Activation-induced cytidine deaminase (AID) initiates immunoglobulin gene somatic hypermutation, gene conversion and class switch recombination (CSR) by inflicting DNA lesions at specific genomic loci via DNA cytosine deamination (that converts cytosine to uracil). While these lesions are essential for the production of optimized antibodies against infections, they are also threats to the genome integrity. AID-associated oncogenic mutations and chromosomal translocations are frequently seen in tumors of B cell origin. We propose three specific aims to address several significant gaps in our knowledge about the mechanism of CSR.
In aim 1, we will manipulate the transcription control elements (promoters/enhancers) at IgH ? locus in CH12F3 cells to identify cis-acting DNA elements critical for targeting AID to switch (S) regions.
In aim 2, we will determine the frequency and precise positions of AID footprints in S regions to delineate AID actions in vivo during CSR.
In aim 3, we will determine which DNA ligase is responsible for alternative end-joining of S region breaks.

Public Health Relevance

This proposed project focuses on elucidating the mechanism of a DNA recombination event through which cells in our immune system can produce the optimal antibody against infection. Studying the mechanism of this reaction and how it is regulated has a major impact on understanding the biology of DNA recombination, the pathology of a variety of immunological diseases and many forms of blood cancers.

National Institute of Health (NIH)
National Institute of Allergy and Infectious Diseases (NIAID)
High Priority, Short Term Project Award (R56)
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Cellular and Molecular Immunology - A Study Section (CMIA)
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Nasseri, M Faraz
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Michigan State University
Schools of Medicine
East Lansing
United States
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Ramachandran, Shaliny; Haddad, Dania; Li, Conglei et al. (2016) The SAGA Deubiquitination Module Promotes DNA Repair and Class Switch Recombination through ATM and DNAPK-Mediated ?H2AX Formation. Cell Rep 15:1554-1565
Kim, Ahrom; Han, Li; Santiago, Gabriel E et al. (2016) Class-Switch Recombination in the Absence of the IgH 3' Regulatory Region. J Immunol 197:2930-5
Masani, Shahnaz; Han, Li; Meek, Katheryn et al. (2016) Redundant function of DNA ligase 1 and 3 in alternative end-joining during immunoglobulin class switch recombination. Proc Natl Acad Sci U S A 113:1261-6
Zhang, Zheng Z; Pannunzio, Nicholas R; Lu, Zhengfei et al. (2015) The repetitive portion of the Xenopus IgH Mu switch region mediates orientation-dependent class switch recombination. Mol Immunol 67:524-31
Zhang, Zheng Z; Hsieh, Chih-Lin; Okitsu, Cindy Yen et al. (2015) Effect of CpG dinucleotides within IgH switch region repeats on immunoglobulin class switch recombination. Mol Immunol 66:284-9