HoxC4 binds to the promoter of the cytidine deaminase AID gene to induce AID expression, class-switch DNA recombination and somatic hypermutation.
The cytidine deaminase AID (encoded by Aicda in mice and AICDA in humans) is critical for immunoglobulin class-switch recombination (CSR) and somatic hypermutation (SHM). Here we show that AID expression was induced by the HoxC4 homeodomain transcription factor, which bound to a highly conserved HoxC4-Oct site in the Aicda or AICDA promoter. This site functioned in synergy with a conserved binding site for the transcription factors Sp1, Sp3 and NF-kappaB. HoxC4 was 'preferentially' expressed in germinal center B cells and was upregulated by engagement of CD40 by CD154, as well as by lipopolysaccharide and interleukin 4. HoxC4 deficiency resulted in impaired CSR and SHM because of lower AID expression and not some other putative HoxC4-dependent activity. Enforced expression of AID in Hoxc4(-/-) B cells fully restored CSR. Thus, HoxC4 directly activates the Aicda promoter, thereby inducing AID expression, CSR and SHM.
Institute for Immunology, School of Medicine and School of Biological Sciences, University of California, Irvine, California, USA.
Seok-Rae
SR
Park
Hong
H
Zan
Zsuzsanna
Z
Pal
Jinsong
J
Zhang
Ahmed
A
Al-Qahtani
Egest J
EJ
Pone
Zhenming
Z
Xu
Thach
T
Mai
Paolo
P
Casali
D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology*; D001483:Base Sequence; D017124:Conserved Sequence; D003564:Cytidine Deaminase / Q000235:genetics* / Q000378:metabolism; D024202:Electrophoretic Mobility Shift Assay; D005434:Flow Cytometry; D005786:Gene Expression Regulation / Q000276:immunology*; D018858:Germinal Center / Q000166:cytology / Q000276:immunology; D018398:Homeodomain Proteins / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D006801:Humans; D017578:Immunoglobulin Class Switching / Q000276:immunology*; D047468:Immunoprecipitation; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D010581:Peyer's Patches / Q000166:cytology / Q000276:immunology; D011401:Promoter Regions, Genetic / Q000235:genetics; D011995:Recombination, Genetic; D020133:Reverse Transcriptase Polymerase Chain Reaction; D027041:Somatic Hypermutation, Immunoglobulin / Q000276:immunology*; D013154:Spleen / Q000166:cytology / Q000276:immunology; D013601:T-Lymphocytes; D000098830:AICDA (Activation-Induced Cytidine Deaminase)
D018398:Homeodomain Proteins; C490904:Hoxc4 protein, mouse; D000098830:AICDA (Activation-Induced Cytidine Deaminase); D003564:Cytidine Deaminase