of mutations in Sμ core upstream sequences. Mutations obtained for normal controls are represented above the 295 nucleotides of the Sμ core upstream sequence, and those from XP-V patients are below. The G position of the RGYW motif (and the C position of the complementary WRCY motif on the other strand) is highlighted in gray. Nucleotide substitution preferences are corrected for base composition. A, 28.5%; G, 28.8%; C: 20.0%; T, 22.7%.
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fig2: Mutation pattern of JH4 intronic sequences and Sμ core upstream regions in normal controls and XP-V patients. (a) Distribution and nucleotide substitution preference of mutations in JH4 intronic sequences. The distribution of mutations is represented along the 283 bp of intronic JH4 sequence, with the proportion of mutated clones in ordinates. Mutations from normal controls are represented above the nucleotide position, and those from XP-V patients are below. Nucleotide substitution preferences are corrected for base composition. A, 18.0%; G, 31.1%; C, 32.2%; T, 18.7%. (b) Distribution and nucleotide substitution preference of mutations in Sμ core upstream sequences. Mutations obtained for normal controls are represented above the 295 nucleotides of the Sμ core upstream sequence, and those from XP-V patients are below. The G position of the RGYW motif (and the C position of the complementary WRCY motif on the other strand) is highlighted in gray. Nucleotide substitution preferences are corrected for base composition. A, 28.5%; G, 28.8%; C: 20.0%; T, 22.7%.

Mentions: The JH4 intron downstream from rearranged VH genes was amplified using a 5′ FR3 primer consensus for all human VH genes, and 283 bp starting at the border of JH4 intron were sequenced. Only sequences corresponding to different V-D-J junctions were considered. The JH4 segment was used in 50% of rearranged VH genes; such an approach allows a large sampling of unselected sequences (Fig. 2 a; reference 15). The mutation frequency was 2.0/100 bp for the controls, and 1.5 for the XP-V patients (Table I). In both groups, mutations bore the hallmark of somatic mutations: prevalence of base substitutions (with 6–9% of total mutations representing deletions or duplications), bias for transitions (47–51% of all mutations), and targeting of RGYW motifs (Table II). This targeting was calculated taking into account mutations occurring at the G position of the hotspot motif only (considered for both strands of DNA), as compared with mutations at other G/C positions. Moreover, normal controls showed a marked preference for mutations at A over T positions. In accordance with Zeng et al. (5), we observed a drastic reduction of mutations on A/T bases in XP-V patients as compared with the controls (10.7 vs. 54.0%; Fig. 2 a), thus confirming the implication of pol η. The lower number of events on A/T bases also correlates with a slight reduction in the total amount of mutations, obviously only noticeable on such unselected targets.


DNA polymerase eta is involved in hypermutation occurring during immunoglobulin class switch recombination.

Faili A, Aoufouchi S, Weller S, Vuillier F, Stary A, Sarasin A, Reynaud CA, Weill JC - J. Exp. Med. (2004)

Mutation pattern of JH4 intronic sequences and Sμ core upstream regions in normal controls and XP-V patients. (a) Distribution and nucleotide substitution preference of mutations in JH4 intronic sequences. The distribution of mutations is represented along the 283 bp of intronic JH4 sequence, with the proportion of mutated clones in ordinates. Mutations from normal controls are represented above the nucleotide position, and those from XP-V patients are below. Nucleotide substitution preferences are corrected for base composition. A, 18.0%; G, 31.1%; C, 32.2%; T, 18.7%. (b) Distribution and nucleotide substitution preference of mutations in Sμ core upstream sequences. Mutations obtained for normal controls are represented above the 295 nucleotides of the Sμ core upstream sequence, and those from XP-V patients are below. The G position of the RGYW motif (and the C position of the complementary WRCY motif on the other strand) is highlighted in gray. Nucleotide substitution preferences are corrected for base composition. A, 28.5%; G, 28.8%; C: 20.0%; T, 22.7%.
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Related In: Results  -  Collection

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fig2: Mutation pattern of JH4 intronic sequences and Sμ core upstream regions in normal controls and XP-V patients. (a) Distribution and nucleotide substitution preference of mutations in JH4 intronic sequences. The distribution of mutations is represented along the 283 bp of intronic JH4 sequence, with the proportion of mutated clones in ordinates. Mutations from normal controls are represented above the nucleotide position, and those from XP-V patients are below. Nucleotide substitution preferences are corrected for base composition. A, 18.0%; G, 31.1%; C, 32.2%; T, 18.7%. (b) Distribution and nucleotide substitution preference of mutations in Sμ core upstream sequences. Mutations obtained for normal controls are represented above the 295 nucleotides of the Sμ core upstream sequence, and those from XP-V patients are below. The G position of the RGYW motif (and the C position of the complementary WRCY motif on the other strand) is highlighted in gray. Nucleotide substitution preferences are corrected for base composition. A, 28.5%; G, 28.8%; C: 20.0%; T, 22.7%.
Mentions: The JH4 intron downstream from rearranged VH genes was amplified using a 5′ FR3 primer consensus for all human VH genes, and 283 bp starting at the border of JH4 intron were sequenced. Only sequences corresponding to different V-D-J junctions were considered. The JH4 segment was used in 50% of rearranged VH genes; such an approach allows a large sampling of unselected sequences (Fig. 2 a; reference 15). The mutation frequency was 2.0/100 bp for the controls, and 1.5 for the XP-V patients (Table I). In both groups, mutations bore the hallmark of somatic mutations: prevalence of base substitutions (with 6–9% of total mutations representing deletions or duplications), bias for transitions (47–51% of all mutations), and targeting of RGYW motifs (Table II). This targeting was calculated taking into account mutations occurring at the G position of the hotspot motif only (considered for both strands of DNA), as compared with mutations at other G/C positions. Moreover, normal controls showed a marked preference for mutations at A over T positions. In accordance with Zeng et al. (5), we observed a drastic reduction of mutations on A/T bases in XP-V patients as compared with the controls (10.7 vs. 54.0%; Fig. 2 a), thus confirming the implication of pol η. The lower number of events on A/T bases also correlates with a slight reduction in the total amount of mutations, obviously only noticeable on such unselected targets.

Bottom Line: Base substitutions, deletions, and duplications are observed at the immunoglobulin locus in DNA sequences involved in class switch recombination (CSR).These mutations are dependent upon activation-induced cytidine deaminase (AID) and present all the characteristics of the ones observed during V gene somatic hypermutation, implying that they could be generated by the same mutational complex.Here we show, by analyzing switched memory B cells from two XP-V patients, that pol eta is also an A/T mutator during CSR, in both the switch region of tandem repeats as well as upstream of it, thus suggesting that the same error-prone translesional polymerases are involved, together with AID, in both processes.

View Article: PubMed Central - PubMed

Affiliation: INSERM U373, Faculté de Médecine Necker-Enfants Malades, Université Paris V, France.

ABSTRACT
Base substitutions, deletions, and duplications are observed at the immunoglobulin locus in DNA sequences involved in class switch recombination (CSR). These mutations are dependent upon activation-induced cytidine deaminase (AID) and present all the characteristics of the ones observed during V gene somatic hypermutation, implying that they could be generated by the same mutational complex. It has been proposed, based on the V gene mutation pattern of patients with the cancer-prone xeroderma pigmentosum variant (XP-V) syndrome who are deficient in DNA polymerase eta (pol eta), that this enzyme could be responsible for a large part of the mutations occurring on A/T bases. Here we show, by analyzing switched memory B cells from two XP-V patients, that pol eta is also an A/T mutator during CSR, in both the switch region of tandem repeats as well as upstream of it, thus suggesting that the same error-prone translesional polymerases are involved, together with AID, in both processes.

Show MeSH
Related in: MedlinePlus