RESUMEN
BAZF, a family member of Bcl6, can function as a sequence-specific transcriptional repressor. We determined BAZF-binding DNA sequence. The consensus binding sequence (CBS) of BAZF is almost the same as those of Bcl6 previously described. Three nucleotides of T, G and A at position 6, 8, and 9 in the CBS (5'-ATTCCTAGAAAG-3') are important nucleotides for binding of both BAZF and Bcl6. Since a part (5'-TTC-CTA-GAA-3') of the CBS resembled the sequence motif (5'-TTC-(N3-4)-GAA-3') bound by STAT factors, BAZF and Bcl6 can bind to the CD23b-STAT6-binding sequence (5'-TTTC-TTA-GAAAT-3'), the immunoglobulin germline epsilon-STAT6-binding sequence (5'-CTTC-CCAA-GAAC-3'), and the IL4-STAT6-binding sequence (5'-TTTC-CCA-GAAAA-3') with weak affinity. However, a mutation of C nucleotide to T nucleotide in the IL4-STAT6-binding sequence (5'-TTTC-CTA-GAAAA-3') strongly increased the binding activity of BAZF and Bcl6. These results suggest that BAZF and Bcl6 can repress some of STAT-induced transcription by binding to DNA sequences recognized by STAT factors.
Asunto(s)
Proteínas de Unión al ADN/metabolismo , ADN/metabolismo , Proteínas Proto-Oncogénicas/metabolismo , Secuencias Reguladoras de Ácidos Nucleicos/fisiología , Proteínas Represoras/metabolismo , Transactivadores/metabolismo , Factores de Transcripción/metabolismo , Animales , Unión Competitiva/efectos de los fármacos , Unión Competitiva/fisiología , Línea Celular , Secuencia de Consenso , Proteínas de Unión al ADN/genética , Expresión Génica , Glutatión Transferasa/genética , Interleucina-4/metabolismo , Ratones , Mutagénesis Sitio-Dirigida , Oligonucleótidos/genética , Oligonucleótidos/metabolismo , Oligonucleótidos/farmacología , Proteínas Proto-Oncogénicas/genética , Proteínas Proto-Oncogénicas c-bcl-6 , Proteínas Recombinantes de Fusión/genética , Proteínas Recombinantes de Fusión/metabolismo , Proteínas Represoras/genética , Factor de Transcripción STAT6 , Análisis de Secuencia de ADN , Transducción de Señal/fisiología , Factores de Transcripción/genética , Transfección , Dedos de Zinc/fisiologíaRESUMEN
BACKGROUND/AIMS: Hepatitis C virus (HCV) is a major etiologic agent of chronic hepatitis, cirrhosis, and hepatocellular carcinoma. The aim of this study was to elucidate pathological effects of HCV-core protein on liver cells. METHODS: We have generated transgenic mice carrying HCV-core cDNA (Px-core) and pathologically examined livers of Px-core mice. RESULTS: HCV-core protein was detectable in livers from lines 5 (C5) and 8 (C8) of Px-core transgenic mice. Since chronic hepatitis and cirrhosis precede hepatocellular carcinoma in patients with HCV infection, we tried to examine the effect of repetitive injection of a small dose of anti-Fas antibody in the transgenic mice. Surprisingly, an initial injection of anti-Fas antibody induced resistance of liver cells to the second injection of anti-Fas antibody in both Px-core and littermate control mice. The insensitivity of liver cells induced in the control mice continued for more than 24 weeks after the first injection but was broken within 1 week after partial hepatectomy. However, the sensitivity was restored in the Px-core mice within 12 weeks after the injection. CONCLUSION: HCV-core protein in liver cells may affect persistence of Fas-mediated liver cell injury.