Lin-Marq N, Clarkson S G
Départment de Génétique et Microbiologie, Centre Médical Universitaire, Genève, Switzerland.
J Mol Biol. 1995 Jan 13;245(2):81-5. doi: 10.1006/jmbi.1994.0008.
The La protein is a 47 kDa polypeptide that frequently acts as an autoantigen in systemic lupus erythematosus and Sjögren's syndrome patients. A key property of this protein is its association with the U-rich termini of newly synthesized RNA polymerase III transcripts. Here we characterize a 32 kDa protein from Saccharomyces cerevisiae that shows sequence similarity to the N termini of vertebrate La proteins. This yeast protein also functionally resembles La in that it binds preferentially in vitro to RNAs ending with a series of U residues, and at least 53 amino acids can be deleted from the C terminus without impeding this activity. Such RNA binding activity can be detected in crude yeast extracts by immunoprecipitation of ribonucleoprotein particles by an antibody to frog La protein. However, the same antibody fails to react with the 32 kDa protein. In addition, the gene encoding this protein is not essential for viability. Together, these results suggest that additional La homologue(s) exist in yeast.
La蛋白是一种47 kDa的多肽，在系统性红斑狼疮和干燥综合征患者中常作为自身抗原。该蛋白的一个关键特性是它与新合成的RNA聚合酶III转录本富含U的末端相关联。在这里，我们鉴定了一种来自酿酒酵母的32 kDa蛋白，它与脊椎动物La蛋白的N末端具有序列相似性。这种酵母蛋白在功能上也类似于La蛋白，因为它在体外优先结合以一系列U残基结尾的RNA，并且从C末端删除至少53个氨基酸不会妨碍这种活性。通过用抗青蛙La蛋白的抗体免疫沉淀核糖核蛋白颗粒，可以在粗制酵母提取物中检测到这种RNA结合活性。然而，相同的抗体不能与32 kDa蛋白发生反应。此外，编码该蛋白的基因对于细胞存活不是必需的。这些结果共同表明酵母中存在其他La同源物。
