Pms2 and uracil-DNA glycosylases act jointly in the mismatch repair pathway to generate Ig gene mutations at A-T base pairs

Zubani, Giulia Girelli; Zivojnovic, Marija; Smet, Annie De; Albagli-Curiel, Olivier; Huetz, François; Weill, Jean‐Claude; Reynaud, Claude‐Agnès; Storck, Sébastien

doi:10.1084/jem.20161576

Cited by 22 publications

(26 citation statements)

References 58 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…MutL-alpha (MutLα), composed of MutL homolog 1 (Mlh1) and Pms1 homolog 2 (Pms2), can nick the DNA on the 5′ side of the mismatch via Pms2 endonuclease activity, but Pms2 endonuclease-deficient mice displayed normal A:T mutagenesis (van Oers et al, 2010, 2). However, loss of both Pms2 and Ung resulted in a 50% reduction of A:T mutations, suggesting that both Pms2 and Ung contribute to DNA incision required for Exo1 entry (Girelli Zubani et al, 2017).…”

Section: Introductionmentioning

confidence: 98%

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

Bahjat

Stratigopoulou

Pilzecker

et al. 2020

Preprint

View full text Add to dashboard Cite

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 β (Polβ), 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 Polβ relates to hypoxia that characterizes the GC microenvironment.

show abstract

Section: Introductionmentioning

confidence: 98%

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

Bahjat

Stratigopoulou

Pilzecker

et al. 2020

Preprint

View full text Add to dashboard Cite

show abstract

“…Because the number of sequenced A's and T's in our data was not exactly the same (24.7–25.9% A's, 20.8–21.5% T's), we first corrected the number of mutations at A's and T's for the number of sequenced A's and T's to calculate the A/T ratio (Figure 3A, Supplemental Methods). In the HCs, the average A/T ratio was 1.7 (range 1.5–2) (Figure 3B), indicating that the non-transcribed strand is mutated ~3 times more than the transcribed strand, leading to a 3:1 strand bias (24, 43).…”

Section: Resultsmentioning

confidence: 99%

“…We excluded reviews, publications without transition tables or information about the nucleotide composition of the sequenced region, and publications in which the SHM was measured in cell lines or in the switch regions. Eight publications matched these criteria (8, 18, 19, 21, 24, 40–42). In addition, we received a transition table on three of the four MSH6 patients from the Gardes et al publication, which were also included in the analysis (26).…”

Section: Methodsmentioning

confidence: 99%

“…Although, a lot is known about the mechanism of SHM in mice, it is still not completely clear what the roles of Pms2 and Mlh1 are in SHM. They were long thought to be dispensable for SHM (19–23); however, a recent publication by Girelli Zubani et al showed that Ung/Pms2 double knockout mice have a 50% reduction in the number of mutations at AT base pairs (24). They suggest that the Pms2/Mlh1 complex provides the nick required for AT mutagenesis and that in the absence of the Pms2/Mlh1 complex, Ung can compensate for its function.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Repertoire Sequencing of B Cells Elucidates the Role of UNG and Mismatch Repair Proteins in Somatic Hypermutation in Humans

et al. 2019

View full text Add to dashboard Cite

The generation of high-affinity antibodies depends on somatic hypermutation (SHM). SHM is initiated by the activation-induced cytidine deaminase (AID), which generates uracil (U) lesions in the B-cell receptor (BCR) encoding genes. Error-prone processing of U lesions creates a typical spectrum of point mutations during SHM. The aim of this study was to determine the molecular mechanism of SHM in humans; currently available knowledge is limited by the number of mutations analyzed per patient. We collected a unique cohort of 10 well-defined patients with bi-allelic mutations in genes involved in base excision repair (BER) ( UNG ) or mismatch repair (MMR) ( MSH2, MSH6 , or PMS2 ) and are the first to present next-generation sequencing (NGS) data of the BCR, allowing us to study SHM extensively in humans. Analysis using ARGalaxy revealed selective skewing of SHM mutation patterns specific for each genetic defect, which are in line with the five-pathway model of SHM that was recently proposed based on mice data. However, trans-species comparison revealed differences in the role of PMS2 and MSH2 in strand targeting between mice and man. In conclusion, our results indicate a role for UNG, MSH2, MSH6, and PMS2 in the generation of SHM in humans comparable to their function in mice. However, we observed differences in strand targeting between humans and mice, emphasizing the importance of studying molecular mechanisms in a human setting. The here developed method combining NGS and ARGalaxy analysis of BCR mutation data forms the basis for efficient SHM analyses of other immune deficiencies.

show abstract

“…MSH2-MSH6 pathway has recently been identified as PMS2 (40,41). Recognition of the U:G mismatch by the MSH2-MSH6 heterodimer (42) recruits the PMS2-MLH1 heterodimer to produce nicks in the vicinity and creates a gap using EXO1 (43).…”

Section: Discussionmentioning

confidence: 99%

DNA Breaks in Ig V Regions Are Predominantly Single Stranded and Are Generated by UNG and MSH6 DNA Repair Pathways

Zanotti

Maul

Yang

et al. 2019

The Journal of Immunology

View full text Add to dashboard Cite

Antibody diversity is initiated by activation-induced deaminase (AID), which deaminates cytosine to uracil in DNA. Uracils in the Ig gene loci can be recognized by uracil DNA glycosylase (UNG) or mutS homologs 2 and 6 (MSH2-MSH6) proteins, and then processed into DNA breaks. Breaks in switch regions of the H chain locus cause isotype switching and have been extensively characterized as staggered and blunt double-strand breaks. However, breaks in V regions that arise during somatic hypermutation are poorly understood. In this study, we characterize AID-dependent break formation in J H introns from mouse germinal center B cells. We used a ligation-mediated PCR assay to detect single-strand breaks and double-strand breaks that were either staggered or blunt. In contrast to switch regions, V regions contained predominantly single-strand breaks, which peaked 10 d after immunization. We then examined the pathways used to generate these breaks in UNG-and MSH6-deficient mice. Surprisingly, both DNA repair pathways contributed substantially to break formation, and in the absence of both UNG and MSH6, the frequency of breaks was severely reduced. When the breaks were sequenced and mapped, they were widely distributed over a 1000-bp intron region downstream of J H 3 and J H 4 exons and were unexpectedly located at all 4 nt. These data suggest that during DNA repair, nicks are generated at distal sites from the original deaminated cytosine, and these repair intermediates could generate both faithful and mutagenic repair. During mutagenesis, single-strand breaks would allow entry for low-fidelity DNA polymerases to generate somatic hypermutation.

show abstract

Pms2 and uracil-DNA glycosylases act jointly in the mismatch repair pathway to generate Ig gene mutations at A-T base pairs

Abstract: Girelli Zubani et al. show that the Pms2 component of the mismatch repair complex and multiple uracil glycosylases contribute, each with a distinct strand bias, to enlarge the Ig gene mutation spectrum from G-C to A-T bases.

Cited by 22 publications

References 58 publications

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

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

Repertoire Sequencing of B Cells Elucidates the Role of UNG and Mismatch Repair Proteins in Somatic Hypermutation in Humans

DNA Breaks in Ig V Regions Are Predominantly Single Stranded and Are Generated by UNG and MSH6 DNA Repair Pathways

Contact Info

Product

Resources

About