title: Both CpG methylation and activation-induced deaminase are required for the fragility of the human bcl-2 major breakpoint region: implications for the timing of the breaks in the t(14;18) translocation.
abstract: The t(14;18) chromosomal translocation typically involves breakage at the bcl-2 major breakpoint region (MBR) to cause human follicular lymphoma. A theory to explain the striking propensity of the MBR breaks at three CpG clusters within the 175-bp MBR region invoked activation-induced deaminase (AID). In a test of that theory, we used here minichromosomal substrates in human pre-B cell lines. Consistent with the essential elements of the theory, we found that the MBR breakage process is indeed highly dependent on DNA methylation at the CpG sites and highly dependent on the AID enzyme to create lesions at peak locations within the MBR. Interestingly, breakage of the phosphodiester bonds at the AID-initiated MBR lesions is RAG dependent, but, unexpectedly, most are also dependent on Artemis. We found that Artemis is capable of nicking small heteroduplex structures and is even able to nick single-base mismatches. This raises the possibility that activated Artemis, derived from the unjoined D to J(H) DNA ends at the IgH locus on chromosome 14, nicks AID-generated TG mismatches at methyl CpG sites, and this would explain why the breaks at the chromosome 18 MBR occur within the same time window as those on chromosome 14.
authors.affiliation: USC Norris Cancer Center, Los Angeles, California, USA.
authors.forename: Xiaoping
authors.initials: X
authors.lastname: Cui
authors.forename: Zhengfei
authors.initials: Z
authors.lastname: Lu
authors.forename: Aya
authors.initials: A
authors.lastname: Kurosawa
authors.forename: Lars
authors.initials: L
authors.lastname: Klemm
authors.forename: Andrew T
authors.initials: AT
authors.lastname: Bagshaw
authors.forename: Albert G
authors.initials: AG
authors.lastname: Tsai
authors.forename: Neil
authors.initials: N
authors.lastname: Gemmell
authors.forename: Markus
authors.initials: M
authors.lastname: Müschen
authors.forename: Noritaka
authors.initials: N
authors.lastname: Adachi
authors.forename: Chih-Lin
authors.initials: CL
authors.lastname: Hsieh
authors.forename: Michael R
authors.initials: MR
authors.lastname: Lieber
mesh_terms: D001402:B-Lymphocytes / Q000378:metabolism; D002460:Cell Line; D056905:Chromosome Breakpoints; D002883:Chromosomes, Human, Pair 14 / Q000235:genetics / Q000378:metabolism; D002887:Chromosomes, Human, Pair 18 / Q000235:genetics / Q000378:metabolism; D018899:CpG Islands; D003564:Cytidine Deaminase / Q000378:metabolism*; D004247:DNA / Q000235:genetics / Q000378:metabolism; D019175:DNA Methylation; D004268:DNA-Binding Proteins; D004720:Endonucleases; D055786:Gene Knockout Techniques; D019254:Genes, bcl-2; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics*; D014178:Translocation, Genetic; D000098830:AICDA (Activation-Induced Cytidine Deaminase)
chemical_list: D004268:DNA-Binding Proteins; D018398:Homeodomain Proteins; D009687:Nuclear Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; C064658:RAG-1 protein; D004247:DNA; C426344:DCLRE1C protein, human; D004720:Endonucleases; D000098830:AICDA (Activation-Induced Cytidine Deaminase); D003564:Cytidine Deaminase