TY - JOUR
T1 - Detection of chromatin-associated single-stranded DNA in regions targeted for somatic hypermutation
AU - Ronai, Diana
AU - Iglesias-Ussel, Maria D.
AU - Fan, Manxia
AU - Li, Ziqiang
AU - Martin, Alberto
AU - Scharff, Matthew D.
PY - 2007/1/22
Y1 - 2007/1/22
N2 - After encounter with antigen, the antibody repertoire is shaped by somatic hypermutation (SHM), which leads to an increase in the affinity of antibodies for the antigen, and class-switch recombination (CSR), which results in a change in the effector function of antibodies. Both SHM and CSR are initiated by activation-induced cytidine deaminase (AID), which deaminates deoxycytidine to deoxyuridine in single-stranded DNA (ssDNA). The precise mechanism responsible for the formation of ssDNA in V regions undergoing SHM has yet to be experimentally established. In this study, we searched for ssDNA in mutating V regions in which DNA-protein complexes were preserved in the context of chromatin in human B cell lines and in primary mouse B cells. We found that V regions that undergo SHM were enriched in short patches of ssDNA, rather than R loops, on both the coding and noncoding strands. Detection of these patches depended on the presence of DNA-associated proteins and required active transcription. Consistent with this, we found that both DNA strands in the V region were transcribed. We conclude that regions of DNA that are targets of SHM assemble protein-DNA complexes in which ssDNA is exposed, making it accessible to AID. JEM
AB - After encounter with antigen, the antibody repertoire is shaped by somatic hypermutation (SHM), which leads to an increase in the affinity of antibodies for the antigen, and class-switch recombination (CSR), which results in a change in the effector function of antibodies. Both SHM and CSR are initiated by activation-induced cytidine deaminase (AID), which deaminates deoxycytidine to deoxyuridine in single-stranded DNA (ssDNA). The precise mechanism responsible for the formation of ssDNA in V regions undergoing SHM has yet to be experimentally established. In this study, we searched for ssDNA in mutating V regions in which DNA-protein complexes were preserved in the context of chromatin in human B cell lines and in primary mouse B cells. We found that V regions that undergo SHM were enriched in short patches of ssDNA, rather than R loops, on both the coding and noncoding strands. Detection of these patches depended on the presence of DNA-associated proteins and required active transcription. Consistent with this, we found that both DNA strands in the V region were transcribed. We conclude that regions of DNA that are targets of SHM assemble protein-DNA complexes in which ssDNA is exposed, making it accessible to AID. JEM
UR - http://www.scopus.com/inward/record.url?scp=33846424933&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=33846424933&partnerID=8YFLogxK
U2 - 10.1084/jem.20062032
DO - 10.1084/jem.20062032
M3 - Article
C2 - 17227912
AN - SCOPUS:33846424933
SN - 0022-1007
VL - 204
SP - 181
EP - 190
JO - Journal of Experimental Medicine
JF - Journal of Experimental Medicine
IS - 1
ER -