• KSBB Journal
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• v.24 no.4
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• pp.403-409
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• 2009

H2AX, a crucial component of chromatin, is implicated in DNA repair, cell cycle check point and tumor suppression. The aim of this study was to identify direct binding partners of H2AX to regulate cellular responses to above mechanisms. Literature reviews and bioinformatical tools were attempted intensively to find binding partners of H2AX, which resulted in identifying two potential proteins, breast cancer-1 (BRCA1) and BRCA1-associated RING domain 1 (BARD1). Although it has been reported in vivo that BRCA1 co-localizes with H2AX at the site of DNA damage, their biochemical mechanism for H2AX were however only known that the complex monoubiquitinates histone monomers, including unphosphorylated H2AX in vitro. Therefore, it is important to know whether the complex directly interacts with H2AX, and also which regions of these are specifically mediated for the interaction. Using in vitro GST pull-down assay, we present here that BRCA1 and BARD1 directly bind to H2AX. Moreover, through combinational approaches of domain analysis, fragment clonings and in vitro binding assay, we revealed molecular details of the BRCA1-H2AX and BARD1-H2AX complex. These data provide the potential evidence that each of the BRCA1 nuclear localization signal (NLS) and BARD1 BRCA1 C-terminal (BRCT) repeat domain is the novel mediator of H2AX recognition.

• Pediatric Gastroenterology, Hepatology & Nutrition
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• v.5 no.1
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• pp.1-10
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• 2002

Purpose; Dysregulation of gastric epithelial cell proliferation and apoptosis are important in development of ulcer, atrophy and neoplasia in Helicobacter pylori (H. pylori) infection. The aim of this study was to investigate the effect of infection of H. pylori on gastric epithelial cell proliferation and apoptosis in children. Methods: Histological grading by updated Sydney system, PCNA immunostaining and TUNEL method were performed in H. pylori positive (N=58) and negative (N=40) gastric biopsy specimens. Results: In H. pylori positive children, there were significantly higher grade of polymorphonuclear neutrophil activity (P=0.000), chronic inflammation (P=0.000), epithelial damage (P=0.000) and lymphoid follicles (P=0.000) than in H. pylori negative children. Intestinal metaplasia was not seen in H. pylori positive children. PCNA index was significantly different between H. pylori positive children ($67.8{\pm}18.13$) and H. pylori negative children ($54.8{\pm}14.46$, P=0.000). There was positive correlation between PCNA index and H. pylori density (r=0.277, P=0.007), polymorphonuclear neutrophil activity (r=0.280, P=0.007) and chronic inflammation (r=0.284, P=0.006). Apoptosis index of H. pylori positive children ($0.44{\pm}0.447$) was significantly higher than of H. pylori negative children ($0.14{\pm}0.196$, P=0.000). There was positive correlation between apoptosis index and H. pylori density (r=0.472, P=0.000), polymorphonuclear neutrophil activity (r=0.370, P=0.001) and chronic inflammation (r=0.483, P=0.000). There was positive correlation between PCNA index and apoptosis index (r=0.353, P=0.003). Conclusion: The PCNA and apoptosis index in H. pylori positive children were significantly higher than in H. pylori negative children. This study suggested that gastric epithelial cell proliferation and apoptosis are important to pathogenesis of H. pylori infection in children.