Transcription-induced cleavage of immunoglobulin switch regions by nucleotide excision repair nucleases in vitro.
Immunoglobulin (Ig) heavy chain class switch recombination (CSR) mediates isotype switching during B cell development. CSR occurs between switch (S) regions that precede each Ig heavy chain constant region gene. Various studies have demonstrated that transcription plays an essential role in CSR in vivo. In this study, we show that in vitro transcription of S regions in their physiological orientation induces the formation of stable R loops. Furthermore, we show that the nucleotide excision repair nucleases XPF-ERCC1 and XPG can cleave the R loops formed in the S regions. Based on these findings, we propose that CSR is initiated via a mechanism that involves transcription-dependent S region cleavage by DNA structure-specific endonucleases that function in general DNA repair processes. Such a mechanism also may underlie transcription-dependent mutagenic processes such as somatic hypermutation, and contribute to genomic instability in general.
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Howard Hughes Medical Institute, Children's Hospital, and Center for Blood Research, Harvard Medical School, Boston, Massachusetts 02115, USA.
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D004260:DNA Repair; D004268:DNA-Binding Proteins / Q000378:metabolism; D004720:Endonucleases / Q000378:metabolism*; D007134:Immunoglobulin Switch Region / Q000235:genetics*; D008957:Models, Genetic; D009687:Nuclear Proteins; D009690:Nucleic Acid Conformation; D011506:Proteins / Q000378:metabolism; D011995:Recombination, Genetic; D013379:Substrate Specificity; D014157:Transcription Factors; D014158:Transcription, Genetic; D000099250:DNA Excision Repair Protein ERCC-5
D004268:DNA-Binding Proteins; D004720:Endonucleases; D009687:Nuclear Proteins; D011506:Proteins; D014157:Transcription Factors; D000099250:DNA Excision Repair Protein ERCC-5; C095888:xeroderma pigmentosum group F protein