Brennwald P, Liao X, Holm K, Porter G, Wise J A
Department of Biochemistry, University of Illinois, Urbana-Champaign 61801.
Mol Cell Biol. 1988 Apr;8(4):1580-90. doi: 10.1128/mcb.8.4.1580-1590.1988.
We have cloned the gene encoding a novel small cytoplasmic RNA from the fission yeast Schizosaccharomyces pombe. Four lines of evidence support the idea that this RNA is a homolog of the 7SL RNA component of mammalian signal recognition particle (SRP), which targets presecretory proteins to the endoplasmic reticulum membrane. First, it shares limited but significant primary sequence homology with previously identified 7SL RNAs and can be folded into a similar secondary structure. Second, it possesses the 5' triphosphate characteristic of unprocessed RNA polymerase III transcripts, and moreover, it is the only fission yeast RNA in this size range with such a terminus. Third, its behavior in cell fractionation experiments suggests that it is part of a small ribonucleoprotein which forms salt-labile contacts with larger structures. Fourth, the particle containing S. pombe 7SL RNA resembles mammalian SRP in both size (11S) and affinity for DEAE-Sepharose. Disruption of the single-copy gene, designated slr1+, reveals that the RNA is indispensable for growth in fission yeast. This result is not surprising, since secretion is an essential cellular process.
我们从裂殖酵母粟酒裂殖酵母中克隆了编码一种新型小细胞质RNA的基因。四条证据支持这一观点，即这种RNA是哺乳动物信号识别颗粒（SRP）的7SL RNA组分的同源物，SRP将分泌前蛋白靶向内质网膜。第一，它与先前鉴定的7SL RNA具有有限但显著的一级序列同源性，并且可以折叠成相似的二级结构。第二，它具有未加工的RNA聚合酶III转录本的5'三磷酸特征，此外，它是这个大小范围内唯一具有这种末端的裂殖酵母RNA。第三，它在细胞分级分离实验中的行为表明它是一个小核糖核蛋白的一部分，该小核糖核蛋白与更大的结构形成对盐敏感的接触。第四，含有粟酒裂殖酵母7SL RNA的颗粒在大小（11S）和对DEAE-琼脂糖的亲和力方面都类似于哺乳动物SRP。破坏单拷贝基因slr1+表明该RNA对于裂殖酵母的生长是不可或缺的。这一结果并不令人惊讶，因为分泌是一个基本的细胞过程。
