{"title":"Necessity of HuR/ELAVL1 for the activation-induced cytidine deaminase-dependent decrease in topoisomerase 1 in antibody diversification.","authors":"Wajid Amin, Shoki Nishio, Tasuku Honjo, Maki Kobayashi","doi":"10.1093/intimm/dxad011","DOIUrl":null,"url":null,"abstract":"<p><p>Activation-induced cytidine deaminase (AID)-dependent DNA cleavage is the initial event of antibody gene-diversification processes such as class switch recombination (CSR) and somatic hypermutation (SHM). We previously reported the requirement of an AID-dependent decrease of topoisomerase 1 (Top1) for efficient DNA cleavage, but the underlying molecular mechanism has remained elusive. This study focuses on HuR/ELAVL1, a protein that binds to AU-rich elements in RNA. HuR-knockout (KO) CH12 cells derived from murine B lymphoma cells were found to have lower CSR and hypermutation efficiencies due to decreased AID-dependent DNA cleavage levels. The HuR-KO CH12 cells do not show impairment in cell cycles and Myc expression, which have been reported in HuR-reduced spleen B cells. Furthermore, drugs that scavenge reactive oxygen species (ROS) do not rescue the lower CSR in HuR-KO CH12 cells, meaning that ROS or decreased c-Myc protein amount is not the reason for the deficiencies of CSR and hypermutation in HuR-KO CH12 cells. We show that HuR binds to Top1 mRNA and that complete deletion of HuR abolishes AID-dependent repression of Top1 protein synthesis in CH12 cells. Additionally, reduction of CSR to IgG3 in HuR-KO cells is rescued by knockdown of Top1, indicating that elimination of the AID-dependent Top1 decrease is the cause of the inefficiency of DNA cleavage, CSR and hypermutation in HuR-KO cells. These results show that HuR is required for initiation of antibody diversification and acquired immunity through the regulation of AID-dependent DNA cleavage by repressing Top1 protein synthesis.</p>","PeriodicalId":13743,"journal":{"name":"International immunology","volume":"35 8","pages":"361-375"},"PeriodicalIF":4.8000,"publicationDate":"2023-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"International immunology","FirstCategoryId":"3","ListUrlMain":"https://doi.org/10.1093/intimm/dxad011","RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"IMMUNOLOGY","Score":null,"Total":0}
引用次数: 0
Abstract
Activation-induced cytidine deaminase (AID)-dependent DNA cleavage is the initial event of antibody gene-diversification processes such as class switch recombination (CSR) and somatic hypermutation (SHM). We previously reported the requirement of an AID-dependent decrease of topoisomerase 1 (Top1) for efficient DNA cleavage, but the underlying molecular mechanism has remained elusive. This study focuses on HuR/ELAVL1, a protein that binds to AU-rich elements in RNA. HuR-knockout (KO) CH12 cells derived from murine B lymphoma cells were found to have lower CSR and hypermutation efficiencies due to decreased AID-dependent DNA cleavage levels. The HuR-KO CH12 cells do not show impairment in cell cycles and Myc expression, which have been reported in HuR-reduced spleen B cells. Furthermore, drugs that scavenge reactive oxygen species (ROS) do not rescue the lower CSR in HuR-KO CH12 cells, meaning that ROS or decreased c-Myc protein amount is not the reason for the deficiencies of CSR and hypermutation in HuR-KO CH12 cells. We show that HuR binds to Top1 mRNA and that complete deletion of HuR abolishes AID-dependent repression of Top1 protein synthesis in CH12 cells. Additionally, reduction of CSR to IgG3 in HuR-KO cells is rescued by knockdown of Top1, indicating that elimination of the AID-dependent Top1 decrease is the cause of the inefficiency of DNA cleavage, CSR and hypermutation in HuR-KO cells. These results show that HuR is required for initiation of antibody diversification and acquired immunity through the regulation of AID-dependent DNA cleavage by repressing Top1 protein synthesis.
期刊介绍:
International Immunology is an online only (from Jan 2018) journal that publishes basic research and clinical studies from all areas of immunology and includes research conducted in laboratories throughout the world.