Class switch recombination (CSR) is an important mechanism for diversification of the humoral immune response. It is initiated by activation induced cytidine deaminase (AID), an enzyme that converts cytidine to uracyl in single stranded DNA thereby creating U:G mismatches that are recognized and processed by mismatch repair enzymes or Uracyl DNA glycosylase (UNG) to produce double strand DNA (dsDNA) breaks. CSR is a deletional recombination reaction that requires formation of paired DSBs that can be separated by as much as 200 kbps in the antibody gene. These breaks must be synapsed and re-ligated efficiently to avoid genomic instability and to create an antibody gene that directs to synthesis of secondary isotypes. During the last funding period we found that the dsDNA break created by AID activates the DNA damage response, which involves recruitment of factors involved in dsDNA break detection, and signaling. We find that in addition to their signaling function these factors are also essential for normal CSR, because in their absence there is preferential loss of the long distance joining between switch regions. In contrast, resolution of closely apposed intra-switch region DSBs proceeds normally even in the absence of dsDNA break detection, and signaling factors suggesting that these factors might be involved in dsDNA break synapsis. An important additional consequence of aberrant repair in the absence of factors such as Nbs1/Mre11Rad50 that detect the break, or the Ataxia Telangectasia Mutated kinase (ATM) which signals to the nucleus chromosome translocation. Among DNA repair factors the most severe defect in CSR is found in the absence of 53BP1, however there is little mechanistic understanding of how DSBs at a distance are synapsed during CSR or how 53BP1 might be involved in this process. The focus of the proposed research is to examine the role of distance between paired DSBs on the same chromosome in repair and how 53BP1 contributes to repair of widely separated breaks during CSR. The long-term goal of the proposal is to understand the molecular mechanisms that regulate CSR and how abnormalities in CSR lead to cancer causing chromosome translocations.

Public Health Relevance

The research proposed is directed at clarifying mechanisms of antibody diversification a process that is essential to all immune serological responses to pathogens. It also seeks to uncover the mechanisms involved in cancer producing translocations.

National Institute of Health (NIH)
National Institute of Allergy and Infectious Diseases (NIAID)
Research Project (R01)
Project #
Application #
Study Section
Cellular and Molecular Immunology - A Study Section (CMIA)
Program Officer
Nasseri, M Faraz
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
Rockefeller University
Other Domestic Higher Education
New York
United States
Zip Code
Qian, Jason; Wang, Qiao; Dose, Marei et al. (2014) B cell super-enhancers and regulatory clusters recruit AID tumorigenic activity. Cell 159:1524-37
Shulman, Ziv; Gitlin, Alexander D; Weinstein, Jason S et al. (2014) Dynamic signaling by T follicular helper cells during germinal center B cell selection. Science 345:1058-62
Silva, Israel T; Rosales, Rafael A; Holanda, Adriano J et al. (2014) Identification of chromosomal translocation hotspots via scan statistics. Bioinformatics 30:2551-8
Gitlin, Alexander D; Shulman, Ziv; Nussenzweig, Michel C (2014) Clonal selection in the germinal centre by regulated proliferation and hypermutation. Nature 509:637-40
Shulman, Ziv; Gitlin, Alexander D; Targ, Sasha et al. (2013) T follicular helper cell dynamics in germinal centers. Science 341:673-7
Di Virgilio, Michela; Callen, Elsa; Yamane, Arito et al. (2013) Rif1 prevents resection of DNA breaks and promotes immunoglobulin class switching. Science 339:711-5
Jankovic, Mila; Feldhahn, Niklas; Oliveira, Thiago Y et al. (2013) 53BP1 alters the landscape of DNA rearrangements and suppresses AID-induced B cell lymphoma. Mol Cell 49:623-31
Bothmer, Anne; Rommel, Philipp C; Gazumyan, Anna et al. (2013) Mechanism of DNA resection during intrachromosomal recombination and immunoglobulin class switching. J Exp Med 210:115-23
Janovitz, Tyler; Klein, Isaac A; Oliveira, Thiago et al. (2013) High-throughput sequencing reveals principles of adeno-associated virus serotype 2 integration. J Virol 87:8559-68
Rommel, Philipp C; Bosque, David; Gitlin, Alexander D et al. (2013) Fate mapping for activation-induced cytidine deaminase (AID) marks non-lymphoid cells during mouse development. PLoS One 8:e69208

Showing the most recent 10 out of 35 publications