scholarly journals A/T mutagenesis in hypermutated immunoglobulin genes strongly depends on PCNAK164 modification

2007 ◽  
Vol 204 (8) ◽  
pp. 1989-1998 ◽  
Author(s):  
Petra Langerak ◽  
Anders O.H. Nygren ◽  
Peter H.L. Krijger ◽  
Paul C.M. van den Berk ◽  
Heinz Jacobs
Keyword(s):  
B Cells ◽  
Somatic Hypermutation ◽  
Cytidine Deaminase ◽  
Nuclear Antigen ◽  
Translesion Dna Synthesis ◽  
Class Switch ◽  
Activation Induced Cytidine Deaminase ◽  
Mismatch Recognition ◽  
Proliferating Cell

B cells use translesion DNA synthesis (TLS) to introduce somatic mutations around genetic lesions caused by activation-induced cytidine deaminase. Monoubiquitination at lysine164 of proliferating cell nuclear antigen (PCNAK164) stimulates TLS. To determine the role of PCNAK164 modifications in somatic hypermutation, PCNAK164R knock-in mice were generated. PCNAK164R/K164R mutants are born at a sub-Mendelian frequency. Although PCNAK164R/K164R B cells proliferate and class switch normally, the mutation spectrum of hypermutated immunoglobulin (Ig) genes alters dramatically. A strong reduction of mutations at template A/T is associated with a compensatory increase at G/C, which is a phenotype similar to polymerase η (Polη) and mismatch repair–deficient B cells. Mismatch recognition, monoubiquitinated PCNA, and Polη likely cooperate in establishing mutations at template A/T during replication of Ig genes.

scholarly journals Post-translational regulation of activation-induced cytidine deaminase

2008 ◽  
Vol 364 (1517) ◽  
pp. 667-673 ◽  
Author(s):  
Uttiya Basu ◽  
Andrew Franklin ◽  
Frederick W Alt
Keyword(s):  
Translational Regulation ◽  
Somatic Hypermutation ◽  
Cytidine Deaminase ◽  
Specific Protein ◽  
Antibody Repertoire ◽  
Dna Modification ◽  
Class Switch ◽  
Protein Factor ◽  
Activation Induced Cytidine Deaminase

The assembled immunoglobulin genes in the B cells of mice and humans are altered by distinct processes known as class switch recombination (CSR) and somatic hypermutation, leading to diversification of the antibody repertoire. These two DNA modification processes are initiated by the B cell-specific protein factor activation-induced cytidine deaminase (AID). AID is post-translationally modified by phosphorylation at multiple sites, although functional significance during CSR has been implicated only for phosphorylation at serine-38 (S38). Although multiple laboratories have demonstrated that AID function is regulated via phosphorylation at S38, the precise biological role of S38 phosphorylation has been a topic of debate. Here, we discuss our interpretation of the significance of AID regulation via phosphorylation and also discuss how this form of AID regulation may have evolved in higher organisms.

Chronic lymphocytic leukemia B cells expressing AID display dissociation between class switch recombination and somatic hypermutation

Blood ◽  
2003 ◽  
Vol 101 (10) ◽  
pp. 4029-4032 ◽  
Author(s):  
Pablo Oppezzo ◽  
Françoise Vuillier ◽  
Yuri Vasconcelos ◽  
Gérard Dumas ◽  
Christian Magnac ◽  
...  
Keyword(s):  
B Cells ◽  
Chronic Lymphocytic Leukemia ◽  
Gene Product ◽  
Mode Of Action ◽  
Somatic Hypermutation ◽  
Cytidine Deaminase ◽  
Class Switch Recombination ◽  
Lymphocytic Leukemia ◽  
Class Switch ◽  
Activation Induced Cytidine Deaminase

Abstract In B cells, somatic hypermutation (SHM) and class switch recombination (CSR) depend on the activation-induced cytidine deaminase (AID) gene product, although the precise mode of action of AID remains unknown. Because some chronic lymphocytic leukemia (CLL) B cells can undergo CSR without SHM, it constitutes a useful model to dissect AID function. In this work, we have studied AID expression, the presence of mutations in the preswitch μ DNA region, CSR, and the SHM in 65 CLL patients. Our results demonstrate that unmutated CLL B cells can constitutively express AID and that AID expression is associated with the presence of mutations in the preswitch region and in clonally related isotype-switched transcripts. They also demonstrate that in CLL without constitutive AID expression, AID induction on stimulation results in preswitch mutations and the CSR process. Our results show a dissociation between SHM and CSR in CLL and suggest that, in this disease, AID would require additional help for carrying out the SHM process.

scholarly journals Strand-biased defect in C/G transversions in hypermutating immunoglobulin genes in Rev1-deficient mice

2006 ◽  
Vol 203 (2) ◽  
pp. 319-323 ◽  
Author(s):  
Jacob G. Jansen ◽  
Petra Langerak ◽  
Anastasia Tsaalbi-Shtylik ◽  
Paul van den Berk ◽  
Heinz Jacobs ◽  
...  
Keyword(s):  
B Cells ◽  
Somatic Hypermutation ◽  
Cytidine Deaminase ◽  
Translesion Synthesis ◽  
Uracil Dna Glycosylase ◽  
Abasic Sites ◽  
Activation Induced Cytidine Deaminase ◽  
Deficient Mice

Somatic hypermutation of Ig genes enables B cells of the germinal center to generate high-affinity immunoglobulin variants. Key intermediates in somatic hypermutation are deoxyuridine lesions, introduced by activation-induced cytidine deaminase. These lesions can be processed further to abasic sites by uracil DNA glycosylase. Mutagenic replication of deoxyuridine, or of its abasic derivative, by translesion synthesis polymerases is hypothesized to underlie somatic hypermutation. Rev1 is a translesion synthesis polymerase that in vitro incorporates uniquely deoxycytidine opposite deoxyuridine and abasic residues. To investigate a role of Rev1 in mammalian somatic hypermutation we have generated mice deficient for Rev1. Although Rev1−/− mice display transient growth retardation, proliferation of Rev1−/− LPS-stimulated B cells is indistinguishable from wild-type cells. In mutated Ig genes from Rev1−/− mice, C to G transversions were virtually absent in the nontranscribed (coding) strand and reduced in the transcribed strand. This defect is associated with an increase of A to T, C to A, and T to C substitutions. These results indicate that Rev1 incorporates deoxycytidine residues, most likely opposite abasic nucleotides, during somatic hypermutation. In addition, loss of Rev1 causes compensatory increase in mutagenesis by other translesion synthesis polymerases.

scholarly journals Phosphorylation promotes activation-induced cytidine deaminase activity at the Myc oncogene

2017 ◽  
Vol 214 (12) ◽  
pp. 3543-3552 ◽  
Author(s):  
Yunxiang Mu ◽  
Monika A. Zelazowska ◽  
Kevin M. McBride
Keyword(s):  
Somatic Hypermutation ◽  
Cytidine Deaminase ◽  
Switch Region ◽  
Myc Oncogene ◽  
Class Switch ◽  
Oncogenic Mutations ◽  
Cytidine Deaminase Activity ◽  
Activation Induced Cytidine Deaminase ◽  
Myc Gene

Activation-induced cytidine deaminase (AID) is a mutator enzyme that targets immunoglobulin (Ig) genes to initiate antibody somatic hypermutation (SHM) and class switch recombination (CSR). Off-target AID association also occurs, which causes oncogenic mutations and chromosome rearrangements. However, AID occupancy does not directly correlate with DNA damage, suggesting that factors beyond AID association contribute to mutation targeting. CSR and SHM are regulated by phosphorylation on AID serine38 (pS38), but the role of pS38 in off-target activity has not been evaluated. We determined that lithium, a clinically used therapeutic, induced high AID pS38 levels. Using lithium and an AID-S38 phospho mutant, we compared the role of pS38 in AID activity at the Ig switch region and off-target Myc gene. We found that deficient pS38 abated AID chromatin association and CSR but not mutation at Myc. Enhanced pS38 elevated Myc translocation and mutation frequency but not CSR or Ig switch region mutation. Thus, AID activity can be differentially targeted by phosphorylation to induce oncogenic lesions.

scholarly journals Switch recombination and somatic hypermutation are controlled by the heavy chain 3′ enhancer region

2009 ◽  
Vol 206 (12) ◽  
pp. 2613-2623 ◽  
Author(s):  
Wesley A. Dunnick ◽  
John T. Collins ◽  
Jian Shi ◽  
Gerwin Westfield ◽  
Clinton Fontaine ◽  
...  
Keyword(s):  
Heavy Chain ◽  
Somatic Hypermutation ◽  
Cytidine Deaminase ◽  
Insertion Site ◽  
Enhancer Region ◽  
Class Switch ◽  
Activation Induced Cytidine Deaminase ◽  
Heavy Chain Constant Region ◽  
Bac Transgene

Both class switch recombination (CSR) and somatic hypermutation (SHM) require transcription and the trans-acting factor activation-induced cytidine deaminase (AID), and must be up-regulated during antigen-dependent differentiation of B lymphocytes. To test the role of the heavy chain 3′ enhancers in both CSR and SHM, we used a BAC transgene of the entire heavy chain constant region locus. Using Cre-loxP recombination to delete a 28-kb region that contains the four known 3′ heavy chain enhancers, we isolated lines of BAC transgenic mice with an intact heavy chain locus and paired lines in the same chromosomal insertion site lacking the 3′ enhancers. Intact heavy chain transgenes undergo CSR to all heavy chain genes and mutate their transgenic VDJ exon. In paired transgenes lacking the 3′ enhancer region, CSR to most heavy chain genes is reduced to ∼1% of the levels for intact heavy chain loci; SHM is also reduced. Finally, we find that in B cells with a transgene lacking the 3′ enhancers, interchromosomal recombination between the transgenic VDJ exon and the endogenous heavy chain C genes is more easily detected than CSR within the transgene.

Different isoforms of BSAP regulate expression of AID in normal and chronic lymphocytic leukemia B cells

Blood ◽  
2005 ◽  
Vol 105 (6) ◽  
pp. 2495-2503 ◽  
Author(s):  
Pablo Oppezzo ◽  
Gérard Dumas ◽  
Ana Inés Lalanne ◽  
Béatrice Payelle-Brogard ◽  
Christian Magnac ◽  
...  
Keyword(s):  
B Cells ◽  
Chronic Lymphocytic Leukemia ◽  
Somatic Hypermutation ◽  
Cytidine Deaminase ◽  
Lymphocytic Leukemia ◽  
Interleukin 4 ◽  
Class Switch ◽  
Activation Induced Cytidine Deaminase ◽  
Complete Form ◽  
Lower Expression

Abstract Activation-induced cytidine deaminase (AID) is key to initiating somatic hypermutation (SHM) and class switch recombination (CSR), but its mode of action and regulation remains unclear. Since Pax-5 and Id-2 transcription factors play an opposing role in AID regulation, we have studied the expression of Pax-5, Id-2, and prdm-1 genes in 54 chronic lymphocytic leukemia (CLL) B cells. In 21 cases, presence of AID is constantly associated with high expression of the complete form of the Pax-5 gene (Pax-5a) and lower expression of the Id-2 and prdm-1 transcripts. In 33 cases, the absence of AID expression and CSR is associated with a reduction of Pax-5a and the appearance of a spliced form with a deletion in exon 8 (Pax-5/Δ-Ex8). Stimulation with CD40L+interleukin 4 (IL-4) induces CSR, the presence of AID transcripts, up-regulation of Pax-5a and down-regulation of Pax-5/Δ-Ex8, and Id-2 and prdm-1 transcripts. Pax-5a and Pax-5/Δ-Ex8 are translated into 2 isoforms of the B-cell–specific activator protein (BSAP) and both are able to bind the AID-promoter region. Overall, these results suggest that Pax-5/Δ-Ex8 could play an important role in the control of its own transcription and indirectly in AID expression and CSR.

scholarly journals Regulation of activation-induced cytidine deaminase DNA deamination activity in B-cells by Ser38 phosphorylation

2009 ◽  
Vol 37 (3) ◽  
pp. 561-568 ◽  
Author(s):  
Uttiya Basu ◽  
Andrew Franklin ◽  
Bjoern Schwer ◽  
Hwei-Ling Cheng ◽  
Jayanta Chaudhuri ◽  
...  
Keyword(s):  
B Cells ◽  
Somatic Hypermutation ◽  
Cytidine Deaminase ◽  
Variable Region ◽  
Microrna Regulation ◽  
Class Switch ◽  
Regulatory Processes ◽  
Activation Induced Cytidine Deaminase ◽  
Dna Deamination ◽  
Activated B Cells

Human and mouse Ig genes are diversified in mature B-cells by distinct processes known as Ig heavy-chain CSR (class switch recombination) and Ig variable-region exon SHM (somatic hypermutation). These DNA-modification processes are initiated by AID (activation-induced cytidine deaminase), a DNA cytidine deaminase predominantly expressed in activated B-cells. AID is post-transcriptionally regulated via multiple mechanisms, including microRNA regulation, nucleocytoplasmic shuttling, ubiquitination and phosphorylation. Among these regulatory processes, AID phosphorylation at Ser38 has been a focus of particularly intense study and debate. In the present paper, we discuss recent biochemical and mouse genetic studies that begin to elucidate the functional significance of AID Ser38 phosphorylation in the context of the evolution of this mode of AID regulation and the potential roles that it may play in activated B-cells during a normal immune response.

Nuclear and cytoplasmic AID in extrafollicular and germinal center B cells

Blood ◽  
2006 ◽  
Vol 107 (10) ◽  
pp. 3967-3975 ◽  
Author(s):  
Giorgio Cattoretti ◽  
Maike Büttner ◽  
Rita Shaknovich ◽  
Elisabeth Kremmer ◽  
Bachir Alobeid ◽  
...  
Keyword(s):  
T Cells ◽  
B Cells ◽  
Somatic Hypermutation ◽  
Cytidine Deaminase ◽  
Structural Similarity ◽  
Outer Zone ◽  
Bhlh Protein ◽  
Class Switch ◽  
Activation Induced Cytidine Deaminase ◽  
Cytoplasmic Location

Activation-induced cytidine deaminase (AID) is necessary for immunoglobulin somatic hypermutation (SHM) and class switch recombination (CSR) in T-dependent immune response in germinal centers (GCs). The structural similarity of AID with RNA-editing enzymes and its largely cytoplasmic location have fueled controversial views of its mode of interaction with DNA. We show that AID, a mature B-cell–restricted cytoplasmic antigen, is relocated into the nucleus in 2.5% of CDKN1B–, CCNB1– GC cells. The GC dark zone and the outer zone (OZ), but not the light zone, contain nuclear and cytoplasmic AID+ blasts. AID+ cells in the OZ are in contact with T cells and CD23– follicular dendritic cells. In addition, AID is expressed in extrafollicular large proliferating B cells, 14% of which have nuclear AID. GC and extrafollicular AID+ cells express E47 but not the inhibiting BHLH protein Id2. Outside the GC, AID+ B cells are in contact with T cells and show partial evidence of CD40 plus bcr stimulation-dependent signature (CCL22, JunB, cMYC, CD30) but lack early and late plasma cell markers. The distribution of nuclear AID is consistent with the topography of SHM and CSR inside the GC and in extrafollicular activated B cells.

scholarly journals Disparate roles of ATR and ATM in immunoglobulin class switch recombination and somatic hypermutation

2006 ◽  
Vol 203 (1) ◽  
pp. 99-110 ◽  
Author(s):  
Qiang Pan-Hammarström ◽  
Aleksi Lähdesmäki ◽  
Yaofeng Zhao ◽  
Likun Du ◽  
Zhihui Zhao ◽  
...  
Keyword(s):  
Ataxia Telangiectasia ◽  
Somatic Hypermutation ◽  
Cytidine Deaminase ◽  
Class Switch Recombination ◽  
End Joining ◽  
Class Switch ◽  
Activation Induced Cytidine Deaminase ◽  
Variable Heavy

Class switch recombination (CSR) and somatic hypermutation (SHM) are mechanistically related processes initiated by activation-induced cytidine deaminase. Here, we have studied the role of ataxia telangiectasia and Rad3-related protein (ATR) in CSR by analyzing the recombinational junctions, resulting from in vivo switching, in cells from patients with mutations in the ATR gene. The proportion of cells that have switched to immunoglobulin (Ig)A and IgG in the peripheral blood seems to be normal in ATR-deficient (ATRD) patients and the recombined S regions show a normal “blunt end-joining,” but impaired end joining with partially complementary (1–3 bp) DNA ends. There was also an increased usage of microhomology at the μ-α switch junctions, but only up to 9 bp, suggesting that the end-joining pathway requiring longer microhomologies (≥10 bp) may be ATR dependent. The SHM pattern in the Ig variable heavy chain genes is altered, with fewer mutations occurring at A and more mutations at T residues and thus a loss of strand bias in targeting A/T pairs within certain hotspots. These data suggest that the role of ATR is partially overlapping with that of ataxia telangiectasia–mutated protein, but that the former is also endowed with unique functional properties in the repair processes during CSR and SHM.

scholarly journals Msh2 ATPase Activity Is Essential for Somatic Hypermutation at A-T Basepairs and for Efficient Class Switch Recombination

2003 ◽  
Vol 198 (8) ◽  
pp. 1171-1178 ◽  
Author(s):  
Alberto Martin ◽  
Ziqiang Li ◽  
Diana P. Lin ◽  
Philip D. Bardwell ◽  
Maria D. Iglesias-Ussel ◽  
...  
Keyword(s):  
Mismatch Repair ◽  
Adenosine Triphosphatase ◽  
Somatic Hypermutation ◽  
Cytidine Deaminase ◽  
Class Switch Recombination ◽  
Class Switch ◽  
Activation Induced Cytidine Deaminase ◽  
Postmeiotic Segregation ◽  
Cytidine Deamination

Somatic hypermutation (SHM) and class switch recombination (CSR) are initiated by activation-induced cytidine deaminase–mediated cytidine deamination of immunoglobulin genes. MutS homologue (Msh) 2−/− mice have reduced A-T mutations and CSR. This suggests that Msh2 may play a role in repairing activation-induced cytidine deaminase–generated G-U mismatches. However, because Msh2 not only initiates mismatch repair but also has other functions, such as signaling for apoptosis, it is not known which activity of Msh2 is responsible for the effects observed, and consequently, many models have been proposed. To further dissect the role of Msh2 in SHM and CSR, mice with a “knockin” mutation in the Msh2 gene that inactivates the adenosine triphosphatase domain were examined. This mutation (i.e., Msh2G674A), which does not affect apoptosis signaling, allows mismatches to be recognized but prevents Msh2 from initiating mismatch repair. Here, we show that, similar to Msh2−/− mice, SHM in Msh2G674A mice is biased toward G-C mutations. However, CSR is partially reduced, and switch junctions are more similar to those of postmeiotic segregation 2−/− mice than to Msh2−/− mice. These results indicate that Msh2 adenosine triphosphatase activity is required for A-T mutations, and suggest that Msh2 has more than one role in CSR.

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