Craig A W, Svitkin Y V, Lee H S, Belsham G J, Sonenberg N
Department of Biochemistry, McGill University, Montreal, Quebec, Canada.
Mol Cell Biol. 1997 Jan;17(1):163-9. doi: 10.1128/MCB.17.1.163.
The La autoantigen is an RNA-binding protein that is involved in initiation and termination of RNA polymerase III transcription. It also binds several viral RNAs, including those of poliovirus and human immunodeficiency virus (HIV). Binding of the La protein to these RNAs enhances their translation in vitro (K. Meerovitch, Y.V. Svitkin, H.S. Lee, F. Lejbkowicz, D.J. Kenan, E.K.L. Chan, V.L. Agol, J.D. Keene, and N. Sonenberg, J. Virol. 67:3798-3807, 1993, and Y.V. Svitkin, A. Pause, and N. Sonenberg, J. Virol. 68:7001-7007, 1994). Here, a functional domain in the carboxy-terminal half of La that is distinct from the RNA-binding domain is described. Deletion of this domain abrogated the ability of La protein to enhance translation of poliovirus RNA and a hybrid HIV trans-activation-response element-chloramphenicol acetyltransferase mRNA. Far-Western assays indicated that the La protein homodimerized in vitro, and the C-terminal deletions that caused a loss of activity in translation also abrogated the dimerization signal. Gel filtration chromatography of recombinant La protein confirmed that La protein exists as a dimer under native conditions. Addition of the purified dimerization domain resulted in a loss of translation stimulatory activity of La protein in cell-free-translation reactions.
La自身抗原是一种RNA结合蛋白，参与RNA聚合酶III转录的起始和终止。它还能结合多种病毒RNA，包括脊髓灰质炎病毒和人类免疫缺陷病毒（HIV）的RNA。La蛋白与这些RNA的结合在体外增强了它们的翻译（K. Meerovitch、Y.V. Svitkin、H.S. Lee、F. Lejbkowicz、D.J. Kenan、E.K.L. Chan、V.L. Agol、J.D. Keene和N. Sonenberg，《病毒学杂志》67:3798 - 3807，1993年；以及Y.V. Svitkin、A. Pause和N. Sonenberg，《病毒学杂志》68:7001 - 7007，1994年）。本文描述了La蛋白羧基末端一半中一个与RNA结合结构域不同的功能结构域。删除该结构域消除了La蛋白增强脊髓灰质炎病毒RNA和HIV反式激活应答元件 - 氯霉素乙酰转移酶杂交mRNA翻译的能力。Far - Western分析表明La蛋白在体外形成同源二聚体，导致翻译活性丧失的C末端缺失也消除了二聚化信号。重组La蛋白的凝胶过滤色谱法证实La蛋白在天然条件下以二聚体形式存在。在无细胞翻译反应中添加纯化的二聚化结构域导致La蛋白的翻译刺激活性丧失。
