THE HUMAN-T(1-19) TRANSLOCATION IN PRE-B ALL PRODUCES MULTIPLE NUCLEAR E2A-PBX1 FUSION PROTEINS WITH DIFFERING TRANSFORMING POTENTIALS
THE HUMAN-T(1-19) TRANSLOCATION IN PRE-B ALL PRODUCES MULTIPLE NUCLEAR E2A-PBX1 FUSION PROTEINS WITH DIFFERING TRANSFORMING POTENTIALS
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DOI：
10.1101/gad.5.3.358
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发表时间：
1991-03-01
影响因子：
10.5
通讯作者：
BALTIMORE, D
中科院分区：
文献类型：
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作者：
KAMPS, MP;LOOK, AT;BALTIMORE, D
t（1; 19）易位产生嵌合基因，该嵌合基因将编码E2 A的转录激活子结构域的5'序列与部分编码称为pbx 1的新基因的同源盒结构域的3'序列连接。两个E2 A-pbx 1转录本已被克隆。它们编码推定的融合蛋白p85 E2 A-Pbx 1和p77 E2 A-Pbx 1，它们仅在Pbx 1序列上不同，含有独特的羧基末端，其序列在Pbx 1同源盒后分叉。在这项研究中，Pbx 1的抗血清被用来调查的身份和丰富的E2 A-Pbx 1融合蛋白的前B ALL细胞系，697，并在冷冻保存的白血病骨髓细胞，从6名儿童t（1;19）-阳性前B ALL。在所有含有t（1;19）的细胞中鉴定出五种E2 A-Pbx 1蛋白，其中两种与体外翻译的p85 E2 A-Pbx 1和p77 E2 A-Pbx 1无法区分。为了评估p85 E2 A-Pbx 1和p77 E2 A-Pbx 1在成纤维细胞中的生物学特性，将编码这些蛋白的cDNA克隆到逆转录病毒载体中，并将每一个导入NIH-3 T3细胞。p85 E2 A-Pbx 1和p77 E2 A-Pbx 1均定位于细胞核中，并且通过在裸鼠中的肿瘤形成来测定，任一者的表达导致NIH-3 T3细胞的恶性转化。当通过焦点形成、密度非依赖性生长和琼脂测定中的生长进行评分时，p77 E2 A-Pbx 1是比p85 E2 A-Pbx 1更有效的转化蛋白。由于p85 E2 A-Pbx 1的微小突变将其转化活性转化为p77 E2 A-Pbx 1的转化活性，因此我们认为p85 E2 A-Pbx 1的独特羧基末端内的序列起到负调节其生化活性的作用。
The t(1;19) translocation that characterizes 25% of pediatric pre-B cell acute lymphoblastic leukemias (pre-B ALL) produces a chimeric gene, joining 5' sequences that encode a transcriptional activator domain of E2A with 3' sequences that, in part, encode a homeo box domain of a new gene called pbx1. Two E2A-pbx1 transcripts have been cloned. They encode the putative fusion proteins, p85E2A-Pbx1 and p77E2A-Pbx1, which differ in Pbx1 sequences alone, containing unique carboxyl termini whose sequences diverge after the Pbx1 homeo box. In this study, an antiserum to Pbx1 was used to investigate the identity and abundance of E2A-Pbx1 fusion proteins in both the pre-B ALL cell line, 697, and in cryopreserved leukemic bone marrow cells, obtained from six children with t(1;19)-positive pre-B ALL. Five species of E2A-Pbx1 proteins were identified in all cells containing t(1;19), two of which were indistinguishable from in vitro-translated p85E2A-Pbx1 and p77E2A-Pbx1. To assess the biological properties of p85E2A-Pbx1 and p77E2A-Pbx1 in fibroblasts, the cDNAs encoding these proteins were cloned into retroviral vectors, and each was introduced into NIH-3T3 cells. Both p85E2A-Pbx1 and p77E2A-Pbx1 are localized in the nucleus, and expression of either resulted in malignant conversion of NIH-3T3 cells as assayed by tumor formation in nude mice. When scored by focus formation, density-independent growth, and growth in agar assays, p77E2A-Pbx1 was a much more potent transforming protein than was p85E2A-Pbx1. Because subtle mutations in p85E2A-Pbx1 converted its transforming activity into that of p77E2A-Pbx1, we suggest that a sequence within the unique carboxyl terminus of p85E2A-Pbx1 serves to negatively regulate its biochemical activity.