In response to antigens, activated B cells undergo somatic hypermutation (SHM) and class switch recombination (CSR) to enhance antibody diversity. SHM and CSR each require the Activation Induced Deaminase (AID), which catalyses DNA-specific cytidine deaminase activity. AID targets the highly repetitive switch (S) regions of immunoglobulin heavy chain (Igh) loci to induce DNA double strand breaks (DSBs), which are intermediates in CSR. When targeting to variable (V) region exons of IgH and IgL loci, AID predominantly induces point mutations, termed SHM, resulting in the increased affinity of antibody for antigen. Intensive efforts have identified potential AID co-factors, which could bind S region DNA or RNA transcripts of Igh loci. This suggests a link between AID targeting and transcriptional pausing or RNA processing of S regions. In contrast to the relatively well studied targeting mechanisms for CSR, the mechanism of AID targeting to V region locus is much less well understood. Although AID has the ability to deaminate any transcribed substrate in vitro and could potentially access the genome widely to induce genomic instability in B cells, its physiological targets during SHM are almost exclusively restricted to V regions of Ig loci. However, due to the lack of robust experimental systems, it remains largely unknown how AID is specifically targeted to V regions, which is one of the most interesting unresolved questions in the field of AID regulation. Thus, we have established a unique experimental system, and propose to address these fundamental questions. The completion of our proposal will provide novel insights into the regulation of AID-mediated SHM in B cell immune responses and elucidate molecular mechanism of genomic instability in B cell lymphomas.

Public Health Relevance

Our proposed studies will provide major new insights into the regulation of activation induced deaminase (AID) targeting to immunoglobulin (Ig) loci, a fundamental question in basic immunology. Better understanding of these mechanisms will increase our knowledge of AID-directed somatic hypermutation (SHM) and class switch recombination (CSR), as well as genomic instability. Besides the fundamental relevance to immunological control mechanisms, elucidation of SHM and CSR is required to generate effective antibody-mediated immune responses to fight against pathogens. Conversely, abnormal SHM/CSR can underlie immunological diseases such as infection, immunodeficiency, and autoimmunity, and contribute to oncogenic chromosomal translocations.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Exploratory/Developmental Grants (R21)
Project #
1R21AI110777-01A1
Application #
8819992
Study Section
Cellular and Molecular Immunology - B Study Section (CMIB)
Program Officer
Nasseri, M Faraz
Project Start
2014-11-06
Project End
2016-10-31
Budget Start
2014-11-06
Budget End
2015-10-31
Support Year
1
Fiscal Year
2015
Total Cost
$193,958
Indirect Cost
$68,958
Name
University of Colorado Denver
Department
Microbiology/Immun/Virology
Type
Schools of Medicine
DUNS #
041096314
City
Aurora
State
CO
Country
United States
Zip Code
80045
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