Study for the mechanism of lymphocyte development by Bach2 transcription factor and clinical analysis of Bach2 gene

转录因子Bach1和Bach2是btb -碱性区亮氨酸拉链（bZip）因子家族的成员，通过与maf相关转录因子形成同二聚体或异二聚体，与12- o -十四烷醇-13-乙酸酯（TPA）响应元件和相关的maf识别元件（MARE）结合。在人造血细胞系（12种骨髓细胞系和16种淋巴细胞系）中，BACH2仅在部分b淋巴细胞系中丰富表达。在不表达内源性BACH2的人Burkitt细胞系RAJI中，强制表达BACH2导致克隆生成活性明显降低，表明BACH2对细胞增殖具有抑制作用。利用cDNA芯片双色荧光杂交技术，对不内源BACH2表达的人B细胞系与BACH2过表达亚系的表达谱进行了大规模比较，鉴定出具有抗凋亡活性的Bcl-2同源基因A1和具有抗凋亡活性的Bcl-2同源基因EBI3作为BACH2的靶基因，其与IL-12 （p40）同源。A1和EBI3在不表达BACH2的人b细胞系中均有表达。然而，在表达BACH2的b细胞系中未检测到表达。荧光素酶报告和凝胶阻滞实验揭示了人类A1基因5'区的应答元件。因此，Bach2可能参与了b细胞分化早期A1基因的抑制和b细胞凋亡的调控。通过荧光原位杂交，BACH2基因定位在6q15染色体上。由于6号染色体长臂缺失（6q）是人类b细胞淋巴瘤中最常见的染色体改变之一，我们检测了人类b细胞非霍奇金淋巴瘤（NHL）中BACH2基因杂合性缺失（LOH）。在25例资料丰富的病例中，5例（20%）表现为LOH。为了分析BACH2基因在这些淋巴瘤中的突变，我们检测了BACH2基因的结构，并确定了所有编码外显子的序列和外显子-内含子边界。通过直接序列分析，在携带BACH2基因LOH的f淋巴瘤样本中未检测到突变。这些结果表明BACH2在B细胞增殖调控中起重要作用，尽管BACH2功能缺失是否参与B细胞肿瘤发生尚不明确

The transcription factors Bach1 and Bach2, members of the BTB-basic region leucine zipper (bZip) factor family, bind to a 12-O-tetradecanoylphorbol-13-acetate (TPA)-responsive element and the related Maf-recognition element (MARE) by forming homodimers or heterodirners with Maf-related transcription factors. Among human hematopoietic cell lines (12 myeloid cell lines and 16 lymphocytic cell lines), BACH2 is expressed abundantly only in some B-lymphocytic cell lines. Enforced expression of BACH2 in a human Burkitt cell line, RAJI that does not express endogenous BACH2, resulted in marked reduction of clonogenic activity, indicating that BACH2 possesses an inhibitory effect on cell proliferation. A large-scale comparison of the expression profiles between a human B cell line without endogenous BACH2 expression and a BACH2-overexpressing subline, using two-color fluorescence hybridization of cDNA microarray, led to the identification of Bcl-2 homologue A1 with anti-apoptotic activity and … More EBI3 which is a homologue to IL-12 (p40) as target genes of Bach2. A1 and EBI3 were expressed in all human B-cell lines which do not express BACH2. However, no expression was detected in B-cell lines expressing BACH2. Luciferase reporter and gel retardation assays revealed the responsive elements in the 5' region of the human A1 gene. Hence Bach2 might be involved in repression of A1 gene at earlier stages of B-cell differentiation and control of B-cell apoptosis.By fluorescent in situ hybridization, the BACH2 gene was localized to chromosome 6q15. Because deletion of the long arm of chromosome 6 (6q) is one of the commonest chromosomal alterations in human B-cell lymphoma, we examined for the loss of heterozygosity (LOH) of the BACH2 gene in human B-cell non-Hodgkin's lymphomas (NHL). Among 25 informative cases, 5 (20 %) showed LOH. To analyze the mutations of BACH2 gene in these lymphomas, we examine the structure of the BACH2 gene and determined the sequences of the all coding exons and the exon-intron boundaries. By direct sequence analysis, no mutations were detected in the f lymphoma samples with the LOH of BACH2 gene. These results indicate that BACH2 plays important roles irregulation of B cell proliferation, although it remains still elusive whether loss of BACH2 function is involved in B-cell tumorigenesis Less