BAG-1--A NOVEL BCL-2 BINDING PROTEIN

bcl-2基因是程序性细胞死亡的阻断剂，其表达 在大部分人类癌症中变得失调，包括 乳腺、前列腺和结肠腺癌，鳞状细胞癌 以及淋巴瘤和白血病。 Bcl-2的过度表达 蛋白质已被证明可以使肿瘤细胞对 几乎所有的化疗药物和放射都能诱导细胞死亡， 这表明bcl-2在某种程度上可以被视为一种多药药物， 抗性基因 bcl-2基因的产物是一个完整的膜 位于线粒体外膜、核内的蛋白质 包膜和内质网。 预测的氨基酸序列 然而，这种蛋白质的生物化学机制未能表明， 行动上 为了进一步了解Bcl-2的作用机制， 技术用于鉴定编码Bcl-2结合蛋白的cDNA， 从而发现了一种新的蛋白质BAG-1。 重组BAG-1 通过几种方法显示蛋白质特异性结合Bcl-2， 在体外，这两种蛋白可以从哺乳动物中免疫共沉淀 细胞 免疫显微镜显示BAG-1和Bcl-2可能存在于 至少部分位于相同的亚细胞位置。 共转染BAG- 1和Bcl-2编码的表达质粒导致增强的抑制 与单独的BAG-1或Bcl-2相比， 人类BAG-1 基因定位于染色体9 p13，这一区域可能与遗传有关。 提示发育性细胞死亡缺陷的综合征。 对结构、表达和功能的全面研究 提出了BAG-1基因的测定，包括测定（i） 人和小鼠BAG-1基因的外显子/内含子组织;（ii） BAG-1蛋白的亚细胞定位及其体内表达模式 （iii）BAG-1与Bcl-2结合的特异性位点和BAG-1与Bcl-2结合的特异性位点。 这种相互作用对Bcl-2功能的重要性;（iv）生物化学 （v）BAG-1蛋白的体内功能 通过创建转基因和敲除小鼠;和（vi） 癌症和遗传综合征中BAG-1改变的可能性 映射到9 p13。

The bcl-2 gene is a blocker of programmed cell death, whose expression becomes dysregulated in a large proportion of human cancers, including adenocarcinomas of the breast, prostate, and colon, squamous carcinomas of the lung, and lymphomas and leukemias. Over-production of the Bcl-2 protein has been shown to make tumor cells strikingly more resistant to cell death induced by nearly all chemotherapeutic drugs and radiation, suggesting that bcl-2 can in some ways be viewed as a multidrug- resistance gene. The product of the bcl-2 gene is an integral membrane protein that resides in the outer mitochondrial membrane, nuclear envelope, and endoplasmic reticulum. The predicted amino-acid sequence of this protein however has failed to suggest a biochemical mechanism of action. To gain further insights into Bcl-2 mechanisms, an interaction cloning technique was used to identify cDNAs that encode Bcl-2 binding proteins, leading to the discovery of a novel protein, BAG-1. Recombinant BAG-1 protein was shown by several methods to specifically bind to Bcl-2 in vitro, and the two proteins could be co-immunoprecipitated from mammalian cells. Immunomicroscopy suggests that BAG-1 and Bcl-2 may reside at least in part in the same subcellular locations. Co-transfection of BAG- 1 and Bcl-2-encoding expression plasmids results in enhanced suppression of apoptosis compared to either BAG-1 or Bcl-2 alone. The human BAG-1 gene maps to chromosome 9p13, a region possibly involved in hereditary syndromes that suggest a defect in developmental cell death. A comprehensive investigation of the structure, expression, and function of the BAG-1 gene is proposed, including determination of (i) the exon/intron organization of the human and mouse BAG-1 genes; (ii) the subcellular location of the BAG-1 protein and its in vivo patterns of production; (iii) the specific sites where BAG-1 binds to Bcl-2 and the importance of this interaction for Bcl-2 function; (iv) the biochemical properties of the BAG-1 protein; (v) the in vivo function of BAG-1 through creation of transgenic and knock-out mice; and (vi) the possibility of alterations in BAG-1 in cancers and hereditary syndromes mapped to 9p13.