al-Katib A M, Mohammad R M, Maki A, Smith M R
Department of Internal Medicine, Wayne State University, School of Medicine, Detroit, Michigan 48201, USA.
Cell Growth Differ. 1995 Feb;6(2):211-7.
To identify potential effector molecules of human B-cell differentiation, the acute lymphoblastic leukemia cells (Reh) were induced to terminal differentiation in vitro using the phorbol ester, 12-O-tetradecanoylphorbol-13-acetate. Proteins of parent and differentiated Reh cells were mapped using powerful two-dimensional gel electrophoresis coupled with ultrasensitive silver stain. New protein (MW-pl; p34-5.3) spot was induced in the differentiated Reh cells. The NH2-terminal sequencing of this protein revealed 100% homology with the ubiquitin COOH-terminal hydrolase isozyme L1 (UCH-L1). The presence of UCH-L1 protein in the differentiated Reh cells but not in parent cells was confirmed by immunocytochemistry and Western blot. The cDNA for this enzyme was cloned from the differentiated Reh cells, and the UCH-L1 mRNA was detected in both parent and 12-O-tetradecanoylphorbol-13-acetate-induced cells. However, the message was more abundant in the differentiated cells than parent cells, indicating a posttranscriptional regulation. Until now, UCH-L1 was thought to be neuron-specific. The induced expression of UCH-L1 in differentiated Reh cells argues for a role of this enzyme, and the ubiquitin system, in B-cell differentiation.
为了鉴定人类B细胞分化的潜在效应分子，使用佛波酯12 - O - 十四酰佛波醇 - 13 - 乙酸酯在体外诱导急性淋巴细胞白血病细胞（Reh）向终末分化。利用强大的二维凝胶电泳结合超灵敏银染技术对未分化和分化后的Reh细胞蛋白质进行图谱分析。在分化后的Reh细胞中诱导产生了新的蛋白质斑点（分子量-等电点；p34 - 5.3）。对该蛋白质的氨基末端测序显示，它与泛素羧基末端水解酶同工酶L1（UCH - L1）具有100%的同源性。通过免疫细胞化学和蛋白质印迹法证实，UCH - L1蛋白存在于分化后的Reh细胞中，而不存在于未分化细胞中。从分化后的Reh细胞中克隆出了该酶的cDNA，并且在未分化细胞和经12 - O - 十四酰佛波醇 - 13 - 乙酸酯诱导的细胞中均检测到了UCH - L1 mRNA。然而，在分化后的细胞中该信使RNA比未分化细胞中更为丰富，这表明存在转录后调控。到目前为止，UCH - L1被认为是神经元特异性的。在分化后的Reh细胞中诱导表达UCH - L1表明该酶以及泛素系统在B细胞分化中发挥作用。
