ABSTRACT
Polycomb group (PcG) proteins are chromatin modifiers that are necessary for the maintenance and renewal of embryonic and adult stem cells. However, overexpression of the PcG protein, Bmi-1, causes lymphoma in transgenic mice. We show that Bmi-1 is up-regulated in Hodgkin lymphoma (HL) cells by the Epstein-Barr virus (EBV) oncogene latent membrane protein-1 (LMP1) and that this up-regulation is mediated by NF-kappaB signaling. We also show that Bmi-1 is up-regulated by NF-kappaB in EBV-negative HL cells. Down-regulation of LMP1 and Bmi-1 decreased the survival of HL cells, suggesting that Bmi-1 may mediate the prosurvival effects of LMP1-induced NF-kappaB signaling in HL cells. Transcriptional targets of Bmi-1 were identified after its knockdown in an HL cell line. We show here that Bmi-1 and LMP1 down-regulate the ataxia telangiectasia-mutated (ATM) tumor suppressor and conclude that Bmi-1 contributes to LMP1-induced oncogenesis in HL.
Subject(s)
Gene Expression Regulation, Neoplastic , Herpesvirus 4, Human/metabolism , Hodgkin Disease/metabolism , Nuclear Proteins/metabolism , Proto-Oncogene Proteins/metabolism , Repressor Proteins/metabolism , Viral Matrix Proteins/metabolism , Ataxia Telangiectasia Mutated Proteins , Cell Cycle Proteins/genetics , Cell Cycle Proteins/metabolism , Cell Line , Cell Survival , DNA-Binding Proteins/genetics , DNA-Binding Proteins/metabolism , Down-Regulation , Gene Expression Profiling , Hodgkin Disease/genetics , Hodgkin Disease/pathology , Humans , NF-kappa B/metabolism , Nuclear Proteins/genetics , Polycomb Repressive Complex 1 , Protein Serine-Threonine Kinases/genetics , Protein Serine-Threonine Kinases/metabolism , Proto-Oncogene Proteins/genetics , Repressor Proteins/genetics , Tumor Suppressor Proteins/genetics , Tumor Suppressor Proteins/metabolism , Up-Regulation , Viral Matrix Proteins/geneticsABSTRACT
Nijmegen breakage syndrome (NBS) is a rare autosomal recessive disorder resulting from mutations in the NBS1 gene, which encodes for the DNA double strand break repair protein nibrin. NBS is clinically characterized by microcephaly, dysmorphic features, immunodeficiency, and increased susceptibility to malignancy, mainly of lymphoid origin. Here, we describe a 7-year-old girl with NBS who is homozygous for the NBS1 698del4 mutation. She had been diagnosed with perianal rhabdomyosarcoma (RMS) and experienced severe toxicity from chemotherapy. RMS arising perianally is extremely uncommon but has been previously described in two cases with NBS. The strong association of perianal RMS with NBS should, therefore, be considered when confronted with a perianal RMS, as this carries important clinical implications in terms of potential need for therapy modification and follow up investigations. In addition, it suggests a role for the NBS1 gene and the nibrin dependent pathway in the pathogenesis of RMS, especially those arising perianally.
Subject(s)
Abnormalities, Multiple/diagnosis , Microcephaly/diagnosis , Rhabdomyosarcoma/diagnosis , Soft Tissue Neoplasms/diagnosis , Abnormalities, Multiple/genetics , Anus Neoplasms/diagnosis , Base Sequence , Cell Cycle Proteins/genetics , Child , Chromosome Breakage , Facies , Female , Growth Disorders/diagnosis , Humans , Karyotyping , Microcephaly/genetics , Nuclear Proteins/genetics , Sequence Deletion , SyndromeABSTRACT
Ataxia telangiectasia (A-T) is an autosomal recessive neurodegenerative disorder that arises because of mutations in the ATM gene. The 5762ins137 A-->G point mutation activates a cryptic splice donor site resulting in a 137 bp intronic insert being aberrantly spliced into the ATM transcript. However, normal ATM transcript also is produced from this affected allele, albeit at significantly reduced levels. An exceptionally mild A-T phenotype occurs as a result of homozygosity for the 5762ins137 mutation because of relative preservation of ATM protein expression/kinase activity.
