title: Mutations of the BCL6 proto-oncogene disrupt its negative autoregulation in diffuse large B-cell lymphoma.
abstract: The BCL6 proto-oncogene encodes a transcriptional repressor whose expression is deregulated by chromosomal translocations in approximately 40% of diffuse large B-cell lymphomas (DLBCLs). The BCL6 regulatory sequences are also targeted by somatic hypermutation in germinal center (GC) B cells and in a fraction of all GC-derived lymphomas. However, the functional consequences of these mutations are unknown. Here we report that a subset of mutations specifically associated with DLBCL causes deregulated BCL6 transcription. These mutations affect 2 adjacent BCL6 binding sites located within the first noncoding exon of the gene, and they prevent BCL6 from binding its own promoter, thereby disrupting its negative autoregulatory circuit. These alterations were found in approximately 16% of DLBCLs devoid of chromosomal translocations involving the BCL6 locus, but they were not found in normal GC B cells. This study establishes a novel mechanism for BCL6 deregulation and reveals a broader involvement of this gene in DLBCL pathogenesis.
authors.affiliation: Institute for Cancer Genetics and the Department of Pathology, Columbia University, New York, NY 10032, USA.
authors.forename: Laura
authors.initials: L
authors.lastname: Pasqualucci
authors.forename: Anna
authors.initials: A
authors.lastname: Migliazza
authors.forename: Katia
authors.initials: K
authors.lastname: Basso
authors.forename: Jane
authors.initials: J
authors.lastname: Houldsworth
authors.forename: R S K
authors.initials: RS
authors.lastname: Chaganti
authors.forename: Riccardo
authors.initials: R
authors.lastname: Dalla-Favera
mesh_terms: D001665:Binding Sites; D004252:DNA Mutational Analysis; D004273:DNA, Neoplasm / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000502:physiology; D005091:Exons / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic; D018858:Germinal Center / Q000473:pathology; D006801:Humans; D016403:Lymphoma, Large B-Cell, Diffuse / Q000209:etiology / Q000235:genetics* / Q000473:pathology; D009363:Neoplasm Proteins / Q000235:genetics* / Q000502:physiology; D011401:Promoter Regions, Genetic; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins / Q000235:genetics* / Q000502:physiology; D051560:Proto-Oncogene Proteins c-bcl-6; D011519:Proto-Oncogenes; D012097:Repressor Proteins / Q000235:genetics* / Q000502:physiology; D014157:Transcription Factors / Q000235:genetics* / Q000502:physiology; D014162:Transfection; D014407:Tumor Cells, Cultured
chemical_list: D004273:DNA, Neoplasm; D004268:DNA-Binding Proteins; C000715470:MAS1 protein, human; D009363:Neoplasm Proteins; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins; D051560:Proto-Oncogene Proteins c-bcl-6; D012097:Repressor Proteins; D014157:Transcription Factors