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The recurring AGCT motif in S region DNA specifically recruits 14‐3‐3 adaptor proteins that are critical for the unfolding of CSR
Author(s) -
Xu Zhenming,
Fulop Zsolt,
Zhang Jinsong,
AlQahtani Ahmed,
Pone Egest,
Pal Zsuzsanna,
Park SeokRae,
Zan Hong,
Fu Haian,
Yates John,
Casali Paolo
Publication year - 2008
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.22.1_supplement.849.9
Subject(s) - gene isoform , signal transducing adaptor protein , germinal center , biology , microbiology and biotechnology , mutant , somatic hypermutation , immunoglobulin class switching , protein subunit , gene , genetics , b cell , antibody
Somatic hypermutation (SHM) and class switch DNA recombination (CSR) are central to the maturation of the antibody response and occur mainly in germinal centers (GCs). To identify critical switch (S) region cis ‐elements, we analyzed S region DNA sequences and identified AGCT motifs occurring at a high frequency in Sμ and all other downstream S regions in human, mouse and Xenopus laevis . 14‐3‐3 adaptor proteins were the major AGCT‐binding proteins and preferentially localized to S regions in switching B cells. Expression of 14‐3‐3 was induced in GC B cells in vivo and B cells stimulated to undergo CSR in vitro . The differential induction of the seven 14‐3‐3 isoforms in these B cells suggests an isoform‐specific role of 14‐3‐3 in CSR. This was confirmed by different degrees of CSR inhibition in B cells that were null in 14‐3‐3γ or expressed a semi‐dominant 14‐3‐3σ mutant or reduced levels of 14‐3‐3τ or 14‐3‐3ε. Further, 14‐3‐3 interacted with critical CSR factors, such as AID and Ku80/Ku86. Finally, difopein, a pan‐14‐3‐3 isoform peptide inhibitor that disrupts interaction between 14‐3‐3 and its protein ligands, reduced the level of resected double strand DNA breaks (DSBs), the obligatory intermediates in CSR. Thus, our findings demonstrate that the recurring AGCT motif in S regions specifically recruit 14‐3‐3 adaptor proteins that are critical for the unfolding of CSR. Supported by NIH grants AI 45011, AI 60573 and AR 40908.